Crop improvement can be achieved through both sexual and asexual reproduction. Sexual reproduction combines genes from two parents, creating new combinations, while asexual reproduction clones the parent plant. Vegetative propagation methods include cuttings, grafting, and tissue culture. Genetic engineering allows for direct transfer of genes between organisms. Traditional breeding techniques also improve crops through selection of desirable traits over generations. [/SUMMARY]
Many farmers plant only a single crop in the same place year after year. This is what is known as themonoculture crops. Supporters claim it is a more profitable way to farm than switching crops around each year. When the farmer grows only one type of crop he can specialize in that crop and purchase only the aids and machinery needed to deal with that crop. However, those against monocropping claim that it is very much hard on the environment and actually much less profitable than organic means of farming.
Monocropping or monoculture is a process to culture a single crop in a farm land. Monocropping is a process by which a clear assessment of interaction of crop on soil land can be observedDisadvantages of Monoculture
Farming planting the same crop in the same place each and every year zaps nutrients from the earth and leaves soil weak and unable to support the healthy plant growth. Because soil structure and quality is so poor, farmers are forced to use the chemical fertilizers to encourage plant growth and fruit production. These fertilizers, in turn, specifically disrupt the natural makeup of the soil and contribute further to the nutrient depletion. Monocropping also creates the spread of pests and diseases, which must be treated very well, with yet more chemicals.
RICE
Oryza sativa (2n=24)
Rice is one of the oldest cultivated crops. The two cultivated species of rice are i) Oryza sativa - Asian rice
ii) O. glaberrima - African rice. The three races in cultivated Asian rice are
i) indica
ii) Japonica (Sinica)
iii) Javanica.
Origin of cultivated rice.
The views regarding the origin of rice can be grouped in to two classes viz., a) Polyphyletic origin
b) Monophyletic origin.
i.Polyphyletic: Originated from several species. According to this theory, the two forms of cultivated rice viz., Asian rice O.sativa and African rice O.glaberrima have evolved independently in their respective regions from several species.
Common ancestor
South & South East Asia Tropical Africa Perennial O.rufipogon O.longistaminata Annual O.nivara Weedy annual O.barthii
O.spontanea
O.sativa O.Staffii O.glaberrima
indica japonica javanica
ii. Monophyletic : According to this theory both Asian rice and African rice arose from a common parent (O.perennis). This view is the most accepted one because both Asian rice and African rice are similar except in glume pubescence, ligule size and colour of pericarp which is red in African rice.
O.perennis
O.glaberrima O.sativa
According to polyphyletic origin the present day rice varieties have originated from several species. According to monophyletic origin a single species has given rise to all varieties of cultivated rice. Viz.,
Oryza sativa
Oryza glaberrima
most of the modern rice workers believe that origin of cultivated rice monophyletic. From oryza perennis rose the Asian rice in South East tropical Asia and African rice in the upper valley of Niger River in Africa.
Species in the genus oryza:
According to the latest view the genus oryza include 20 wild species. Out of these two are cultivated diploids viz. O.sativa and O.glaberrima and rest are wild species which include both diploid and tetraploid forms.
Liquid Biofertilizer Manufacturing Industry. Production of Liquid Bio-Fertiliser. Profitable Biofertilizers Production Business Ideas
Liquid Biofertilizer a substance which helps to grow plants rapidly and produce fruits, flower and vegetable more quantity in proper time, otherwise fertilizer be a compound which fulfill the needed minerals or Clements require for the growth of plants and vegetables to grow and fruits in proper time.
Liquid Biofertilizer is natural fertilizers which are microbial inoculants of bacteria algae fungi alone or in combination and they augment the availability of nutrients to the plants.
See more
https://goo.gl/AXBLyk
https://goo.gl/7viQBz
https://goo.gl/1pBJTv
Contact us:
Niir Project Consultancy Services
An ISO 9001:2015 Company
106-E, Kamla Nagar, Opp. Spark Mall,
New Delhi-110007, India.
