Integrated physiological and genetic data reveal key-traits for heat tolerance in tomato

As global temperatures continue to rise, high summer temperatures severely affect crop growth, reducing yield and quality. The projections of annual declines in crop yield require more in-depth multidisciplinary studies on plant tolerance to abiotic stresses. As tomato is a major crop in the Mediterranean region, its response to heat stress has become important to be addressed in order to identify those traits affecting stress tolerance. In this study, physiological and genomic analyses were performed on two heat-tolerant genotypes (LA3120 and E42) grown at high temperatures during the entire life cycle. The results showed that heat stress diversely affected gas exchange and fluorescence parameters in the two genotypes. In particular, E42 regulated the photosynthetic machinery under heat stress by modulating the electron transport chain, whereas LA3120 was less affected by the applied stress. Genotyping data obtained from a GBS (genotyping by sequencing) analysis were used to explore the genetic variability of both genotypes with the aim of identifying candidate genes that might regulate their stress response. These results further deepen our understanding of the physiological mechanisms activated in response to heat stress and allowed to select key traits that could be used in breeding program to select thermotolerant tomato genotypes.