Principles of plant breeding


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Principles of plant breeding

  1. 1. [1] Compiled by Dr Hari Krishna Rama Prasad Saripalli M.Sc., M.Phil., Ph.D. @Aksum University, Axum
  2. 2. [2] ABOUT THE AUTHOR ………. HARI KRISHNA RAMA PRASAD. SARIPALLI M.Sc., M M M., M.A., M.Sc IT., M.Phil, DASM (IBAM), DMLT, RDBMS., Ph.D (BioTech). has been Assistant Professor of Biotechnology at College of Natural and Computational Sciences, Aksum University, Axum, Ethiopia, North East Africa. He has 14 years of experince in academics, administration and research in various institutes like K. L. University, St. Ann’s College for women, Southren Institute of Medical Sciences, Hindu College of Pharmacy, St. Joseph’s College of Nursing and St. Ann’s College of Nursing. He received his B.Sc degree in Chemistry, Botany, Zoology from Andhra Loyola College(Autonomus), Affiliated to ANU, India (where he learned fundamentals of microbiology with Prof. Madhavarao), M.Sc degree in Microbiology from Campus College of ANU in the year 1997. He obtained his research degree M.Phil in Botany and Microbiology from Campus College of ANU with Prof. Vijaya Lakshmi.M, and his Ph.D in Biotechnology from RPSC-MU,Patna with Prof. Madan Prasad and also guided by Prof. Vijaya Lakshmi.M. A part from life sciences, he has versatile academic degrees like Marketing Management, Medical
  3. 3. [3] Sociology, Information Technology, Medical Lab Technology, Alternative Medicine and Database Management System. Dr. H K R Prasad. Saripalli is recipient of the South Asian Foundation fellowship (2003), University rank in Microbiology programme(1997). While at St.Ann’s College, he has received the Best Teacher Award(selected by students and management). He is a co-author, with Prof. R.P.Singh, of the text Biological Chemistry and Microbiology; with Prof. T. Pullaiah, of the texts, Emerging trends in Biological Sciences(2009), Recent Trends in Plant Sciences (2005); and other texts, Diversity of Microbes and Cryptogams and Gymnosperms, plant anatomy, ecology and biotechnology. He was elected to the Board of studies, Industrial microbiology, JMJ College (ANU). He is a founder and a member of the Scientific Advisory Board of Association of Global Science Innovations (AGSI). He published twenty three research papers in both national and international peer reviewed journals.
  4. 4. [4] Contents 1. Introduction to Plant Breeding 2. Nature of Plant Breeding 3. History of Plant Breeding 4. Objectives of Plant Breeding 5. Achievement of Plant Breeding 6. Scope of Plant Breeding (Future Prospects) 7. Genetic in Relation to Plant Breeding 8. Mechanism of Heredity 9. Role of Various Genetic Concepts and Principles in Crop Improvement 10. Reproduction in Flowering Plants 11. Male Gametophyte or Microsporogenesis 12. Female Gametophyte or Megasporogenesis 13. Fertilization and Significance of Fertilization in Flowering Plants 14. Modes of Reproduction in Plants 15. Sporogenesis 16. Gametogenesis 17. Mode of Pollination 18. Methods of Breeding in Self Pollinated Crops 19. Methods of Breeding in Self Pollinated Crops – Introduction 20. Plant Introduction Agencies in India
  5. 5. [5] 21. Purpose and Achievement of Plant Introduction Method of Breeding 22. Varieties Selected and Developed from Introduction 23. Merits and Demerits for Plant Introduction Method of Breeding 24. Method of Plant Breeding in Self Pollinated Plants - Selection 25. Method of Plant Breeding in Self Pollinated Plants – Pure Line Selection 26. Method of Plant Breeding in Self Pollinated Plants – Mass Selection 27. Difference between Pure Line and Mass Selection 28. Method of Plant Breeding in Self Pollinated Plants – Hybridization 29. Types of Hybridization 30. Steps Involved in Hybridization 31. Method of Plant Breeding in Self Pollinated Plants – Pedigree Methods 32. Procedure of Pedigree Method 33. Merits, Demerits and Achievements of Pedigree Method 34. Difference between Pureline and Pedigree Selection 35. Method of Plant Breeding in Self Pollinated Plants - Bulk Population Method 36. Method of Plant Breeding in Self Pollinated Plants - Single Seed Descent Method 37. Method of Plant Breeding in Self Pollinated Plants - Multiple Crossing 38. Method of Plant Breeding in Self Pollinated Plants - Multiline Varieties 39. Method of Plant Breeding in Self Pollinated Plants - Population Approach 40. Method of Plant Breeding in Self Pollinated Plants - Back Cross Method 41. Procedure of Back Cross Method of Breeding in Self Pollinated Crops 42. Merits, Demerits and Achievements of Backcross Method of Breeding 43. Breeding Methods in Cross Pollinated Crop
  6. 6. [6] 44. Brief Account of Breeding Methods 45. Method of Plant Breeding in Cross Pollinated Plants – Introduction and Acclimatization 46. Method of Plant Breeding in Cross Pollinated Plants – Selection with Progeny Testing 47. Method of Plant Breeding in Cross Pollinated Plants – Line Breeding and Mass Selection 48. Method of Plant Breeding in Cross Pollinated Plants – Recurrent Selection 49. Method of Plant Breeding in Cross Pollinated Plants – Hybridization 50. Development of Hybrid Varieties in Cross Pollinated Crops 51. Male Sterility 52. Self Incompatibility 53. Heterosis 54. Methods for Estimation of Heterosis 55. Theories of Heterosis 56. Comparison of Dominance and Overdominace Theories of Heterosis 57. Effects and Use of Heterosis in Plant Breeding 58. Inbreeding and Inbreeding Depression 59. Effects of Inbreeding 60. Degree of Inbreeding Depression 61. Homozygous and Heterozygous Balance 62. Heritability 63. Synthetic Variety 64. Merits, Demerits and Achievement of Synthetic Varieties 65. Composite Variety 66. Difference between Synthetic and Composite Variety
  7. 7. [7] 67. Breeding Methods in Asexually Propagated Crop 68. Clone and Characteristics of Clones 69. Genetic Variation within Clones 70. Breeding Proceduresof Clonal Selection 71. Merits and Demeritsof Clonal Selection 72. Breeding Method in Asexually Propagated Crop – Hybridization 73. Problems in Breeding of Asexually Propagated Crops 74. Achievements of Problems in Breeding Methods of Asexually Propagated Crops 75. Methods Used for Determination of Organic Carbon
  8. 8. [8] Introduction to Plant Breeding Definition of Plant Breeding: Plant breeding is an applied branch of Botany, which deals with improvement of agricultural crops. This branch of agricultural science has contributed maximum to the increase in food production all over the world and therefore, now a day it assuming ever increasing importance in field of agriculture in every country. Riley, 1978 defined plant breeding as a technology of developing superior crop plants/ varieties for various purpose. Frankel, 1958 defined plant breeding as the genetic adjustment of plants to the service man. Plant breeding is a branch of biology concerned with changing the genotype of plant so that they become more useful. The food grain production of India has increased from 54 millions tonnes to 206 million tonns. As a result of this the nation has become almost self sufficient in food grain, this thing is achieved only due to green revolution has tookes place in 1965-66. Green revolution in our country particularly in Rice and Wheat increases our food grain production in our country particularly in Rice and Wheat increases our food grain production and today we are exporting several million tonns food grain to many developed and developing country. On the other hand population of our country after independence also increasing at an arming rate of 2.5% per year, this make it necessity that the food grains production should increases at least at the same rate or faster than the population rate. Therefore, it is the necessity of modern farmers. Progressive farmers to apply plant breeding science, techniques for the development of new high yielding varieties, to meet the need of this tremendous growing population. In India more than 70% population is depend on agriculture, however majority of them are marginal farmers and landless labour. The input like fertilizer, pesticides, insecticides required for agriculture are expensive and therefore farmers are looking forward for improved high yielding, disease and pest resistance and Earliness varieties. Govt of India also trying to made every effort after independence for increasing agricultural production.
  9. 9. [9] Nature of Plant Breeding Plant breeding is an art or science and is as old as agriculture, started since man learnt to cultivate the plants. In earlier days, man depends on his skill and judgement in selecting better plants. His knowledge about the plant was very limited. He knew nothing about the inheritance of characters, role of environment in producing them and the basis of variation in various plant characters. His method of selection was designed without the understanding of the principle of inheritance. Therefore during primitive time plant breeding was largely an art and very less science was involved in that, but the present breeding methods are entirely based on the scientific principles of plant sciences, particularly of genetics a cytogenetic. Thus, plant breeding is purely science with very little art involved. Science is the knowledge gathered through scientific method. The scientific method consists of observation, formulation of hypothesis, experimentation and conclusion either to accept or reject the hypothesis. Plant breeding is considered as the current phase of crop evolution. As the knowledge of genetics and other related science progresses plant breeding become less art and more science. Especially discovery of Mendels work in 1900, added lot to the knowledge of science. Selection of desirable plant even today is an art it depends on the skill of a person but alone skill is not enough, modern plant breeding is based on through understanding and use of genetics principles. To be successful, a plant breeder must know each and everything about the crop with he is working. He should have an understanding of principles of difference disciplines viz. genetics, cytology, Morphology and Taxonomy, plant Physiology , Plant Pathology, Entomology, Agronomy, and Soil Science, Biochemistry, Statistics, and Biometrics. Computer and Plant biotechnology. Thus plant breeding is an art science and a technology of developing genetically superior plants in terms of the economics utility for the mankind.
