PHYSIOLOGICAL AND MOLECULAR ASPECTS OF HEAT TOLERANCE IN WHEAT

Abiotic stresses are major constraints to crop production and food security. The situation is critical due to rapid changes in climatic conditions. Heat stress for wheat is one of the most important stresses having a severe impact on plant growth and productivity. Various studies have indicated that average maximum temperature higher than 32 degrees C during the reproductive phase negatively influenced wheat grain yield and average yield loss of up to 30% was reported. To screen or to develop a heat tolerant variety, it is very important to understand the physiological and molecular changes occurring inside the plant under heat stress. Terminal heat stress led to reduction in grain filling duration, thousand grain weight, grain number per head, and final yield. Furthermore, the elevated temperature- driven interruption in the transport of photosynthate from green foliage (source) to anther tissues (sink) leads to high pollen mortality and thereby decreases grain yield. This review provides a current update about heat induced physiological and molecular changes in wheat and the traits suitable for breeding of heat tolerant wheat genotypes. Previous studies conducted in the past have proven that wheat growth and yield were negatively influenced by abnormal temperatures due to physiological disruption. During recent years, many QTLs with significant effect on heat tolerance were identified. Further, heat stress has multilayered impact and, therefore, is very complex to understand completely. A better understanding of plant responses to heat stress has pragmatic implications for wheat breeding.