2006 Volume 75 Issue 2 Pages 191-198
Crossability of Kurume azaleas (Rhododendron obtusum (Lindley) Planch.) as a seed parents, to hybridize with R. japonicum (A. Gray) J. V. Suringar f. flavum Nakai was tested based on the number of viable seedlings per pollinated flower (crossability). The traits of the seed parents, which produced the viable seedlings were recorded. Thirty-nine cultivars of Kurume azalea as seed parents were hybridized with a pollen parent of R. japonicum f. flavum. Seeds derived from 26 out of 39 crosses produced no viable seedling two years after sowing. The remaining 13 crosses yielded 0.2 to 23.2 viable seedlings per pollinated flower, indicating that the difference in the crossing capacity existed among the Kurume azalea cultivars. Stepwise fit and Bayesian approach revealed that the ovules penetrated by pollen tubes (fertilization rate) and the viable seedlings/the seedlings, excluding albinos, (survival rate) were related to the crossability. When the Kurume azalea cultivars possessed morphological leaf surface features which were similar to R. macrosepalum Maxim. and R. ripense Makino, the survival rate and the crossability were high. The data reveal that certain Kurume azaleas can serve as seed parents unilaterally with R. japonicum f. flavum.