Email: npcs.ei@gmail.com , info@entrepreneurindia.co
Tel: +91-11-23843955, 23845654, 23845886, 8800733955
Mobile: +91-9811043595
Website: www.entrepreneurindia.co , www.niir.org
Tags
#Production_of_Liquid_Biofertilizers, #Liquid_Bio_Fertilizers, #Liquid_Biofertilizer_Production, Liquid Biofertilizers Unit, Liquid Biofertilizer Manufacturing Plant, #Bio_Fertilizer_Plant, Liquid Bio Fertilizer Plant, Liquid Biofertilizer Manufacture, Bio-Fertilizer Unit, Liquid Biofertilizer Manufacturing, Manufacturing of Liquid Biofertilizers, Biofertilizers for Plants, Bio Fertilizer Plant Cost in India, Fertilizer Manufacturing Plant Cost in India, #Small_Scale_Biofertilizer_Production, Liquid Biofertilizer Formulation Pdf, Liquid Biofertilizer Formulation PPT, Setting Up of Liquid Biofertilizer Manufacturing Plant, Biofertilizer Manufacturing Business Ideas, Setting up a Bio-Fertilizers Unit, Bio Fertilizer Production, Biofertilizer Manufacturing Business, #How_to_Start_Biofertiliser_Production_Unit, Liquid Bio Fertilizer Manufacture India in India, Manufacturing of Biofertilizers, Liquid Biofertilizer Production Unit, Production of a Potential Liquid Plant, Formulation of New Liquid Biofertilizer, #Biofertilizer_Production_Process_Pdf, Start a Biofertilizer Manufaturing Unit, #Project_Report_on_Liquid_Biofertilizer_Manufacturing_Industry, Detailed Project Report on Liquid Biofertilizer Manufacturing, #Project_Report_on_Liquid_Biofertilizer_Production, Pre-Investment Feasibility Study on Liquid Biofertilizer Manufacturing Industry, Techno-Economic feasibility study on Liquid Biofertilizer Production, Feasibility report on Liquid Biofertilizer Production, Free Project Profile on Liquid Biofertilizer Manufacturing Business, Project profile on Liquid Biofertilizer Production, Download free project profile on Liquid Biofertilizer Production, Commercial Liquid Biofertilizers for growth of Plants, Bio Fertilizer Business Opportunities, Small Scale Biofertilizer Production, Liquid Biofertilizer Manufacture, Bio Fertilizer Manufacturing Process, Profitable Liquid Biofertilizer Production Business Ideas
Rice is one of main food crops in the worlds so knowing about how is origin may important to the people engage in the agriculture extension or advisory or education
Many farmers plant only a single crop in the same place year after year. This is what is known as themonoculture crops. Supporters claim it is a more profitable way to farm than switching crops around each year. When the farmer grows only one type of crop he can specialize in that crop and purchase only the aids and machinery needed to deal with that crop. However, those against monocropping claim that it is very much hard on the environment and actually much less profitable than organic means of farming.
Monocropping or monoculture is a process to culture a single crop in a farm land. Monocropping is a process by which a clear assessment of interaction of crop on soil land can be observedDisadvantages of Monoculture
Farming planting the same crop in the same place each and every year zaps nutrients from the earth and leaves soil weak and unable to support the healthy plant growth. Because soil structure and quality is so poor, farmers are forced to use the chemical fertilizers to encourage plant growth and fruit production. These fertilizers, in turn, specifically disrupt the natural makeup of the soil and contribute further to the nutrient depletion. Monocropping also creates the spread of pests and diseases, which must be treated very well, with yet more chemicals.
RICE
Oryza sativa (2n=24)
Rice is one of the oldest cultivated crops. The two cultivated species of rice are i) Oryza sativa - Asian rice
ii) O. glaberrima - African rice. The three races in cultivated Asian rice are
i) indica
ii) Japonica (Sinica)
iii) Javanica.
Origin of cultivated rice.