  10. 10. [10] History of Plant Breeding Several significant contribution have been made in plant breeding by varies workers from time to time. The significant landmarks made in the history of plant breeding are briefly presented in ascending order. Landmark in Plant Breeding: 1717: Thomas Fairchild: Developed first Inter specific hybrid between sweat William and Carnation Species of Dianthus. 1800: Knight, T.A (English): First used Artificial Hybridization in Fruit Crops. 1840: John Le Couteur: They developed the concept of progeny test individual plant selection in cereals. 1856: De Vimorin (French Biologist): Further elaborated the concept of progeny test and used same in Sugarbeet. 1865: Mendel, G.J (Austria): Discovered principles of inheritance in garden pea. 1890: Rimpu (Sweden): First made inheritance cross between bread wheat (Triticum aestivum) and rye ( Secale cereale ), which later on gave birth to triticale. 1900: De Varies (Holland) Correns (Germany) Tschermak ( Austria) Rediscovered Mendel laws of inheritance independently. 1900: Nilson, H (Swedish) : Elaborated individual plant selection method. 1903: Johannsen, W.L: Developed the concept of pure line. 1908: Shull, G.H (US) East , E.M ( US) proposed over dominance hypothesis independently working with maize. 1908: Devenport, C.B: First proposed dominance hypothesis of heterosis. 1910: Bruce, A.B. keable, F. and Pellew, C. Elaborated the dominance hypothesis of heterosis proposed by davenport. 1914: Shull, G.H: First used the term heterosis for hybrid vigour. 1919: Hays, H.K. Garber, R.J Gave initial idea about recurrent selection. They first suggested use of synthetic varieties for commercial cultivation in maize. 1920: East E.M and Jones, D.F, also gave initial idea about recurrent selection.
  11. 11. [11] 1925: East, E.M and Mangelsdorf, A.J: First discovered gametophytic system of self incompatibitlity in Nicotiana sanderae. 1926: Vavilov, N.I: Identified 8 main centers and 3 sub centers of crop diversity. He also developed concept of parallel series of variation or law of homologous series of variation. 1928: Stadler, L.J (US): First used X-rays for induction of mutations. 1936: East, E.M: Supported over dominance hypothesis of heterosis proposed by East and Shull in 1908. 1939: Goulden, C.H: First suggested the use of single seed descent method for advancing segregating generations of self pollinating crops. 1940: Jenkins, M.T: Described the procedure of recurrent selection. 1945: Hull, F.H: Coined the terms recurrent selection and overdominance working with maize. 1950: Hughes and Babcock: First discovered sporophytic system of self incompatibility in Crepis foetida. 1952: Jensen, N.F: First suggested the use of multi lines in oats. 1953: Borlaug, N.E: First outlined the method of developing multi lines in Wheat. 1964: Borlaug, N.E: Developed high yielding semi dwarf varieties of wheat which resulted in green revolution. 1965: Grafius, J.E: First applied Single Seed Descent (SSD) method in oats. 1970: Patel, C.T: Developed world’s first cotton hybrid for commercial cultivation in India. 1976: Yuan Long Ping et al: Developed world’s first rice hybrid ( CMS based) for commercial cultivation in China. 1987: Monsanto: Developed world’s transgonic cotton plant in USA. 1991: ICRISAT: Developed world’s first pigeon pea hybrid (ICPH 8) for commercial cultivation in India. 1908: Monsanto. USA: Identificaton of traitor gene, which responds to specific brand of fertilizers and insecticides.
  12. 12. [12] Indian Scientist: Dr. M.S. Swaminathan – Mutation breeding, developed semidwarf wheat varieties at IARI, New Delhi. 1) Maheshwari and Guha (1964)- Produced haploid plant in Vitro from pollen grain. 2) Barber and T.S venkatraman – Nobilization of sugarcane. 3) Dr. Athwal – Pioneer of Bajara breeder. 4) Ramiah- Pioneer of rice breeder 5) Dr. N.G.P. Rao – Sorghum breeder. 6) Dr. Yogendra Nerkar- Former vice Chanceller of M.P.K.V develops Prabhavati mutant Rice variety.
  13. 13. [13] Objectives of Plant Breeding The prime aim of plant breeding is to improve the characteristics of plants that they become more useful automatically and economically. Some of the objectives may be summarized as follows. 1. Higher Yield: Higher yield of grain, fodder, fibre, sugar, oil etc. developing hybrid varieties of Jawar, Maize, Bajara, etc. 2. Improved Quality: The quality characters may vary from one crop to another such as grain size, shape, colour, milling and backing quality of wheat, cooks quality in rice, malting in barley. Size shape and flavour in fruits and keeping quality of vegetables, protein contents in legumes, methionine and tryptophan contents in pulses etc. 3. Disease and Pest Resistance: Resistant varieties offer the cheapest and most convenient method of disease and pest control. They not only helps to increase the production but also stabilize the productivity e.g. Rust resistance in wheat. 4. Maturity Duration: It permits new crop rotation and extends crop area. Thus breeding for early maturing varieties suitable for different dates of planting. This enables the farmer to take two-three crops in a year. 5. Agronomic Characters: Three includes the characters such as dwarf, profuse tillering, branching erect resistance and fertilizer responsiveness. 6. Photo and Thermo Insensitivity: Development of photo and thermo insensitive varieties in rice and wheat will permit to extend their cultivation to new areas. E.g Cultivation of wheat in Kerala and West Bengal, Cultivation of rice in Punjab and Himachal Pradesh. 7. Synchronous Maturity: It is desirable in crops like mung ( Vigna radiate) where several pickings are necessary. 8. Non-Shattering Characteristics:
  14. 14. [14] E.g. Mung, Black Gram, Horse Gram, etc. 9. Determinate Growth Habit: It is desirable in mung, pigeon pea and cotton, etc. 10. Dormancy: In some crops, seeds germinate even before harvesting if there are rains at the time of maturity. E.g Mung, barley, etc. A period of dormancy in such cases would check the loss due to germination while in other cases it may be removed it. 11. Varieties for a New Season: Breeding crops suitable for seasons. E.g Maize (Kharif) which is grown in Rabi and summer also. 12. Moisture Stress and Salt Tolerance: Development of varieties for a rainfed area and saline soils would help to increase crop production in India. 13. Elimination of Toxic Substance: It will help to make them safe for consumption E.g Khesari ( Lathyrus sativus) seeds have a neurotoxin causing paralysis. 14. Wider Adaptability: It helps in stabilizing the crop production over region and seasons. 15. Useful for Mechanical Cultivation: The variety developed should give response to application of fertilizers, manures and irrigation, suitable for mechanical cultivation etc.
  15. 15. [15] Achievement of Plant Breeding Today crop plants are different from the crop from which they are originated i.e is wild species. This change has been brought about man through plant breeding. The important achievement of plant breeding are : A) Production of Dwarf and Semi Dwarf Cereal Varieties: Many dwarf and semi dwarf varieties are developed in crop like wheat and Rice Dr. Borlaug used a apenese variety NORIN-10 as a source of dwarfing gene, in wheat at CIMMYT (Mexico). In 1963 ICAR has introduced some dwarf selection from CMMYT. Variety Kalyansona and Sonalika were selected from these materials. In India majority of the wheat varieties grown are semi dwarf, and are resistant to water lodging, responsive to fertilizer doses etc. Similarly the development of semi dwarf varieties of Rice has revolutioned rice cultivation. These varieties were developed by introducing the gene Dee-Geo-Woo-Gene. Ex TN. 1 developed at Taiwan and IR-8 at IRRI Philippines, both were introduced in India in 1966. B) Nobilization of Sugarcane: The Indian canes were of Saccharum barberi, largely grown in North India. They were hardy but poor in yield and sugar content, while tropical cane of Saccharum oficinarum had thicker stem and higher sugar content but it performed badly in North India due to low winter temperature. C.A Barber and T.S Venkatraman at Sugarcane Breeding Institute, Coimbtore transferred thick stem higher sugar content and other desirable characters from the noble cane to Indian cane is commonly referred as nobilization on of Indian canes. C) Development of Hybrid and Synthetic: a) Maize: Canga series of hybrid, Ganga safed-2, African Tall, Manjari, Deccan etc. b) Sorghum : CSH-1,2,3,4,5,6,7,8,910,12,14 and 15 R. c) Bajara: WCC-75, PHB-10, ICTP-8203, Shradha and Saburi. d) Cotton: H-4, Var.Laxmi, Savitri, NH-44, Jaylaxmi, etc.
  16. 16. [16] Scope of Plant Breeding (Future Prospects) I) Genetic manipulation of population by increasing the frequency of desirable alleles in cross pollinated crops and introducing male sterile in self pollinated crops like wheat and Rice. II) Intensive breeding of pulses and oil seed crops as it was done in cereals and other crops. III) Proper breeding methods with improved crop management practises. IV) Use of heritability methods with improved crop management practises. V) Development of improved high yielding varieties of vegetable and seed crops. VI) Quality Improvement in Oil seed and Vegetables. VII) Use of transgenic plants as a medicine. E.g. Potato. VIII) Development of varieties which are desirable for mechanical threshing and cultivation. Tools of Plant Breeding: New tools of plant breeding include. a) Mutation breeding b) Polyploidy c) Plant Biotechnology d) In Vitro Techniques and e) Genetic engineering a) Mutation Breeding: Mutation is a sudden heritable change in a characteristic of an organism and utilization of variation created by mutation in crop improvements is known as mutation breeding. Agents used for induction of mutation known as mutagenes. It may be physical or chemical mutagenes. b) Polyploidy: An individual with more than two sets of homologous chromosome or genome known as polyploidy. Changes in chromosome number may involve loss or gain of one of few chromosomes or the whole genome. Polyploidy may be induced spontaneously or can be induced artificially by using chemicals. c) Plant Biotechnology: Utilization of biological agents or their components for generation products for the welfare of mankind, known as biotechnology. Plant biotechnology is related to such activities other than
  17. 17. [17] conventional approaches. It aims at improving the genetic make up, phenotypic performance and multiplication of economical plants. d) In Vitro Techniques: It is the cultivation of plant organs, tissue or cell in test tube on artificial media. In certain situation conventional breeding methods are not efficient. In that situation these methods have been supplemented by in vitro techniques/ tissue culture to increase the efficiency of crop. Ex: Eucalyptus – Yashwant Banana- Shrimati e) Genetic Engineering: Isolation of the desired from an organize, its integration into a suitable vector and its introduction into another organism (host) with a view to obtain multiple copies (Replica) of the desire gene. The gene may remain in vector or may got integrated into the chromosome of the host later it produces transgenic plant.
  18. 18. [18] Genetic in Relation to Plant Breeding Plant breeding is an application of Genetic principles to the improvement of plants. The following genetic principles are useful to improve the heredity of plants. Variation: Differences among be due to genotype or environment. Environmental variation may be observed by growing the plants with similar genotypes under different environment. Ex. Rice, Wheat plants grown on fertile soil will show more vigorous and productivity than infertile soil. These variations in growth and development result from the effect of particular environment in which the plants are grown. Genotypic variation is the results of plant processing different genetic characters and it remains unaltered by environmental conditions. Generally they may be observed it different varieties or species are grown under similar environment. Ex. Colour of the seed, presence of awn etc. Heritable variation in plants originates from gene recombination after hybridization, spontaneous mutating and polyploidy this processes plant species have been evolved in nature and reached present stage of development. These two types of variation are not independent of each other, but they interact and affect on the plant.
