Preliminary studies were conducted to determine taxonomic relationships among native and introduced azaleas and to obtain their interspecific hybrids. Pollen storage method, interspecific fertility, pollen morphology, and isoenzyme pattern were studied and the results are as follows:
○ Studies on pollen storage
1. Pollens of two native and three introduced azalea species did not germinate after 150days of storage at room temperature. In Rhododendron mucronulatum, some pollens survived after the storage when stored at -5℃, pollen of R. mucronulatum and R. yedoense var. poukhanense showed fairly high survival rate. In R. mucronulatum and R. scabrum × R. simsii cv. Benifusa, most pollens germinated after storage at -10℃. R. schlippenbachii and R. yedoense var. poukhanense also showed high pollen survival rate at -20℃ as well as -10℃. However, few pollens germinated in azalea (cv. Mission Bell) and -20℃ of storage temperature.
2. When stored for 60days at 5℃, pollens of three native azaleas. R. `zasanhong´ R. `Koreayeongsanhong´ and R. japonicum germinated with high survival rates. However, in two introduced azaleas, pollen survival rate was low. The survival rates become lower as the storage period incleased. After 300days of storage, pollens of most azaleas except R. mucronulatum and R. `Koreayeongsanhong´ did not germinate.
○ Studies on interspecific fertility in native and introduced azaleas
1. In general, while interspecific hybrids between sections of introduced and native azaleas showed low or no fertility, those within section showed high levels of fertility.
2. All interspecific crosses within Tsutsutsi section resulted in fertile hybrids. R. mucronulatum in Dauricum section R. schlippenbachii in Brachycarys section showed no fertility with other species in different section.
3. R. japonicum in Rhodora section showed high fertility with the species in Tsutsutsi section used as pollen parents and the some results were obtained from the opposite crosses.
4. Interspecific crosses showed different fertility when species were exchanged as pollen parents.
○ Studies on pollen morphology
1. Among five species of azalea, while R. yedoense var. poukhanense has the largest pollen size and aperture diameter, R. obtusum showes the smallest ones.
2. Cluster analysis based on pollen morphology and plant morphologic characteristics indicated that there are big taxonomic differences among species.
○ Studies on isoenzyme
1. Twenty eight isoenzyme bands were recognized in five enzymes of native and introduced azaleas.
2. Based on the number of species specific band among those 28 isoenzyme bands, it was suggested that R. yedoense var. poukhanense is the most closely related with R. schlippenbachii, and R. `Koreayeongsanhong´ with R. obtusum and R. simsii hybrids. Further relationships of others were also discussed.
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