plant breeding basics
TRANSCRIPT
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Introduction to Maize Breeding
Nathan Schnur
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Overview
What is Plant Breeding?
Basic Genetics
Mendelian Genetics
Principles of Breeding Maize
Plant Breeding Methods
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Plant Breeding
What is it?
Is the science and art of improving crop plants through the
study and application of genetics, agronomy, statistics, plant
pathology, entomology, and other related sciences.
Goals
Nutritional enhancement, yield improvement, environmental
stress tolerance, improved plant structure, or pest and
disease resistance
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Basic Plant Genetics
DNA Primary carries of
heritable information
Composed of thousandsof genes
Genes Contain actual heritable
information
There can be manyversions of genes calledalleles
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Basic Plant Genetics Cont
There are two alleles for any gene Dominant and Recessive
Two dominant alleles are denoted as
AA and called homozygous dominant Two recessive alleles are denoted as
aa and called homozygous recessive
If one dominant and one recessive
allele is present then it is denoted asAa and called heterozygous.
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Basic Plant Genetics Cont
Alleles which are heterozygous
or homozygous affect the
phenotypes and genotypes ofplants
Phenotype
Visual appearance of the plant
Genotype
Genetic makeup of the plant
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Mendelian Genetics
Gregor Mendel
Famous geneticist from 1800s
His research consisted of selectivelybreeding garden peas
He developed two important laws of
genetics Law of Segregation
Law of Independent Assortment
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Mendelian Genetics Example
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Principles of Breeding Maize
Three Main Principles
Inbreeding
Hybridization
Heterosis
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Inbreeding
Main Goals
Increase the homozygosity at all or specific loci
in the plant genome Produce a plant which breeds true
Produce uniform plants
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Hybridization of Maize
Hybridization occurs when inbred parents aremated (cross pollinated)
Creates a heterozygous individual
Benefits
Increased heterosis (vigor) in F1 generation
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Heterosis (Hybrid Vigor)
Heterosis occurs when two homozygousindividuals are cross pollinated. This causes all loci to become heterozygous
The increased heterozygosity causesincreased plant vigor
Benefits of Increased Vigor Increased yield
Better standability
Better germination Overall better plant performance
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Maize Breeding Methods
Main Methods of Maize Breeding
Selfing (Inbreeding)
Sib Mating
Crossing
Test Crossing
Backcrossing
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Selfing
Selfing is the process ofpollinating a plant with itsown pollen
Benefits Increased homozygosity
Plants which breed true fromgeneration to generation
Decreased Segregation Disadvantages
Many generations of selfinglead to inbreeding depression
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Crossing and Test Crossing
Crossing is useful when trying tocreate hybrid seed. Ex. By crossing Inbred A x Inbred a you
would obtain an F1 hybrid Aa Crossing is used to produce the hybrid
seed farmers use to plant in the spring
Test Crossing is useful to test generalcombining ability of an individual
Ex. Inbred A is x to a tester which has adiverse selection of genotypes
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Backcrossing
Backcrossing is a methodwhich is used to improve atrait which a plant is deficient
in. Method
A hybrid plant which has thetrait of interest is crossed withone of its parents
The offspring are then crossedback to the parent, thusincreasing the frequency ofthe trait.
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Conclusion
Plant breeding is a complicated butbeneficial process.
There are many processes involvedwhich are used in the development ofnew varieties.
Remember if it wasnt for plantbreeding we wouldnt have such highyielding crops
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References
Fehr, W. Principles of Cultivar Development.1993. Volume 1
Photos Courtesy of www.pioneer.com
www.britannica.com
www.psu.edu
http://imbgl.cropsci.uiuc.edu www.nsf.gov
www.scienceclarified.com
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Questions
Questions?