Adv Plant Breeding - Exam 1

what are we doing???????!???

Replications

• how many times each genotype is planted in the field

Genotypes

• amount of genotypes present in the field

Error

• variation that is not attributable to any other listed sources of variation

Degrees of freedom

• number of independent values that can vary in an analysis w/o breaking any constraints

• used to calculate mean square estimate

sum of squares

• dispersion of data points, how much dispersion, not the direction

Diallel design

• randomly select individuals in a population

• cross selected individuals in all combinations

  • all parental crosses

  • reciprocal crosses

  • self parents

• cross all possible combinations

• estimate of general and specific combining ability

Half sibs = general combining ability

Full sibs = specific combining ability

Design 1/Nested system

• randomly select individuals in a population

• designate male and female plants

• each male is crossed to an equal number of females

• a different group of females is used for each male

• variation among single crosses is divided into variation among males and variation among females nested in males (???)

• each cross creates a specific hybrid

Design 2/Factorial Design

• randomly select individuals in a population

• designate male and female parents

• male parents are not crossed to each other and female parents are not crossed to each other

• variation among crosses is divided into variation among males, variation among females, and the interaction of male and female parents

covariance

• average variance between two variables

variance components

• all of your sources of variance inputted into the left side of the anova table

• sort of like independent variables, kinda

• ex- replication, genotypes, year, etc.

hardy Weinberg equilibrium

• when gene and genotypic frequencies do not change from one generation to the next

Reciprocal

• making a cross between f and m plant, then making the inverse

  • so if plant 1 f x plant 2 m, then you cross plant 2 f and plant 1 m to see both

Additive gene effects

• Each gene added enhances the expression of the trait

Dominance Gene Effects

• Heterozygote is more like one parent than the other

Epistatic Gene Effects

• Genes have no affect individually but do when combined

Overdominance Gene Effects

• Each allele has an effect when separate and a greater effect when combined

Broad Sense heritability

• Total genetic variance/phenotypic variance

• more meaningful when all types of genetic variance can be exploited, as in selection among clones of an asexually propagated species or selection among single crosses between inbreds

• Inbred/hybrid cultivars

Narrow sense heritability

• Additive variance/phenotypic variance

• determines the amount of progress that can be made from selecting and recombining the best individuals in a population

• pure line cultivars

Coupling Linkage

• dominant alleles at 2 loci are on one chromosome and the recessive alleles are on another

• offspring more like parents

repulsion linkage

• dominant allele at one locus is on the same chromosome as a recessive allele at another locus

• heterozygous

HW assumptions

1. random mating

2. no artificial selection

3. change by mutation should affect both alleles equally

4. no loss or addition of alleles from outside sources

5. population size is large enough that alleles are not excluded from genetic by genetic drift.

when is it more efficient to make your selection and why?

before pollination because in an open populated area you can choose both male and female plants but after pollination you can only choose the female

general combining ability

• average contribution of an inbred line to the performance of its hybrid

• avg contribution/performance of an inbred in a series of hybrid combinations

specific combining ability

• cross with a specific inbred line to others, not comparing one inbred line to others with another inbred line

• the performance of a combination of a specific inbred in a particular cross

Steps to estimating phenotypic and genetic variances

1. one or more types of progeny are developed

2. progeny are evaluated in a set of environments

3. variance components are estimated from the mean squares in the anova

4. variance components are interpreted in terms of the covariance between relatives

Genetic Gain

• the improvement in the mean performance of a population that is realized with each cycle of selection

1 cycle of selection

• avg 4-5yrs

• develop a segregating population with genotypes for evaluation

• evaluate genotypes

• select superior genotypes

• use superior genotypes as parents

Pedigree method

• select single plants to create plant families

• select individual plants within plant families

Heritability

• the proportion of the total phenotypic variation expressed among genotypes that can be attributed to genetic differences among them

h²

heritability

D

selection differential

σph

phenotypic variance

Parental control (C)

• the relationship between the plant or seed used for identifying superior genotype and the plant or seed used for recombination

the selection unit is the same as the recombination unit and only the female parent is selected

C = ½

when the selection unit is the same as the recombination unit and both parents are selected

C = 1

when the selection unit and the recombination unit are not the same

C = 2

Steps to predicting genetic gain

• list alternatives for the species being considered

  • basically, the type of cultivar you are releasing, hybrids, inbreds, clonally propagated, etc.

• define the resources available

• obtain estimates for the variables in the prediction equation from doing field trials and an analysis of variance table (anova)

• compute predicted genetic gain for variance alternatives

• summarize computed values

speed breeding

• adjusting the lighting of the growing season by reducing the light so you have a shorter season

1 season per yr

• yield evaluation and all breeding operations can be conducted in one year

• referred to as one season

two similar seasons

• two seasons per yr can be used for yield evaluation and breeding operations

• usually occurs in tropical areas

two nonsimilar seasons

• two seasons per yr, one of which can be used for yield evaluation and all other breeding operations and the second of which can be used for all breeding operations, except yield evaluation

• usually occurs when one season can be grown in a temperate climate, and a second season is grown in a greenhouse or tropics winter nursery

three seasons

• three seasons per yr in which the first can be used for yield and all other breeding operations and the second and third can be used for all other breeding operations except yield

• occurs when greenhouse/winter nurseries are used

o²

plot to plot variance

o²_w

variance among plants within a plot

o²_u

environmental variance

gxe expected mean sq formula

o²e + Ro²ge

(error variance + R(gxe))

g expected mean sq formula

o²e+Ro²ge+REo²g

(error variance + R(gxe variance) +R(E)(g variance)