RESPONSES OF WHEAT GENOTYPES TO LATE PLANTING HEAT STRESS

Abstract

An experiment was conducted at the Research farm and laboratory of Crop Physiology and Ecology Department, Hajee Mohammad Danesh Science and Technology University, Dinajpur during November 2009 to May 2010 to study the influence of late planting heat stress on some physiological traits and yield and yield contributing characters of wheat. The experiment was laid out in Split Plot design with three replications. Two sowing dates (November 30 and December 30) were considered as main plot treatment and four wheat genotypes (Bijoy, BAW 1059, BAW 1064, and Sonora) were considered as sub plot treatment. Based on membrane thermostability test, Bijoy, BAW 1059 and BAW 1064) showed less than 50% membrane injury and were considered as heat tolerant (HT) genotypes and Sonora showed more than 50% membrane injury and was considered as heat sensitive genotype (HS). The HT genotypes maintained higher level of proline both in flag leaf and kernel in late planting heat stress condition than that of normal growing condition but HS Sonora produced less quantity of proline in late planting heat stress condition compared to that of normal growing condition. Due to late planting heat stress condition, Sonora exhibited greater decrease in fresh leaf chlorophyll (98%) than that of HT genotypes, Bijoy and BAW 1064 (64%). But another HT genotype BAW 1059 showed greater reduction in flag leaf chlorophyll content as like as HS genotype. Irrespective of growing conditions, dry matter accumulation in ear showed a typical sigmoidal pattern in all genotypes. Due to late planting heat stress, the quantity of dry matter accumulation at peak and duration required to attain peak was higher in HT genotypes than the sensitive one. The heat tolerant genotypes showed longer ear growth duration, higher stem reserve utilization, lesser reduction in grain dry weight per main ear, greater ear number per m?, higher individual grain size, greater grain number per ear, higher relative grain yield and low susceptibility index for grain yield under late planting heat stress condition compared to heat sensitive genotype.The overall result indicated that determination of heat tolerance in wheat genotypes based on increased proline level, greater utilization of stem reserve and lesser reduction of grain dry weight per main stem ear as found in present study were equally comparative with widely used cell membrane thermostability test.