Evaluation of different wheat (Triticum aestivum L.) varieties for terminal heat stress on the basis of their morpho-physiological and yield traits

A field experiment was conducted during Rabi 2006–07 and 2007–08, to identify high yielding bread wheat genotypes against terminal heat stress at Student Instructional Farm of Narendra Deva University of Agriculture & Technology, Narendra Nagar (Kumarganj), Faizabad, U.P. India. The treatment consisted of three dates of sowing viz., 10^th December, 25^th December and 10^th January in order to expose the reproductive period of crop to high temperature in field conditions. The genotypes included in the trial were selected on the basis of yield performance and other agronomic characters under normal and late planting conditions. A total fifteen wheat varieties viz., Halna, Raj 3765, NW 1014, PBW 242, HD 2643, HP 1744, NW 2036, PBW 14, NW 1076, Sonalika, HD 2285, HD 2307, K 8962, UP 2425, and HP 1633 were taken for study purpose. The experiment was planned under split plot design with three replications. Statistical analysis of the data revealed that significant differences in plant height, number of tillers/plant, biological yield, total chlorophyll, total soluble protein, total soluble carbohydrate, starch content, membrane injury index in leaves, days to 50% flowering, days to physiological maturity and grain yield were observed for all the genotypes with respect to all dates of sowing. The results indicated that the overall performance of the genotypes was the best with respect to normal sowing. Though all the characters were negatively affected as a result of late sowing yet the genotypes Raj 3765, HD 2285, K 8962, Sonalika and NW 2036 comparatively recorded less reduction in above traits under late sowing. However, higher reduction was found in UP 2425, PBW 343 and HP 1633. Moreover, under 30 days late sowing maximum grain yield was found in NW 2036 followed by Raj 3765, Sonalika and HD 2285 and yield reduction in these varieties ranged from 34 to 39%. However, higher grain yield reduction (51–59%) was observed in HP 1744, PBW 343, UP 2425, HP 1633 and HD 2643.