FRUITING AND LINT YIELD OF COTTON CULTIVARS UNDER IRRIGATED AND NONIRRIGATED CONDITIONS

Cotton (Gossypium hirsutum L.) production in the United States often is located in semi-arid, nonirrigated regions where poorly distributed or insufficient rainfall limits yields. A 2-year field study was conducted to evaluate six cotton cultivars for flower and boll production, lint yield, and earliness under nonirrigated (dryland) and irrigated treatments, and to determine the effect of water stress on the measured traits. In addition, two commercially available cultivars, which represented the near-extreme range for lint production in the nonirrigated treatment were evaluated for water use efficiency (WUE) in a greenhouse experiment. Cultivars included in the studies were: 'Tamcot CD3H' (CD3H), 'Tamcot SP37H' (SP37H), TX-CABUCS-2-1-83 (CABUCS), TX-MACAOS-3-84 (MACAOS), ' Deltapine 41' (DPL41), and 'Paymaster 303' (PAY303). Cultivars differed significantly for flower and boll production, lint yield, and earliness in crop maturity. CD3H and CABUCS produced significantly greater nonirrigated lint yields (290 and 276 kg ha-1, respectively) compared to SP37H, MACAOS, and PAY303 (211, 206, and 196 kg ha-1, respectively). Nonirrigated yield results indicated differences between CABUCS and CD3H compared to PAY303 could be related to the lack of flower production by PAY303 under soil water deficits, as well as possible escape mechanisms associated with earliness in crop maturity. Average lint yield under irrigation was 310% greater than nonirrigated yield. A greenhouse experiment indicated that CD3H, a relatively drought-tolerant cultivar, had a greater WUE in the nonstress treatment than PAY303, a drought susceptible cultivar. Results demonstrated that genetic variability exists among currently available cotton germplasm sources for flower and boll production, lint yield, earliness and water use efficiency. Among cultivars evaluated in this study, flowering potential appeared to have a major role in drought tolerance. Identification of germplasm with increased drought tolerance could provide breeders with valuable genetic traits and mechanisms for increasing lint yield in areas subject to soil water deficits.