  19. 19. [19] Mechanism of Heredity The mechanism of heredity is dependent upon the behaviour of chromosome and the gene they carry some facts regarding characters. I) A mixed population of plant species having heredity variation is used by the breeder to select plants with traits or characters for development of improved variety. E.g. Seed colours, size, plant height, leaf size, shape, disease resistant etc. Heritable variation results when different plants exhibit contrasting form of these characters. The contrasting traits are determined by alternative form of gene and their interaction. II) The genes are located on the chromosome and are determine of the characters of a plant. These genes are having specific position on the chromosome and are duplicated when the chromosome divide. The alternative form of a gene called alleles, which determine contrasting form of characters. The genes may be dominant or recessive (R or r). The plant with similar identical genes at a given locus on homologous chromosome are said to be homozygous and with unlike genes are said to be heterozygous. The appearance of plant is phenotype, while genetic constitution is genotype. The chromosomes are red shape body present in a nucleus of cell. They carry genes hence important in heredity. A chromosome occurs singly (haploid) in spores and in pairs (diploid) in body cell. The chromosome number is constant in any species and it divides longitudinally during mitosis and homologue chromosome separate during moysis. The mechanism of heredity can be explained with a single gene characters. Phenotype: Red X White Genotype: RR X rr Gametes: R X r F1: Rr – Red (dominant and heterozygous) F2: F1 X F1 Genotype: Rr X Rr Gametes: R r R r F2: RR Rr Rr rr RR- Red Rr- Red rr- White Genotypic Ratio: 1:2:1
  20. 20. [20] Phenotypic Ratio: 3:1 III) Linkage: The tendency of genes to be inherited in a group on to the next generation is known as linkage which occurs due to the residence of genes on the same chromosome. The string of gene in a chromosome is linkage group. The number of linkage group in any species is equal to the pairs of chromosome. If the genes are completely linked on a chromosome, there would be no combination of genes within the same linkage group, and due to this there would be certain restriction on breeders to obtain new recombination of linked genes. Recombination of linked genes occurs due to crossing over (Exchange of segment between nonsister chromatides of homologous chromosome). A breeder may select plants with recombination of linked genes for desirable characters. Linkage may be coupling phase or repulsion phase. In coupling phase two dominant genes are linked with recessive gene (AB/ab). In repulsion phase one dominant and recessive genes are linked with one recessive and dominant genes ( Ab/aB). IV) Gene Interaction: The phenomenon of two or more gene affecting the expression of each other in a various ways for the development of a single character of an organism is known as gene interaction or it is the phenomenon in which two pairs of nonalleic gene affect the same character. In gene interaction when two dominant genes come together, they usually produce different phenotype than their own and it result into the modification of normal F2 phenotypic ratio. Gene interaction effect the expression of one character of an individual. It adds variability by producing new phenotype. V) Heterosis or Hybrid Vigour: When two homozygous inbred of genet cally unlike constitution are crossed together the resulting hybrid are usually vigorous, productive taller and sturdier than either parents. This increased productivity or superiority of the hybrid over the parents is known as heterosis or hybrid vigour. The term heterosis was coin by G.H. shull (1914). He derived from the Greek word heterosis mean different and Osis means condition, therefore , literally means a different condition. VI) Polyploidy and Plant Breeding: Polyploidy is the condition in which an organism having more than two sets of chromosome or genomes in their somatic cell. In contrast to the normal of ploid they may be triploid (3n), tetraploid (4n) , penataploid ( Sn) and so on. Polyploids may be Euploids ( An organism having the exact multiple of the basic chromosome number in 3n, 4n, etc) or Aneuploid ( An organism having unequal number of chromosome i.e monosomic ( 2n-1), nullisomic ( 2n-1) , Trisomic ( 2n +1) etc.
  21. 21. [21] Autopolyploid: When polyploidy are developed from two or more sp by crossing known as allopolyploids. They are sterile but it can be overcome by doubling the chromosome number by colchicines treatments. Ex. Triticale Wheat. Polyploidy is of special significance in plant breeding because it adds genetic diversity in the plant kingdom. It increases the complexity of genetic ratios . E.g hexaploid wheat. Therefore, it has an important factor in the evolution of plant species. VII) Male Sterile and Self- incompatibility: Male Sterility: It refers to the absence of functional male gametes (Pollen grains), while female gametes functional gametes functional normally. The ability to set seed after self or cross pollination within the species ore genera must be known to breeder. Sterility is the inability to obtain seed set due to either failure of pollen grain or ovues. Male sterility is recorded in many crops in which, male sexual organ (Stamens) are malformed or aborted and non-viable pollen grains are produced. The male sterility may be occurs due to gene, cytoplasm or combination of both. On the basis of this, it is classified in to genetic male sterility, cytoplasmic male sterility and genetic cytoplasmic male sterility. Self – incompatibility: It refers to the failure of pollen grain to fertilize the same flower or other flower on the same plants. In this case both pollen and ovule are functional, but they could not fertilize the flower and set seeds due to some physiological hindrances. Incompatibility may occur due to the lot of season. 1) Pollen grain fails to germinate on the stigma. 2) Pollen grain germinates but the pollen tube fails to enter the stigma. 3) Some times pollen tube enters the style but growth is very slow to effect fertilization. 4) Pollen tube enters the ovule but there is no fertilization due to degeneration of egg cell. 5) Fertilization is effected but embryo degenerate at very early stage.
  22. 22. [22] Role of Various Genetic Concepts and Principles in Crop Improvement 1) Mitosis: Essential for normal growth and development of living organisms. Leads to production of identical progeny in asexually propagated crop. 2) Meiosis: It generates variability through recombination and segregation of genes, also maintains chromosome number constant in a species. 3) Chromosome Number: Useful in transfer of genes from one species to another and structure development of hybrid and development of alien addition and alien substitution lines. 4) Structural Chromosomal: Play an important role in formation of new species and change transfer of small chromosome segment from one species to another. 5) Numerical Chromosomal: It is useful in inter specific and inter generic gene transfer, overcoming sterility in such hybrids, conservation of heterosis, development of new crop species etc. 6) Gene Interaction: It helps in the study of inheritance and gene transfer. Sometimes, it leads to production of new phenotypes. 7) Linkage: Linkage affects genetic variances, genetic correlation between characters and efficiency of selection. 8) Chrossing- over: It releases genetic variability by forming new gene combinations. Variability is essential for improvement by selection. 9) Pleiotropy: It affects the efficiency of selection. If the side effects of a gene are desirable, it helps in crop improvement and vice versa.
  23. 23. [23] 10) Penetrance and Expressivity: Help in selection of elite types in the breeding population. 11) Cytoplasmic Inheritance: It helps in the development of cytoplasmic male sterility for use in development of hybrids. Also adds to variability through mutation of plasma genes. i.e Chloroplast and mitochondria DNA. 12) Mutations: They are useful in improving yield, quality, resistance to biotic and abiotic factors, generating new variability developing male sterility , overcoming self incompatibility etc.
  24. 24. [24] Reproduction in Flowering Plants Sporogeesis, Gametogenesis and Fertilization: It is in herent property of the living organisms to continue their race by mechanism of reproduction. The reproduction is a process by which the living beings propagate or duplicate their own kinds. There are three methods of reproduction. 1) Vegetative reproduction 2) Asexual reproduction and 3) Sexual reproduction 1) Vegetative Reproduction: The reproduction takes place through vegetative parts such as bulbils, corms, rhizome, bulbs, stem cutting, root cutting, etc. 2) Asexual Reproduction: In asexual reproduction, special cells or asexual reproduction units are produced by the parent body which grow themselves into new individuals. Therefore, the development of new individuals without fusion of male and female gametes is known as asexual reproduction. The asexual reproduction usually includes mitotic division of the body (somatic) cells, it is therefore, also known as somatogenetic or blastogenic reproduction. The asexual reproduction is common only in lower plants and animals and may be of fission, budding, gemmule formation and regeneration types. 3) Sexual Reproduction: In sexual reproduction development of new individual take place by the fusion of sex called male and female gametes. It is the most common type of reproduction among plants and animals. There are two types of sexual reproduction. i) Isogamy ii) Heterogamy i) Isogamy: Union of two similar gametes which cannot be distinguished into male and female gametes is called Isogamy. Fusion of such gametes is called conjugation. It is observed in lower plants like mucor and spirogyra. ii) Heterogamy:
  25. 25. [25] Union of two dissimilar gametes i.e male and female gametes is known as fertilization and the zygote is called Oospores. This type of reproduction is common in flowering plants. And can be divided into A) Apomixis B) Amphimixis A) Apomixis: It is an abnormal sexual reproduction in which embryo develops from the egg cell, without fertilization and with or without meiosis. It is of various types- a) Parthenogenesis b) Apogamy c) Apospory a) Parthenogenesis: In this case embryo develops directly from the egg cell or male gamete without fertilization. It gives haploid plants. b) Apogamy: In this case embryo develops directly from haploid muclei other than egg cells i.e it develops from synergids or antipodal cells of the new embryo sac. c) Apospory: In this case embryo develops directly from the somatic cell i.e. it develops from integuments of nucleus. B) Amphimixis: This is normal sexual reproduction in which embryo develops from the union of male and female gametes in plants and sperm and egg or ovum in animals. The process of male gamete formation is known as microsporogenesis and female gamete formation as megasporogenesis in plants.
  26. 26. [26] Male Gametophyte or Microsporogenesis Stamens are reproductive organs in flowering plants and are known as microsporophyll. Each anther of four pollen sacs called micro sporangia. It consists of outer wall, a single layer of nutritive cells called tapetur and central mass of pollen mother cells (PMC) or microsporocyte with 2n chromosome compliment. Each pollen mother cell undergoes meiosis and give rise to four microspores or pollen grains, consisting of haploid (n) chromosome compliment. This is known as microsporogenesis. Each pollen grain (Microspore) consists of two coats called exine and intine. The nucleus of pollen grain divides mitotically and gives rise to two nuclei called tube nucleus and generative nucleus. The generative nucleus divides mitotically and produces two sperm nuclei called male gametes.