The views regarding the origin of rice can be grouped in to two classes viz., a) Polyphyletic origin
b) Monophyletic origin.
i.Polyphyletic: Originated from several species. According to this theory, the two forms of cultivated rice viz., Asian rice O.sativa and African rice O.glaberrima have evolved independently in their respective regions from several species.
Common ancestor
South & South East Asia Tropical Africa Perennial O.rufipogon O.longistaminata Annual O.nivara Weedy annual O.barthii
O.spontanea
O.sativa O.Staffii O.glaberrima
indica japonica javanica
ii. Monophyletic : According to this theory both Asian rice and African rice arose from a common parent (O.perennis). This view is the most accepted one because both Asian rice and African rice are similar except in glume pubescence, ligule size and colour of pericarp which is red in African rice.
O.perennis
O.glaberrima O.sativa
According to polyphyletic origin the present day rice varieties have originated from several species. According to monophyletic origin a single species has given rise to all varieties of cultivated rice. Viz.,
Oryza sativa
Oryza glaberrima
most of the modern rice workers believe that origin of cultivated rice monophyletic. From oryza perennis rose the Asian rice in South East tropical Asia and African rice in the upper valley of Niger River in Africa.
Species in the genus oryza:
According to the latest view the genus oryza include 20 wild species. Out of these two are cultivated diploids viz. O.sativa and O.glaberrima and rest are wild species which include both diploid and tetraploid forms.
Liquid Biofertilizer Manufacturing Industry. Production of Liquid Bio-Fertiliser. Profitable Biofertilizers Production Business Ideas
Liquid Biofertilizer a substance which helps to grow plants rapidly and produce fruits, flower and vegetable more quantity in proper time, otherwise fertilizer be a compound which fulfill the needed minerals or Clements require for the growth of plants and vegetables to grow and fruits in proper time.
Liquid Biofertilizer is natural fertilizers which are microbial inoculants of bacteria algae fungi alone or in combination and they augment the availability of nutrients to the plants.
See more
https://goo.gl/AXBLyk
https://goo.gl/7viQBz
https://goo.gl/1pBJTv
Contact us:
Niir Project Consultancy Services
An ISO 9001:2015 Company
106-E, Kamla Nagar, Opp. Spark Mall,
New Delhi-110007, India.
Email: npcs.ei@gmail.com , info@entrepreneurindia.co
Tel: +91-11-23843955, 23845654, 23845886, 8800733955
Mobile: +91-9811043595
Website: www.entrepreneurindia.co , www.niir.org
Tags
#Production_of_Liquid_Biofertilizers, #Liquid_Bio_Fertilizers, #Liquid_Biofertilizer_Production, Liquid Biofertilizers Unit, Liquid Biofertilizer Manufacturing Plant, #Bio_Fertilizer_Plant, Liquid Bio Fertilizer Plant, Liquid Biofertilizer Manufacture, Bio-Fertilizer Unit, Liquid Biofertilizer Manufacturing, Manufacturing of Liquid Biofertilizers, Biofertilizers for Plants, Bio Fertilizer Plant Cost in India, Fertilizer Manufacturing Plant Cost in India, #Small_Scale_Biofertilizer_Production, Liquid Biofertilizer Formulation Pdf, Liquid Biofertilizer Formulation PPT, Setting Up of Liquid Biofertilizer Manufacturing Plant, Biofertilizer Manufacturing Business Ideas, Setting up a Bio-Fertilizers Unit, Bio Fertilizer Production, Biofertilizer Manufacturing Business, #How_to_Start_Biofertiliser_Production_Unit, Liquid Bio Fertilizer Manufacture India in India, Manufacturing of Biofertilizers, Liquid Biofertilizer Production Unit, Production of a Potential Liquid Plant, Formulation of New Liquid Biofertilizer, #Biofertilizer_Production_Process_Pdf, Start a Biofertilizer Manufaturing Unit, #Project_Report_on_Liquid_Biofertilizer_Manufacturing_Industry, Detailed Project Report on Liquid Biofertilizer Manufacturing, #Project_Report_on_Liquid_Biofertilizer_Production, Pre-Investment Feasibility Study on Liquid Biofertilizer Manufacturing Industry, Techno-Economic feasibility study on Liquid Biofertilizer Production, Feasibility report on Liquid Biofertilizer Production, Free Project Profile on Liquid Biofertilizer Manufacturing Business, Project profile on Liquid Biofertilizer Production, Download free project profile on Liquid Biofertilizer Production, Commercial Liquid Biofertilizers for growth of Plants, Bio Fertilizer Business Opportunities, Small Scale Biofertilizer Production, Liquid Biofertilizer Manufacture, Bio Fertilizer Manufacturing Process, Profitable Liquid Biofertilizer Production Business Ideas
