INTERSPECIFIC HYBRIDIZATION IN THE TRIBE GENISTEAE USING IN VITRO EMBRYO RESCUE

Since 2005, the Eurogeni GIE , in cooperation with joint research unit IRHS (Institut de Recherche en Horticulture et Semences), has developed a breeding program within the tribe Genisteae (Fabaceae) using interspecific hybridization with the aim to obtain innovative hybrids with novel flower colors. To overcome post-zygotic incompatibility and embryo abortion in vitro embryo rescue was performed. In total 13 interspecific cross combinations between Cytisus scoparius, Cytisus supinus and Cytisus × boskoopii as female parents and Cytisus purpureus as male parent were performed. Immature fruits were collected 4 to 6 days after pollination and ovules were initiated in vitro. Germination of the ovules occurred 1 to 9 months later. In total, 38 F1 seedlings were obtained, with at least one seedling for each cross combination. Only 29 F₁ seedlings survived until rooting in vitro and 22 F₁ seedlings are already acclimatized in the greenhouse. Those seedlings were determined as hybrids through molecular ISSR markers and flow cytometric measurements. Based on these genome size determinations, 3 hybrids appeared to be tetraploid (4.3 pg/2C), while all parent plants are diploid (1.9 pg/2C - 2.4 pg/2C). The available hybrids did not flower yet. In this paper, we highlight the importance of parental genotype choice related to breeding success within Genisteae.