Scientific insights into genetic and physiological response of heat stress in tomato

This study is a systematic review of heat stress-driven changes in tomato morphology and physiology, thermotolerance mechanisms, and crop improvement methods. Tomato is a widely cultivated and utilized crop. However, climate change poses a direct threat to food systems by diminishing the productivity and indirectly limiting the genetic diversity of crops and their wild relatives. Consequently, this limits future options for breeding improved varieties and makes it harder to adapt crops to new challenges. This is particularly concerning as the average global surface temperature is anticipated to increase by 0.3 °C over the next 10 years. Because of their sessile nature, tomato plants have developed complex signalling networks that allow them to detect changes in ambient temperature. However, high-temperature stress can negatively impact the morphology, physiology, and biochemistry of tomato plants at every stage of development, from vegetative to reproductive. This heat stress leads to significant yield losses due to induced changes in crop phenology, growth patterns, sensitivity to pests, shrinkage of the maturity period, and accelerated senescence. Finding novel sources of heat tolerance and identifying the genes involved in those pathways have become significant challenges in the modern era due to global warming. This complexity is further increased by significant genotype-environment and epistatic interactions, making it difficult for breeders to develop and select heat-tolerant genotypes. The current review aims to provide insights into physiological processes related to heat stress, the molecular underpinnings of tomato heat tolerance, germplasm and quantitative trait loci governing tolerance, and the different crop improvement techniques utilized in breeding for heat tolerance of tomato. Deciphering various physiological processes and the development of different breeding techniques are critical to assist in the evolution of thermotolerant tomato cultivars.