Study On The Resistance Of Fusarium Oxysporum From Vegetables To Prochloraz And Fludioxonil

Fusarium wilt of vegetables caused by Fusarium oxysporum is one of the diseases which is very difficult to prevent and control, caused great economic lossesin agricultural production.Chemical control is the main means. Frequent applications of the single fungicide over a long time have caused a serious resistance problem, resulting in chemical control effect reducing. In order to analyze the resistance problem of Fusarium oxysporum to mainly fungicides, preliminary study on the inhibitory effect and action mechanism of phenylpyrrole fungicide fludioxonil and azole fungicide prochloraz against Fusarium oxysporum was conducted in this paper. The main research results are as follows:1. The sensitivity baseline of Fusarium oxysporum to prochloraz was established. The frequency of 112 isolates with different sensitivity to prochloraz distributed as a unimodal curve,and there was no sub-group with declining sensitivity.The mean EC50 value was 0.0301 ±0.0304 μg/mL, and it could be considered as the sensitivity baseline.2. The biological characteristics of the Fusarium oxysporum mutants resistant to prochloraz were identified. Seven resistant mutants of F. oxysporum to prochloraz were obtained by means of fungicide adaptation,with the resistance levels ranging from 6.2～26.8 fold.The growth rate of mycelium on PDA,the dry weight of mycelium,and the virulence of seven resistant mutants were significantly lower than that of their parent isolates. Only the resistance of mutant HG13052701-R1 could be stably inherited.No cross-resistance existed between prochloraz and carbendazim, tebuconazole and hymexazol.3. The molecular resistance mechanism of Fusarium oxysporum to prochloraz was preliminary clarified. Sequence alignment analysis showed thatan amino acid substitution namely G102V in 14-a-demethylase encoded by the target gene CYP51B is probably related to prochloraz resistance of Fusarium oxysporum.4. The inhibitory effect of phenylpyrrole fungicide fludioxonil against Fusarium oxysporum was preliminary clarified.Under series of concentrations of fludioxonil treatment the effect on the mycelial growth of Fusarium oxysporum, spore germination, sporulation and pathogenicity is not regular. Overall low concentration interval (0-0.5 μg/mL) of fludioxonil dosage has a very excellent inhibitory effect on Fusarium oxysporum; while increasing fludioxonil concentration intervaldosage, inhibitory effect decreased. Fludioxonil has teratogenic effects on hyphae and spores of Fusarium oxysporum, and damage the cell membrane, decrease virulence and increase expression levels of target gene histidine protein kinase Fhkl.In this study,the sensitivity baseline of Fusarium oxysporum to prochloraz was established for the first time, the biological characteristics of the Fusarium oxysporum mutants resistant to prochloraz were identified, the molecular resistance mechanism of Fusarium oxysporum to prochloraz was preliminary clarified,all these results provide references for field monitoring prochloraz-resistant strains and resistance risk assessment.The mode of action of fludioxonil on Fusarium oxysporum was explored,which laid foundation for further study of fludioxonil action mechanism.