Abstract:

Objective: In this study, the antifungal activity of essential oils (EOs) of cinnamon(Cinnamomum cassia), citronella(Cymbopogon nardus var. lenabatu), garlic(Allium sativum) and tea tree(Melaleuca alternifolia) against 12 kinds of pathogenic fungi of bamboo was investigated, and the effective antibacterial components of the four kinds of essential oils were compared. The purpose of this study are to make a good use of EOs in preventing and controlling bamboo forest diseases and developing an efficient, economical and pollution-free biological pesticide for bamboo. Method: Four essential oils of cinnamon, citronella, garlic and tea were emulsified with 3% polyvinyl alcohol, and PDA medium containing essential oils of different concentrations (0.005%-2.0%) was used to test the effects of four essential oils on 12 kinds of pathogenic fungi. MIC (minimum inhibitory concentration) and MFC (minimal fungicidal concentration) of 4 EOs to 12 bamboo pathogenic fungi (Schizophyllum commune, Arthrinium phaeospermum, Rhizoctonia sp., Helminthosporium sp., Fusarium oxysporum, Cladosporium oxysporium, Fusarium solani, Alternaria alternate, Aureobasidium pullulans, Epicoccum nigrum, Aciculosporium take, Shiraia bambusicola) were detected. According to the result of MIC and MFC, different concentrations of essential oil were selected:0.01% cinnamon (0.02% cinnamon for Epicoccum nigrum and Aciculosporium take), 0.05% garlic, 0.1% citronella (0.03% citronella for Alternaria alternate used), 0.1% tea tree for Cladosporium oxysporium, Alternaria alternate, Aureobasidium pullulans, Epicoccum nigrum and Aciculosporium take and 0.5% tea tree for other 7 kinds of fungi. The concentration of trans-cinnamaldehyde, diallyl disulfide, diallyl sulfide, citronellal and terpine-4-ol was the same as the corresponding EOs, and the concentration of citronellol and geraniol was 25% of citronella EO. The antifungal ability was evaluated by continuously recording the growth diameter of the fungus. Result: The EOs of cinnamon, citronella, garlic and tea tree all had to different degrees inhibitory effects on 12 tested pathogens. MIC of cinnamon EO was mainly 0.005% to 10 fungi (0.010% to 2 pathogen fungi), and the MFC was 0.01%-0.10%. MIC of garlic EO was 0.005%-0.010% to 11 fungi (0.200% to 1 pathogen fungus), and the MFC was 0.1% -1.5% (2 fungi exceeded the test concentration by 2.0%). MIC of citronella EO was 0.005%-0.030%, and the MFC is 0.04%-0.50%. MIC of tea tree EO was 0.03%-0.20%, and MFC is 0.2%-1.5%. According to the analysis of drug resistance (MFC/MIC), cinnamon and tea tree EOs had better drug resistance, followed by citronella EO, and garlic EO was the worst. In addition, it has been verified that the effective antifungal components of cinnamon, citronella, tea tree and garlic EOs were trans-cinnamaldehyde, citronella and geraniol, terpine-4-alcohol, and diallyl sulfide, respectively. Conclusion: Cinnamon, citronella, tea tree and garlic EOs have antifungal effect of pathogenic fungi from bamboo. Comprehensive assessment of 4 EOs, cinnamon EO is the best; citronella and tea tree EOs followed, but tea tree EO has low economic value for biological pesticide due to its expensive price; garlic EO is not suitable for development and utilization due to its high MFC and drug resistance.

Key words: plant essential oils, pathogenic fungi of bamboo, biological pesticides, chemical composition