  27. 27. [27] Female Gametophyte or Megasporogenesis The pistils are the female reprocutive organs called as megasporophyll in the flowering plants. The ovary of the carpel contains ovules (megasporangia). Each Ovule consists of megasporophytes or megaspore mother cells (MMC). Each megaspore mother cell undergoes meiosis and produces four haploid megaspores arranged in the linear row. Out of four megaspores, three degenrrates and one remains functional. This process of development of megaspores is known as megasporogenesis. The functional megaspore divides three times mitotically giving rise to eight nucleate structure called female gametophyte or embryo sac. One nucleus from each end passes to the centre to form polar nuclei. The three nuclei at micropylar region are organised into three cells forming egg apparatus. One of the largest called egg cell or female gamete. The other two cells called synergids or helpers. The three nuclei at chalazal end (region) are organised into three cells called antipodal cells. By this way embryo sac is developed.
  28. 28. [28] Fertilization and Significance of Fertilization in Flowering Plants Fertilization: After formation of both the gametophytes, the pollens grains are pollinated on the stigma of the ovary. The pollen grain germinates on the stigma and produces pollen tube. The pollen tube carrying two male gametes passes thorugh micropyle and reaches are liberated into the embryo sac. One of the male gametes moves towards the female gamete (egg) and fuses with it to and form zygote. This fusion of male and female gametes is known as fertilization. The other male gamete passes to the centre of the embryo sac and unites with secondary nucleus, which develops into endosperm. Here union of three haploid nuclei take place, it is known as triple fusion. Endosperm contain triploid chromosome (3n) compliment. The fusion of one male gamete with egg along with fusion of second male gamete with polar nuclei is together called double fertilization. Significance of Fertilization: 1) Fertilization ensures diploid of the organism by fusion of haploid male and female gametes. 2) Fertilization provides new genetic constitution to the zygote. 3) Fertilization process increases the metabolic activities and the rate of protein synthesis of the egg. 4) Fertilization initiates embryogenesis.
  29. 29. [29] Modes of Reproduction in Plants A mode of reproduction determine the genetic constitution of crop plant and provides the basis for understanding the mechanism of heredity, which are required for handling the desired characters during breeding work. This is the inherent property of the living organism to continue or maintain their races by the mechanism of reproduction. It is the process by which living being propagate or duplicates their own kinds. The modes of reproduction in crop plants are broadly grouped into asexual and sexual. Asexual: It does not involve the fusion of male and female gametes. In this new plants may develop from vegetative part of the plant (vegetative reproduction or may develop from embryos without fertilization ( apomixis). A) Vegetative Reproduction: In this new plants developed from a portion of the plant body. This may be occurred thorough modified under ground and subarea stems or through bulbs, for example Rhizome –Ginger, Tuber potato, Bulos- onion, corm-gladious, while sub aerial stems gives rise to new plants in strawberry rose etc. Similarly artificial vegetative methods stem cutting ( Sugarcane, Durant a), Root cutting ( Lemon, citrus) ;layering, budding, gooties ( Grapes, lichi) and grafting ( mango) are common methods in propagation of fruits and ornamental horticultural crops. B) Apomixis: It is the type of asexual reproduction in which seeds are formed and embryo developed without fertilization. Thus plants developed are dentical in genotype to the parent plant. In apomixis, reproduction is either suppressed or absent. When it occurs, the apomixis is said to be facultative, but when absent it, referred to as obligate. Many crops species show apomixis but it is generally facultative. Apomisix may be of following type: i) Adventive Embryony: Embryo directly developed from vegetative cells of the ovule such as integuments and chalaza. Development of embryo sac of embryo does not involve production of embryo sac E.g, Mango, Citrus. ii) Apospory: Some vegetative cells of ovule developed into unreduced embryo sacs after meiosis. Embryo may be developed from egg cell or other cell of embryo sac. E.g Crepis. iii) Displospory: Embryo sac is developed from the megaspore, which may haploid or diploid.
  30. 30. [30] a) Parthenogenesis: In this embryo is directly developed from egg cell with fertilization. Depending upon whether the embryo sac is haploid or diploid termed as haploid or diploid parthenogenesis. Haploid parthenogenesis are: 1) Natural Selection: In nature there is a continuous selection by natural forces. E.g temp, soil, humidity, pest, disease, etc. As a result the genotype more suited to a given environment leaves behind more progeny than the less adapted one, this process is known as natural selection. 2) Artificial Selection: The selection by man often permit only the selected plants to reproduce, the progeny from the remaining plants are generally discarded. The natural selection considerably retains variability in the species while artificial selection gradually reduces the variability accidentally and reported in solanum, nigrum, Nicotiana and maize, diploid parthenogenesis in many grasses like taraxacum. In many plants like Datura, Rice, Nicotiana, pollen grains are induced in vitro to produce haploids called androgenesis. The phenomenon in which the fruit is developed due to parthenogenesis is called parthinocrpy. b) Apogamy: Embryo develops from haploid nuclei other than egg cell i.e synergids or antipodal which may be haploid or diploid. E.g Allium cepa (onion). Sexual Reproduction: It involves fusion of male and female gametes to form a zygote, which develops into an embryo. It may be a) Isogamy: Union of two similar gameties is called Isogamy and uniting undistinguishable gametes are isogametes E.g Mucor spirogyra, etc. b) Heterogamy: Union of two dissimilar gametes is called fertilization or syngamy and the gametes called heterogametes. In crops plants, male and female gametes are produced in a specialized structure called flower which consists of four whorls viz calyx, corolla, androecium and gynoecium. A flower containing all whorls’s called complete flower while incomplete flower lacks one or other parts. A flower containing both stamens and pistil is said to be perfect flower or hermaphrodite flower. It may be imperfect flower, when stamens are absent (pistil- late) or carpeles absent ( staminate) flowered. The male gamete is produced in stamen while the pistil produces the female gamete. Fertilization:
  31. 31. [31] It refers to the fusion of one of the two sperms with egg cell to form a zygote. Double Fertilization: One male gametes unite with the eggs cell known as syngamy or fertilization and another male gamete fuse with the pollar nuclei known as triple fusion, when these two processes occurs simultaneously known as double fertilization.
  32. 32. [32] Sporogenesis Production of microspore and megaspore is known as Sporogenesis. Microspore i.e pollen grains are produced in anther, while megaspore produced in ovules. a) Microsporogenesis: Each anther has four pollen sac and each pollen sac contains numerous pollen mother cells (P.M.C) which undergoes meiosis. i.e two meiotic division to produce four haploid cells or microspore. This process is known as micro-Sporogenesis. The microspores mature into pollen grains mainly by thickening of their walls. b) Megasporogenesis: It occurs in ovule, which are present in ovary. A single cell in each ovule differentials into Megaspore mother cell ( M.M.C). Each megaspore mother cell undergoes meiosis to produced four haploid megaspore. Out of these three- megaspore degenerate and only one functional megaspore is remaining per ovule.
  33. 33. [33] Gametogenesis Production of male and female gametes in micro and mega spores is known as Gametogenesis. a) Microgametogenesis: It refers to the production of male gametes or sperm cells. The pollen grain consists of two coating, in which outer is exine and inner is intine. After maturation of pollen grain nucleus divides mitotically into two nuclei known as generative nuclei and vegetative or tube nuclei. As soon as pollen reaches to stigma, they swell up by absorbing moisture and due to this exine burst and intine continue to grow in the form of tube called as pollen tube. The pollen tube penetrative into stigma and style and at the stage only generative nuclei undergoes a mitotic division to produce two male gametes. The pollen tube finally enters into the ovule through micro Pyle and discharge, the two male gamete into embryo sac and then fertilization take place. The pollen along with pollen tube and two sperms is called micro gametophyte. b) Megagametogenesis: Development of embryo sac from a megaspore is known as Megagametogenesis. The nucleus of functional megaspore divides mitotically to produce two nuclei, which again divide mitotically then to produce eight nuclei. Out of these two nuclei, moves toward one pole i.e micropyle pole ( produced one eggs cells and two synergids) another three nuclei migrate towards the opposite pole i.e chalazal pole ( produced these antipodal cells) and two nuclei migrate at the centre to form polar nuclei. Finally, the megaspore is developed into the embryo sac which contains one eggs cell , two synargids, two polar nuclei and three antipodal cells.
  34. 34. [34] Mode of Pollination Pollination refers to the transfer of pollen grain from anthers to stigmas. Pollen from an anther may fall on the stigma of the same flower leading to self pollination or auto gamy. Some times pollen from an anther may fall on the stigma of another flower of different plants leading to cross pollination or allogamy. Some times pollen from an anther fall on the stigma of the anther flower of same plant leading to the geitonogamy. Self Pollination: It is transfer of pollens from and to the stigma within the same flower , is always found in bisexual flower. In most of these species self-pollination is not complete and cross- pollination may occur up to 5%. There are various mechanism / contrivances that promote / facilitate self- pollination. i) Bisexuality: Male and female sexual organs present in the same flower e.g Wheat, rice, groundnut, etc. ii) Homogamy: Male and female sexual organs mature at the same time e.g wheat, groundnut, etc. iii) Cleistogamy: In this condition flowers does not open at all and ensure complete self pollination e.g Oat, Barley, Wheat, Grasses, etc. iv) Chasmogamy: In some species, flower open but only after pollination has taken place. E.g Barley, Wheat, Oat, and many cereals. v) In crop like Tomato and Brinjal stigma are closely surrounded by anthers , hence pollination occurs after opening of flower but the position of anther in relation to stigma ensure self – pollination. vi) In crop like pea, bean, soybean, the flower open but stigma and anther are hidden by floral organ and ensures self – pollination. vii) In few species stigmas become receptive and elongate through staminal column, ensures self pollination. Genetic Consequences of Self – Pollination:
  35. 35. [35] i) It leads to a very rapid increase in homozygosity; therefore self pollinated species highly homozygous in nature. ii) Self pollinated species do not show inbreeding depression, exhibit considerable heterosis. Cross Pollination: The transfer of pollen from a flower to the stigma of the other flower of different flower plant. In cross pollinated species pollination may be brought about by wind, water insect or animals. Wind (anemophily) , water ( hydrophily) , insect ( entomophily) and animal ( Zoophily). In most of the cross pollinated sp. Viz. Bajara, maize, sunflower, alfalfa, castor, cross pollination is not complete and self pollination may occurs 5-10%. There are several mechanism contrivances that facilitate cross pollination. i) Dicliny (Unisexuality): It is a condition in which flower is either staminate or pistilate. a)Monoecy: Staminate and pistilate flowers occur in the same plant either in the same inflorescence. E.g Mango, banana, coconut or in the separate inflorescence. E.g Maize, Cucurbit, Strawberry, etc. b) Dioecy: The male and female flowers are present on different plants i.e. the in such species are male or female i.e. sec is governed by a single gene. E.g. Papaya, hemp, date, palm, etc. ii) Dichogamy: Anther and stigma of hermaphrodite flower mature at different time, facilitating cross pollination. a) Protogyny: Gynoecium matures earlier than the androecium E.g. Bajara. b) Protandry: Androecium matures earlier than gynoecium. E.g. marigold, maize, cotton, etc. iii) Heterostyly: Different length of style and filaments E.g Linseed.
