Late planting heat stress on ear growth physiology of wheat

Grain yield of wheat in Bangladesh is low as it is severely affected by various biotic and abiotic stresses, among them; heat stress (terminal high temperature) is one of the major causes of lower wheat yield in Bangladesh. This paper focuses on the assessment and performance of some wheat genotypes under different temperature regimes and to fix up of suitable potential lines, for high temperature-stressed environments. Four wheat genotypes (Bijoy, BAW 1059, BAW 1064, and Sonora) were tested under normal and heat stress condition to study the influence of late planting heat stress on ear growth physiology of wheat. In membrane thermostability (MT) 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 reverse result. In late planting heat stress condition, Sonora exhibited greater decrease in flag leaf chlorophyll (98%) than that of HT genotypes, Bijoy and BAW 1064 (64%) and BAW 1059 (70%). Due to late planting heat stress, the quantity of ear dry matter accumulation at peak and duration required to attain peak was higher in HT genotypes than the sensitive one. The HT genotypes showed longer ear growth duration, higher stem reserve utilization, higher relative grain yield and low heat susceptibility index (HSI) for grain yield under late planting heat stress condition compared to HS genotype.