Effect of Monoecious Trait on Fruit Shape and Total Soluble Solid Contents of Melon

Abstract

Monoecious melon cultivars have several advantages, such as a low cost and high efficiency of seed production. Melon breeders in Japan, however, have been hesitating to introduce a monoecious trait to melon cultivars for fear of an unsuitable elongated fruit shape and low sugar content. The effect of a monoecious trait on the fruit shape and total soluble solid contents in the Japanese Earl's type melon was studied using: 1) an F 2 population derived from a cross between an andromonoecious 'Earl's Favourite Harukei 3' and a monoecious M09-♀1, and 2) genetically similar background lines of an andromonoecious M03-7 and monoecious lines of M09-♀1 and M09-♀2. The fruit shape of monoecious F 2 plants was clearly longer than that of andromonoecious F 2 plants. As for the total soluble solid contents, monoecious F 2 plants showed clearly lower levels than andromonoecious F 2 plants. However, the distributions of the fruit shape and total soluble solid contents in F 2 plants were wide. F 2 plants with a nearly globular shape or higher total soluble solid content were found in this study. A difference between homozygous and heterozygous plants for a monoecious gene was slightly observed only in the total soluble solid contents and not in other traits such as the fruit shape. There was no difference in the accumulation pattern of total soluble solid contents among the andromonoecious and monoecious lines. Judging from these results, it was suggested that there is possibility of selecting a plant with a globular shape fruit and a higher sugar content through using a large segregating population. We also discussed the availability of monoecious oval/oblong fruit in the food service industry.