Effect of self-generation for initial selection on breeding better cotton

Abstract

In a hypothetic population of cotton, Gossypium hirsutum L., segregating for 26 independent alleles, individuals with all desired alleles are more abundant in early generations (F2 or F3), but a high proportion of allelic loci are homozygous in late generations (F4 or F5). This dichotomy needs to be considered to establish a successful breeding strategy. In this study, we examined the effectiveness of two pedigree procedures in cotton with their key difference in the self-generations used for single plant selection. The conventional procedure started single plant selection at F3 by hand-harvest of a 30-boll sample from individual plants, then in the follow-up generation, only those derived lines retained after culling for lint percent and High Volume Instrument (HVI) fibre quality entered the progeny row test. The alternative procedure used single-locule descent for pass-through of early generations; at F5, only two mature bolls were harvested from selected individual plants, and their derived lines were grown and culled in single-row plot nursery by visual assessment, and by lint percent and HVI fibre properties measured from a 30-boll sample. When each procedure was used to develop elite inbred lines in two populations derived from outstanding cotton lines, both procedures were effective at identifying elite lines from the populations. The alternative procedure captured more elites than the conventional one, based on the retention rate against the initial population size, particularly in one population, and required less resources in the process. Thus, the alternative procedure with delayed single plant selection is effective and efficient for cotton improvement.