Rice is one of main food crops in the worlds so knowing about how is origin may important to the people engage in the agriculture extension or advisory or education
Introduction to Principles of Inheritance and Variation in Genetics and Evolution:
The study of genetics and evolution unveils the intricate mechanisms governing the transmission of traits from one generation to the next, showcasing the principles of inheritance and variation. Inheritance refers to the passage of genetic information from parents to offspring, while variation encompasses the diversity observed among individuals within a population. These fundamental principles are central to our understanding of how living organisms evolve over time.
For more information, visit- www.vavaclasses.com
Mendelian Inheritance and Post-Mendelian Developments.pptxBhanu Yadav
This Project Aims at discussing Mendel's Laws of Inheritance with a brief introduction to his work, followed up by the developments that occured post mendelism
Genetics: The study of heredity.
Heredity is the relations between successive generations.
Why do children look a little bit like their parents but also different?What is responsible for these similarities and differences? this slides try to explain why these things are happening.
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
This is a presentation by Dada Robert in a Your Skill Boost masterclass organised by the Excellence Foundation for South Sudan (EFSS) on Saturday, the 25th and Sunday, the 26th of May 2024.
He discussed the concept of quality improvement, emphasizing its applicability to various aspects of life, including personal, project, and program improvements. He defined quality as doing the right thing at the right time in the right way to achieve the best possible results and discussed the concept of the "gap" between what we know and what we do, and how this gap represents the areas we need to improve. He explained the scientific approach to quality improvement, which involves systematic performance analysis, testing and learning, and implementing change ideas. He also highlighted the importance of client focus and a team approach to quality improvement.
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
Andreas Schleicher presents at the OECD webinar ‘Digital devices in schools: detrimental distraction or secret to success?’ on 27 May 2024. The presentation was based on findings from PISA 2022 results and the webinar helped launch the PISA in Focus ‘Managing screen time: How to protect and equip students against distraction’ https://www.oecd-ilibrary.org/education/managing-screen-time_7c225af4-en and the OECD Education Policy Perspective ‘Students, digital devices and success’ can be found here - https://oe.cd/il/5yV
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
The Indian economy is classified into different sectors to simplify the analysis and understanding of economic activities. For Class 10, it's essential to grasp the sectors of the Indian economy, understand their characteristics, and recognize their importance. This guide will provide detailed notes on the Sectors of the Indian Economy Class 10, using specific long-tail keywords to enhance comprehension.
For more information, visit-www.vavaclasses.com
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
How to Create Map Views in the Odoo 17 ERPCeline George
The map views are useful for providing a geographical representation of data. They allow users to visualize and analyze the data in a more intuitive manner.
Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
In this webinar you will learn how your organization can access TechSoup's wide variety of product discount and donation programs. From hardware to software, we'll give you a tour of the tools available to help your nonprofit with productivity, collaboration, financial management, donor tracking, security, and more.
2. Sexual and Asexual Reproduction
•
Long term survival requires reproduction. Even the longest-lived
organisms are less than 10,000 years old.
– Cellular machinery wears out, or gets clogged with waste products.
