Back to Contents

FREE FULL TEXT PDF

GENOTYPIC VARIATION FOR DROUGHT TOLERANCE IN COTTON (GOSSYPIUM HIRSUTUM L.): SEED COTTON YIELD RESPONSES

IHSAN ULLAH, MEHBOOB-UR-RAHMAN AND YUSUF ZAFAR

Abstract: Instability of cotton yield is partly caused by drought susceptibility. The purpose of this study was to assess genotypic variation for drought tolerance in a set of cotton germplasm using geometric mean (GM) and drought susceptibility index (DSI) as selection criteria and to determine association of these measures with some productivity and physiological attributes. Thirty-two cotton cultivars were evaluated under well-watered (W₁) and water-limited (W₂) regimes in the field during 2003 and 2004. Drought stress determined by the drought intensity index was more sever in 2004 (0.43) as compared to 2003 (0.21). Genotypic variation was detected for both indices in both the years. Significant negative association of DSI with seed cotton yield, boll number and certain physiological attributes conferring drought tolerance in W₂ (P<0.01) suggested DSI as a useful predictor of drought tolerance in cotton. However, selection based solely on DSI may be misleading as it does not differentiate between potentially drought-tolerant genotypes and those that possessed low overall yield. Substantial variation in GM ranging from 28.9 to 63.9 and 20.7 to 66.7 g was found among the cotton cultivars in 2003 and 2004, respectively. Significant correlation between GM and physio-economic traits under water stress provides support for using GM as a stress tolerance predictor. Non association between DSI and GM suggested that each index is a potential indicator of different biological responses to drought and selection for genotypes with low to moderate DSI and high GM will resulted in combing different traits associated with each index and thus helping to improve tolerance against drought in cotton.

Plant Genomics & Molecular Breeding (PGMB) Labs, National Institute for Biotechnology and Genetic Engineering (NIBGE), P.O. Box 577, Faisalabad, Pakistan
Corresponding Author: Mehboob-ur-Rahman; mehboob_pbd@yahoo.com; Tel: +92-41-2554378