Unreduced gametes are the major causal factor for the production of polyploid interspecific hybrids in Primula

Abstract

The genus Primula (Primulaceae) consists of approximately 420 species that mainly inhabit temperate to cold regions of the Northern hemisphere. Although most species have attractive flowers with high ornamental value, few have been cultivated as ornamental plants. To develop novel ornamental crops and to introduce novel useful characters, these unexploited rich germplasms of the genus Primula have the potential to serve as breeding materials through the use of interspecific hybridization. However, interspecific hybrids of this genus have rarely been produced, and embryo rescue is one of the most useful strategies to overcome the difficulty of achieving successful hybridization, especially in wide crosses. In recent studies, we successfully obtained various interspecific hybrids in wide cross combinations in Primula using the embryo rescue technique, and showed that unexpected polyploid hybrids were frequently produced by the fertilization of unreduced female and/or male gametes, which were formed in most of the species examined. Some of the resultant hybrids have useful and attractive characters, and they have already been used directly as novel cultivars or incorporated into commercial breeding of novel types of primulas.