Production of Interspecific Hybrids between Lilium regale and L. rubellum via Ovule Culture.

Lilium regale and L. rubellum were crossed reciprocally to introduce economically and horticulturally desirable traits of L. regale, such as vigorous growth and disease resistance, into L. rubellum.1. In L. regale ×L. rubellum, seeds containing an embryo were obtained with a low frequency (3.3 %) by stigmatic pollination at anthesis, but they did not germinate in soil or in vitro. Seedlings were successfully obtained with frequencies of 5.3 to 6.7 % by applying ovule culture 30 to 60 days after pollination.2. In L. rubellum ×L. regale, the growth of pollen tubes was inhibited in the style after stigmatic pollination at anthesis; hence, no ovule with an embryo was obtained. Growth of pollen tubes was promoted by stigmatic pollination when the pollination was done 2 to 5 days after anthesis. Embryos definitely formed if stigmatic pollination was carried out 5 days after anthesis, but they could not be rescued even when ovule culture was utilized. Cut-style pollination had no effect on production of ovules with an embryo.3. Hybridity of seedlings resulted from L. regale × L. rubellum was confirmed by nuclear rDNA analysis. All of the hybrid plants analyzed were diploid with 2n = 24 chromosomes and showed pollen fertilities of below 3 %. Flower color of the hybrids was light pink. A single hybrid clone produced a double flower.