| oybean disease is a devastating disease in soybean production,caused by Phytophthora sojae.The use of metalaxyl for the prevention of soybean diseases appeared resistance isolate,and the use of the same type of high-efficiency bactericide benalaxyl in the fields was less.In addition,fluopicolide is a newly developed benzamide class fungicide.There are related studies on Phytophthora capsici at home and abroad,and no report has been reported on Phytophthora sojae.Therefore,this study mainly focused on the resistance assessment of two fungicides against Phytophthora sojae,the physiological and biochemical mechanisms of resistance,and the effective removal of plant extracts.The main results of the study are as follows:1.Nine mutants resistant to fluopicolide were acquired by Sexual reproduction and UV irradiating mycelia with a mutation frequency of 2.25%.The resistant strains’ resistance ratios was 502.9 ~ 1063.3 times.Six mutants resistant to benalaxyl were acquired by Sexual reproduction,with a mutation frequencyof 6%,and the resistant strains’ resistance ratios was 52.0-97.2 times.the mutants resistant to fluopicolide F6-1,F6-3,F6-4,F7-1,F7-2 and F7-4 could be inherited.Although the mycelial growth,sporangium production and oospore production were significantly lower than the parental strain,but they had the capability of sporulation and virulence.The mutants resistant to benalaxyl B6-4,B6-5 and B6-7 could inherit and the mycelium growth significantly higher than the parental strains,but the sporangium production and virulence were significantly lower than parental strains,but they also had the ability of virulence and spore-forming.The results of cross-resistance showed that fluopicolide was no cross-resistance with Metalaxy1 cymoxanil,pyrimorph and kresoxim-methyl.A nd the results of cross-resistance showed that benalaxyl was no cross-resistance withfluopicolide,pyrimorph and kresoxim-methyl but there was cross-resistance with the cymoxanil.In summary,there was a certain resistance risk of P.sojae to fluopicolide and benalaxy.Therefore,it was suggested that the fluopicolide and benalaxy should be used alternately with other fungicides which was no cross-resistance in my studies.2.After compare the biochemical and physiological indexes of P.sojae mutants which resistant to the fluopicolide and benalaxyl and their parental strains.The results showed that the mutants resistant to fluopicolide were more sensitive to the osmotic pressure than their parental strains,while the mutants resistant to benalaxyl were less sensitive.And as the treated time increased,the β-1,3-glucanase activity of mutants and parental strains both tended to decrease,In different time period,the soluble protein content of mutants resistant to the benalaxyl were higher than their parental strains,but the soluble protein content of the mutants resistant to the fluopicolide were inability to count.These results can help us to understand the resistant mechanism to fluopicolide and benalaxyl.3.This study developed a Phenotype microarray protocol PM1 and PM3 assess the utilization of carbon and nitrogen sources in the fluopicolide-resistant P.sojae and the benalaxyl-resistant P.sojae strains and parental strains.The results showed that almost all positive assays for C-source utilization using the PM1 screen and N-source utilization from the PM3 screen.Utilization of carbon sources by resistant strain F7-2was higher than that of the parental strain P7076,while the Utilization of nitrogen was less than it’s parental strain P7076.4.The mutants and parental strains were tested the sensitivity of a variety of plant extracts by the method of mycelia growth rate.The results showed that Honokiol,5,5’-Dially-2,2’-biphenyldiol,hydrochloride are useful to Phytophthora sojae.This study can be useful to the explore of novel and better fungicides. |
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