Molecular genetic approaches for enhancing stress tolerance and fruit quality of tomato

Numerous efforts have been made to genetically improve tomato (Solanum lycopersicum) cultivars using various conventional breeding methods, despite severe restrictions to improve some target traits. Molecular approaches such as metabolic genetic engineering and genome editing tools have been able to overcome the restrictions and have achieved the generation of tomatoes with improved, commercially important traits. Due to continuing global climate change and market competition, the molecular approaches have been greatly applied in genetic improvement of agronomic (e.g., biotic and abiotic stress tolerance) and fruit quality (e.g., antioxidant enrichment and prolongation of shelf-life) traits in tomato. In this review, we summarize the results of previous studies that achieved genetic improvement of tomato agronomic and fruit quality traits using the molecular approaches and highlight how the molecular approaches are crucial for the genetic improvement of tomato. In addition, this review describes the functional roles of genes that enhance fruit quality and improve biotic/abiotic stress tolerance; therefore, it will also provide information of the specific genes for further genetic improvement in other tomato cultivars or horticultural crops using the molecular approaches, thus allowing for a time-saving approach to advancing plant biology and the horticultural industry.