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Analysis of Cotton Genotypic Differences for Plant Responses to Drought

Marc Jean Lacape, Daniel J.M. Annerose, Eric Jallas and Jacques Wery


The objective of this study was to analyze, through different frameworks, the effects of a post-floral drought on growth, development and yield of cotton genotypes grown under field conditions. Three experiments were conducted under subsahelian conditions in Senegal. Five varieties were compared under different irrigation treatments differentiated after flowering. Despite large differences of soil water content between years and irrigation treatments, the fraction of transpirable soil water, FTSW, was closely related to the predawn leaf water potential measured on the same day. Genotypic differences for plant water status variables were found on some days, but they were frequently associated with genotypic differences in FTSW. The relationships between these variables and FTSW, over two years of measurements and contrasting soil water profiles, were adjusted to typical logistic functions, previously used in other species. Significant genotypic differences were found in the relationships of RWC, CWSI and ET/ETm with FTSW. Reductions of leaf area index and intercepted radiation by soil water deficit resulted from combined effects on the rate of leaf emergence out of the shoot tip, on individual leaf area and on the duration of the period of leaf production. Despite significant differences between cultivars in the rate of development as well as in the individual leaf size, the 5 cultivars had the same LAI. Water deficit induced an earlier termination of plant development (cutout, when NAWF = 5) that reduced the effective flowering period. The effects of irrigation treatments on seed cotton yield varied from year to year, as rainfall pattern in the pre-flowering period differed. The overall variation in yield between years and experiments was accounted for by the length of the reproductive period and by the average FTSW during this period. The different frameworks of analysis of the seed cotton yield (number of bolls and average boll weight, total biomass and harvest index), allowed a common analysis of plant responses to drought as observed under the various years, irrigation conditions, and for the various genotypes. Duration of the flowering period and harvest index were the most efficient variables to explain genotypic differences in yield under the various conditions of water supply.

Reprinted from Proceedings of the 1998 Beltwide Cotton Conferences pp. 1383 - 1392
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998