Breeding for High Yield and Fruit Quality in Melon

Melons are cultivated across nearly all continents and major agro-climatic zones, with Asia ranking as the largest contributor, followed by the Americas and Europe. The crop belongs to the Cucurbitaceae family, which includes cucumber, watermelon, squash, and gourds. The topics discussed in this chapter set the direction for future melon breeding, facilitating the development of climate-resilient and stable cultivars with high fruit yield and quality. Understanding the genetic basis of desirable traits is vital for breeding varieties with improved yield, total soluble solids, flavor, aroma, and shelf life. Over the years, researchers have identified numerous quantitative trait loci and candidate genes that are responsible for fruit yield and quality. However, these traits are difficult to breed due to their quantitative inheritance and strong genotype × environment interactions. Given that most melon cultivars are hybrids, breeding for heterosis is a preferred approach. Heterosis is a complex phenomenon and is not always correlated with genetic distance. Researchers who use diallel analysis to estimate heterosis have reported associations between high heterosis and improved fruit yield (number and size) and quality (total soluble solids, flesh firmness, shape, and volatile compounds). Next-generation sequencing technologies and the growing availability of whole-genome assemblies are rapidly increasing our ability to study heterosis.