High temperature stress induced changes in physiological, biochemical, hormonal and gene expression patterns in contrasting tomato genotypes

Tomato crops are struggling to cope with the rising heat, posing significant challenges for the growers and the food industry. As global temperatures rise, the resilience of tomatoes is being is put into test. Given the significance of tomatoes in human diet, understanding their response to elevated temperatures is crucial for developing heat-tolerant varieties. We evaluated the effects of high temperature stress (HS) on tomato genotypes—Vellayani Vijay, Kashi Vishesh and Anagha were identified as tolerant through preliminary phenotypic screening, and further characterized by means of physiological, biochemical and yield trait analysis in contrast to the susceptible genotypes, Pusa Rohini, PKM-1 and Arka Vikas. The tolerant genotypes displayed higher pollen viability (96.25% in Vellayani Vijay and 92.32% in Kashi Vishesh), leaf membrane thermostability, antioxidant levels, increased superoxide dismutase activity, and enhanced hormonal regulation in response to stress. Retention of pollen viability under HS via maintaining higher levels of total sugar and flavanols in pollen and enhanced phytohormone concentration were noticed in tolerant genotypes. Gene expression analysis of tolerant genotypes revealed the upregulation of MYB33, HSFA1a, HSFB2a and alpha-amylase transcription factors which are imparting high-temperature stress tolerance. The genotypes identified are potential candidates for high-temperature stress tolerance, and can be applied successfully to programs aimed at improving stress tolerance.