Biochemical analyses-based profiling of doubled haploids derived from synthetic hexaploid wheat (Triticum aestivum L.) under juvenile and terminal heat stress conditions

Abstract

Wheat (Triticum aestivum L.) thrives best in cool climates and is recommended to be sown during the first fortnight of November at a temperature range between 20-26 oC in northwestern plain zones (NWPZ). However, being a thermo-sensitive crop, high temperature is one of the limiting factors for growth and productivity. This pressing challenge underscores the need to deploy heat-resilient wheat genotypes capable of maintaining physiological and biochemical stability under rising temperature regimes. Thus, an experiment was conducted to investigate the impact of elevated temperatures on introgression lines derived from three different crosses, viz., SHW14102 x BWL4444, SHW14102 x BWL3531, and SHW3761 x BWL4444 sown for three distinct sowing dates for the years 2020-21 and 2021-2022. This population was developed using synthetics and was exposed to high temperatures by shifting the normal date (first fortnight of November) of sowing to early dates (second fortnight of October), and late dates (second fortnight of December) thus ensuring heat stress to the crop at seedling stage and grain-filling stage respectively to assess the biochemical and yield/yield contributing traits. Cluster analysis was performed to identify superior heat stress-tolerant lines. In line with this analysis, 15 doubled haploid lines exhibiting high grain weight out of the 100 evaluated lines were selected for further detailed biochemical estimations. Exposure to elevated heat stress resulted in a progressive increase in membrane lipid peroxidation, as indicated by higher malondialdehyde (MDA) content, along with a notable accumulation of hydrogen peroxide (H₂O₂) in the leaf tissues. Proline content, a key osmoprotectant, also varied significantly among the introgression lines, reflecting differential physiological responses to heat-induced oxidative stress. Overall, H2O2 and MDA accumulated to substantially higher levels in leaf tissues under elevated temperatures, underscoring the intensified oxidative damage and membrane instability associated with prolonged heat stress. Therefore, in the present study, the lines DH45, DH79, DH121, DH63, and DH31 consistently exhibited favorable biochemical traits under heat stress, suggesting strong potential for breeding heat-resilient wheat genotypes with improved stress tolerance and yield stability across variable sowing conditions.