Hybridization Between the Canary Melon and a Vietnamese Non-sweet Melon Cultivar Aiming to Improve the Growth Performance and Fruit Quality in Melon ( Cucumis melo L.)

Canary melon has been widely consumed as a dessert fruit due to its fragrance, sweetness, and flavorful taste. However, the cultivation of this cultivar has been challenged in Vietnam because of its weak growth performance and high susceptibility to local pathogens. In this study, we aim to generate the hybrid melon lines between the Canary melon and a local non-sweet melon that are expected to produce good quality fruits as well as to show better growth performance in the local cultivation conditions. Two crossing pairs including (1) MS hybrid (♂ non-sweet melon × ♀ Canary melon) and (2) MN-S hybrid (♂ Canary melon × ♀ non-sweet melon) were carried out and two hybrid lines were subsequently obtained. Next, different phenotypic and physiological parameters such as stem length, stem diameter, 10th leaf diameter, fruit size, fruit weight, and fruit sweetness (pH, °Brix, and soluble sugar contents) were examined and compared between the parental lines (Canary melon and non-sweet melon) and the hybrid lines (MS and MN-S). The results showed that the stem length and fruit size and weight of MS and MN-S hybrids were higher than those of Canary melon. Basically, the content of sugars (sucrose, glucose, and fructose) is a primary and important factor in determining the sweetness of the melon. The pH, °Brix, sucrose and glucose contents of MS hybrid and Canary melon fruits were higher in comparison to MN-S and non-sweet melon fruits. Accordingly, the transcript levels of different sugar metabolism-related genes including SUCROSE SYNTHASE 1 ( SUS1 ), SUS2 , UDPGLC EPIMERASE 3 ( UGE3 ), and SUCROSE-P SYNTHASE 2 ( SPS2 ) were examined in all studied lines. In the fruits, the expression levels of these genes were found to be highest in the Canary melon, average in the MS hybrid, and relatively low in the MN-S hybrid and non-sweet melons. Taken together, the heterosis in terms of plant and fruit size was obviously observed in this crossing approach. The relatively high fruit sweetness in the MS hybrid (the mother is Canary melon) also implies that the choice of the mother for crossing is very important since it can determine the fruit quality of the offspring.