  36. 36. [36] iv) Herkogamy: Presence of physical barrier or mechanical obstacles between the anther and stigma ensures cross pollination. E.g. Rui (Calotropic gigantia). v) In lucerne or alfalfa stigma are covered by waxy film and it does not become receptive unless this waxy film is broken by honeybees. vi) A combination of two or more of the above mechanism may occurs in some species, E.g Maize, - Monoecy and Protandry. vii) Self –Incompatibility: It refers to the failure of pollen from a flower to fertilize the same flower or other flowers on the some plants. It may be saprophytic or gametophilic e,g mustard , tobacco, sunflowers, reddish. Viii) Male Sterility: It refers to the absence of functional pollen grains in hermaphrodite flower. Genetic Consequences of Cross Pollination: 1) It preserves and promotes heterozygosity in population. 2) Cross pollinated species shows inbreeding depression and considerable heterosis. 3) Usually hybrid and syntheticwitout reducing heterozygosity. Often Cross Pollination: In this type plants are self pollinated, however the extent of cross pollination often exceed 5 to 50 % such species are generally known as often cross pollinated species. E.g. Jawar, Cotton, Safflower, Arhar, etc. The genetic architecture of such crop is intermediate between self and cross pollinated crops and breeding methods suitable for both of them may be profitably applied.
  37. 37. [37] Methods of Breeding in Self Pollinated Crops The main objective of plant breeding is to produce the new varieties, which superior in all aspects than the existing one. The principle methods of breeding self pollinated crops are: 1) Introduction and Acclimatization: 2) Selection: a) Pure Selection b) Mass selection 3) Hybridization: a) Pedigree method b) Bulk population method. c) Back cross method d) Multiple crossing. 4) Other Method: a) Multiline varieties b) Single seed descent method c) Hybrids d) Population approach 5) Mutation Breeding: 6) Polyploidy Breeding:
  38. 38. [38] Methods of Breeding in Self Pollinated Crops – Introduction Introduction: According to Allard (1960) plant introduction is the acquisition of superior varieties by importing them from other areas. Or plant introduction is the process of taking / introducing plants/ genotype or group of genotype into new environment where they were not being grown before. Introduction may involve new varieties of a crop already grown in the area wild relatives of the crop species or totally new crop species for that area. Plant introduction may within the country between the countries or confirmed between the states or within the state. The plant may be introduced from the country of another continent. Ex. Introduction of Ridley wheat varieties from Australia. Introduction may be classified into two categories: a) Primary b) Secondary a) Primary Introduction: When the introduced variety is well suited to the new environment and is directly released for commercial cultivation without any change the original genotype, known as primary introduction. Ex. Introduction of semi dwarf wheat varieties Sonora, Lerma Rojo and semi dwarf Rice Var. TN-1, IR-8, IR-28, and IR-36. 2) Secondary Introduction: The introduced variety is subjected to selection, to isolate superior variety or may be hybridized with local variety to transfer one or few desirable characters to the local variety, known as secondary introduction. Secondary introduction is much more common than primary introduction particularly in countries having well- organised crop improvement programme. Ex. Kalyan sona and sonalika varieties selected from the material introduced from CIMMYT. Mexico (Centro International de Mejoramieno de maize ‘Y’ Trigo) commonly known as Internation centre for maize and wheat Research. Procedure of Plant Introduction: Plant introduction is one of the very old and effective methods of plant breeding. It consists of following steps: i) Procurement of Germplasm:
  39. 39. [39] Any individual or scientist or institute can introduce germplasm, but the entire introduction must be routed through NBPGR, from the known source of the country or neighbouring countries. While introducing germplasm scientist has to allow two routes. In case of the first route individual make a direct request to individual or institution abroad and in the second route individual submit his requirement to the NBPGR, by giving much detail information about the requirement. Generally, the required materials are obtained through correspondence as gift, an exchange, purchased etc. The plant part to be introduced depend upon the crop species, it may be seed, tubers, runners, suckers, stolons, bulbs, Rhizome, cutting, bud or seedling. The part of the plant used for the propagation of a species is known as propagule. The nature of propagules varies from species to species. Seeds general have more viability than propagules and are packed and transported more easily, while propagules require special packing techniques. ii) Quarantine: Quarantine means to keep the materials in isolation to prevent the spread of disease, weeds etc. all the introduced material is thoroughly inspected for contamination with weed, disease and insect pests. The material is fumigated or treated to avoid the contamination. If necessary, the materials are grown in isolation for observation of disease, insect, pest and weeds, this entire process is known as quarantine and the rules prescribed them are known as quarantine rules. All the materials being introduced must be covered by an authentic phytosanitary certificate from the source of country i.e the must be declared free from disease, weed and pests. If any country or material does not fulfil the quarantine rules, that materials are likely to be destroyed by NBPGR or would return to the source country. The quarantine controls is exercised by NBPGR at prescribed part of entry. E.g Mumbai, Calcatta and Madras and this process is required at least three weeks. III) Catloguing: The introduced material is entered in assession register and is given on entry number. The information regarding the name of the species, crop variety, and place of ongin, adoption and morphological character are reduced. The plant materials are classified into three groups viz. a) Exotic Collection (EC) b) Indigenous Collection (IC) c) Indigenous Wild Collection (IW) IV) Evaluation: The introduced material is evaluated to assess the potential of new introduction and their performance. These materials are evaluated at different substation. The material resistance to disease and pest is evaluated under favourable environment conditions, and the promising one is either released as such as a variety or subjected to selection or hybridization. V) Multiplication and Distribution:
  40. 40. [40] After evaluation promising material from production may be increased by multiplication and released for general cultivation as varieties after necessary trials. Most of there are identified for desirable character and maintain for future use. Acclimatisation: The process that leads to the adoption of a variety to a new environment is known as acclimatisation. Generally the introduced varieties perform poorly because they are often not adapted to the new environment. Sometimes the performances of that variety improve in the new environment by growing it for number of generations. Acclimatisation is brought about by a faster growing it for number of generations. Acclimatisation is brought about by a faster multiplication of those genotype that are better adopted to new environment. The population having more variability is easily acclimatised i.e cross pollinated crops are easily acclimatised than self pollinated crop.
  41. 41. [41] Plant Introduction Agencies in India In India centralized plant introduction agency was initiated at IARI (Indian Agricultural Research Institute) in 1946 at New Delhi. In 1956 it was expanded as the “Plant Introduction and Exploration Organization” and in 1961, it was made an independent division in IARI as the “Division of Plant Introduction”. In 1976 division was reorganized as NBPGR (National Bureau of Plant Genetic Resources). This bureau is responsible for the introduction and maintenance of germplasm of Agricultural and horticultural crops. In addition to bureau there are some other agencies, which are concerned with plant introduction viz. i) FRI (Forest Research Institute): Dehradun established for the Introduction and Maintenance of forest species ii) Botanical Survey of India: It was established in 1890 and responsible for introduction testing and maintenance of medicinal and botanical plants. But at present introduction and improvement of medicinal plan looked after by NBPGR. iii) The Central Research Institute: For various crops e.g. Tea, Coffee. Sugarcane, Potato, Tobacco, etc introduce, test and maintain plant material of their interest, but their activities are coordinated by NBPGR. iv) NBPGR: NBPGR has its head quarter at IARI, Delhi. It has four substations for testing of the introduced materials viz. Simla, Jodhpur, Kanyakumari and Akola. They represent the temperate zone, arid zone, tropical zone and mixed climatic zone respectively. The Activities Functions of NBPGR: 1) It introduces the required germplasm from its counter plants. 2) It arranges explorations inside and outside the country to collect valuable germplasm. 3) It is responsible for inspection and quarantine of all the introduced plant materials. 4) It is responsible for testing, multiplication and maintenance of germplasm obtained through various sources. 5) Maintenance of record of introduced plants. 6) To supply on request germplasm of various scientists or institution. 7) Improvement of medicinal and aromatic plants. 8) To set up natural gene sanctuaries of plants, where genetic resources are available. 9) To supply germplasm to its counterparts or other agencies in other countries.
  42. 42. [42] Purpose and Achievement of Plant Introduction Method of Breeding Purpose / Object of Plant Introduction: i) To obtain an entirely new crop plants E.g. Maize, potato, tobacco, soybean, gobhi, Sarson (Brassica napus). ii) To serve as new varieties. E.g. Sonara-64, Lerma Rojo, TN-1, IR-8 , IR-26. iii) To be used in crop improvement is introduced material is subjected to hybridization. E.g Pusa Ruby. iv)To save the crop from disease and pests. E.g. Coffee was introduced to South America from Africa to prevent from leaf rust. v) For scientific studies. The introduced material is used for studies or biosystematics evolution and origin of plant species. vi) For arsthetic value: Ornamental shrubs and lawns grasses are introduced to satisfy the tired human being and are used for decoration. Achievement of Plant Introduction: In India introduced materials have been used directly as varieties, released as a varieties as a varieties after selection or used in hybridization programme. Some of the achievements of introduction are: I) New Crop Species: The crop introduced in India includes Potato, Maize, Chilli, coffee. Hevea rubber, guava, grape, papaya, soybean, Jojoba. II) Directly Released as Varieties: Semi dwarf wheat varieties, sonara-64 and lerma Rajo introduced from Mexico. TN-1 rice variety introduced from Tawan and other varieties IR-8, IR-28 and IR-36 introduced from IRRI Philippines, Bonnevilla- pea, Rice, Wheat from Australia.
