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

Reciprocal crosses between Spiraea thunbergii Sieb.ex Blurne.and S.japonica L.fil. were carried out, to incorporate red color to S.thunbergii. In vitr o germination rate of the stored pollen, germination of pollen grains on th e stigma, growth of the pollen tubes, and the development of ovule were inv estigated, in addition ovule culture was tried to obtain interspecific hybr ids. 1. Since the flowering time of both species differed, pollen grains of both species were stored dry at -30 degreesC, 5 degreesC, and 20 degreesC. Only the pollen of both species stored at -30 degreesC for 360 days remained vi able for crossing. 2. Pollen grains of S.japonica, stored at -30 degreesC, 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 p ollens of S.thunbergii germinated well on the stigma of S.japonica, but whe ther the pollen tubes reached the ovary it was not confirmed. 3. In the interspecific crosses between S.thunbergii(female) and S.japonica (male), enlarged ovules excised 16 days after pollination were cultured in 1/2MS medium containing 30 g (.) liter(-1) sucrose and 8 g (.) lite(-1) ag ar. The resulting plantlets seem to be true hybrids between S.thunbergii an d S.japonica., based on several morphological characteristics and the RAPID banding patterns which exhibited the same bands as the parents.