In Vitro Rapid Propagtion And Plantlet Regeneration Of Davidia Involucrata

Davidia involucrata Baill.is a unique single-genus plant and a national-level protected plant in China.It is also a relic species of the Tertiary paleotropical flora.It has high economic value,ornamental value,scientific value and ecological value.Davidia involucrata is traditionally propagated by seeds.Due to the hard seed shell,it usually takes 2～3 years to germinate.In addition,the phenomenon of seed abortion is serious,which greatly affects the number of species and landscape applications.Therefore,it is necessary to develop new ways of breeding technology.In this study,modern plant tissue culture biotechnology was used to regenerate Davidia involucrata plants through direct organogenesis and indirect organogenesis.The key factors affecting the establishment of aseptic materials,axillary bud germination,stem bud proliferation,callus induction,bud differentiation,and rooting culture were studied in order to provide a basis for the establishment of Davidia involucrata rapid propagation system.The main results are as follows:（1）The young stems of Davidia involucrata in Qinling National Botanical Garden were used as experimental materials to study the effects of sampling season,explant site and disinfection time on the acquisition of aseptic materials of Davidia involucrata and the effects of medium type and plant hormones on the germination and proliferation of axillary buds.The results showed that June was the best sampling season for explants.The suitable sterilization method was 75%alcohol disinfection for 1 min,sterile water washing three times,10%Na Cl O soaking for 10 min,sterile water washing four times.The survival rate was 63%.The best medium for axillary bud germination was 1/2MS+6-BA 1.0mg/L+GA₃1.5mg/L,and the induction rate was 92%.The optimum medium for subculture proliferation of Davidia involucrata axillary buds was 1/2MS+6-BA 2.0 mg/L+NAA 1.0 mg/L+GA₃1.0 mg/L,and 6-BA had a significant effect on subculture proliferation.（2）The effects of basic medium types and different concentrations of plant hormones on callus induction of Davidia involucrata were studied by using petioles and leaves of aseptic seedlings as experimental materials.The results showed that the optimum medium for callus induction was WPM+NAA 2.0 mg/L+KT 1.0 mg/L+2,4-D 1.0 mg/L.The petiole was easier to induce callus than the leaf,and the hormone 2,4-D had a significant effect on callus induction.The optimal medium for callus subculture proliferation was WPM+6-BA 1.0 mg/L+2,4-D 1.0 mg/L,and the proliferation rate was faster.In the process of callus subculture,adding VC 1.0 mg/L can reduce the browning degree of callus;the optimum medium for callus differentiation was WPM+6-BA 2.0 mg/L+IBA 0.5 mg/L,and the differentiation rate of adventitious buds was 16%.（3）The effects of basic medium and plant hormones on the rooting of tissue culture seedlings of Davidia involucrata were studied.The results showed that the suitable medium for rooting was WPM+NAA 0.5 mg/L+AC 0.5 mg/L,the rooting rate was 89%,the average root number was 10,and the root system was strong and grew well.The optimum time for seedling hardening was 3 days.The best substrate for transplanting tissue culture seedlings was peat and perlite volume ratio of 2:1,the survival rate was 77%,and the plants grew well after transplanting.In summary,this paper preliminarily determined the regeneration of Davidia involucrata Baill.by tissue culture organogenesis,and explored the establishment of aseptic materials,axillary bud germination,stem bud proliferation,callus induction,bud differentiation,and rooting culture.The key factors laid the foundation for the establishment of an efficient and rapid propagation system.