Diallel Analysis of Fiber Quality Traits with an Emphasis on Elongation in Upland Cotton

The upland cotton (Gossypium hirsutum L.) industry in the United States has shifted from a domestic market to an export-based market that mandates simultaneous improvements of yield and various fiber traits to maintain competitiveness. Fiber elongation (ability to stretch before breaking) is one of the key fiber parameters in determining yarn quality. It is a trait that is largely understudied due to an absence of monetary incentives for growers to produce high-elongation cotton fibers. Five upland genotypes were selected as representatives of major upland cotton germplasm pools in the United States. These genotypes and their 10 F-1 progenies were grown in College Station, TX, in 2010 and 2011, and fiber properties were tested in a diallel analysis. Overall, general combining ability was greater than specific combining ability for fiber elongation, suggesting the predominance of additive gene action. Two parental lines, cultivar PSC 355 and germplasm line Dever Line 8, were identified as good combiners for fiber elongation when fibers were measured with the High Volume Instrument (HVI) and the Stelometer. A highly significant negative correlation was observed between fiber upper-half mean length and elongation, whereas a slight negative correlation was observed for elongation and strength. Stelometer and HVI readings for elongation were correlated with r value of 0.69.