Climacteric and Non-Climacteric Ripening Patterns of Melons with Focus on Carbohydrate Metabolism and Osmotic Potential

This study investigated the differences between ripening patterns of two homozygous lineages of melons, yellow A5, a non-climacteric inodorus, and Charentais C1, a climacteric cantalupensis, regarding the physiological processes related to postharvest quality with a focus on carbohydrate metabolism and osmotic potential. Melons underwent significant changes as maturation progressed from 24 to 34 days after pollination (DAP) for the non-climacteric A5 lineage and from 18 to 28 DAP for the C1 climacteric lineage. The most discriminant variables for the non-climacteric pattern of A5 melons were the higher activity of cell wall hydrolase PME and lower firmness, the higher activity of enzymes involved in carbohydrate metabolism, and sucrose accumulation. In contrast, climacteric C1 melons reach physiological maturity at 24 DAP, do not accumulate sucrose, and enzyme β-GAL plays a key role in cell wall breakdown, contributing to softening and to soluble solids content. A5 melons exhibited greater TSS and soluble solids content, and even though the osmotic potential did not change significantly, the VIP results highlighted it as an important variable for discriminating between its maturation stages. Meanwhile, in the C1 melon, the increase in soluble solids content influences the more negative values of osmotic potential, not by changes in TSS content, and thus may be associated with fruit growth.