Growth promotion of interspecific hybrid embryos between Cucumis anguria and Melon (C. melo) by fruit heating

Abstract

Wild species of the genus Cucumis, such as C. anguria, are resistant to various melon (C. melo) diseases such as Fusarium wilt race 1.2 and are anticipated as genetic resources of melon. However, in the interspecific crosses between C. anguria and melon, the abortion of the embryos was observed in the early growth stage and could not be regenerated even when cultured. Therefore, for embryo rescue, it is necessary to promote embryo growth during abortion occurrence. This study investigated the effects of fruit heating on embryo growth in interspecific hybrids of C. anguria and melon. In the heating device, the minimum night temperature around the fruit was maintained above 21.5 °C. The ovule grain area of C. anguria × MR-1 with fruit heating was significantly enlarged compared to that without fruit-heating. It was also significantly enlarged compared with the ovule grain area of C. anguria self-pollination. Although, in C. anguria × MR-1 without fruit-heating, no embryo was observed until 10 days after pollination (DAP), and pre-embryos were observed at 13 DAP. Conversely, in C. anguria × MR-1 with fruit-heating, pre-embryos were even observed at 10 DAP. These results suggest that the possibility of embryo or ovule culture regeneration has increased due to embryo growth promotion.