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Introduction to Maize Breeding

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Presentation on theme: "Introduction to Maize Breeding"— Presentation transcript:

1 Introduction to Maize Breeding
Nathan Schnur

2 Overview What is Plant Breeding? Basic Genetics Mendelian Genetics
Principles of Breeding Maize Plant Breeding Methods

3 Plant Breeding What is it? Goals
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

4 Basic Plant Genetics DNA Genes
Primary carries of heritable information Composed of thousands of genes Genes Contain actual heritable information There can be many versions of genes called alleles

5 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 as “Aa” and called heterozygous.

6 Basic Plant Genetics Cont’
Alleles which are heterozygous or homozygous affect the phenotypes and genotypes of plants Phenotype Visual appearance of the plant Genotype Genetic makeup of the plant

7 Mendelian Genetics Gregor Mendel Famous geneticist from 1800’s
His research consisted of selectively breeding garden peas He developed two important laws of genetics Law of Segregation Law of Independent Assortment

8 Mendelian Genetics Example

9 Principles of Breeding Maize
Three Main Principles Inbreeding Hybridization Heterosis

10 Inbreeding Main Goals Increase the homozygosity at all or specific loci in the plant genome Produce a plant which breeds true Produce uniform plants

11 Hybridization of Maize
Hybridization occurs when inbred parents are mated (cross pollinated) Creates a heterozygous individual Benefits Increased heterosis (vigor) in F1 generation

12 Heterosis (Hybrid Vigor)
Heterosis occurs when two homozygous individuals are cross pollinated. This causes all loci to become heterozygous The increased heterozygosity causes increased plant vigor Benefits of Increased Vigor Increased yield Better standability Better germination Overall better plant performance

13 Maize Breeding Methods
Main Methods of Maize Breeding Selfing (Inbreeding) Sib Mating Crossing Test Crossing Backcrossing

14 Selfing Selfing is the process of pollinating a plant with its own pollen Benefits Increased homozygosity Plants which breed true from generation to generation Decreased Segregation Disadvantages Many generations of selfing lead to inbreeding depression

15 Crossing and Test Crossing
Crossing is useful when trying to create 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 general combining ability of an individual Ex. Inbred A is x to a tester which has a diverse selection of genotypes

16 Backcrossing Backcrossing is a method which is used to improve a trait which a plant is deficient in. Method A hybrid plant which has the trait of interest is crossed with one of its parents The offspring are then crossed back to the parent, thus increasing the frequency of the trait.

17 Conclusion Plant breeding is a complicated but beneficial process.
There are many processes involved which are used in the development of new varieties. Remember if it wasn’t for plant breeding we wouldn’t have such high yielding crops

18 References Fehr, W. Principles of Cultivar Development. 1993. Volume 1
Photos Courtesy of

19 Questions Questions?

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