Pathogen identification of stem rot on Xanthium strumarium and indoor screening of fungicides
[Objective]The present paper aimed to explore the pathogen fungi of stem rot of Xanthium strumarium and investigate the inhibito-ry effects of seven fungicides in carbendazim,imazalil,procymidon,thiabendazole,topsin-methyl,fludioxonil and prochloraz on it in vivo.[Method]The pathogenic fungi were isolated from the stem base of X.strumarium by hyphal tip cutting method,and the pathogen of stem rot on X.strumarium was confirmed by Koch's rule verification.To identify the pathogen species,morphological characteristics of the pathogen-ic colonies,mycelium and sclerotium were noted,internal transcribed spacer(ITS)and translation elongation factor 1-α(TEF1-α)se-quences were amplified by molecular biological PCR,cloned and sequenced to further analyze and identify the pathogen species.[Result]The six pathogens were isolated,and their morphological characteristics were consistent with Athellia rolfsii.About l week after the mycelium and sclerotium of the pathogen were respectively inoculated on the base of healthy X.strumarium stems,the symptoms of the most experi-mental group were the same as those of diseased plants in the field.The sequence of NCXS-1 clone was 100％consistent with the corre-sponding sequences of A.rolfsii strains in the database.Among the seven screened pesticide fungicides,NCXS-1 was not sensitive to carben-dazim,imazalil,procymidone,thiabendazole and topsin-methyl,and both fludioxonil and prochloraz had certain inhibitory effect on the col-ony growth of A.rolfsii,where fludioxonil had the strongest inhibitory effect with EC50 as 0.12 mg/L.[Conclusion]The pathogen causing stem rot of X.strumarium was identified as A.rolfsii,and fludioxonil was the most effective fungicide for inhibiting the growth of stem rot of X.strumarium in 7 kinds of pesticides.The results can provide useful guidance for the effective control of X.strumarium stem rot.
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