GENETIC VARIABILITY IN DIFFERENT BIOCHEMICAL TRAITS AND THEIR RELATIONSHIP WITH YIELD AND YIELD PARAMETERS OF COTTON CULTIVARS GROWN UNDER WATER STRESS CONDITIONS

Abstract

Water scarcity is an important factor limiting cotton production worldwide particularly in Pakistan. To identify drought tolerant genotypes, it is vital to understand their genetic variation for different biochemical traits under water limited conditions. In the present study, 24 genotypes of cotton (Gossypium hirsutum L.) were evaluated under two irrigation regimes viz., well watered (W1) and limited water (W2) conditions. Before physiological maturity, cotton leaves were collected and analyzed for nitrate and nitrite reductase activities, and total free amino acids. At maturity, data regarding yield and yield parameters were recorded. Significant reduction in case of all the activities of nitrate and nitrite reductase, and yield parameters was observed under W2 condition in all the genotypes; however, total free amino acids were substantially increased under W2 condition. Correlation between the yield parameters of cotton and biochemical traits was determined. Non-significant correlation between nitrate reductase activity and yield parameters was observed under limited water condition. The genotypes evaluated exhibited decrease in the activities of nitrate and nitrite reductase whereas total free amino acids accumulation was higher under drought conditions that showed comparatively higher yield. This study shows that these biochemical traits were regulated genetically and environmentally in the tested cotton genotypes. It was concluded that these biochemical traits can be used as biochemical markers for screening cotton germplasm for drought tolerance as well as for evolving high yielding drought tolerant varieties of this crop. The findings are useful in bridging plant biochemistry and molecular biology for identifying and selecting genes involved in conferring drought tolerance in cotton.