Interspecific hybridization between Hibiscus syriacus L. and Hibiscus paramutabilis Bailey

Different Hibiscus syriacus L. cultivars (diploid `Melwhite' and `Oiseau Bleu' and tetraploid `Red Heart cv' and `Purple cv') were used in a breeding program with Hibiscus paramutabilis Bailey. Compared to Hibiscus syriacus, a well-known winter hardy ornamental shrub, Hibiscus paramutabilis grows more vigorously, with larger leaves and flowers. When used as a seed parent, H, paramutabilis failed to set fruits. However, when pollinated by H. paramutabilis, H.s. `Oiseau Bleu' and H.s. `Red Heart cv' reacted by fruit setting. Fruits containing swollen (=fertilized) ovules were not observed on H.s. `Melwhite' or H.s. `Purple cv'. After putting the isolated embryos in vitro 5 H.s. `Red Heart cv' x H. paramutabilis embryos and 7 H.s. `Oiseau Bleu' x H, paramutabilis embryos could be converted. Respectively 1 and 6 plants were acclimatized and put in soil; they grew vigorously and leaves of all showed strong morphological similarities with H. paramutabilis. Ploidy analysis of these potential hybrids revealed that the H.s. `Red Heart cv' offspring was triploid, as was expected. AFLP analysis confirmed the hybrid character of all tested seedlings.