– Environmental conditions change
•
Plants often reproduce asexually, through cuttings or runners or buds
(e.g. potatoes). The resulting plants are clones: they are genetically
identical to the parent.
– Used to preserve good combinations of traits.
•
Sexual reproduction is also found in plants, and in all animals. Sexual
reproduction means combining genes from two different parents,
resulting in new combinations of genes. Each parent contributes a
randomly-chosen half of their genes to the offspring.
– This can be a good thing, because some new combinations will survive
better than the old ones.
– It can also be bad: lack of uniformity in the offspring.
3. Vegetative Propagation
•
•
•
•
Plant meristems are usually capable of generating
all the tissue types found in a plant.
Some plants naturally propagate vegetatively,
usually through modified stems: flower bulbs,
corms, and rhizomes; suckers; stolons (runners).
Artificial vegetative propagation can be down by
taking a cutting from the stem (containing at least
one meristem) and encouraging it to grow roots.
More advanced methods include grafting and
tissue culture.
4. Grafting
•
•
•
•
•
Grafting is common among fruit trees: the stem
tissue of one plant is fused to a stem from
another plant.
Commonly done: a hardy rootstock is grafted to
the stem of a better fruit variety.
Another method: attaching a bud form one plant
to the stem of another. You can produce an
apple tree bearing several different types of apple
this way.
The cambium layers of the two plants being
grafted need to be brought into contact. This
allows the xylem and phloem to connect to each
other
It is possible to graft a potato rootstock to a
tomato top, so both underground potato tubers
and aboveground tomato fruits are formed on
the same plant.
5. Tissue Culture
•
A more modern way of propagating plants
vegetatively is through tissue culture. This is often
called “micropropagation”.
– Useful for genetically engineered plants, for plants
that don’t set viable seeds, and for rare and valuable
plants.
•
•
•
•
Unlike animals, many plant cells, especially in the
meristems, are totipotent: they can generate an
entire plant under the proper conditions.
Pieces of the plant are cut out and placed on an
agar medium under sterile conditions.
Manipulating plant hormones is the key: an excess
of auxin produces roots, and excess of cytokinin
produces shoots, and a balanced mixture allows the
cells to multiply as an undifferentiated mass of cells
called a callus.
Pieces of the callus can be cut out and propagated
indefinitely.
6. Sexual Reproduction
•
Diploid: having 2 copies of each chromosome, one set from each
parent.
– Humans have 46 chromosomes, 23 from each parent.
– Almost any organisms you can see: plant, animal, fungus, is diploid.
•
Haploid: having only 1 copy of each chromosome.
– Sperm and eggs (=gametes) are haploid
– moss, a primitive plant, is haploid for most of its life
•
Plants, animals, and other eukaryotes alternate between haploid and
diploid phases. This is called alternation of generations.
7. Life Cycle
• Diploid organism generates haploid
gametes using the process of meiosis.
The gametes combine during the process
of fertilization to form a new diploid
organism.
• In animals, the haploid phase is just one
cell generation, the gametes, which
immediately do fertilization to produce a
diploid zygote, the first cell of the new
individual.
• In plants, the haploid phase is several cell
generations at least.
– Lower plants are mostly haploid
– Higher plants are haploid for only a few
cell generations
• The diploid plant is called the sporophyte,
and the haploid plant is called the
gametophyte.
8. Genetics
•
The science of genetics is devoted to understanding the patterns of how
traits are inherited during sexual reproduction. It was founded by Gregor
Mendel in the 1850's, using pea plants. Despite the obvious differences,
humans and peas have very similar inheritance patterns.
•
The fundamental observation of genetics: within a species, there are a fixed
number of genes, and each gene has a fixed location on one of the
chromosomes.
– This allows genes to be mapped: a gene's neighbors are always the same.
– Most species of higher organism have about 25,000 different genes distributed
onto 10-30 different chromosomes.
9. Genetics
•
Alleles. Many genes have several variant forms, which are called
alleles.
