GENETIC-ANALYSIS BY USE OF POTATO HAPLOID POPULATIONS

A total of 522 haploids were obtained from six 4x parents. They were used to analyze the genetics of total tuber yield (TTY), average tuber weight (ATW), number of tubers in two hills (NTP), specific gravity (SG), tuber dormancy (TD), vine maturity (VM), after-harvest glucose ratings (GRH), and after-storage glucose ratings (GRS). The analysis of frequency distribution for each trait in the haploid populations provided a means of estimating the main type of gene action, the genetic load for different traits, and the genotypic differences among the parents for these traits. The genetics of the traits was determined by comparing the value of haploid families ("living gametes") to that of their 4x parents. SG and TD represent traits in which additive effects were important. Both additive and nonadditive effects were important in VM, NTP, GRH. TTY, ATW, and GRS were traits in which nonadditive effects were very important. The main type of gene action estimated for TTY and ATW indicates the importance of heterozygosity and epistasis. The reduction in TTY and ATW in haploid populations with respect to the 4x parents was adequately explained as a result of loss of intra- and inter-locus interactions rather than a result of the genetic load of the 4x parents.