Watermelon and melon fruit quality: The genotypic and agro-environmental factors implicated

Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] and melon (Cucumis melo L) are popular annual fruit crops of the gourd family Cucurbitaceae, drawing from discrete botanical backgrounds. For both these dessert fruits, quality is what mainly influences consumer behavior and formulates recurring purchasing habits and brand loyalty within reasonable cost. The current review examines the configuration of sensorial quality attributes during development and ripening, as compounded by highly coordinated growth and differentiation processes of various fruit tissues associated with differential expression of stage-specific genes, which affect flavor, aroma, color and texture. The genotypic effect on fruit quality is examined, which in the case of sweet melon is ramified into varietal groups demonstrating differential ripening physiology of climacteric or non climacteric nature with important implications for key sensorial characteristics, especially aroma and texture. Current advances on the role of key agronomic factors influential on quality are discussed, such as grafting and rootstock-scion interaction, controlled water and thermal stress, targeted plant nutrition applications, and the genotype x environment x management interaction. Several cardinal issues warranting further research were identified: the ripening-dependent accumulation and metabolism of carotenoids and the link between carotenoid profiles and volatile fractions, particularly the role of apocarotenoids as substrates in the synthesis of aroma volatile molecules; the coexistence of ethylene-dependent and ethylene-independent regulation of ripening processes in melons; physiological incompatibility in melon graft combinations and its implications for fruit quality; rootstock mediation of watermelon volatile fraction; the role of osmoregulatory molecules as L-citrulline in cell expansion and turgor affecting mesocarp firmness; stage-specific carbohydrate partitioning and metabolism in developing fruit and its potential manipulation through thermal treatments; robust model building on transplanting dates, resilient to genotype x environment interaction. Understanding the concerted effects of the genotypic, physiological and agro-environmental factors visited in the current review is instrumental in the efforts for improving quality and expanding market share for watermelon and melon fruit.