  43. 43. [43] Varieties Selected and Developed from Introduction Varieties Selected from Introduction: Kalayan sona and sonalika selected from the material introduced from Mexico, Bajara- Jamnnagar and Sweet Potato –Pusa lal and Pusa Sunehari. Varieties Developed through Hybridization: All dwarf varieties of wheat derived from crosses with Mexican varieties. All but few semi dwarf rice varieties posses the dwarfing gene from Dee-geo-woo gene from TN-1 or IR-8. Pusa ruby tomato – meeruti X Sioux and pusa early dwarf – meeruti X red cloud ,etc.
  44. 44. [44] Merits and Demerits for Plant Introduction Method of Breeding Merits of Introduction: It provides entirely new crops. i) It provides superior variety directly after selection. ii) It protects the variability from genetic erosion by collecting germplasm. iii) It is a very quick and economical method of crop improvement. iv) It provides protection to the crop by introducing into new disease free areas. E .g Coffee and rubber. Demerits of Introduction: i) Introduction of noxious weeds E. g Argemone Mexicana, Parthenium argantatum, water hyacinth, etc. ii) Introduction of disease E. g Late blight of potato from Europe in 1883, flag smut of wheat from Australia and Bunchy top of Banana from Ceylon. iii) Introduction of pests E. g Potato tuber moth from Italy. iv) Ornamentals turned weeds E. g Water hyacinth and lantana camera. v) Threat to Ecological balance, Eucalyptus sp. Introduced from Australia.
  45. 45. [45] Method of Plant Breeding in Self Pollinated Plants - Selection One of the oldest method of breeding and is the basis for all crop improvement, practised by farmer in ancient times. Selection is essentially based on the phenotype of plants. Consequently the effectiveness of selection primarily depends upon the degree to which the phenotypes of plants reflect their genotype. Selection may be natural or artificial by which individual or group of plants are isolated from a mixed population. Before domestication, crop species were subjected for natural selection. Natural selection is the rule and has resulted in evolution of several local varieties of crop. After domestication man has knowingly or unknowingly practiced some selection known as the artificial selection. For a long period under domestication natural selection was perhaps the more selection is a little value and current breeding method entirely depends on artificial selection. Selection has two basic characteristics or limitation i) Selection is effective for heritable differences. ii) Selection does not create variation, it only utilise the variation already present in the population. Thus the two basic requirement of selection are a) Variation must be present in the population and b) Variation must be heritable. Two methods of selection are practised in breeding self pollinated crops i) Pure Line Selection ii) Mass Selection.
  46. 46. [46] Method of Plant Breeding in Self Pollinated Plants – Pure Line Selection Johansons Pure Line Theory (1903): The concept of pure line was proposed by Danish botanist Johan seen in 1903 on the basis of his studies on Princess beans (Phaseolus vulgaris) , which is highly self pollinated species. He obtained commercial seed lot of princess variety of bean. The commercial seed lot showed variation for seed size. He selected large and small seeds and grew them separately. The progenies thus obtained differed in seed size. The progenies of larger seeds are generally larger than those obtained from smaller seeds. This clearly showed that the variation in seed size in the commercial seed lot of princess’s variety of French bean had genetic basis, due to which selection for seed size was effective. Johanssen further studied and established 19 pure line, each line was a progeny of a single seed from the original seed lot. Within each pure line has again selected large and small seeds. The progenies of the large and small seeds from a single pure line varied in weight of individual seed, but the average weight of progeny from larger seed was quite similar to the average weight of progeny from the small seed within the same pure line. Johanssen postulated that the original seed lot was a mixture of pure lines. The variation for seed size in the original lot of Princess bean had a general basis, was heritable. Thus each of the 19 lines had no genetic basis and is entirely due to environment and therefore non-heritable. He concludes that the population of self-fertilized species consists of several homozygous genotypes. Variation in such a population has genetic base and therefore, selection is effective. The progenies of single self fertilized homozygous plants having identical genotypes sare Pure Lines and the variation within pure lines is purely environment and thus selection within pure lines is ineffective. Pure Line: It is the progeny of single self- fertilized homozygous plant. Pure Line Selection: In pure line selection, large numbers of plants are selected from a self-pollinated crop and is harvested individually, individual plant progenies from them are evaluated separately and the best one is released as pure line variety. Therefore it is also known as individual plant selection. Characteristics of Pure Line: 1. All plant within a pure line has same genotype as the plants from which the pure lines are cerived. 2. The phenotypic differences (variation) within a pure line is environmental and therefore non heritable.
  47. 47. [47] 3. The pure line becomes genetically variable with time, due to mechanical mixture, mutation, etc. Uses of Pure Line: 1. Superior line is used as variety. 2. It is used as parent in development of new variety by hybridization. 3. Pure lines are used for studying mutations and other biological investigations such as medicine, immunology, physiology, and biochemistry. Procedure of Pure Line Selection: The pure line selection has three steps. 1. Selection of individual plants from a local variety or from mixed population. 2. Visual evaluation of individual plant progenies. 3. Yield Trials. First Year: Select large number of plants (200-3000) from Deshi or local variety or some other mixed population and their seeds are harvested separately. In case of individual plants can’t be identified individual heads may be selected on the basis of easily observable characters, such as flowering, maturity duration disease, resistance, presence of awns , plant height etc. It is advisable to select plants for easily observable characteristics. Second Year: Selected individual plants progenies are grown with proper spacing weak along with standard variety row. Progenies are evaluated visually and poor weak and defective segregating progenies are rejected on the basis of visual characteristics. The member of progenies selected should be less to facilitate replicated yield trials if necessary this process may be repeated for one or more years. Third Year: Grow the selected progenies in a replicated trails for critical evaluation. The best variety is used as a check for comparison and planted after every 20-25 progenies. If sufficient seeds are available, preliminary yield trial may be conducted. Selection is made for easily observable, preliminary yield trial may be conducted. Selection is made for easily observable characters including disease resistance and numbers of progenies are reduced. Fourth to Seventh Year: Replicated main yield trails are conducted using best variety as a check quality test is also conducted and used as a basis of selection. Each progeny is an experimental stain as it is pure
  48. 48. [48] line. The promising strains are evaluated at several locations along with other strains in cordianted yield trials. The most promising strains are identified. Eight Year: The best progeny is released as a new variety and its seed is multiplied for distribution to farmers. Merits of Pure Line Selection Method: 1. Pure line selection achieves maximum possible improvement over the original variety. 2. Being extremely uniform, more liked by farmers and consumers than those developed by other methods like mass selection. 3. It is easier than hybridization required less skill. 4. Used for developing inbred lines and pure lines. 5. Due to extreme uniformly, it is easily indentified in seed certification. Demerits of Pure Line Selection Method: 1. It is not practised in cross pollinated crops because it is expensive, laborious. 2. The variety developed can’t be easily maintained by the farmers. 3. The varieties developed by pure line selection don’t have wide adaptability and stability in production. 4. The upper limit on the improvement is created by the genetic variation present in the original population. 5. It requires more time and laborious than mass selection. 6. The breeder’s has to devote more time to pure line selection than mass selection. Applications of Pure Line Selection: 1. It is used for improvement of local varieties, have a considerable genetic variability, e.g Wheat var.NP-4 and NP-52. 2. It is practised in introduced material to develop suitable varieties e.g shining mung -1 selected from Kulu type-1, Kalyan sona from CIMMYT. 3. It is used for improvement of old pure line varieties, e.g Chafa, from No.816 (gram) , Jalgaon 781 from China Mung 781. 4. It provides an opportunity for selection of new characteristics, such as disease resistance, grain type , plant type, etc. 5. It provides an opportunity for selection in the segregating generation from crosses. Achievements: A large number of improved varieties have been developed in self pollinated crop like wheat, barley, rice, pulses, and oilseeds, cotton and many vegetables etc. Many wheat varieties developed include NP-4, NP-6, NP-12, NP-28, Mung Var, T-1, B-1, tobacco chatham special-9, etc.
  49. 49. [49] Method of Plant Breeding in Self Pollinated Plants – Mass Selection Mass Selection: Mass selection is a simplest , common and oldest method of crop improvement, in which large number of plants of similar phenotype are selected and their seeds are harvested and mixed together to constitute the new variety. This method is practised in both self and cross – pollinated crops and plants are selected on the basis of their phenotype of appearance. Therefore, selection is done for easily observable characteristics such as plant height, ear/type, grain colour, grain size, etc. The original population would have been a mixture of several pure lines and the plants selected from it would be homozygous. But the variety developed through mass selection would have a considerable genetic variation and consequently, further mass selection or pure line selection may be done in such a variety. Generally, the plants selected in mass selection are not subjected to progeny test. There are two methods of mass selection. 1) Hallets Method (1869): In this method the crop is grown under the best environmental conditions and maximum amounts of water and fertilization to given and then mass selection practised. 2) Rimpar Method (1867): In this method the crop is grown under ordinary condition or unfavourable conditions with minimum water and fertilizers and the mass selection is practised. It is more effective and easily applicable. Application of Mass Selection: In self pollinated crops, mass selection has two major applications. i.e i) Improvement of local varieties ii) Purification of existing pure line varieties. i) Improvement of Local or Deshi Varieties: The local varieties are mixtures of several genotypes, which may differ in flowering or maturity plant height, disease resistant etc. Many of these plants type would be inferior and low yielding, such plants will be eliminated through mass selection and local variety would be improved without adversely affecting its adaptability and stability. Because the new variety would be made up of the most of the superior plants type present in the original local variety. ii) Purification of Existing Pure Line Varieties:
  50. 50. [50] Pure lines tend to become variable with time due to mechanical mixtures, natural hybridization, mutation etc. therefore, it is necessary that the purity of pure line varieties be maintained through regular mass selection. Mass selection is generally important and practised in cross-pollinated crop and has the only limited application in self pollinated crop. Procedure of Mass Selection: First Year: A large number of phenotypically similar plants are selected at the time of harvest on the basis of their vigour, plant type, disease resistance and other desirable characteristics. Few hundreds to several thousands plants are selected. The unit of selection may be plant, head of seed. The selected plants are harvested and seed mixed together to grow next generation. Selection of too more plants should be avoided in the first year. Second Year: The composite seed is planted in a preliminary yield trial along with standard variety as a check. If this method is used for purification of old mixed variety from which the selection was made, should also be included as a check. Observe the phenotypic characters critically. The best performances are retained and others are discarded. Third to Sixth Year: The superior strains are evaluated for their performance in co-ordinated yield trails at several locations, first in an initial evaluation trail (IET) for one year, if found promising promoted to uniform variety trail (UVT) for two or more years. Only promising one is identified for release as new variety. Seventh Year: Promising strain may be released for cultivation by multiplication and distribution to the farmer for general cultivation. If recommended by central variety release committee. Advantages of Mass Selection: 1. Since large numbers of plants are selected, the variety developed through mass selection is more widely adapted than pure lines. 2. It is easiest , simplest and quickest method of plant breeding because there is no controlled pollination, no progeny testing and prolonged yield trials as well as it is more of an than a science. 3. Mass selection retains considerable genetic variability and hence variety can be improved after few years by another mass selection. 4. The breeder can developed more time to another programme as it is less demanding method. 5. Used for improving wind local variations to meet the immediate need of the farmers.
