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.
