Changes in Traits Associated with Fruit and Seed Maturation during Fruit Development in Taiwanese Cultivars of Japanese Apricot

Abstract

In this study, we investigated the traits associated with fruit and seed maturation during fruit development of Japanese apricot (Prunus mume Sieb. et Zucc.) fruit in Taiwanese cultivars (‘Ellching’, ‘ST’ and ‘Taiwan’; TCs) and then compared them with the Japanese cultivar ‘Nanko’. In on-tree fruits, ethylene production either remained below the detection limit or at 1 μL kg^–1 h^–1 until mid-June, and there were no differences among cultivars. In collected fruits, an increase in ethylene production or the response to propylene (analog of ethylene) was observed between May 14 and 29, suggesting a shift to system-2 ethylene synthesis at the same time between TCs and ‘Nanko’. The h* value, which decreases with fruit yellowing, showed a similar change in on-tree ‘Ellching’ and ‘Nanko’, but remained high in ‘ST’ and ‘Taiwan’ until the end of June or early July. Fruit firmness showed similar changes in TCs and ‘Nanko’ for both on-tree and collected fruits. The color chart index for the stone surface, seed germination rate and normal seedling rate did not differ significantly from year to year, and the seed maturity date was not significantly different between TCs and ‘Nanko’. The date when the color chart index went over 3 (except for ‘ST’), that when the seed germination rate exceeded 80%, and that of an ethylene production increase in collected fruits were the same for all cultivars. These results suggest that seed maturation and transition to system-2 occurs at the same time in TCs and ‘Nanko’, but that there are differences in the speed of fruit maturation after that time, which may be the cause of the different fruit maturity date of these cultivars.