Interspecific hybridization by embryo rescue in the genus Cyclamen

Abstract

Numerous cultivars of cyclamen have been developed by improving wild plants of Cyclamen persicum, and they are now among the most important pot plants. However, no cultivars have yet been produced in the other 21 Cyclamen species. Furthermore, these 21 wild species have not yet been used for improving C. persicum cultivars due to hybrid inviability and hybrid sterility. In recent studies, hybrid inviability caused by abortion of hybrid embryos was overcome by an embryo rescue technique involving culture of ovules with placenta, which resulted in the production of interspecific hybrids between C. persicum and each of ten wild species. Hybrid sterility caused by abnormal meiotic chromosome behavior in hybrids (allodiploids) between diploid C. persicum and each of two diploid wild species was overcome by chromosome doubling using in vitro colchicine treatment, resulting in the production of two types of fertile amphidiploids (allotetraploids). On the other hand, three types of allotetraploids were produced between autotetraploid cultivars of C. persicum and each of three autotetraploid wild species by the embryo rescue technique without chromosome doubling. Embryo rescue and in vitro chromosome doubling are simple and useful methods for overcoming hybrid inviability and hybrid sterility in interspecific hybridization in the genus Cyclamen. Some of the fertile amphidiploids thus produced have already been incorporated into commercial breeding of novel types of cyclamens with important traits such as flower fragrance and disease resistance.