Production and characterization of wide hybrid plants in the genus Tricyrtis using transgenic plants carrying the gibberellin 2-oxidase gene from Torenia fournieri

Abstract

We have previously produced transgenic plants of the liliaceous ornamental plant Tricyrtis sp. carrying the gibberellin 2-oxidase (GA2ox) gene from Torenia fournieri (TfGA2ox2). One transgenic line (G2-55) was tetraploid (2n=4x=52) and showed a semi-dwarf phenotype and high pollen fertility. In the present study, we examined production of various hybrid plants between G2-55 and non-transgenic Tricyrtis spp. (T. formosana cultivars, T. affinis and T. macranthopsis) via ovule culture. The hybridity of ovule culture-derived plantlets was confirmed by flow cytometry (FCM) and random amplified polymorphic DNA (RAPD) analyses, and totally 21 hybrid plants were obtained from five cross-combinations. Hybrid plants produced flowers, which showed novel morphological characteristics compared with their corresponding parents. Several hybrids carried the transgene TfGA2ox2 from G2-55 and showed semi-dwarf phenotypes. Quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that the degree of dwarfism was correlated with the expression level of TfGA2ox2. Thus, semi-dwarf hybrids carrying TfGA2ox2 were successfully obtained by using G2-55 as one parent. These results indicate that transgenic plants with valuable transgenes are also useful as a cross-breeding material in ornamental plants.