  51. 51. [51] Disadvantages of Mass Selection: 1. The varieties developed by this method show variation and are not uniform as pure lines hence less preferred by the farmers than pure lines. 2. In the absence of progeny test, it is not possible to determine whether the selected plats are homozygous for specific characters. Similarly, whether phenotypic superiority of selected plants is due to environment of the genotype can’t be determined. 3. The varieties developed by mass selection are more difficult to identify than pure lines in seed certification programme. 4. It utilizes the variability already present, in the population hence, it can’t generate new genetic variability. 5. It is not useful for improvement in quantitative characters, such as yield because phenotypic and environmental effects can’t be separated out. 6. Improvement is short lived, since the variety produced is a mixture of different genotypes, hence, required to be repeated every year in cross-pollinated crops.
  52. 52. [52] Difference between Pure Line and Mass Selection Sr.No Pure Line Selection Mass Selection 1 The variety developed as a pure line The variety is a mixture of several pure lines. 2 It is not practised by farmers. It is practised by the farmers unknowingly. 3 It is practised in self- pollinated crops. Practised in self as well as cross pollinated crops. 4 The varieties developed are highly uniform and the variation is purely environmental. The variety is heterozygous hence not uniform and having genetic variation. 5 The selected plants are subjected to progeny test. Progeny test is not carried out. 6 The variety is best pure line present in the original population. The variety is inferior to the best pure line. 7 Varieties are having narrower adaptability and stability in performance than mixture of pure lines. The varieties developed have wider adaptability and greater stability than pure line varieties. 8 Pollination is controlled. Pollination is not controlled. 9 The variety developed is homozygous, uniform in quality. The variety developed in a mixture of several types hence heterozygous. 10 About 9-10 years required for developing variety. About 5-7 years period is required to develop variety. 11 Once developed variety is maintained easily. It is repeated every year to maintain purity. 12 The variety is easily identified in seed certification programme. The variety developed is relatively difficult to identify in seed certification programme.
  53. 53. [53] Method of Plant Breeding in Self Pollinated Plants – Hybridization Hybridization: Different type’s steps involved selection procedure after hybridization. Pedigree method, def pedigree record, procedure, merits and demerits. Hybridization is one of the methods for developing new variety by crossing two lines or plants having unlike genetic constitution or it is the mating or crossing of two plants or lines of dissimilar genotype in order to combine desirable characters from both the parents. The chief objective of hybridization is to create genetic variation. When two plants having unlike genetic constitution are crossed, the genes from both the parents are brought together. Segregation and recombination produce many new gene combinations in F2 and the subsequent generation. The degree of variation produced by hybridization in the segregating generation depends upon the number of heterozygous genes in the F1, and this depends upon the number of gene for which two parents differ. The aim of hybridization may be transfer of one or few qualitative characters, the improvement in one or more quantitative character or the use of F1 as a hybrid variety. These objectives are grouped into two classes. 1) Combination Breeding: The main aim of combination breeding is the transfer of one or more characters into a single variety, from other varieties. These characteristics may be governed by oligogenes or Polygenes. 2) Transgressive Breeding: Transgressive breeding aims at improving yield or its contributing character through Transgressive segregation. Transgressive segregation is the production of plants in F2 generation that are superior to both the parents for one or more characters.
  54. 54. [54] Types of Hybridization Based on the taxonomic relationship of the two parents, hybridization may be classified into two broad groups. 1) Intervarietal Hybridization: The parents involved in hybridization belong to the same species. In crop improvement programme this type of hybridization is commonly used E. g crossing of two varieties of wheat or other crops. The Intervarietal crosses may be simple or complex depending upon the number of parents involved. a) Simple Cross: In simple cross, two parents are crossed to produce the F1. The F1 is self to produce F2 or is used in a back cross programme. E .g A X B F1 (AX B) b) Complex Cross: More than two parents are crossed to produce the F1 hybrid, which is then used to produce F2 or used in back cross. The cross is also known as convergent cross, because it brings genes from several parents into a single hybrid. E.g A, B, C (Three Parents) A X B F1: (A X B) X C = Complex hybrid (AX B) X C Ex: Four Parents (A, B, C, D) A X B C X D Complex hybrid (A X B) X (C X D) Ex. Eight parent (A, B, C, D, E, F, G, H) A X B C X D E X F G X H F1: (A X B) X (C X D) X (E X F) X (G X H)
  55. 55. [55] Complex hybrid < (AX B) X (C X D)> X <( E X F) X ( G X H)> 2) Distant Hybridization: The parents involved belong to the different species of the same genus or of different genera. When two different species of the same genes are crossed known as inter specific hybridization. Ex. Sugarcane varieties have been developed by crossing Saccharum oficinarum X Saccharum barberi, while in cotton G.arboreum X G. hirsutum. When two different species belongs to different genera known as Intergeneric hybridization. Ex. Triticale is developed by crossing Triticum aestivum X secale cereal (Rye). Generally the objectives of such crosses are to transfer one or few characters, like disease resistance.
  56. 56. [56] Steps Involved in Hybridization The process of hybridization involved following steps: i) Choice of the Parents: ii) Evaluation of the parents, iii) Selfing of parents, iv) Emasculation, v) Bagging vi) Tagging vii) Pollination viii) Harvesting ix) Threshing, drying and storage etc.
  57. 57. [57] Method of Plant Breeding in Self Pollinated Plants – Pedigree Methods Mass selection and pure line selection cannot be applied to segregating population. E. g F2, F3 etc. The method is generally used for handling segregation generation may be grouped into three categories. i) Pedigree Method ii) Bulk Method iii) Back Cross Method The objectives of all these methods are to develop pure line varieties. In pedigree method, individual plants are selected from F2 and the subsequent generation and their progenies are tested. During the entire operation, a record of the entire parent’s offspring relationship is kept, is known as pedigree record. The selection of individual plant is continued till the progenies show no segregation. At this stage, selection is done among the progenies, because there would be no genetic variation within progenies. Pedigree Record: In Pedigree method, a detailed record of the relationship between the selected plants and their progenies is maintained as a result of this each progeny in every generation can be traced back to the F2 plant from which it originated, such record is known as pedigree record or pedigree. The pedigree may be defined as a description of the ancestors of an individual and it generally goes back to some distant ancestors. Thus, it describes the parents grandparents, great grandparents so on of an individual. Maintenance of Pedigree Record: Pedigree record may be kept in several ways, but it should be simple and accurate. Generally, each cross is given a number. The first two digits of this number refer to the year in which the cross was made, and the remaining digits denote the serial number of the cross in that year. For example, the number 7911, denotes the cross number 11 of the year 79. In the segregating generation one of the two systems of designation may be followed. I) System: In this system, the individual plant progenies in each generation are assigned row number, corresponding to their location in the plot. In addition each progeny in F4 and the subsequent generation is assigned the row number of the progeny in the preveious generation from which it was derived.
  58. 58. [58] Generation Number Description F3 7911-7 Progeny in the 7 th row in the F3 plot. F4 7911-7-4 Progeny in the 4 th row in the F4 plot, selected from the progeny in the 7 th row of the F3 plot. F5 7911-4-14 Progeny in the 14 th row in the F5 plot selected from the progeny in the 4 th row of the F4 plot. F6 7911-14-3 Progeny in the 3 rd row in the F6 plot selected from the progeny in the 14 th row of the F5 plot. Thus each progeny can be traced back to the F3 progeny or F2 plants, from which it originated. But for determining the pedigree of a progeny the breeder has to consult the records of the preveious year. II) System-II: In this system, in each generation the selected plants are assigned serial numbers within individual progenies. Each progeny or selected plant bear the serial number of all the plants in the preveious generation, related to it by direct descent. Thus, the plants selected in F2 are given serial numbers of their parents ( F2 plants). The plants selected from a progeny in F3 are given the number of that progeny and in each generation the selected plant also given a serial number. Generation Number Description F3 7911-7 Progeny obtained from plant number 7 selected in F2 F4 7911-7-4 Progeny from plant No.4 selected from F3 progeny , derived from the plant No.7 selected in F2 F5 7911-7-4-2 Progeny from plant No.2 selected from the F4 progeny derived from plant no.4 , selected from the F3 progeny, obtained from the plant No.7 selected in F2. F6 7911-7-4-2-8 Progeny from plant No 8, selected from the F5 progeny, derived from the plant N0.2 selected from the F4 progeny of the plant No.4 selected from F3 progeny of the Plant No.7 selected in F2. In this system, the pedigree of a progeny is immediately known and one done not have to refer to the preveious year record. But there are greater chances of error, since more number are to be recorded. In both the systems, the progenies are assigned a different serial number, when they become homozygous and are included in preliminary yield trials. This number is given to those
  59. 59. [59] homozygous lines that are included in preliminary yield trials. For keeping a pedigree records following point are important. 1) Only important characteristics should be recorded. 2) Only the promising should be included in the record. Poor progenies may be simply marked discard. 3) The pedigree record must be accurate. Application of Pedigree Method: 1) Selection of desirable plants from the segregating population in self- pollinated crops. 2) This method is commonly used to correct some specific weaknesses of an established variety (Combination breeding). 3) It is also used in the selection of new superior recombinant type’s i.e Transgressive breeding. 4) This method is suitable for improving specific characteristics such as disease resistant, plant height, maturity etc.
