Variation in Crossability among Rhododendron japonicum f. flavum Plants as Pollen Parents when Crossed with Evergreen Species, R. eriocarpum

Abstract

An attempt was made to obtain the paternal parental stock to hybridize evergreen azaleas (seed parent) with Rhododendron japonicum (A. Gray) J. V. Suringar f. flavum Nakai (pollen parent). To examine the variation in hybridization barriers and crossability, pollen from nine accessions of R. japonicum f. flavum were used to pollinate one plant of R. eriocarpum (Hayata) Nakai. Significant differences among R. japonicum f. flavum accessions appeared in fertilization rate, mature seed numbers per capsule, albino rate, survival rate, and the crossability. Pollination with pollen of R. japonicum f. flavum accessions 27026136 and 27026139 yielded a relatively large number of viable seedlings per pollinated flower as compared to the others. Our results suggest that it is important to select highly crossable R. japonicum f. flavum plants as the pollen parent to obtain true hybrids.