Incompatibility in Rubus With Special Reference to R. Idaeus L.

Self-incompatibility is demonstrated in 11 out of 23 Rubus species, including wild raspberry R. idaeus, in which stylar inhibition of self-pollen-tubes occurs. In contrast, nearly all raspberry cultivars are fully self-fertile, probably, as is demonstrated for a derivative of Burnetholm, through mutation of S alleles to the St condition.Unilateral interspecific incompatibility in crosses with the self-compatible R. occidentalis occurs equally with self-incompatible wild raspberry or self-compatible raspberry cultivars as seed parents, showing that the latter retain their stylar activity. This suggests recent aquisition of self-fertility, cultivars being in the 'Sc' condition of Lewis and Crowe.It is suggested that vegetative propagation in R. idaeus provides many of the advantages of inbreeding and this, together with intense selection for vigour, ensures the maintenance of obligate outbreeding in the wild.