LILY BREEDING RESEARCH IN THE NETHERLANDS.

Abstract

At the Centre for Plant Breeding and Reproduction Research (CPRO-DLO) in Wageningen lily breeding research in the Netherlands is concentrated. To this end sources of germplasm (genetic material) are maintained in a lily species and cultivar collection. Research is done on long term storage of this collection by use of low temperature and minimal growth conditions in vitro. Main themes of our breeding research are breeding for resistance (to Fusarium oxysporum, Pythium and virus diseases), breeding for quality traits (flower longevity lily; forcing ability; bulbgrowth of Lilium longiflorum), interspecific hybridization and genetic modification. A molecular marker system using RAPD's is developed in lily to link Fusarium resistance with molecular markers and to construct a genetic map of lily. A system for in vitro pollination, fertilization and embryo rescue has been developed for lily. By combining pollination techniques to overcome prefertilization barriers with in vitro methods to overcome postfertilization barriers, wide interspecific crosses could be made more efficiently. This resulted into a range of new interspecific hybrids, which have led to completely new hybrid groups in the lily assortment. To overcome F1-sterility of interspecific hybrids, owing to lack of chromosome pairing during meiosis, colchicine and oryzalin are used for the induction of mitotic tetraploids. Interspecific crosses at tetraploid level between complex hybrids of L. longiflorum, L. henryi, L. candidum, Asiatic and Oriental hybrid lilies have been made. To develop efficient methods for breeding at tetraploid level, meiotic polyploidization is investigated. Procedures of genetic modification of lily are developed in several directions. At the University of Leiden, for the introduction of virus resistances a transformation technique is in development by particle bombardment on bulb-scale explants. An approach followed by CPRO-DLO is pollen transformation: isolated pollen bombarded with particles coated with DNA containing the kanamycin resistance gene and the B-glucuronidase gene are used to obtain transgenic plants. Other biotechnological techniques are based on protoplast regeneration for either somatic hybridization or direct DNA transfer and microspore culture for the induction of haploidy.