Oryzalin-induced allotetraploids of an intersubgeneric hybrid between evergreen and deciduous azaleas

Pollen viability of. intersubgeneric hybrids between evergreen and deciduous azaleas was much lower than that of their parents. No capsule set in the crossings with the hybrids when used either as seed or pollen parents. In vitro chromosome doubling with oryzalin was attempted for restoring the fertility of the hybrid. Survival rates of the explants were more than 50% in oryzalin treatments, though high concentration and long term treatments brought the survival rates and number of shoots per explant low, under which number of shoots per explant also decreased. Twenty tetraploid and 28 mixoploid (2x + 4x) plants were obtained by the treatments from 123 individuals. The most suitable conditions for obtaining tetraploids appeared to be 0.01% oryzalin treatment for 48 hours.