Study On Artificial Hybridization And Propagation Of Two Rhododendron Species

Rhododendron molle(Bl.) G. Don and R. molle subsp. japonicum are belong to Subgen. Pentanthera(G. Don) Pojarkova of Rhododendron genus in Ericaceae. In this paper, the flowering phenology and crossbreeding of Rhododendron molle and R. molle subsp. japonicum were discussed by studying the pollination biology and breeding system; Meanwhile, the cutting propagation and tissue culture rapid propagation technology of them were studied in order to give reference and theoretical foundation for studying the artificial hybrid and genetic resource conservation of this genus, and also provide some technical support for large-scale and marketized breeding of the two Rhododendron species. The results are as follows:1. Pollination biology and artificial hybrid: the flowering phase of R. molle and R. molle subsp. japonicum are all from March to May, and the flower-visiting insect is only Apis cerana cerana Fabricius. Stigma receptivity is the maximum 2-4 days after flowering. The hybridization of R. molle and R. molle subsp. japonicum are compatible. Both of them are self-compatible, which are not like anemophilous flower but need pollinator. The average germination rate of hybrid seeds is 78%, and environmental suitability of the hybrid offspring is superior to the parents.2. Tissue culture rapid technology: The seeds of the two Rhododendron species were used as explants to investigate tissue culture rapid technology. the result shows that after sterilizing for the seeds of R. molle and R. molle subsp. japonicum with 75% ethyl alcohol for 30 s, and then with 0.1%Hgcl2 to sterilize for 3min, the sterilizing effect could be the best. The optimum culture medium for seeds to germinate is Anderson +NAA 1mg/L. The germination rates of R. molle and R. molle subsp. japonicum reached 88.0% and 92.4%. The optimum enrichment medium is Anderson +NAA 0.05mg/L +ZT 0.06mg/L +GA3 1mg/L. The growth coefficient of R. molle is 4.9. The growth coefficient of R. molle subsp. japonicum is 4.5. The best strong seeding effect can be reached by using Anderson +NAA 1mg/L+AC 1g/L. The root medium was Anderson +NAA 0.02 mg/L +ZT 0.06mg/L, and the rooting percentage of R. molle could be up to 98.8%. The rooting percentage of R. molle subsp. japonicum could be up to 96.4%.3. Cutting propagation technology: semi-wooden branch of R. molle and R. molle subsp. japonicum was used as material,(1) 4 groups of culture mediums were set, and 5 pH gradients were set for each culture medium, and then the cutting slips were stained with rooting powder to insert;(2) Cutting slips were put into 6 groups of solution where there were cytokinin ZT and 6-BA with plant growth hormones NAA, IAA and IBA, and clear water to soak for 2 hours respectively, and then inserted in the medium of perlite+leaf mould +river sand(1:1:1). The result shows that the two Rhododendron species were processed did not grow root.