This document discusses modern trends in plant breeding, including marker-assisted selection (MAS) and micropropagation. It describes how MAS uses molecular markers linked to genes of interest to predict traits, providing examples of its use in developing disease-resistant rice and quality protein maize. Micropropagation, or clonal propagation in vitro, allows for rapid mass production of plantlets from a single individual. Other applications discussed include germplasm preservation and seed production. The document also covers double haploid production for generating homozygous lines more quickly.

1. MODERN TRENDS IN
PLANT BREEDING
Presented by
Swetha S Menon
2nd MSc Botany

2. INTRODUCTION
• Plant breeding is a science based on
principles of genetics and cytogenetic. It
aims at improving the genetic makeup of
the crop plants.
• Improved varieties are developed through
plant breeding. Its objectives are to improve
yield, quality, disease-resistance, drought
and frost-tolerance and important
characteristics of the crops.

3. • The modern age of plant breeding began in
the early part of the twentieth century, after
Mendel’s work was rediscovered. Today plant
breeding is a specialized technology based on
genetics. It is now clearly understood that
within a given environment, crop
improvement has to be achieved through
superior heredity.

4. MOLECULAR BREEDING
- (MARKER ASSISTED
SELECTION, MAS)
MOLECULAR BREEDING
[MARKER ASSISTED
SELECTION, MAS]

5. Plant breeders now use molecular marker-
assisted selection
Helps to identify specific genes by molecular
markers
The markers located near the DNA sequance
of the desired gene
Since the markers and the genes are close
together on the same chromosom, they tend
to stay together as each generation of plants is
produced –Genetic linkage

6. Helps to predict whether a plant will have the
desired gene

7. Markers Used
MAS makes use of various types of molecular markers.
The most commonly used molecular markers are;
Amplified fragment length polymorphisms (AFLP)
 Restriction fragment length polymorphisms (RFLP)
 Random amplified polymorphic DNA (RAPD)
 Simple sequence repeats (SSR) or Micro satellites
Single nucleotide polymorphisms (SNP) etc.
The use of molecular markers differs from species to
species also.

8. Steps in Marker Assisted Selection
(MAS)
• Selection of parents
• Development of breeding population
• Isolation of DNA from each plant
• Scoring RFLPs
• Correlation with morphological traits.

9. Achievements of Marker Assisted
Selection (MAS):
• MAS has been used for genetic improvement
of different field crops such as maize, barley,
rice, wheat, sorghum, soybean, chickpea,
pea, sunflower, tomato, potato and some
fruit crops for various economic characters.
MAS has been mainly used for developing
disease resistant cultivars in different crops

11. Some notable examples of the use of
MAS
i. Rice:
• In rice MAS has been successfully used for developing
cultivars resistant to bacterial blight and blast. For bacterial
blight resistance four genes (Xa4, Xa5, Xa13 and Xa21) have
been pyramided using STS (sequence tagged site) markers.
• The pyramided lines showed higher level of resistance to
bacterial blight pathogen. In Indonesia, two bacterial blight
resistant varieties of rice viz Angke and Conde have been
released through MAS. For blast resistance, three genes
(Pil, Piz5 and Pita) have been pyramided in a susceptible
rice variety Co 39 using RFLP and PCR based markers.

12. • ii. Maize
• In maize, normal lines have been converted
into quality protein maize (QPM) lines through
MAS using opaque 2 recessive allele. This
work has been done at CIMMYT (international
centre for wheat and maize improvement,
Mexico).
• Three SSR markers (Umc 1066, Phi 057 and
Phi 112) present within opaque 2 gene have
been used for this purpose. The MAS used for
conversion of normal maize lines into QPM is
simple, rapid and accurate

13. Advantages of Marker Assisted
Selection (MAS)
i. Accuracy
ii. Rapid Method
iii. Non-transgenic Product
iv. Identification of Recessive Alleles
v. Early Detection of Traits
vi. Screening of Difficult Traits
vii. Gene Pyramiding
viii. Small Sample for Testing
ix. Permits QTL Mapping
x. Highly Reproducible

14. MICRO PROPAGATION

15. • Clonal Propagation in vitro is called Micro-
propagation.
• clonal propagation is the multiplication of the
genetically identical individuals by asexual
reproduction while clone is a plant population
derived from a single individual by asexual
individuals

16. • The significant advantage offered by the
aseptic method of clonal propagation
(Micropropagaion) over the Conventional
methods is that in a relatively short span of
time and space, a large number of plants can
be produced starting from a single individuals.
Some potential uses of clonal propagation in
agronomical crops are:

17. • Large scale increase of a heterozygous
genotypes
• Increase of self incompatible genotypes
• Increase of a male sterile parent in a hybrid
seed program
• Production of a disease free rootstock
• Preservation and international exchange of
germplasm.

18. Advantages of Micropropagation
• A small amount of plant tissue is needed as
the initial explant for regeneration of
millions of clonal plants in one year.
• The invitro stocks can be quickly proliferated
at any time of the year.
• The invitro technique provides a method for
speedly international exchange of plant
materials.
• Production of disease free plants.

19. • Germplasm storage: Plant breeding
programme rely heavily on the germplasm.
Preservation of the germplasm is a mean to
assure the availability of genetic materials as
the need arises.
• Seed Production: For Seed production in
some of the crops, a major limiting factor is
the high degree of genetic conservation
required. In such cases micropropagation can
be used.

20. Double Haploid Production

21. • In the double haploid procedure, haploid
plants are generated from anther of F1 plants,
or by other means, and the chromosomes of
the haploid plants are doubled with
colchicines treatment to produce diploid
plants
Regeneration of plantlets: a0 colchicine
treated explants producing healthy
shoot and root system on MS medium
supplemented with BAP (0.1 mg/l);
b) Untreated explant showing shoot and
root development in presence of BAP
(0.1 mg/l)

22. • An example of the double haploid procedure
using anther culture
• Crossing generation: Crossing cultivar A and
Cultivar B
• F1 Generation: Culture Anther to produce
2000 t0 3000 haploid plants.
• F2 Generation: Double chromosome of the
haploid plants and harvest seeds from double
haploid plants produced.
• F3 Generation: Grow progeny rows from
double haploid plants and harvest seeds from
superior rows

23. • F4 Generation: Grow progeny rows in the field
and select superior rows.
• F5 Generation: Grow Preliminary Yield Trial.
• F6 to F8 Generation: Continues yield trials.
• F9 and F10 Generation: Increase and
distribute superior lines as a new cultivars

24. • Double haploid plants are normally
homozygous at all loci and it is unnecessary to
grow segregating generation. Lines generated
by the double-haploid procedures may reach
preliminary yield trials two to three
generation earlier than with the pedigree-
selection or Bulk selection procedures

25. • Like the single seed descent procedure, early
generations are not exposed to environmental
stresses in the field, and attrition of lines is
greater in initial field evaluation trials than with
pedigree selection or bulk population
procedures, in which early generations are field
grown.
• The double haploid plants should be vigorous,
stable, free from tissue culture induced
variations, and represents a random selection of
F1 pollen gametes.

26. Reference
• Chawla,H.S. (2009). Introduction to Plant
Boitechnology.
• Singh, B.D., (2009).Eight Edition. Plant
Breeding Principles & Methods.
• https://www.biologydisscusion.com