Stability and transferability assessment of the cotton fiber strength QTL qFS-c7-1 on chromosome A07

Previously we identified a major cotton fiber strength QTL(qFS-c7-1)on chromosome A07 using a multiparent advanced generation intercross(MAGIC)population.To assess the stability and transferability of this QTL and its utility in cotton breeding,we made ten new populations.These populations were developed from crosses between MAGIC recombinant inbred lines,or between cotton cultivars that are different from the MAGIC parents.A total of 2801 F_(2) plants were grown and their fiber quality traits were measured.We also selected a subset of F_(3) seeds from two populations,and grew F_(3) progeny plots to further evaluate the stability of this QTL.Our results showed that the peak of qFS-c7-1 is at 70–72 Mb region.This QTL had a major effect on fiber strength explaining 21.9%phenotypic variance.Its effect on other fiber quality attributes such as micronaire,short fiber content,length and uniformity varied between populations,and no effect on fiber elongation was observed.The QTL effects were stable in the populations analyzed,and in different generations of the same population.The SSR and SNP markers near and within the QTL peak reported herein will assist selecting superior fiber quality traits in breeding,with a recommendation that the parental cotton lines should be analyzed using the seven DNA markers within the QTL peak before fully implementing marker assisted selection in a cotton breeding program.

A New Fuzzless Seed Locus in an Upland Cotton (<i>Gossypium hirsutum</i>L.) Mutant

Various fiber mutants of cotton have been reported since 1920. Two of the best characterized mutants are the naked seed loci, N1N1 and n2n2. Recently, a naked-tufted mutant called 9023 nt4 was developed from the cultivar SC 9023 through chemical mutagenesis. The mutant was tested to determine if it was allelic to either N1, or n2 or was a unique mutant in a new uncharacterized locus. In 1999, one M3 plant from SC 9023 with tufted partially naked seed coat (fuzzless) was identified. In 2004, 2006, and 2007 (Lubbock, TX), 2007 (College Station, TX), and 2011 (Stoneville, MS), the homozygous naked seed mutant was evaluated with the non-mutated wild type parent (SC 9023) in rep-licated trials for agronomic and fiber traits. Crosses between the mutant and the wild type was made at Stoneville, MS in 2009. The F2 of this cross segregated in a 3 fuzzy: 1 fuzzless ratio indicating that the fuzzless trait in the mutant is controlled by a recessive locus. Allelism tests with N1N1, n2n2 and n3n3, lint percent, and fiber trait data indicated that the new locus in the mutant differs from the previously characterized fuzzless seed alleles in that it does not appear to decrease lint percent. We have putatively designated this gene nt4nt4 .