COTTON SEEDLING AND 1ST-BLOOM PLANT CHARACTERISTICS - RELATIONSHIPS WITH DROUGHT-INFLUENCED BOLL ABSCISSION AND LINT YIELD

Root growth and distribution are important plant adaptations to conditions where limited soil water availability is a major constraint to crop growth and yield. Field studies were conducted to evaluate root characteristics at seedling stage and first bloom of six cotton (Gossypium hirsutum L.) genotypes, and to determine the relationship between root growth parameters and drought-influenced boll abscission and lint yield. Genotypes included in the studies were: Tamcot SP37H (SP37H), Tamcot CD3H (CD3H), TX-CABUCS-2-1-83 (CABUCS), TX-MACAOS-3-84 (MACAOS), Paymaster 303 (PAY303), and Deltapine 41 (DPL41). Significant differences occurred between genotypes for seedling and first-bloom plant measurements, with CD3H and CABUCS having higher levels of seedling vigor, more rapid root system establishment and lower root-to-shoot ratios. Regression analyses indicated a positive association (R2 = 0.47, P < 0.01) between drought-induced boll abscission and root-to-shoot ratio at first bloom, while a negative relationship (R2 = 0.30, P < 0.01) was observed between dryland lint yield and first-bloom root-to-shoot ratio. Results suggest that selection for and incorporation of increased seedling vigor, rapid root-system establishment and lower root-to-shoot ratios into future cotton germplasm could improve drought tolerance and lint yields in regions subjected to limited or poorly distributed rainfall conditions.