QTL Analysis of Fiber Quality Traits In Interconnected Cotton Populations.

In addition to high yields, improving the quality of cotton (Gossypium hirsutum L.) fiber has become an increasingly important component of the value of cotton, especially for marketing in the international trade.  Because of the need to improve cotton fiber quality, the present study was designed to identify sources of variation for fiber quality in F₂ populations.  These populations were genotyped with SSR markers, and the genotypic and phenotypic information combined to detect quantitative trait loci.  Seven Upland cotton cultivars (TM1, 7235, SG125, Fibermax832, CAMD-E, MD51, and DPL50) were selected to represent a range in fiber quality and productivity.  They were crossed in a diallel design without reciprocals to obtain 21 F₁ crosses, which were used to develop F₂ populations.  In 2004, 200 plants from each of the 21 F₂ populations along with their respective parents were measured to obtain yield and fiber data.  In addition, leaf tissue was collected from individual F₂ and parent plants for SSR marker analysis.  Results of the phenotypic data show that the F₂ populations significantly differ for 2.5% span length, micronaire, and elongation.  For SSR analysis, bulked segregant analysis was used to bulk DNA of the ten high and low plants in each F₂ population based fiber strength and length.  Different alleles amplified in these high and low bulks for strength and length in these populations.  These preliminary results indicate that there is variation for several cotton fiber measurements among these F₂ populations that will be useful in identifying regions of the cotton genome specific for fiber quality traits.