Intrasubgeneric and interploid cross compatibility in evergreen and deciduous azaleas

Twenty-three diploids, six triploids, nine tetraploids and four mixoploids in evergreen azaleas and eight diploids and five tetraploids in deciduous azaleas were identified by flow cytometric analysis of ploidy in species, interspecific hybrids and cultivars. Sizes of guard cells and pollen grains tended to increase in proportion to the increase in the ploidy. Intrasubgeneric and intra- or interploid hybridizations were conducted with evergreen and deciduous azaleas. Tetraploids of evergreen azaleas had relatively high cross-ability as seed and/or pollen parents, and triploid evergreen azaleas had fertility as seed parents only. Deciduous tetraploids had high pollen fertility and, therefore, capsules set relatively frequently in the interploid crosses of 2x × 4x. No capsules set in the reciprocal crosses.