Risk Assessment Of Resistance To Prochloraz In Peyronellaea Arachidicola

Peanut web blotch,caused by Peyronellaea arachidicola,is a kind of worldwide peanut disease which seriously harms peanut production.At present,the only agent registered on peanut web blotch disease is multi-manganese zinc.If long-term use of similar fungicides,it will greatly increase the risk of field pathogen resistance to fungicides.Prochloraz is a highly effective,low-toxicity and broad-spectrum Sterol demethylation inhibitors（DMIs）.It was found that prochloraz showed good antibacterial activity against peanut web blotch,but the specific control effect and resistant risk of prochloraz against peanut web blotch remain unclear.The objective of this study was to clarify the biological activity and resistance risk of prochloraz against peanut web blotch,so as to provide technical support for the effective control of prochloraz against peanut web blotch,and to provide an important reference for the resistance control of peanut web blotch.The main research results are as follows:1.The sensitivity frequency distribution of 96 strains of peanut web blotch was established by mycelium growth rate method.The range of EC₅₀was 0.0511-2.5032μg/m L,the average EC₅₀was 1.2700±0.7786μg/m L,and the sensitivity frequency distribution showed a unipeak curve.The results showed that prochloraz showed high antibacterial activity against the mycelium growth of peanut web blotch,and no high prochloraz-resistance of P.arachidicola were found in the field.2.Three susceptible strains of peanut web blotch disease（AHHF2103,AHHF2104,AHHF2112）were randomly selected for physiological and biochemical tests.The results showed that prochloraz significantly inhibited the synthesis of ergosterol and damaged the structure of cell membrane and the integrity of cell membrane and cell wall.The q RT-PCR test showed that prochloraz significantly increased the expression levels of Pa CYP51 and Pa Atr B genes.3.This study found that prochloraz had both curative activity and protective activity on isolated peanut web blotch leaves,and the protective activity was superior to the curative activity.When the concentration of prochloraz was 20μg/m L,the curative and preventive effect of prochloraz on peanut web blotch was 44.74%,and the protective effect was 55.88%.The protective activity of prochloraz was better than that of carbendazim and difenoconazole at the same concentration.4.In this study,5 strains of peanut web blotch were selected for indoor fungicide domestication,and 80 strains of prochloraz resistance were finally obtained.The resistance frequency was relatively low,0.67%.Based on the resistance level of differentiated dose method,medium and high resistance accounted for only 31.25%Biological fitness tests were conducted on 12 representative resistant strains,and it was found that the prochloraz-resistant strains were not genetically stable,and the biological fitness（mycelium growth rate and pathogenicity）of prochloraz-resistant strains were significantly reduced compared with sensitive strains.5.Cross-resistance experiments were conducted on the 12 prochloraz-resistant strains.The results showed that imidazole had positive cross-resistance with other sterol synthesis inhibitors,such as flumidazole,pentazolol and phenyloconazole,but did not have cross-resistance with carbendazim（Methylbenzimidazole carbamate）,and pydiflumetofen（Succinate Dehydrogenase Inhibitors）.6.The expression levels of resistance-related genes in 12 prochloraz resistant strains and their parents were determined by q RT-PCR.It was found that the expression levels of Pa CYP51 gene in 12 resistant strains were significantly up-regulated compared with their parents,and some strains also showed an up-regulated trend of Pa Atr B gene.In summary,this study analyzed the inherent resistance risks of peanut web blotch,such as agricultural operation risk,pathogen risk,and fungicide risk.Combined with the results of this experiment,the resistance risk of peanut web blotch pathogen to prochloraz was defined as"low to medium".In the actual production process,attention should be paid to the application of DMI fungicides in the prevention and control of peanut web blotch disease,and it is recommended to mix prochloraz with other fungicides of action mechanism,so as to slow down the generation and development of prochloraz resistance to peanut web blotch bacteria and extend the service life of agents.