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High temperature during reproductive stage of winter crops causes sterility of pollen grains and reduced yield. It is essential to find the genotypes with higher pollen viability, as it is most sensitive to temperature extremes. A field study was conducted with wheat (Triticum aestivum L.) genotypes to understand the effect of high temperature on pollen viability and grain yield for 2 years under timely (TS) and late sown (LS) conditions. A strong correlation was observed between higher pollen viability and higher grain yield under heat stress condition. Genotypes like K7903, HD2932, WH730 and RAJ3765 showed higher pollen viability, whereas DBW17, HUW468, RAJ4014 and UP2425 had lower pollen viability under LS condition. Further, the quantification of antioxidant enzymes activity mainly, Super oxide dismutase (SOD), Catalase (CAT), Peroxidase (POD) and Glutathione peroxidase (GPX) has showed significant variation among study genotypes. Thus, the identified high pollen viability genotypes can serve as a potential source for trait based breeding under heat stress in wheat. The present study is a first of its kind to assess more number of wheat genotypes for pollen viability and antioxidants activity under field condition. It also confirms that pollen viability can be used as a potential trait to screen genotypes for heat stress tolerance in wheat.

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Drought and heat are the key environmental stressors significantly decreasing wheat productivity (86 and 69%, respectively) and weakening food security in the major wheat growing regions worldwide. Wheat crops have regularly experienced combined (Heat+Drought) stress in the field and the joint effects are more detrimental to wheat growth than the effects of each stress separately.Drought and heat stress have shown synergistic, antagonistic, or hypo-additive impacts on growth, grain filling, and yield parameters when combined. In order to escape and/or tolerate these unfavorable environmental conditions, wheat has developed advancedresponses at various levels. This review explores how physiological, morphological, biochemical and molecular traits work together to provide tolerance to coupled stresses. Importance of specific traits such as, canopy temperature, assimilate partitioning and water use efficiency along with reproductive traitswhich provide tolerance against these combined stressors has also been explained. This review also highlighted the potential of altered agronomic practices, application of micronutrients, biopriming of seeds (endophytes) against abiotic stresses. Further emphasize has been given to promising novel technologies like, genome editing (CRISPR),identification of novel QTL's and alleles to improve both heat and drought tolerance for sustainable wheat production.

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