Climate resilient vegetables: Breeding for heat stress tolerance

Abstract

Global warming is becoming a serious threat to vegetable production as the temperature is rising above the optimal limits for most of the vegetable crops. Heat stress affects seed germination, vegetative and reproductive growth of the plants and leads to many morphological and physiological injuries in vegetables. Physiological processes such as photosynthesis, respiration, and membrane stability are mainly disturbed due to the oxidative stress created by excessive generation of Reactive Oxygen Species (ROS). In response to heat stress, plants have evolved different avoidance and tolerance-based mechanisms. The avoidance mechanisms which plants exhibit in conditions of heat stress are both morphological and physiological, which includes leaf orientation change, leaf pubescence, early maturing and membrane lipid alteration. The tolerance mechanisms involve osmoprotectants, antioxidant molecules, hormonal changes, transcription factors etc. Traditional breeding approaches including selection and hybridization have contributed significantly in developing heat tolerant cultivars, but the complexity of the trait and strong interactions between genotype and environment limits the progress. Genomic tools such as marker assisted selection, QTL (Quantitative Trait Loci) mapping, GWAS (Genome Wide Association Studies), recombinant DNA technology and genome editing are currently being used for the development of heat tolerant cultivars. Besides, advanced phenotyping platforms help breeders identify heat tolerant genotypes more accurately and faster by linking physiological traits with genetic data.