Screening Of Antagonistic Trichoderma To Potato Late Blight And Pepper Phytophthora Blight And Study On The Biocontrol Mechanisms

Phytophthora pathogen which is one of the serious crop diseases can sharply reduces plant yield by20%-40%, Serious year can lead to crop failure. Biological control has drawn more and more attention in recent years for its safty to environment, and human and animal. The purpose of this study was to screen Trichoderma that had good control effect against potato late blight and pepper Phytophthora blight and to investigate biocontrol mechanism, so as to provide effective strains and practical guidance for industrialization of biocontrol strains.Twenty strains which have strong antagonistic effect against potato late blight and pepper Phytophthora blight were screened from325Trichoderma strains isolated from potato and pepper rhizosphere and tubers with Screening method of simulating natural environment and Plate screening method. Through the potted experiment, four Trichoderma strains (HNA14, HNA12, LNF5and HBJ5) had significant control effect agaist P. infenstans, four Trichoderma strains (HNA12, HNN8, LNF5and HBJ5) had significant control effect against P. capsici. In the Rongchang field test from2010, Trichoderma agent application after21days, disease control effect treated with HNA14strian against the potato late blight achieved51.4%, control effects of strain HNA14was most significant; In the Zunyi field test in2010, four Trichoderma strains (HNA12, HNN8, LNF5and HBJ5) caught significant reduce disease index of pepper Phytophthora blight, respectively, control effects of strain HNA12was most significant, after21days, disease control effect can achieve48.3%. In the Rongchang field test in2011, control effects of HNA14strain against the potato late blight was most significant, control effect achieved49.8%; in the Zunyi pepper field test, control effects of HNA12and HBJ5strains were significant against the pathogen, control effect treated with2strains on the pepper Phytophthora blight can achieve57.8%and51.8%, respectively. In the Wuxi field test from2012, control effect of strain HNA14on the potato late blight was most significant, after28, disease control effect caught achieve54.5%; In the Shizhu field test, control effect of strain HNA12on the pepper Phytophthora blight caught achieve43.3%, and caught increase plant height of pepper by9.6%significantly, control effect against pathogen signifigantly was enhanced. So we decided HNA12and HNA14strains could make as the effective resource of biofungicide to control pepper Phytophthora blight and potato late blight, and further to investigate biocontrol mechanism. By means of molecular biology and morphology methods, isolates HNA12and HNA14were identified as Trichoderma harzianum.The biocontrol mechanisms of strain HNA12and HNA14were studied, two strains caught colonize in the plant root, and the density of the population of antagonist alone, and in both combinations, maintained1x104CFU·g-1potting mix by the end of the fourth week; The results of PCR-DGGE showed HNA14strian could influence the microbiome composition of bacteria and fungi; Antifungal metabolites produced by isolate HNA14and HNA12could significantly prevent the hypha growth of pathogen colony; Treatment of biocontrol strains significantly increased the activity of POD, PPO, PAL and SOD in pepper and potato, the incidence of pathogen reduced significantly. Plants treated with HNA14and HNA12showed lower disease indexes across all the Fe concentrations. Biocontrol fungi reduced the populations of pathogen significantly at lower doses of Fe. Plants treated with biocontrol fungi had highest weights and heights. In conclusion, biocontrol fungi not only protected potato and pepper seedlings from both biotic and abiotic toxic effects stress, but also be able to promote plant growth and development.