Growth and yield response of wheat cultivars to hyper thermal stress

Eight promising wheat cultivars involving traditional tall and modern semi-tall were grown under normal ambient and hyper thermal (+ 3.0°C) conditions to examine the growth and yield response of different wheat cultivars to hyper thermal stress. In general hyper thermal stress enhanced the stature of plant by increasing the length of leaf, internode and culm, and average leaf area mainly by increasing the area of flag leaf. It however, caused reduction in several growth and yield parameters i.e. number of tillers per m², leaf area index, leaf area/tiller, leaf width, leaf weight ratio, number of grains/spike, 1000 grain weight, biological and economic yields, harvest index, total and grain weight/tiller and grain spike ratio to varying extent in almost all the cultivars. As compared to reproductive growth, vegetative growth showed greater stability to hyper thermal stress. High temperature also hastened internode elongation, spike primordia initiation, flowering and finally maturity to varying degrees in all the cultivars. Among the cultivars tested, C 306 and Kundan which are recommended for dry areas and HD 2285 and HD 2643 identified for late sown condition showed greater stability in growth and yield attributes and eventually recorded higher grain yield than those of others under warmer condition.