Department of Crop Botany, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur 1703, Bangladesh.
* Present address: Department of crop Botany, Hajee Mohammad Danesh Science & Technology University, Dinajpur 5200, Bangladesh.
Ten recommended wheat (Triticum aestivum L.) varieties were exposed to two sowing conditions i.e. optimum sowing (November 30) and late sowing (December 30). By late sowing, the varieties were given high temperature stress during reproductive growth phase. The experiment was conducted to determine the relative heat tolerance of the wheat varieties and to evaluate the relative yield performance of heat tolerant and heat sensitive wheat varieties under late seeded conditions. Based on membrane thermostability (MT) test, four varieties (Ananda, Pavon, Aghrani, and Barkat) took maximum heat killing time and were classified as relative heat tolerant, three varieties (Akbar, Kanchan and Protiva) as moderately tolerant and the rest three varieties (Balaka, Sawgat and Sonora) took the shortest heat killing time and considered as heat sensitive. The grain number per ear, 1000 grain weight and main shoot grain weight of tolerant and moderately tolerant varieties showed higher relative performance compared to senitive varieties, But the relative ear number per plant and relative grain yield were found to range low to high in heat tolerant and moderately tolerant varieties. In heat sensitive varieties the relative ear number per plant and relative grain yield were moderate to high. Thus the results suggest in addition to membrane thermostability test, the high relative grain number per ear, 1000 grain weight and main shoot grain weight can be used to determine the heat tolerance of wheat varieties under late seeded warmer conditions.
