ABSTRACT
To explore the effects of crude toxins from Colletotrichum gloeosporioides(C. gloeosporioides)on the growth of Dendrobium officinale Kimura et Migo(D. officinale),and to provide early basis for thescreening and cultivation of the resistant variants of C. gloeosporioides. Methods Seedlings of D. officinal werecultivated in MS medium added with different concentrations of the crude toxins from C. gloeosporioides. Theeffects of the crude toxin on the growth of seedlings were observed, and the optimum resistance -selectionthreshold was preliminarily screened. Results In the concentration range of 5％ - 15％(volume fraction),crudetoxins from C. gloeosporioides increased the plant height,stem diameter,number of new bud,root number,and fresh mass of D. officinale,among which the effect of 5％(volume fraction)of crude toxins was the moststrongest. In the concentration range of 35％ - 40％(volume fraction),crude toxins suppressed the plant height,leaf number,number of new bud,root number,and the fresh mass of D. officinale. When cultured with 20％(volume fraction)crude toxins, D. officinale was blooming, and the flowers appeared variation phenomenon.Conclusion The crude toxins from C. gloeosporioides have biological activity and certain toxicity,which can beconsidered as a selection agent instead of pathogenin in vitro to screen the resistant variant of D. officinale,butthe optimum resistance-selection threshold still needs further research.