Pyramiding novel EMS-generated mutant alleles to improve fiber quality components of elite upland cotton germplasm

Improvement of cotton (Gossypium hirsutum L.) fiber quality, hampered by historical genetic bottlenecks, may benefit from the use of chemical induced mutants that are largely free of linked unfavorable alleles often associated with the use of secondary and tertiary Gossypium gene pools. Two population were developed by intercrossing seven mutant lines with improved fiber quality, one (population R) focused on improving four fiber attributes (micronaire, length, strength and elongation) and the other (population S) to pyramid superior alleles for fiber length. The overall average of both populations was significantly improved for micronaire (lower), fiber length, fiber strength, uniformity and short fiber index compared with parental lines, with 39 lines in population R and 71 in population S showing significant improvement for four or more traits. Multiple lines in these populations showed improvement for all six fiber traits tested. Fiber length of populations S and R was significantly higher than the original (non-mutated) parents (ACALA1517-99 and TAM94L25), local elite germplasm (GA230) and other commercial checks (DeltaPine 393 and Fiber Max 832). As expected, average fiber length of population S was significantly higher by 4.2% than population R. Surprisingly, population S was also significantly better than population R in micronaire, fiber strength, uniformity and short fiber content, adding further support to hypotheses about the complex nature of cotton fiber quantitative trait loci and the corollary that selection for one fiber quality trait may also increase values of other traits. New allele combinations from these mutant lines show promise for improving fiber qualities beyond the levels of current elite varieties.