In order to explore the interspecific cross compatibility of Rhododendron and the feasibility of interspecific cross in germplasrn innovation, reciprocal crosses among five species of Rhododendron in Changbai Mountain were made, In addition, the hybrid embryos were cultured in vitro. The results showed that the species of Rhododendron in Changbai Mountain had significant differences in reciprocal cross compatibility. When Rh. chrysanthum Pall. was used as female parent, it showed high cross compatibilities with Rh. mucronulatum Turcz. （92.55%）, Rh. mucronulamm Turcz. f, album Nakai （94.14%） and Yabuli Rhododendron （92.42%）, and no signifi- cant differences were found in fruit setting rate by serf-poUination. The germination rates of hybrid embryos were 13.60%, 11.59% and 4.12%, respectively. The hybrid seedlings had weak growth vigor and albino status and were trended to be aborted. After 2-3 generations of subculture, the growth vigor of hybrid seedlings were re- covered gradually, and their differentiation rate was also significantly higher than that of Rh. chrysanthum Pall. seedlings. But the hybrid seedlings were still yellowish green. In reciprocal crosses, the fruit setting rates were significantly reduced. The combination with the highest fruit setting rate （36.51%） was Yabuli Rhododendron x Rh chrysanthum Pall The fruit setting rates of reciprocal crosses between Rh chrysan- thum Pall and Rh. mucronulatum Turcz. and Rh.： chrysanthum Pall. and Rh. schlip- penbachii Maxim were 6.52% and 0, respectively. However, the hybrid embryo＇s germination rate （39,81%） of Yabuli Rhododendron x Rh. chrysanthum Pall. was significantly higher than that of their original cross. Moreover, the hybrid seedlings grew strongly and could be directly transplanted without subculture.
[Objective] This study aimed to shorten the multiplication culture and root- ing culture periods of Rh. chrysanthum Pall. [Method] The Rh. chrysanthum Pall tis- sue culture plantlets collected from Changbai Mountain were used as material, and the effects of different hormone combinations and coconut milk on the proliferation and differentiation of Rh. chrysanthum Pall tissue culture plantlets were investigated. In addition, the rooting medium and transplanting matrix for Rh. chrysanthum Pall tissue culture plantlets were explored. [Result] The medium composed of modified MS, iBA （3 mg/L） and ZT （1.5 mg/L） was the optimum medium for subculture mul- tiplication of Rh. chrysanthum Pall tissue culture plantlets. The multiplication multiple and average plant height were significantly improved by adding coconut milk into the medium （150 mg/L）. [Conclusion] For Rh. chrysanthum Pall tissue culture plantlets, the optimum rooting culture medium was composed of modified MS （1/4） and IBA （5.0 mg/L）, and the tissue culture plantlets began to root 8 d after the inoculation. The root induction treatment was carried out after a 15-d sand culture, and the suitable matrix was composed of tufty soil, humus soil and perlite （2：1：1） with a survival rate of 95.66%.
