Potential for Crop Improvement In Ornamental Salvia Via Interspecific Hybridization

Salvia L. is a genus of over 900 species, including many horticulturally important crops grown as annuals and perennials.  Several interspecific hybrids (e.g. S. ×superba Stapf and S. ×jamensis J. Compton) are commercially important; however most of these hybrids are the result of hybridization in the wild or accidental hybridization in cultivation.  Introgressing wild germplasm in Salvia breeding programs has the potential to introduce novel traits, but there is little information on interspecific fertility in the genus.  To evaluate crossability within the genus, nine salvia species were selected to represent a wide diversity of native range, phylogenetic relationship, and chromosome number.  All species were crossed with each other in every possible combination.  Overall, crossability in the genus was low, but exhibited unexpected fertility between phylogenetically and geographically distant species.  Similarly, crosses between species with very different chromosome numbers showed unexpected fertility.  One successful hybrid, S. nemorosa L. × S. transsylvanica Schur ex. Griseb., is of particular interest  as S. nemorosa is a widely used floriculture crop, despite having small flowers.  Salvia transsylvanica has much larger flowers than S. nemorosa, and may be a useful genetic source to increase S. nemerosa floral size.  A large segregating F₂ population has been raised from this cross for genetic mapping of loci controlling flower size and other traits.  The F₂ population individuals exhibited variation in flower size extending beyond the parental values.  Similarly, large variation in flowering time and leaf morphology was observed.    These results indicate a great potential to utilize wild Salvia species to improve and to introduce novel traits into commercial genetics.