Application of in Vitro Pollination and Fertilization Techniques for Breeding and Genetic Manipulation of Lilium

Abstract

Application of in vitro pollination and fertilization for breeding Possibilities for cross combinations in Lilium are limited by incompatibility and incongruity. Sexual barriers preventing interspecific hybridization have been separated into pre- and post- fertilization barriers. In lily, many studies have dealt with methods for overcoming the stylar pre-fertilization barriers (Ascher and Peloquin, 1966; Van Tuyl et al., 1982). In a comparison of several pollination methods, it was concluded that in lily pre- fertilization barriers can be bypassed using the cut-style technique (Van Tuyl et al., 1988). This method comprises the deposition of pollen on the stylar surface after removing part of the style with stigma and allows pollen to circumvent stylar barriers which normally inhibit pollen tube growth. Once fertilization has occurred, post-fertilization barriers may restrain hybrid embryo growth. In several instances these barriers have been overcome using embryo rescue methods (Asano, 1980). In compatible and interspecific combinations embryos can be excised from immature seeds, starting from about 40 days after pollination, and subsequently cultured and germinated in vitro. Apart from these methods, several additional techniques have been developed for overcoming fertilization barriers in other plant species. Pre-fertilization barriers are bypassed using in vitro pollination and fertilization methods (Zenkteler, 1990), while post-fertilization barriers may be overcome by the culture of ovaries immediately after pollination, or by ovule culture (Guha and Johri, 1966). Aim of our work is to establish an integral system for in vitro pollination, fertilization and embryo rescue and to use this procedure for overcoming both pre- and post- fertilization barriers in wide interspecific Lilium crosses.