Ipomoea indica

This species is widely distributed from subtropical to tropical zones. In Japan it is observed on Hatizyo-zima Island, off the southern coast of Kii peninsula, in Sikoku, Kyushu, and Yakushima, and it grows thick on Okinawa. Greatly different from Ipomoea nil, Ipomoea hederacea and Ipomoea purpurea, this species has almost no self-fertilization and so grows vegetatively, extending thick stems and flourishing leaves. The near-absence of self-fertilization is due its to self-incompatible genes.

Thus far the author has collected materials from Hatiizyo-zima Island, Hino-misaki point in Wakayama Prefecture, Muroto-misaki point in Koti Prefecture, Sata-misaki point in Kagoshima Prefecture, Isigaki-zima Island, and Iriomote Island, as well as a strain from Guangzhou city in China. These local varieties were crossed with each other and the hybrids bore seeds and fruits well. When Ipomoea indica is used as a female parent and crossed with species to which it is closely related, the pollen of both Ipomoea nil and Ipomoea purpurea are able to germinate. However, although the pollen tube of either species can enter the styles, the tube cannot elongate more than halfway into the length of the styles. On the other hand, the pollen of Ipomoea hederacea germinated and entered into the style, and the pollen tubes elongated to reach fertilization finally. An interspecific hybrid embryo was recognized after the fifth day of crossings. However, this embryo stopped embyogenesis afterwards, and collapsed. Those experimental results were obtained through the work of Mr. T. Fuzisima (former surname Ooisi).

Ipomoea indica (=Pharbitis congesta)

Slide No. 178-183, 239
Isigakizima Ibarama	Okinawa hontou Komesu	Hatizyozima	Hatizyozima
Satamisaki	Guangzhou city P. R. China	Pollen

References

1. Ooisi, T., Tamaki, S., Yoneda,Y. (1986) Interspecific hybridity in Pharbitis congesta. 70th lecture meeting, Japanese Soc. Breeding (Shizuoka University).
   
2. Yoneda, Y. and Takenaka, Y. (1981) Natural-color illustrated monograph of Japanese morning glory. Hokuryukan.