– For example, a gene the produces color in the flower might have a purple
allele and a white allele. These alleles are designated P and p.
– Differences in alleles are what makes each human different from all
others
•
True-breeding lines. If you cross close relatives with each other for
many generations, eventually all the offspring look alike.
– Mendel started with several true-breeding lines, which differed from
each other in 7 distinctive characteristics
10. Genetics
•
In many plants, you can self-pollinate: cross the
male parts of a plant with the female parts of the
same plant.
– In this case, both copies of any given gene are
identical. This is called homozygous. The plants are
homozygotes, either PP (purple) or pp (white).
– The closest cross you can do in animals is brother x
sister.
•
Hybrids. If you cross two true-breeding lines with
each other and examine some trait where the
parents had different alleles, you produce a
heterozygote: the two copies of the gene are
different.
– Surprisingly, you often find that the heterozygote
looks just like one of the parents. The Pp
heterozygote is purple, just like its PP parent.
– This is the F1 generation in the diagram.
11. Genetics
•
Dominant and recessive. If a heterozygote is
identical to one parent, the allele from that
parent is dominant. The allele from the other
parent is recessive. That is, the heterozygote
looks like the dominant parent.
– This is why we say purple is dominant to white,
and give purple the capital letter P.
•
Phenotype and genotype. Phenotype is the
physical appearance, and genotype is the
genetic constitution.
– The heterozygote in the previous paragraph
has the same phenotype as the homozygous
dominant parent (i.e. purple flowers), but a
different genotype (the heterozygote is Pp and
the parent is PP).
12. Genetics
•
•
Now we want to move to the next
generation, by self-pollinating the
heterozygotes.
When a heterozygote undergoes
meiosis to produce the haploid
gametes, half are P and half are p.
– These gametes combine randomly,
producing 1/4 PP, 1/2 Pp, and 1/4
pp offspring.
•
Since PP and Pp have the same
phenotype, 3/4 of the offspring are
purple and 1/4 are white.
13. Independent Assortment
•
•
•
•
•
•
•
Much of Mendel’s work involved pairs of genes:
how do they affect each other when forming
the gametes and combining the gametes to
form the next generation?
Simple answer: in most cases pairs of genes act
completely independently of each other. Each
gamete gets 1 copy of each gene, chosen
randomly.
Two genes:
1. seed shape. Dominant allele S is smooth;
recessive allele s is wrinkled.
2. seed color. Dominant allele Y is yellow;
recessive allele y is green.
Heterozygous for both has genotype Ss Yy,
which is smooth and yellow. Gametes are
formed by taking 1 copy of each gene randomly,
giving ¼ SY, ¼ Sy, ¼ sY, and ¼ sy.
These gametes can be put into a Punnett square
to show the types of offspring that arise.
– Comes out to 9/16 smooth yellow, 3/16 smooth
green, 3/16 wrinkled yellow, and 1/16 wrinkled
green.
– 3/4 are yellow, 1/4 are green, and 3/4 are round,
1/4 are wrinkled
14. Continuous Variation
•
•
Many traits don’t seem to fall
into discrete categories: height,
for example. Tall parents usually
have tall children. Short parents
have short children, and tall x
short often gives intermediate
height. In all cases, wide
variations occur.
Simple interactions between
several genes can give rise to
continuous variation. Also:
variations caused by
environment, and our inability to
distinguish fine distinctions lead
us to see continuous variation
where there actually are discrete
classes.
15. Linkage
•
•
•
Most pairs of genes assort
independently.
However, if two genes are close
together on the same
chromosome, they are said to be
linked, which means the genes
don’t do into the gametes
independently of each other.
The closer two genes are, the
more the parental combination
of alleles stays together. This
relationship can be used to make
maps of genes on chromosomes.
16. Methods of Crop Improvement
•
•
The idea that we can improve the inherited characteristics of crop
species is fundamental. Very few of the plants we use are unmodified
wild plants: most of them have been modified to make them easier to
grow and harvest, and to increase the quality and quantity of the
desired product.
