Interspecific hybrids between Spiraea thunbergii Sieb. ex Blume. and S. japonica L. fil. via ovule culture

Abstract

Reciprocal crosses between Spiraea thunbergii Sieb.ex Blume. and S.japonica L.fil. were carried out, to incorporate red color to S.thunbergii. In vitro germination rate of the stored pollen, germination of pollen grains on the stigma, growth of the pollen tubes, and the development of ovule were investigated, in addition ovule culture was tried to obtain interspecific hybrids. 1. Since the flowering time of both species differed, pollen grains of both species were stored dry at - 30°C, 5°C , and 20°C. Only the pollen of both species stored at - 30°C for 360 days remained viable for crossing. 2. Pollen grains of S.japonica, stored at - 30°C, germinated well on the stigma of S.thunbergii. The pollen tubes elongated rapidly to the ovary as the developing ovules were observed 10 days after pollination. Stored pollens of S.thunbergii germinated well on the stigma of S.japonica, but whether the pollen tubes reached the ovary it was not confirmed. 3. In the interspecific crosses between S.thunbergii(♀) and S.japonica (♂), enlarged ovules excised 16 days after pollination were cultured in 1/2MS medium containing 30 g·liter-1 sucrose and 8 g·lite-1 agar. The resulting plantlets seem to be true hybrids between S.thunbergii and S.japonica, based on several morphological characteristics and the RAPD banding patterns which exhibited the same bands as the parents.