Pathogen Identification Of Capsicum Anthracnose And Risk Assessment Of Resistance Of Colletotrichum Scovillei To Three Fungicides In Jilin Province And Eastern Inner Mongolia

Capsicum anthracnose is one of the most harmful fungal diseases in pepper production,which has a serious impact on pepper industry.To control capsicum anthracnose,it is necessary to identify the pathogen species of capsicum anthracnose,determine the dominant fungi,understand its biological characteristics and screen out fungicides with high efficiency and low toxicity.In Jilin Province and eastern Inner Mongolia,prochloraz,difenoconazole and pyraclostrobine are commonly used fungicides to control capsicum anthracnose,although they were developed earlier and used frequently in the field.However,there are no reports on the risk of resistance of capsicum anthracnose to these three fungicides,and not clear whether resistant strains exist.In this study,the pathogen of capsicum anthracnose in Jilin Province and eastern Inner Mongolia was identified.The sensitive baseline of Colletotrichum scovillei,the dominant bacterium species of capsicum anthracnose in mentioned regions,to prochloraz,difenoconazole and pyraclostrobine was established,and the resistance monitoring and resistance risk assessment were carried out.Our results provide a theoretical basis for the application of the above three fungicides to control and evaluate the resistance of capsicum anthracnose in Jilin Province and eastern Inner Mongolia.The main results are as follows:1.The pathogens of capsicum anthracnose in Jilin Province and eastern Inner Mongolia were identified.Combined with the morphological characteristics of the pathogen and the phylogenetic tree analysis constructed with ITS,TUB2,ACT,GAPDH and CHS-1 gene sequences,among the 822 pathogens isolated,7 types of capsicum anthracnose were found,which were C.scovillei,C.truncatum,C.nigrum,C.incanum,C.fioriniae,C.sojae and C.spaethianum.Among them,C.scovillei,C.nigrum and C.truncatum were isolated with the highest frequency,which were 53.16%,26.5%and 13.38%,respectively,which were the dominant bacteria in this area.The isolation frequencies of C.incanum,C.fioriniae,C.sojae and C.spaethianum were 3.65%,2.19%,1.22%and 0.61%,respectively.2.The biological characteristics of three representative capsicum anthracnose pathogens were studied,and the sensitivity of fungicides was determined by mycelial growth rate method and spore germination method under indoor conditions.The results showed:The optimum growth conditions of C.scovillei were culture medium,carbon source,nitrogen source,p H,temperature,and light as PDA,D-mannitol,peptone,7,25℃and dark,respectively.The optimum growth conditions of C.nigrum were culture medium,carbon source,nitrogen source,p H,temperature,and light as OA medium,D-maltose,peptone,10,20℃,and dark,respectively.The optimum growth conditions of C.truncatum were culture medium,carbon source,nitrogen source,p H,temperature,and light as V8 medium,peptone,D-maltose,5,30℃and full light,respectively.The mycelial growth and spore germination of C.scovillei were highly sensitive to25%prochloraz EC,42.4%oxazolone·fluramide SC,240 g/L chlorofluoroether·pyrazole ester EC,400 g/L chlorofluoroether·pyrazole ester SC,75%trifloxystrobin·tebuconazole WG,43%oxazolone·fluramide SC,40%oxazolone·tebuconazole SC and 200 g/L fluroxy·benzoxazole SC.The mycelial growth and spore germination of C.nigrum were more sensitive to 400 g/L chlorofluoroether·pyrazole ester SC,240 g/L chlorofluoroether·pyrazole ester EC,42.4%pyraclostrobin·fluoroamide SC,40%pyraclostrobin·tebuconazole SC and 43%pyraclostrobin·fluoroamide SC.The mycelial growth and spore germination of C.truncatum were highly sensitive to 75%trifloxystrobin·tebuconazole WG,40%pyraclostrobin·tebuconazole SC,240 g/L fluoroether·pyrazole EC,43%pyraclostrobin·fluamide SC and 250 g/L azoxystrobin SC.3.The sensitive baselines of C.scovillei to prochloraz,difenoconazole and pyraclostrobine in Jilin Province and eastern Inner Mongolia were 0.0365±0.0162 mg·L^-1,0.2483±0.1158mg·L^-1 and 0.2272±0.2027 mg·L^-1,respectively.4.To determine whether 110 sensitive strains of C.scovillei could grow in a certain concentration range.The MIC values of prochloraz,difenoconazole and pyraclostrobine against C.scovillei were 20 mg·L^-1,500 mg·L^-1 and 400 mg·L^-1,respectively.The resistance of 327isolates of C.scovillei to the three fungicides was monitored and the resistance frequencies were2.45%,0 and 4.28%,respectively,including 8 strains with low resistance to prochloraz,11strains with low resistance to pyraclostrobine and 3 strains with moderate resistance to pyraclostrobine.5.Assessment of resistance risk of C.scovillei to prochloraz,difenoconazole and pyrazolyl carbendazim.Seven resistant mutants were obtained by chemical domestication.There were three prochloraz-resistant mutants of C.scovillei,MTQJ7-3 and MTDFHB6Y-4 were moderately resistant,and MTWF1Y-5 was low resistant;two difenoconazole-resistant mutants of C.scovillei,BTWF1Y-5 and BTDFHB6Y-4 were moderately resistant;two pyraclostrobine-resistant mutants of C.scovillei,b T1-3 was moderately resistant,and b TKL1Y-1 was low resistant.The resistance of the above mutants could be stably inherited.The result of biological characteristics of the resistant mutants showed that the biocompatibility of resistant mutant strains MTQJ7-3,MTDFHB6Y-4,MTWF1Y-5,BTWF1Y-5,BTDFHB6Y-4and b TKL1Y-1 was weaker than that of parent strains,while the adaptability of b T1-3 to environment was not significantly different from that of parent strains.The results of cross resistance showed that prochloraz and pyraclostrobine were not cross resistant to chlorothalonil,azoxystrobin,tebuconazole,hexaconazole and picoxystrobin,while difenoconazole had positive cross resistance to azoxystrobin,hexaconazole and tebuconazole,but not to chlorothalonil and picoxystrobin.