We will see many examples of crop improvement this semester. Here
are some of the basic methods used.
17. Single Gene Traits and Mutation
•
Single gene traits. Many useful traits are controlled
by a single gene. Spontaneous mutations can lead to
important, abrupt changes
– A good example: sweet corn. The recessive mutation su
(sugary) produces kernels that are 5-10% sugar. But,
only when homozygous: the non-sugary allele (Su) is
dominant.
•
Single gene mutations occur rarely, but often enough
so that observant people notice and propagate them.
– Sweet corn was recognized and propagated by several
Native American tribes. The Iroquois introduced it to
European settlers.
– Mutation rate: 1 in 10,000 to 1 in 1,000,000 plants.
– Artificially-induced mutation occasionally works, but
most are spontaneous.
•
Single gene traits are inherited in a Mendelian
fashion:
–
each individual carries one copy of the gene from each
parent,
– the relationship between phenotype (sweet vs. starchy
corn) and genotype (homozygous or heterozygous) is
determined by dominance vs. recessiveness.
Genotype
Phenotype
Su Su
Starchy
Su su
Starchy
su su
Sweet
18. Polygenic Traits and
Selection
•
•
•
•
Polygenic traits. Many traits are controlled
by many genes, each of which contributes a
small amount to the phenotype. Grain yield
is a good example: lots of genes contribute
to this.
Such traits respond well to selection. In the
simplest sense, selection means using the
best seeds to start the next generation. If
this is done consistently, the crop slowly
improves over many generations.
Genetic research has led to an
understanding of what happens during
selection. This allows much faster and
more effective selection than just saving the
best seeds.
This is often called “conventional breeding”
or “traditional plant breeding”. It has been
the main way crops have been improved for
a long time.
19. Polyploidy
•
Normal diploids have 2 copies of every
chromosome. Sometimes it is possible to double
this number, making a tetraploid, 4 copies of
every chromosome.
– The drug colchicine does this by causing meiosis to
produce diploid gametes instead of the normal
haploids. Then, diploid sperm + diploid egg =
tetraploid embryo.
•
Tetraploids are often bigger, healthier, more
nourishing than their diploid parents.
– Examples: cotton, durum wheat, potato, daylily
•
•
Tetraploid is a form of polyploid, which means
having more than 2 sets of chromosomes (2 sets =
diploid).
There are triploid (e.g. banana and watermelon),
hexaploid (bread wheat, chrysanthemum), and
octaploid (strawberry, sugar cane) crops
•
Triploids are sterile
20. Hybridization
•
Plants are not as rigid in maintaining species boundaries as
animals are. It is often possible to produce hybrids between two
different, but closely related species.
– Members of the same genus will often hybridize
•
The resulting plants often have characteristics different
from both parents
– Often sterile, but many plants can be propagated vegetatively
• The grapefruit is a naturally-occurring hybrid between a
pomelo (native to Indonesia) and a sweet orange (native to
Asia).. It was discovered in Barbados in 1750, then brought
to Florida and propagated.
•
•
Hybrids have an “x” in their species name: Citrus x paradisi
Sometimes, a hybrid will spontaneously double its chromosomes,
so you end up with a tetraploid . These interspecies tetraploids
are usually fertile, and they benefit from the general effect of
tetraploidy: bigger, healthier plants.
21. Genetic Engineering
•
•
In the last 30 years it has become possible to take a gene out of one
organism and put it into the DNA of another organism. This process
is called genetic engineering. The resulting organisms are genetically
modified organisms (GMOs) and the gene that has been
transplanted is a transgene.
There are no real interspecies barriers here: all organisms use the
same genetic code, so genes from bacteria (for example) will
produce the correct protein in a corn plant.
– However, some modifications must be made to the signals that control
gene expression, since these are more species-specific.
•
A few examples:
– Bt corn. Bacillus thuringiensis, a soil bacterium, produces a protein that
kills many insect pests, especially the corn earworm. The gene for this
protein has been transplanted into much of the US corn crop.
