Theory and analysis of partial diallel crosses

This study presents theory and analysis of partial diallel crosses based on Hayman's methods. This genetic design consists or crosses among two parent al groups. It should be used when there are two groups of parents, for exam ple, dent and flint maize inbred lines, and the breeder is not interested i n the assessment of crosses between parents of the same group. Analyses are carried out using data from the parents and their F-1 hybrids allowing a d etailed characterization of the polygenic systems under study and the choic e or parents for hybridization. Diallel analysis allows the estimation of g enetic and non-genetic components of variation and genetic parameters and t o assess the following: genetic variability in each group; genotypic differ ences between parents of distinct groups; ii a parent has a common or a rar e genotype in the group to which it does not belong; ii there is dominance; if dominant genes increase or decrease trait expression (direction of domi nance); average degree of dominance in each group; the relative importance of mean effects of genes and dominance in determining a trait; if, in each group, the allelic genes have the same frequency; if genes are equally freq uent in the two groups; the group with the greatest frequency of favorable genes; the group in which dominant genes are most frequent; the relative nu mber of dominant and recessive genes in each parent; if a parent has a comm on or a rare genotype in the group to which it belongs, and the genotypic d ifferences between parents of the same group. An example with common bean v arieties is considered.