SCREENING OF BREAD WHEAT GENOTYPES FOR DROUGHT TOLERANCE
Department of Crop Physiology, Sindh Agriculture University, Tandojam, Pakistan
Six (NIA-AA-10, NIA-AA-11, NIA-MK-122, NIA-MK-134, Khirman and Chakwal) bread wheat (Triticum aestivum L.) genotypes were screened out for their drought tolerance through physiological approach under water deficit environment. Two experiments were conducted for this study. Expt. 1 was conducted in pot-house and Expt. 2 was conducted in the field of Nuclear Institute of Agriculture (NIA) Tandojam, Pakistan. Both experiments were identical in drought treatments (Control and Terminal Drought (TD)), genotypes and replications (03). Expt. 1 was conducted to determine the effect of TD on nitrate reductase activity, osmotic potential and the contents of proline, glycine-betaine, total sugar and total chlorophyll. Whereas Expt. 2 was conducted up to maturity, mainly to determine the effect of terminal drought on height and grain yield traits. Generally, in both the experiments there was significant effect of terminal drought, genotypes and the interaction of terminal drought x genotypes for almost all recorded plant traits. The results obtained from Expt. 1 indicated that over all six genotypes, the wheat plants grown in TD treatment showed significantly higher values of proline, glycine-betaine, and total sugar contents and lower values for total chlorophyll content, nitrate reductase activity and osmotic potential. In the control as well as water deficit treatment, the genotypes Khirman, Chakwal, and NIA-AA-10 displayed higher values for proline, glycine betaine, total sugar contents, nitrate reductase activity and osmtotic potential as compared to the other three tested bread wheat genotypes. Similarly in the Expt. 2 plants grown in TD treatment were significantly shorter in height and had fewer spikes; hence they gave lower grain yield per plant over control. Performance of above three genotypes (Khirman, Chakwal, and NIA-AA-10) also remained outstanding in the Expt.2. These three genotypes were also able to produce taller plants with more spikes and hence gave higher grain weight per plant in normal as well as in terminal drought environment.