Isolation And Identification Of Fungal Antagonist Chaetomium And Pemcillium Against Phytophthora Capsici And Studies On Their Potential Of Biocontrol

Pepper blight caused by Phytophthora capsici is a common soil-borne fungal disease andoccurrs throughout the world. With cultivation and development of the pepper industry, manypepper production bases have been severely affected by this disease in many provinces andcities of our country. Because of its increasing trend year by year, at present, pepper blighthas significantly obstructed the development of the pepper industry and caused seriouseconomic losses.Currently, although the pattern of pathogen infection, pathogenic conditions and itsdevelopment regularity have been mastered now and some prevention measures have beenapplied, such as improvement of cultivation strategies, screening disease-resistant varietiesand chemical therapy and so on, spread of the disease couldn’t still been effectively preventedbecaused of the complex management measures, genetic instability in disease-resistantvarieties and many other problems caused by chemical control including environmentalpollution, resistance to pesticide and residues of pesticide ect. Therefore, what makes usinterested in curing pepper blight is treated with the antagonistic microorganisms given thatthey are friendly to the environment and work effectively on inhibiting growth andreproduction of the fungal pathogen as well as enhancing resistance to plant diseases.Considering these advantages using beneficial microorganisms to control pepper blight hascaused the attention of the researchers.In this study, we used2strains of Chaetomium in our laboratory and7strains ofChaetomium and12strains of Pemcillium separated from eight different plants to screen inorder to find the antagonistic strains against Phytophthora capsici, aiming at exploring theireffects of prevention and biocontrol mechanisms. The research results as follows:1. We seperated strain HTC from9strains of Chaetomium and strains P1and P2from12strains of Pemcillium who have obvious inhibitory effects via plate confrontation test with8kinds of pathogens, degradation test of Phytophthora capsici fungus and effects test ofpreventing pepper blight. We found that nutrition competition, antibiosis of active substancesand mycoparasitism are the main mechanisms in confrontation test with Phytophthora capsici.In addition, the inhibition rates of HTC, P1and P2were60.4%,58.0%and60.4%,espectively in the degradation test; What’ more, the prevention effects of the three strainswere69.19%,63.93%and63.68%in prevention test of pepper blight, respectively. 2. Based on the morphology and biology as well as identification method using18S rDNA,the strain of Chaetomium HTC is denominated Chaetomium aureum; Penicillium strain P1preliminary named Eupenicillium; Strain P2preliminary denominated named Penicillium.3. The fermentation broth of HTC, P1and P2and crude extracted solution of antibioticsubstances all have a stronger inhibitory ability to Phytophthora capsici in the differentgrowth stages. Surprisingly, the inhibition rate in fungus growth is close to100%byfermentation liquor and antibiotic crude extracts; The inhibition rates of P2fermentationliquor in the production and release of zoospores are82.19%and80.46%, respectively. Andthe inhibition rate of antibiotic crude extracts from strain P1on the germination of zoospore isas high as98.45%..4. The control effects of fermentation broth and antibiotic crude extracts of HTC are over70%in control test of pepper blight. It is amazing that peroxidase (POD), polyphenol oxidase(PPO) and phenylalanine ammonia solution (PAL) of the pepper plant could be highlyactivated by the fermentation broth of HTC. Because of rise delay of the three enzymescaused by phytophthora infection, the level of resistance to plant disease is largely enhanced.5. Futhermore, the growth of pepper seedlings could be promoted and content of leafchlorophyll is also elevated via treatment with HTC, P1and P2fermented liquid. Specially,P1fermented liquid can promote the dry weight of pepper seedings by21.05%. Beyond that,moisture content of plant organization is also increased with fermented liquid treatment of thethree strains, which is beneficial to strengthen plant resistance.6. Fungus of HTC, P1and P2could grow on PDA plates with660μg/ml of metalaxyl or100μg/ml of dimethomorph, but the inhibition rates of Phytophthora capsici and Chaetomium LJare100%and66.50%on the PDA plate with dimethomorph, respectively. Both chemicalagents have a delayed effect on germination of HTC spore, but no damage to the spores. Butthe inhibition rate on germination of Phytophthora capsici zoospore is91.87%with thedimethomorph treatment.