| With the strengthening of the concept of environmental protection,people pay more and more attention to the ecological and environmental hazards brought by chemical pesticides,research and development of efficient,environmentally friendly and pollution-free new pesticides is imminent.Plant essential oils have been used in antibacterial,insecticidal,antioxidant and antiseptic applications due to their environmentally friendly,non-toxic and naturally available properties Juniper is an evergreen tree in the north of China,and as a traditional medicinal herb in Mongolian and Tibetan medicine,its branches,needles and cones are used to extract essential oil.As a worldwide important plant disease caused by Botrytis cinerea,gray mold causes serious economic losses to forestry and agriculture.In this paper,by screening the inhibitory effects of three plant essential oils on the mycelial growth of four plant pathogenic fungi and calculating the virulence regression equations,respectively,Juniper essential oil was finally selected as the test agent.To analyze its chemical composition,and to investigate its antifungal activity and mechanism of action against B.cinerea.And the results of the study are as follows:1.All 3 essential oils have a good antifungal effect.The essential oils of juniper,cedar and cypress showed different degrees of inhibitory effects on four pathogenic fungi（B.cinerea,Fusarium oxysporum,Pestalotiopsis neglecta,Alternaria alternata）with concentration-dependent effects.Among them,juniper essential oil had the best inhibitory effect on B.cinerea,and the complete inhibition concentrations for spore germination and mycelial growth were 10μL/m L and 20μL/m L,respectively.The toxicity regression equation was Y=4.647X-3.68,and the values of EC50 were 5.61μL/m L and EC90 were 10.58μL/m L,and were significantly lower than the concentrations of other test agents.2.JEO inhibits the ability of B.cinerea to infest.JEO reduced the incidence and diameter of fruit infested with B.cinerea.The incidence of cherry tomatoes treated with 160μL/m L of JEO was 27.7%,which was significantly lower than that of the control group（P<0.05）.Fruit lesion diameter decreased with increasing concentration of treated juniper essential oil.The average diameter of lesions in the control group without juniper essential oil treatment was 9.3mm,which was 2.97 times higher than that of the 160μL/m L treated group.3.The juniper essential oil has a significant effect on the cell structure of B.cinerea.Treatment with juniper essential oil resulted in significantly higher extracellular conductivity and soluble protein content,and MDA and H2O2 content in the mycelium than in the control（P<0.05）,and increased with the treatment time.It indicates that juniper essential oil destroyed the integrity of the cell membrane of B.cinerea,causes leakage of intracellular material and exacerbating the degree of cell membrane lipid peroxidation.Observation by scanning electron microscopy revealed that JEO treatment affects the normal growth of mycelium of B.cinerea.Causes mycelium to twist,deform rough,uneven surface or even fracture.4.The JEO affects the stability of the enzymatic activity system in B.cinerea.The activities of antioxidant-related enzymes SOD and CAT were significantly higher（P<0.05）than those of the control group after treatment with JEO,and reached the highest level at 12h.In contrast,the pathogenicity-related enzymes EG,PG and PL activity were significantly lower than those of the control group（P<0.05）,and gradually decreased with the increase of treatment time.It indicated that JEO affected the enzymatic activity system of B.cinerea.and causing its own oxidative stress response.Simultaneously weakening its pathogenesis-related enzyme activity,reduces its ability to infest and cause disease.5.The chemical components of essential oil of gin were analyzed and determined by GC-MS.Compared with NIST library,18 compounds accounted for 94%of the total content.Terpenes were the main components（51.02%）,including limonene（15.71%）,2-carene（10.94%）,etc.Alcohols（34.62%）and alkanes（8.35%）followed.In summary,this study determined the antifungal activity and mechanism of juniper essential oil against B.cinerea,and provided a theoretical basis for further development of juniper essential oil as a plant source fungicide. |
