| Alternaria alternate has widely ranged in most tobacco growing regions in worldwide,causing leaf spot disease of tobacco by fungicides.Due to the short incubation,the disease usually cause wide epidemic in a short time under suitable conditions,causing huge economic losses.For many years,using of chemical fungicides has been effective for controlling the disease in the areas of tobacco production.But with the abuse of fungicides,the resistance has became more and more serious,and make the prevention difficult.There are some research have shown that A.alternata has resistance to dimetachlone,thiophanate-methyl and procymidone.The research investigate the sensitivity level of A.alternata to epoxiconazole,propiconazole,boscalid,tebuconazole,difenoconazole,azoxystrobin,trifloxystrobin,kresoxim-methyl and pyraclostrobin,the EC50 of 93 isolates of A.alternata collected from Shandong province,and set up the baseline of the EC50 to azoxystrobin was detected based on inhibition of mycelial growth,and carry out correlation analysis of the sensitivity of same type fungicides evaluated by the methods of mycelia growth rates.Analyze the sensitivity of the same type of fungicide used Sperman's rank correlation coefficient.Determined the synergistic effects of salicylic acid on the sensitivity of azoxystrobin,kresoxim-methyl,trifloxystrobin and pyraclostrobin.The research will be guide for the test of resistance,protection and prevention for A.alternata.The order of toxicity from strong to weak are epoxiconazole,propiconazole,boscalid,tebuconazole,difenoconazole,azoxystrobin,trifloxystrobin,kresoxim-methyland pyraclostrobin.The results showed that the EC50 values of 93 isolates to epoxiconazole with an average of 0.1789±0.0026 mg·L-1,the results showed that the EC50 values of 93 isolates to propiconazole with an average of 0.3779±0.0027 mg·L-1;The results showed that the EC50values of 93 isolates to boscalid with an average of 1.3169±0.0100 mg·L-1,the results showed that the EC50 values of 93 isolates to tebuconazolewith an average of 1.5463±0.0091mg·L-1,the results showed that the EC50 values of 93 isolates to difenoconazole with an average of 6.9189±0.0593 mg·L-1.The results showed that the EC50 values of 93 isolates to azoxystrobin with an average of 94.8655±1.6083 mg·L-1;the results showed that the EC50values of 93 isolates to trifloxystrobin with an average of 87.9054±0.9605 mg·L-1,the results showed that the EC50 values of 93 isolates to kresoxim-methywith an average of 118.0212±1.3480 mg·L-1,the results showed that the EC50 values of 93 isolates to pyraclostrobin with an average of 169.7044±1.0848 mg·L-1.The result of normal distribution by Shapiro-wilk has shown that the EC50 values of A.alternate to these nine fungicides have a continuous skewed distribution.It can be used as the sensitive baseline for the above 9 fungicides.The results of correlation analysis showed that there was no significant correlation between the susceptibility of A.alternata to triazole fungicides,methoxyacrylate fungicides.Correlation analysis of susceptibility of A.alternata to nitenpyram and other fungicides in field,there was a negative correlation between nitenpyram and epoxiconazole,a positive correlation between nitenpyram and kresoxim-methyl,and no significant correlation between nitenpyram and other six fungicides separately.The addition of a certain concentration of salicylic acid can significantly improve the sensitivity of various plant pathogens to QoIs under the terms of the separation.In this paper,the sensitivity of 93 A.alternata to 4 methoxy acrylate bactericides under the synergistic effect of 100 mg/L of salicylic acid was determined by the methods of mycelia growth rates.As the results is shown that,the addition of salicylic acid could significantly improve the toxicity of4 methoxy acrylate bactericides to all the tested A.alternata,however,there was a difference between different fungicides and different bacterial strains.The EC50 values of 93 isolates to azoxystrobin with an average of 31.7577±0.4046 mg·L-1.The toxicity of azoxystrobin alone increased by 0.70-2.98 times,2.00 times averagely.Under the synergistic action of salicylic acid,The EC50 values of 93 isolates to trifloxystrobinwith an average of 13.1189±0.3725 mg·L-1.The toxicity of trifloxystrobin alone increased by3.17-9.12 times,6.21 times averagely.Under the synergistic action of salicylic acid,The EC50values of 93 isolates to kresoxim-methyl with an average of 14.2623±0.1438 mg·L-1.The toxicity of kresoxim-methyl alone increased by 5.18-10.60 times,7.33 times averagely.Under the synergistic action of salicylic acid,the EC50 values of 93 isolates to pyraclostrobin with an average of 21.7280±0.2648 mg·L-1.The toxicity of pyraclostrobin alone increased by4.89-9.09 times,6.93 times averagely. |
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