Genetic analysis of fiber length uniformity in upland cotton

Cotton (Gossypium spp.) has been used from antiquity for its seed hairs in the production of yarn and fabric. Fibers vary in length from less than 12.7 mm, which cannot be spun into yarns, to over 30 mm. Variation in fiber lengths and therefore shape of the distribution curves vary across cultivars with more uniform length and distribution desirable to reduce wastage in spinning and to produce better yarn. A diallel analysis and broad sense heritability (H²) study for three measures of fiber length distribution in upland cotton was conducted in 2001 and 2002 in College Station, TX. Four genotypes with long upper half mean length (UHML), 'TAM 94L-25' (PI 631440), 'Fibermax 832' (PI 603955), 'TTU 202' (PI 613162), and 'Acala 1517-99' (PI 612326), and one genotype with short UHML, 'Tamcot CAMD-E' (PI 529633), were crossed and evaluated in a diallel without reciprocals, including the F₂ generation. Fiber length distributions, based on fiber length by weight (FLw), of parents, F1, and F2 generations were evaluated in terms of cross-entropy, kurtosis, and skewness. Tamcot CAMD-E and Acala 1517-99 were identified as potential parents to increase kurtosis and decrease cross-entropy values. The lack of heterosis and the low H² values among these genotypes suggested that additional potential parents for improving FLw distribution patterns need to be evaluated. Additional information also will be mandatory relative to the most desirable fiber length distribution.