Dissecting the major genetic components underlying cotton lint development

Abstract

Numerous genetic loci and several functionally characterised genes have been linked to determination of lint percentage (lint%), one of the most important cotton yield components, but we still know little about the major genetic components underlying lint%. Here, we first linked the genetic loci containing MYB25-like_At and HD1_At to the fibreless seed trait of SL1-7-1 and found that MYB25-like_At and HD1_At were very lowly expressed in SL1-7-1 ovules during fibre initiation. We then dissected the genetic components involved in determination of lint% using segregating populations derived from crosses of fuzzless mutants and intermediate segregants with different lint%, which not only confirmed the HD1_At locus but identified the HD1_Dt locus as being the major genetic components contributing to fibre initiation and lint%. The segregating populations also allowed us to evaluate the relative contributions of MYB25-like_At, MYB25-like_Dt, HD1_At, and HD1_Dt to lint%. Haplotype analysis of a Upland cotton (Gossypium hirsutum) population with 723 accessions (including 81 fuzzless-seed accessions) showed that lint% of the accessions with the LP allele (higher lint%) at MYB25-like_At, MYB25-like_Dt, or HD1_At was significantly higher than that with the lp allele (lower lint%). The lint% of the Upland cotton accessions with three or four LP alleles at MYB25-like and HD1 was significantly higher than that with two LP alleles. The results prompted us to propose a strategy for breeding high yielding cotton varieties, i.e., pyramiding the LP alleles of MYB25-like and HD1 with new lint% LP alleles without negative impact on seed size and fibre quality.