Generation means analysis for fiber elongation in upland cotton

Each bale (218 kg) of upland cotton (Gossypium hirsutum L.) produced in the United States is graded on the basis of several fiber quality traits, namely, strength, upper-half mean length, micronaire, uniformity index, color, and trash content. To promote production of high-quality cotton, producers are given monetary incentives to meet and exceed market standards. Quantitative inheritance of these quality traits have been the primary research focus of many cotton researchers worldwide in an effort to better understand the genetics governing these traits. Increased fiber bundle elongation (ability to stretch without breaking) has not been considered because of its weak but negative correlation with fiber bundle strength. However, current literature suggests that elongation, along with fiber strength, contributes to yarn tenacity. To better understand the genetics of fiber elongation, six distinctive upland families derived from four parental genotypes representative of elongation variation within modern cotton germplasm pools were analyzed using generation means analysis (GMA). Additive gene effects were predominant over dominance gene effects, and nonallelic gene interactions were minimal for elongation. The large numbers of effective factors identified suggests that parents used in the GMA are carrying different genetic materials or loci for elongation. Considerable gains in elongation may be achieved by selectively crossing some of these materials in a pure-line breeding scheme while holding other important fiber traits constant.