The underlying molecular mechanisms of external factors influencing fruit coloration in fruit trees

Fruit color is a key target for both growers and breeders because consumers prefer brightly colored fruits with ripeness, flavor, taste, and sweetness. Significant progress has been made in the study of fruit color development and regulation in the near past, however, the underlying molecular mechanism has not been thoroughly scrutinized from the perspectives of external factors influencing genetic factors, and transcription of the genes. In this article, we summed up the research on how external factors affect the molecular regulatory machinery resulting in fruit color development in different fruit plant species. Furthermore, the roles of light, temperature, drought stress, nutrients, and exogenous hormonal application in fruit color regulation are thoroughly discussed. The genetic and transcription factors that control pigment especially anthocyanin formation under the influence of external factors are reviewed. The purpose of this review is to shed light on external factors affecting the underlying molecular mechanisms of fruit color regulation which will be extremely useful in the breeding of high-quality colored fruit varieties.