RESUMO
Thermal stress is a major abiotic stress in wheat and is highly complex in mechanism. A large area in northwestern plain zones (NWPZ), which is the wheat bowl of India is affected by heat stress. Climate change also causes an abrupt increase in temperature at different growth stages of wheat. Thus, wiser selection of stress tolerant varieties is an important strategy to combat the climate change effect. The present study aims for physiological and biochemical screening of timely sown NWPZ wheat varieties (WB2, HD3086, DBW88, DPW621-50, DBW17, HD2967 and PBW550) of India for their thermal stress tolerance along with heat tolerant (RAJ3765) and susceptible checks (RAJ4014) at seedling stage. The experiment was conducted in completely randomized design under controlled laboratory condition and heat stress was induced at 37 °C at seedling stage. Later different physio-biochemical traits were studied in both control and stress seedlings. All traits exhibited significant variations among genotypes under heat stress condition. Root and shoot weight, relative water content, chlorophyll content index and chlorophyll fluorescence reduced significantly, whereas membrane leakage, osmotic potential, catalase, ascorbate peroxidase, guaiacol peroxidase, malondialdehyde content and proline content were increased in stress plants. A tolerance matrix was prepared based on stress response of the genotypes for each trait and a final tolerance score was given to each genotype. Based on this tolerance matrix, DBW88 and PBW550 were identified as tolerant, DPW621-50, DBW17 and HD2967 as moderately susceptible and HD3086 and WB2 as susceptible to heat stress. Earlier studies parade that seedling level stress tolerance has high correlation with adult level stress tolerance under field condition in wheat. Hence, this study helps in wiser selection of varieties for sowing in NWPZ based on weather forecast of the location for creating varietal mosaic in context of climate change.
RESUMO
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 2years 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.