Study On The Inhibitory Effect Of Patchouli Extract On Cucumber Anthracnos

Colletotrichum orbiculare is a fungal disease that is highly susceptible to occur in greenhouses and can cause serious economic losses if left untreated;Pogostemon cablin（Blanco）Benth.,as a medicinal plant,has certain fungal inhibitory efficacy of its active ingredients.In this paper,the inhibition effect of different solvent extracts of Pogostemon cablin.on C.orbiculare was determined by mycelial growth rate method,and the virulence test of mycelial growth and spore germination was conducted on petroleum ether extract with better inhibition effect,and the mycelial dry weight and microscopic morphological observation were carried out to clarify its inhibition effect;its effect on mycelial physiological characteristics was determined by conventional physicochemical analysis,and its inhibition physiological mechanism was investigated in detail.The results of the study are as follows:1.Among the four different solvent extracts of Pogostemon cablin.extract,the petroleum ether extract was more effective than the other extracts.40 mg/m L of Pogostemon cablin.petroleum ether extract inhibited the mycelial growth and spore germination of C.orbiculare by 91.10%and 86.87%with IC₅₀ of 10.94 mg/m L and13.40 mg/m L,respectively;the dry weight of mycelium treated with this extract decreased with increasing concentration,and the dry weight of mycelium treated with40 mg/m L extract was only 35.39%of the control.The dry weight of mycelium decreased with increasing concentration,and the dry weight of mycelium under 40mg/m L extract treatment was only 35.39%of the control;under 400×light microscope,the mycelium of C.orbiculare treated with this extract showed more branches,uneven growth and intertwined phenomenon.2.The relative conductivity,malondialdehyde content,and nucleic acid leakage of mycelium gradually increased and the soluble sugar and soluble protein content gradually decreased with the increase of extract concentration.Under the treatment of40 mg/m L Pogostemon cablin.petroleum ether extract,the relative conductivity of mycelium increased by 13.59%（at 5 h）,malondialdehyde content was 7.41 times of the control,and nucleic acid leakage was 2.94 times of the control under the treatment of 30mg/m L extract（at 120 min）,indicating that the extract disrupted the cell membrane structure of C.orbiculare.Under the treatment of 40 mg/m L extract,the soluble sugar and soluble protein contents of mycelium were only 68.98%and 79.12%of the control,indicating that its osmoregulatory system was affected to some extent.3.With the increase of extract concentration,mycelial peroxidase activity gradually increased,polyphenol oxidase,superoxide dismutase and peroxidase activities showed a trend of increasing and then decreasing,and pyruvate content,malate dehydrogenase and succinate dehydrogenase activities gradually decreased.Among them,catalase activity was the highest under 40 mg/m L extract treatment,which was2.64 times that of the control,and polyphenol oxidase,superoxide dismutase and peroxidase activities peaked under 20 mg/m L extract treatment,which were 2.61,2.49and 6.93 times that of the control,indicating that the extract could interfere with the intracellular redox system;under 40 mg/m L extract Under the treatment of 40 mg/m L extract,the pyruvate content in mycelium was only 54.12%of the control,and the malate dehydrogenase and succinate dehydrogenase activities were 64.19%and 30.25%of the control enzyme activities,respectively,indicating that the extract could affect the mitochondrial tricarboxylic acid cycle pathway,leading to mitochondrial dysfunction and finally inhibiting mycelial growth.In summary,this study screened the petroleum ether extract of Pogostemon cablin.with better inhibitory effect on C.orbiculare,and investigated the inhibitory effect of the extract on C.orbiculare as well as the physiological mechanism,which is important for the exploitation of Pogostemon cablin.and the green control of C.orbiculare.