The predictive value of estimates of quantitative genetic parameters in breeding of autogamous crops.

Quantitative genetic theory provides models to predict the probability to obtain superior recombinant inbreds in the offspring of a cross between two pure breeding lines. The prediction procedure is prone to various types of error, which possibly invalidate the prediction procedure: 1) stochastic variation, 2) incorrectness of the genetic assumptions, on which the theory is founded, and 3) genotype- environment interaction, in particular intergenotypic competition. The predictive value of the procedure is evaluated by studying the effects of the individual sources of error.Chapter 2 deals with stochastic variation; it establishes the superiority of an alternative estimator of the additive genotypic variance under most practical circumstances. Chapter 2 also presents a method to optimize the population design (number of lines, size of the lines) with respect to the accuracy of the estimator.Chapter 3 investigates various violations of the assumptions, on which the theory is founded, such as non-normality of genotypic effects, heteroscedasticity, and fixed versus random effects.Chapters 4 and 5 investigate the bias on the estimates of the F∞- mean and -variance, respectively, caused by intergenotypic competition