Genomics of Sex Expression – An Important Factor in Melon Breeding

In Cucurbitaceae, sex expression exhibits significant diversity and represents a crucial trait in breeding due to its direct association with yield, fruit quality, and fruit morphology. Sex expression in Cucurbitaceae is regulated by hormonal balance, primarily through localized ethylene levels, which are determined by both genetic and environmental factors. In contrast to other cucurbit crops such as cucumber and bitter gourd, which are typically harvested as immature fruits, melons are primarily harvested as mature fruits. As a result, the strategies for applying sex expression in breeding differ for melons. In melon, to date, several genes have been cloned as sex determination genes, and the mechanisms of sex determination, primarily focusing on genes involved in ethylene biosynthesis, are gradually being elucidated. These findings hold promise for application in breeding programs. This chapter examines the genetic determinants of sex expression, highlighting recent progress in understanding the mechanisms of sex expression in melon and their potential utilization in breeding strategies.