  60. 60. [60] Procedure of Pedigree Method Hybridization: The selection of parents to be used in a cross is the most important step in a breeding programme based on hybridization. The selected parents are crossed to produce a simple or a complex cross. F1 Generation: F1 seeds are space planted so that each F1 plant produces the maximum F2 seed. Generally, 15- 30 F1 plants should produce enough seed for a good F2 population size. F2 Generation: In F2, 2000-10000 plants are space planted to facilitate selection. About 100-500 plants are selected and their seeds are harvested separately. F3 Generation: Individual plant progenies are space planted; each progeny should have about 30 or more plants. Individual plants with desirable characteristics are selected from superior progeny. The number of plants selected in F3 should be preferably less than the number of F3 progenies. If the number of superior progenies is small the whole cross may be rejected. F4 Generation: Individual plant progenies are space planted; again desirable plants are slected mainly from superior progenies. The no of plants selected in F4 is generally less than that of the F4 progenies. F5 Generation: Individual plant progenies are planted according to the recommended commercial seed rate. Often three or more rows are grown for each progeny to facilitate comparison among progenies. The number of progenies must be reduced to manage the size in preliminary yield trials which is usually 25- 100 progenies. F6 Generation: Individual plant progenies are planted in multi row plot and evaluated visually. Progenies are harvested in bulk since they would have become almost homozygous. The progenies which are reasonably homozygous and have enough seed may be planted in a preliminary yield trial and inferior progenies are eliminated. F7 Generation:
  61. 61. [61] Preliminary yield trials with three or more replications are conducted to identify few superior lines. The progenies are evaluated for plant height, lodging and disease resistance, maturity, etc. Standard commercial varieties must be included as check for comparison. Two to five out standing lines if found superior to check would be advanced to the coordinated yield trials. F8 – F10 Generation: The superior lines are tested in replicated yield trials at several locations for desirable characters. During these trial lines are evaluated for yield, disease resistance, maturity, etc. a line that is superior to the best commercial variety for yield and other characteristics would be released as a new variety. F11 Generation: In F11 generation released var. is multiplies for distribution to the farmers. The breeder is responsible to supply the breeder seed to the N.S.C for production of foundation seed.
  62. 62. [62] Merits, Demerits and Achievements of Pedigree Method Merits of Pedigree Method: 1) This method gives maximum opportunity for breeder to use his skill and judgement for the selection of plants. 2) It is well suited for the improvement of characters, which can be easily identified and simply inherited. 3) Unpromising material is rejected in earlier generation hence only superior plants are promoted. 4) Homozygous is rapidly achieved. 5) Transgressive segregation for yield and other quantitative characters may be recovered. 6) It takes less time than the bulk method to develop a new variety. Demerits of Pedigree Method: 1) This method is more time consuming, laborious and expensive for maintaining pedigree record. 2) Extra attention is required for selection among and within a large number of progenies. 3) The success of this method is largely depends upon the skill of the breeder. 4) Selection for yield in F2 and F3 is ineffective. If care is not taken to retain a sufficient no of progenies. Achievements of Pedigree Method: 1) Wheat: NP-52, NP120, NP125, etc. 2) Rice: Jaya, and Padma (TN-1 X T-141) 3) Cotton: Laxmi (Gadag-1 X CC2) 4) Tomato: Pusa early dwarf (Meeruti X Red cloud) 5) Chickpea: T1, T2, T3, T5, Radhey.
  63. 63. [63] Difference between Pureline and Pedigree Selection Sr.No Pureline Selection Pedigree Selection 1 Selection from mixed population. Selection from segregating population. 2 Record of parent to offspring relationship is not kept Record of parent to offspring relationship is kept 3 Breeder is not able to obtain information about inheritance of characters. Breeder is able to obtain information about inheritance of characters from pedigree records. 4 Not suitable for the improvement of characters which can be easily identified and simply inherited. Suitable for improvement of characters, this can be easily identified and simply inherited. 5 Selection within progeny is not 5 effective. Selection within progeny is effective. 6 The progress is upto limit of variability present in a mixed population. The progress is beyond the limit of variability present in the population. 7 Each progeny in every generation cannot be traced back to the preveious progeny. Each progeny in every generation can be traced back to the F2 from which it was originated.
  64. 64. [64] Method of Plant Breeding in Self Pollinated Plants - Bulk Population Method Bulk population method of breeding in self –pollinated crop is also known as mass method or population method of breeding. It was first used by Nilsson Ehle in 1908. It refers to a species is grown in bulk plot ( from F1 to F5 ) with or without selection, a part of the bulk seed is used to grow the next generation and individual plant selection is practised in F6 or later generation. In this method duration of bulking may vary from 6-7 to 30 generation. Application of Bulk Population Method: This method is suitable and most convenient for handling the segregating generation of cereals, smaller millet, grain legume and oilseeds. This may be used for three different purposes. i) Isolation of homozygous lines. ii) Waiting for the opportunity of selection. iii) Opportunity for natural selection to change the composition of the population. Procedure of Bulk Population Method: 1) Hybridization: Parents are selected according to the objective of the breeding programme and crossed. 2) F1 Generation: The F1 generation ( 10 to 25 F1) is space planted and harvested in bulk. 3) F2-F6 – Generation: F2 to F6 generations are planted at commercial seed rate and spacing. These generations are harvested in bulk. During these generations the population size should be as possible, preferably 30 to 50 thousand plants should be grown in each generation. 4) F7 Generation: About 30 – 50 thousand plants are space planted and out of this only 1000 to 5000 plants with superior phenotypes are selected and their seeds harvested separately. Selection is made on the basis of phenotypes of plants, grain characteristics etc. 5) F8 Generation: Individual plant progenies are grown in single or multi row plots. Most of the progenies would be homozygous and are harvested in bulk. Weak and inferior progenies are rejected and only 100- 300 individual plant progenies with desirable characters are selected. 6) F9 Generation:
  65. 65. [65] Preliminary yield trial is conducted along with standard variety as check. The evaluation of progeny is done for important desirable characteristics. Quality test may be conducted to reject the undesirable progenies. 7) F10- F12 Generation: Replicated yield trails are conducted at several locations using standard commercial varieties as check. The lines are evaluated for important agronomic characteristics. If lines are superior to the standard check, released as new varieties. 8) F13 Generation: Seed multiplication of the newly released variety for distribution to the farmers. Merits of Bulk Population Method: 1) This method simple, convenient and inexpensive. 2) Little work and attention is required in F2 and subsequent generation. 3) No pedigree record is to be kept. 4) It eliminates undesirable types and increases the frequency of desirable types by artificial selection. 5) It is suitable for studies on the survival of genes and genotypes in populations. 6) There are greater chances of isolation of Transgressive segregates than pedigree method. Demerits Bulk Population Method: 1) It takes much longer to develop a new variety. 2) It provides little opportunity for the breeder to exercise his skill in selection. 3) A large number of progenies have to be selected at the end bulking period. 4) Information of inheritance of characters cannot be obtained like that of pedigree method. Achievement: This method has between used in Barley crop for developing some varieties from the crosses ( Allas X Vaughn), like Arival, Beecher, Glacier, etc. In India only one variety “Narendra Rai” has been developed in Brown Mustard. This method has a limited application in practical plant breeding.
  66. 66. [66] Method of Plant Breeding in Self Pollinated Plants - Single Seed Descent Method Single Seed Descent Method: Single seed descent method is the modification of bulk method of breeding. But the modification is in such a way that it allows the equal survival of a segregates. The idea of this method was first suggested by Goulden (1941) and subsequently modified by Brim (1960). General principles involved in this method is that, only one ( single) seed collected from each of the F2 plants ( 10000 to 20000) and then bulked to grow the next ( F3) generation. Similar practised is continued till F5 or F6 generation, when the plant would become nearly homozygous. In F5 and F6 generation, when individual’s plants are selected and harvested separately. Their progenies are also grown separately in next generation. Selection is done among the programme ad promising one is select to conduct replicated yield trails and quality test conducted in F7- F8 generation and coordinated yield trial in F9- F10 generation. Breeding Procedure: In this method, only one seed is selected randomly from each plant n F2 and subsequent generations. The selected seed is bulked and is used to grow the newts generation. This process is continue upto F5 generation. By this time desired level of homozygosity is achieved. In F6, large number of single plant, 200-500 are selected and their progeny are grown separately. In F7 and F8, selections are practised between progeny and superior progeny and are isolated based on preliminary replicated trial. The superior progenies are then tested in multiplication trails and the best progeny is identified for release. The main objectives of single seed descent method is to rapidly advantage the generation of crosses and at the end of method a random sample of homozygous genotype is obtained. Advantages: 1. Single seed descent method advantages the generations with possible speed in a conventional breeding method. 2. It requires very little space, effects and labours. 3. It makes the best use of green house and offseason nursery, facilitates because in that two to three generations can be raised in each year. 4. It ensures that the plants retained at the end population are random sample from F2 population. Disadvantages: 1. It does not permit any form of selection in natural or artificial. 2. In each successive generation the population size between progressive smaller due to poor germination.
  67. 67. [67] Method of Plant Breeding in Self Pollinated Plants - Multiple Crossing It is complex system of crossing in which 8 to 16 parents are systematically crossed to develop new hybrid variety. Ex. Barley. Multiple crosses are produced by crossing pairs of parents, pairs of F1 and pairs of F1’s of F1’ s , till all parents are included into a common progeny. A X B CX D E X F G X H AB X CD EF X GH ABCD X EFGH ABCDEFGH This method of breeding help to accumulate more and more gene quickly from several parents. But some times undesirable combinations may be brought together, since large number of parents are involved. This can be avoided by selecting the desirable combination before including in crossing programme during each generation. These procedures will require a longer time to reach the final cross. Ex. Self Pollinated Crop like Wheat and Rice are common examples.
  68. 68. [68] Method of Plant Breeding in Self Pollinated Plants - Population Approach Self-fertilization of F1 hybrid leads to very rapid increase in homozygosity. Only after 4 generation of selfing about 94% of genes would become homozygous, even in F2 half of the genes are in homozygous state. Thus, self- fertilization quickly separates the progeny from a hybrid into a large number of pure lines. As a result in such segregating population, selection only picks out the gene combination present in the population, which reduces the chances of recombination, between tightly linked genes and rare Transgressive segregants. Similarly, there is no possibility for recovery of changing genotypes of plants produced by recombination of genes in F1, F2 and F3 generation. Merits of Population Approach: 1) This method provides greater opportunity for recombination by restoring heterozygosity through intermating of selected plants. 2) This approach help in accumulation of desirable genes in the population through intermating of selected plants. Demerits of Population Approach: 1) Identification of desirable plants in the F2 or subsequent segregating generation is difficult, for complex characters like yield and the success of this method is depending on this only. 2) This method has limitation in some crops because selfing in many self pollinated crop is difficult and time consuming. 3) The time required develop variety is more than the pedigree method. 4) There is no convincing evidence for the benefits from the population approach.