2 Overview What is Plant Breeding? Basic Genetics Mendelian Genetics Principles of Breeding MaizePlant 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.GoalsNutritional enhancement, yield improvement, environmental stress tolerance, improved plant structure, or pest and disease resistance
4 Basic Plant Genetics DNA Genes Primary carries of heritable informationComposed of thousands of genesGenesContain actual heritable informationThere can be many versions of genes called alleles
5 Basic Plant Genetics Cont’ There are two alleles for any geneDominant and RecessiveTwo dominant alleles are denoted as “AA” and called homozygous dominantTwo recessive alleles are denoted as “aa” and called homozygous recessiveIf 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 plantsPhenotypeVisual appearance of the plantGenotypeGenetic makeup of the plant
7 Mendelian Genetics Gregor Mendel Famous geneticist from 1800’s His research consisted of selectively breeding garden peasHe developed two important laws of geneticsLaw of SegregationLaw of Independent Assortment
9 Principles of Breeding Maize Three Main PrinciplesInbreedingHybridizationHeterosis
10 InbreedingMain GoalsIncrease the homozygosity at all or specific loci in the plant genomeProduce a plant which breeds trueProduce uniform plants
11 Hybridization of Maize Hybridization occurs when inbred parents are mated (cross pollinated)Creates a heterozygous individualBenefitsIncreased heterosis (vigor) in F1 generation
12 Heterosis (Hybrid Vigor) Heterosis occurs when two homozygous individuals are cross pollinated.This causes all loci to become heterozygousThe increased heterozygosity causes increased plant vigorBenefits of Increased VigorIncreased yieldBetter standabilityBetter germinationOverall better plant performance
13 Maize Breeding Methods Main Methods of Maize BreedingSelfing (Inbreeding)Sib MatingCrossingTest CrossingBackcrossing
14 SelfingSelfing is the process of pollinating a plant with its own pollenBenefitsIncreased homozygosityPlants which breed true from generation to generationDecreased SegregationDisadvantagesMany 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 AaCrossing is used to produce the hybrid seed farmers use to plant in the springTest Crossing is useful to test general combining ability of an individualEx. Inbred A is x to a tester which has a diverse selection of genotypes
16 BackcrossingBackcrossing is a method which is used to improve a trait which a plant is deficient in.MethodA hybrid plant which has the trait of interest is crossed with one of its parentsThe 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