| Hot pepper anthracnose, mainly caused by Colletotrichum spp., is one of the main destructive fungal diseases. It is mainly aplliying fungicides to control the disease for present. If a kaind of the fungicide for single continuous long-term has been applied, it is easy to cause fungicide-resistant. The study aims on provide the data basis for developing the new mixtured fungicide. Therefore, toxicity, joint-toxicity and control efficacy of pyraclostrobin and thiophanate-methyl to Colletotrichum spp. and hot pepper anthracnose were detected and evaluated.Firstly,28 isolates of hot pepper anthracnose fungus from the diseased fruits and leaves in Langli town, Changsha, Hunan were obtained by monoconidial isolation, hot pepper which their morphology and of DNA-ITS sequence were studied. The results showed that these isolates had belonged to 3 of species, i.e. C.gloeosporioides C.capsici, and C.coccodes which they included 15,9,4 isolates, respectively. Therefore, C.gloeosporioides is the main pathogen and the other were C.capsici and C.coccodes.Thiophanate-methyl is a common fungicide for the controlling hot pepper anthracnose. In order to improve efficacy and delay resistance of the fungicide to Colletotrichum spp.in hot pepper, joint-toxicity of the mixture of pyraclostrobin, a new fungicide, and thiophanate-methyl at different ratios against mycelial growth and conidium germination of C. gloeosporioides and C. capsici were determined. The results showed that their mixtures of 1:2,1:4,1:16 and 1:32 were additive effect against mycelial growth and conidium germination of C. gloeosporioides and C. capsici, while the 1:8 mixture against their mycelial growth and conidium germination was obviously synergistic interaction, the mixture against mycelial growth and conidium germination of C. gloeosporioides and C. capsici with SR of 1.98,1.93, and 1.95,2.11, respectively.Base on the joint toxicity determination of pyraclostrobin and thiophanate-methyl for C.gloeosporioides in this study, efficacy of different quality complex mixtures of pyraclostrobin:thiophanate-methyl at 1:2,1:4,1:8,1:16 and 1:32 on hot pepper anthracnose in Xiangfu No.5 was evaluated by the needle puncturing method with C gloeosporioides spore suspension (1×105/mL). the results showed that:protective and curative effect of pyraclostrobin at?3.00 mg/L was more than 81.82%; while the protective and curative effect of thiophanate-menthyl at?16.67 mg/L. during 120h after application could reached more than 81.82%;Moreover, the mixture at 1:8 among different quality mixtures of pyraclostrobin ? thiophanate-methyl performed the best protective and curative efficacy with separately over 83.12% and 77.92%. at?3.33mg/LThe toxicity of mixtures of pyraclostrobin and thiophanate methyl of the different mass concentration and the oxidative inhibitor salicylhydroxamic acid (SHAM) at dosage of 100 ug/mL against C-02-1 and C-01-1 and was tested. The results showed that their synergyvalues in mixtures of pyraclostrobin with SHAM against the two isolates wre 15.15 and 11.86, respectively, and their EC50 values were 0.0284 and0.0146 mg/L. respectively; while synergy values in mixtures of thiophanate methyl with SHAM against the same two isolates were 1.62 and 1.34, respectively, the EC50 values were 0.7944 and 0.7110 mg/L, respectively. The crude protein content in mycelium of the treated isolate with the about two fungicides was delected by coomassie brilliant blue method. The results indicated that the effect of the two fungicides (C-02-1 and C-01-1) on the crude protein content of the 2 isolates was consistent trendency, i.e., increasing of protein content during 1-3h, decline from 3 to 12h, then stable after 12h. Addition, the crude protein content of the mycelium in the culture medium with pyraclostrobin and SHAM was significantly decreased, which SHAM played a very synergistic enhancement; however thiophanate-methyl and SHAM did not appear as same effect as the above. |
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