To breed new azalea cultivars between native azaleas and introduced azaleas, the five kinds of breeding trials were conducted, and results are summarized as follows;
1. The fertility rate of reciprocal crossing with native three species and introduced four species was over 40% in self crossing. However R. yedoense var. poukhanense was the highest rate in self cross.
In general, interspecific hybrids between the native and introduced species in section showed high fertility whereas there were no or low fertility in different section among species.
2. The stump pollination could see partially pollen tube elongations in stigma by microscope observation in the cross between R. yedoense var. poukhanense as a male and R. schlippenbachii as a female, which were shown no fertility, and also showed them in the crossing between R. yedoense var. poukhanense and R. japonicum which had shown very low fertility rate.
3. The crossing between R. yedoense var. poukhanense as a male and R. schlippenbachii as a female, R. yedoense var. poukhanense as a male and R. japonicum as a female using self mentor pollen which treated with high temperature and methyl alcohol dipping could observe the pollen tube elongation in stigma, which cross combinations had been sterility.
When the case using the pollen of R. japonicum as a female, the mentor pollens which treated high temperature were to show many pollen tube elongation whereas those of anhydrade alcohol treatment observed no pollen tube elongation by microscope observation.
4. The pollen by the dipped n-hexane solution resulted high rate setting capsule in the interspecific sterile cross combinations whose combinations were between R. yedoense var. poukhanense and R. japonicum, R. schlippenbachii and R. yedoense var. poukhanense, R. japonieum and R. yedoense var. poukhanense.
Among these three crossing combination, the combination between R. yedoense var. poukhanense and R. japonicum showed the highest fertility rate to be 86%.
5. The rate of self crossing among native three azaleas, R. yedoense var. poukhanense showed the highest fertility next to R. mucronulatum and R. schlippenbachii in order. Apomixis fruit setting observed R. simsii hybrids (cv. Mission Bell) and R. mucronulatum among four azalea species.
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