Responses of tomato to concurrent abiotic stresses, high temperature and drought: A review

Abstract

Tomato production is increasingly threatened by the growing occurrence and severity of combined drought and high-temperature stress. Although the individual effects of high temperature and drought stress on tomato growth, physiology, and productivity have been widely investigated, their combined occurrence exerts more severe and complex adverse effects on plant performance and yield. Therefore, a comprehensive understanding of their interactive impacts is essential for developing effective management strategies and breeding climate-resilient tomato cultivars. Here, we review the current understanding of the physiological, biochemical and molecular adaptive responses of tomato to combined drought and heat stresses. Co-occurring stresses during critical growth stages significantly impair photosynthesis through stomatal closure, reduced mesophyll conductance, chlorophyll degradation and disruption of photosystem II efficiency. Combined stress elevates reactive oxygen species (ROS), resulting in oxidative damage to cellular macromolecules despite the activation of antioxidant defences. Reproductive processes, such as pollen viability, fertilisation and fruit set, are highly vulnerable to combined stress. At the molecular level, stress-responsive genes and antioxidant enzymes are differentially regulated, indicating complex interactions among drought and heat signalling pathways. In addition to crop management strategies that alleviate the adverse effects of stresses to some extent, crop improvement strategies such as breeding for stress-tolerant cultivars, integrating omics insights and applying gene-editing tools offer promising avenues for enhancing tolerance to combined stresses. Deciphering integrative mechanisms governing combined drought-heat responses is pivotal for designing climate-adaptive tomato cultivars and sustaining production under global climate change.