Fiber Properties of First and Second Sympodial Position Cotton Bolls

Understanding the nature of fiber properties variation in cotton canopies is critical for designing production systems that will provide more uniform fiber to textile mills. Our objective was to compare first branch node position bolls (FP1) and second branch node position bolls (FP2) for boll weight and AFIS fiber properties. In 2004 and 2005, a 1-m row section of four replicates of Stoneville 1218 Bt/RR and DPL 555 Bt/RR were hand harvested and sympodial and branch node positions of each boll were recorded. These bolls were weighed, hand-ginned, and fiber was subjected to AFIS analysis. Averaged over both years and both cultivars, FP1 bolls were about 12% heavier than FP2 bolls. When differences occurred between FP1 and FP2 bolls for fiber length, they were due primarily to differences in growth environment during boll development. Assimilate competition appears to have influenced fiber fineness and immature fiber content of FP2 bolls, as FP2 bolls from branches where a boll was present at FP1 had lower fiber fineness and higher immature fiber content than FP2 bolls from branches where the FP1 boll was missing.