37 Intersubgeneric Hybridization between Paracurcuma and Eucurcuma via Embryo Rescue T. Puangkrit and C. Nontaswatsri Faculty of Agricultural Production Maejo University, Chiang Mai Thailand Keywords: interspecific hybrids, curcuma, pollen viability, pollen germination, embryo culture Abstract Interspecific hybrids between Paracurcuma (Curcuma alismatifolia and C. parviflora) and Eucurcuma (C. angustifolia and C. aurantiaca) subgenera were obtained by embryo rescue. Pre-fertilization barriers were investigated by observing pollen germination on the stigma surface and pollen tube growth in the pistil. A study on fruit setting revealed that the intersubgeneric crosses between Paracurcuma and Eucurcuma subgenera could set fruit only in direct crosses and producing only a few vigorous seeds per fruit. For the crosses that produced embryos, the 14-28 day-after-pollination (DAP) embryos were excised and cultured in vitro. The embryos obtained from 21 DAP fruits showed high shoot regeneration when cultured on MS medium containing 1 mg L -1 BA, 1 mg L -1 GA and 0.1 mg L -1 NAA. The regenerated hybrids between C. alismatifolia and C. aurantiaca, C. alismatifolia and C. angustifolia, and C. parviflora and C. aurantiaca showed intermediate characteristics between the parents. INTRODUCTION In Thailand, the genus Curcuma consists of 30 species which are distributed throughout the country (Larsen and Larsen, 2006). As Curcuma alismatifolia has an attractive and striking inflorescence it has a great potential for commercial cut flowers, pot plants or bedding plants. Although C. alismatifolia has variation in flower characteristics and colours, the new characteristics always required on the flower market. For new characteristics of ornamental plants, interspecific and intergeneric hybridization is the most important procedure for introduction of new genetic variation (Van Tuly, 1997). In breeding ornamental crops, interspecific hybridization is the most important source of genetic variation. Many of the cultivars have originated from complex species crosses which have given rise to a broad range of shapes and colours to plants and flowers (Van Eijk et al., 1991). Although interspecific hybridization has more potential to increase the genetic variability than intraspecific hybridization, production of interspecific hybrids is usually difficult because of cross incompatibility barrier. To overcome the post- fertilization barriers, embryo rescue has been recognized as a useful technique. The aim of our study is to establish a reliable embryo rescue protocol for overcoming intersubgeneric hybridization between Paracurcuma and Eucurcuma subgenera. MATERIALS AND METHODS Plants Materials Curcuma alismatifolia and C. parviflora of Paracurcuma subgenus and C. angustifolia and C. aurantiaca of Eucurcuma subgenus were used. The plants were grown in 12-inches plastic pots under a plastic greenhouse with natural day length and sprayed with pesticide and fungicide every week to control diseases and insects. Reciprocal diallele crosses between the Paracurcuma and Eucurcuma subgenera were conducted. Proc. IS on Orchids and Ornamental Plants Eds.: N. Chomchalow et al. Acta Hort. 1025, ISHS 2014