Interspecific hybridization inRibes

Abstract

The genusRibes, 2n=16, consisting of over 150 shrubby species has been divided byRehder into 15 sections grouped into four subgenera. Data on interspecies crosses within and between these sections and subgenera made by previous workers and at East Malling are tabulated and discussed.

Species within a section are morphologically similar and will usually cross, forming fertile hybrids; 33 such hybrids in 6 of the 15 sections are known. Inter-sectional and inter-subgeneric crosses between more unlike species often fail, but matur flowering plants have been obtained from crosses involving the following combinations: −Symphocalyx x Calobotrya, Symphocalyx x Eucoreosma, Calobotrya x Eucoreosma, Eucoreosma x Heritiera, Eucoreosma x Ribesia, Eugrossularia x Robsonia, Euberisia x Eugrossularia, Symphocalyx x Eugrossularia, Calobotrya x Eugrossularia, Eucoreosma x Eugrossularia, andRibesia x Eugrossularia. Of these, only the combinationsEugrossularia x Robsonia andCalobotrya x Eucoreosma show any fertility.

On the basis of these results, it is suggested that a more natural classification ofRibes would be to retainRehder's subgeneraBerisia, Grossularia andGrossularioides, while creating from his sevenRibesia sections, six new subgenera, viz.Microsperma, Symphocalyx, Calobotrya (comprising the sectionsCalobotrya andEucoreosma), Cerophyllum, Heritiera, andRibesia. With this classification, in the light of present knowledge, all intra-sectional hybrids are fertile, intra-subgeneric hybrids at least partially fertile, and such inter-subgeneric hybrids as can be raised are sterile.