Production and characterization of intersectional hybrids between Tricyrtis sect. Brachycyrtis and sect. Hirtae via ovule culture.

The liliaceous perennial plants, Tricyrtis spp., have recently become popular as ornamental plants for pot and garden uses. In order to broaden the variability in plant form, flower form and flower color of Tricyrtis spp., intersectional hybridization was examined between four T. formosana cultivars or T. hirta var. albescens (sect. Hirtae) and T. macranthopsis (sect. Brachycyrtis). After cross-pollination, ovary enlargement was observed only when T. macranthopsis was used as a pollen parent. Ovules with placental tissues were excised from enlarged ovaries and cultured on half-strength MS medium without plant growth regulators. From five cross-combinations, 31 ovule culture-derived plantlets were obtained and 20 of them were confirmed to be intersectional hybrids by flow cytometry and inter-simple sequence repeat analyses. Almost all hybrids grew well and produced flowers 1-2 years after transplantation to the greenhouse. Hybrids had semi-cascade-type shoots, which was intermediate between T. formosana cultivars and T. hirta var. albescens (erect-type shoots) and T. macranthopsis (cascade-type shoots). They produced flowers with novel forms and colors compared with the corresponding parents, and some were horticulturally attractive. The results obtained in the present study indicate the validity of intersectional hybridization via ovule culture for breeding of Tricyrtis spp.