Trait based screening and hydrogen peroxide mediated low temperature stress acclimation in wheat: A physio-biochemical, photosynthetic, and metabolomic approach.

Low temperature stress (LTS) is a major abiotic constraint that limits wheat (Triticum aestivum L.) growth, physiological performanceand yield particularly as winter severity increases under climate change . This study evaluated seven wheat cultivars, namely VL-2015, VL-1080, VL-967, VL-2028, VL-953, VL-826, and VL-907, under controlled LTS conditions (12/8°C, day/night) to identify contrasting tolerance levels and to examine the role of exogenous hydrogen peroxide (50 µM H₂O₂) in stress mitigation. Significant cultivar dependent variations were observed across physiological and biochemical traits. An integrated tolerance matrix classified cultivars into four groups, identifying VL-2028 as the most tolerant, with superior photosynthesis, growth and antioxidant capacity coupled with minimal oxidative damage, whereas VL-953 was the most sensitive. Intermediate responses were recorded for moderately tolerant (VL-2015, VL-826, VL-1080) and moderately sensitive (VL-967, VL-907) cultivars, and these groupings were supported by heatmap based clustering. LTS reduced biomass, chlorophyll content, photochemical efficiency Fv/Fm, and ETR, while increasing proline accumulation, malondialdehydeand membrane leakage. Correlation analysis highlighted strong positive associations among growth, RWC and photosynthetic traits, whereas stress indicators showed negative relationships. Antioxidant enzymes such as CAT and APX were closely associated with stress responsive traits. Principal component analysis explained 67.1% of total variance, distinguishing treatments and identifying key contributors to phenotypic variation. Exogenous H₂O₂ (50 µM) effectively alleviated LTS-induced damage by enhancing photosynthetic efficiency and improving stomatal behaviour and chloroplast function. It further strengthened antioxidant defense (SOD, APX, GR), increased GSH and proline accumulation, reduced TBARS and modulated nitrogen assimilation. Overall, these findings highlight the effectiveness of integrative trait-based screening for identifying LT tolerant cultivars and demonstrate the potential of hydrogen peroxide in improving wheat performance under low temperature stress.