| Summary: | 碩士 === 國立中興大學 === 園藝學系所 === 107 === Mulberry (Morus spp.) populations in Taiwan are mostly dioecious. Natural pollination in mulberry primarily involves interspecific hybridization; however, compatibility between parental species remains unclear. This study aimed to estimate the interspecific compatibility of important mulberry cultivars in Taiwan. In this study, M. atropurpurea (‘Shiaying’ and ‘Taisang No. 19’) and M. laevigata (‘Elongated Fruit No. 1’) were used as female parents, whereas M. alba (‘Kairyonezumigaeshi’) and M. latifolia (‘Mizumihaiteku’) were used as male parents for six crossing combinations by hand-pollintion. Pollen viability in vivo as well as pollen–pistil interaction among crossing combinations were firstly examined. Development of berries (fruits), fruitlets, and seeds were then measured, while embryo development was observed by paraffin-sectioning. Fruit traits, seed setting per fruitlet, seed type, and seed germination percentage were measured after fruit ripening. Finally, the F1 progeny were identified using inter-simple sequence repeat (ISSR) analysis.
All pollen tubes elongated to the ovary at 48 h after pollination among crossing combinations. We suggested that six interspecific crossing combinations were compatible and without gametophytic incompatibility; thus, there was no pre-fertilization barrier.
Although the growth trends of fresh weight of berries and fruitlets were similar among all crossing combinations, it differed among varieties. Both the seedless and seeded fruitlets developed within the same berry, which represented facultative parthenocarpy. Embryo development observed in seeded fruitlets showed proembryo formation at 5-7 days after pollination. Subsequently, the endosperm cell developed at 11-12 days after pollination; the cotyledon-shaped embryo was observed at 15-16 days after pollination. The unfertilized ovules that failed to increase in size may have been because of parthenocarpy. The abortion of the developing ovules and remaining endosperm may only be due to stenospermocarpy and the presence of a post-fertilization barrier. Endocarp began to harden during 7-27 days after pollination.
After hand-pollination, three crossing combinations had a high percentage of fruit set and could produce mature fruits. Empty seeds may have resulted from a lack of fertilization, while semi-solid seeds, which could not germinate, may have resulted from the post-fertilization barrier and stenospermocarpy. Seeds with normally developed embryo and endosperm were able to germinate after sowing. Based on the ISSR analysis using primer UBC807 and UBC835, the progeny from ‘Shiaying’ ╳ ‘Kairyonezumigaeshi’ and ‘Taisang No. 19’ ╳ ‘Kairyonezumigaeshi’ had paternal-specific bands, which confirmed it to be a double-fertilization hybrid. However, the selection of desired traits needs to be further studied.
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