– Roundup Ready soybeans (plus other crops). Roundup is the Monsanto
brand name for the herbicide glyphosate. A bacterial gene that confers
resistance to this herbicide has been transplanted to many crops. The
farmer can then spray the fields with glyphosate and kill virtually all the
weeds without harming the crop. About 87% of the US soybean crop is
now Roundup Ready transgenic plants.
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Some cultural issues here: are GMOs safe to eat?
22. Molecular Cloning
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The first step in genetic engineering is
molecular cloning.
Molecular cloning means taking a gene, a piece
of DNA, out of the genome and growing it in
bacteria. The bacteria (usually E. coli) produce
large amounts of this particular gene.
The cloned gene can then be used for further
research, or to produce large amounts of
protein, or to be inserted into cells of another
species (to confer a useful trait).
The basic tools:
1. plasmid vector: small circle of DNA that
grows inside the bacteria. It carries the gene
being cloned
2. Restriction enzymes: cut the DNA at
specific spots, allowing the isolation of specific
genes.
3. DNA ligase, an enzyme that attached
pieces of DNA together.
4. transformation. Putting the DNA back
into living cells and having it function.
23. The Cloning Process
• 1. Cut genomic DNA with a
restriction enzyme.
• 2. Cut plasmid vector with
the same restriction
enzyme.
• 3. Mix the two DNAs
together and join them with
DNA ligase.
• 4. Put the recombinant DNA
back into E. coli by
transformation.
• 5. Grow lots of the E. coli
containing your gene.
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The real trick, however, is to find
the gene that confers your
desired trait.
24. Transgenic Plants
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Once a gene of interest has been identified and cloned, it
must be put into the plant.
Usually done with plant tissue culture. Small pieces of a
plant can be grown as an undifferentiated mass of cells
on an artificial growth medium.
– Then, when treated with the proper plant hormones, these
cells develop roots and shoots. They can then be
transferred to soil and grown as regular plants.
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To make transgenic plants, DNA gets put into the tissue
culture cells, by one of several methods:
One method is the gene gun: tiny gold particles are
coated with the DNA, and then shot at high speed into
the cells. The gold particles penetrate the cell wall and
membrane. Some end up in the nucleus, where the DNA
gets incorporated into the chromosomes.
An important issue: the proteins produced by transgenes
are identical to those produced in the original species,
because the genetic code is universal.
However, the signals needed to express these genes are
plant-specific, not universal.
25. Centers of Domestication
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Primary theory came from Nikolay Vavilov,
– Vavilov was a Russian who came to a bad end in one of Stalin’s prison camps
in Siberia. He believed in Mendelian genetics, which was considered
“bourgeois” and thus evil by the Communist Party. (Lysenko)
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“Centers of domestication”. The idea is that a plant was probably
first domesticated where there are many wild relatives living and
where there is a lot of variation in the domesticated plant. Lots
of diversity near a domestication center.
Eight major centers:
– Southern Mexico and Central America: maize, beans, cotton, pepper, sweet
potato
– South America (mostly Peru): potato, common bean, tomato, cocoa, tobacco
– Mediterranean: pea, mustard, flax, cabbage, asparagus, clover, olive
– Middle East (Turkey and eastward): wheat, alfalfa, rye, lentil, melon, fig
– Ethiopia: barley, millet, coffee, indigo, sorghum
– Central Asia: onion, apple, carrot, almond, grape
– India: sugar cane, yam, cucumber, chickpea, orange, coconut, banana,
pepper
– China: soybean, buckwheat, peach, opium poppy, tea
27. More Domestication
• More recently, Jack Harlan (from U of Illinois)
examined genetic data and found that many
crops were domesticated multiple times in
multiple locations. Also, some were
domesticated over very wide areas that don’t
seem much like “centers”.
• Nevertheless, our current crops come from many
different areas of the world. We will look at the
origins of specific crops as we study them.