[ Objectlve] The paper was to compare the induced resistance of several chemicals on cucumber against Pseudoperonospora cubensis [ Method ] When the cucumber seedlings grew to 4-leaf stage, the second true leaf was tr...[ Objectlve] The paper was to compare the induced resistance of several chemicals on cucumber against Pseudoperonospora cubensis [ Method ] When the cucumber seedlings grew to 4-leaf stage, the second true leaf was treated with salicylic acid, oxalate, chitosan, calcium nitrate and Na2HPO4, the activity of protective enzymes in the third leaf was determined after 7 d. At the same time, inoculation test was also conducted after induced treatment, and the disease condi- tion was coumed. [ Result ] These chemical treatments promoted protective enzyme activities （POD, SOD, PAL, PPO） in different degree, improved the ultra-weak luminescence, and reduced the disease index of cucumber leaves. [ Conclusion] Five chemical treatments expressed good effects on induced resistance. Among the treatments, oxalate had the best induced effect, followed by salicylic acid, chitosan, Na2 HPO4 and calcium nitrate.展开更多
Dimethomorph is a fungicide with high activity against Peronosporomycetes plant pathogens. The present study showed that dimethomorph is effective on controlling the oomycete fungal pathogen Pseudoperonospora cubensis...Dimethomorph is a fungicide with high activity against Peronosporomycetes plant pathogens. The present study showed that dimethomorph is effective on controlling the oomycete fungal pathogen Pseudoperonospora cubensis causing downy mildew on cucumber. The fungicide did not affect zoospores discharge from sporangia of P. cubensis, but it strongly inhibited mycelial growth and sporangial production in vitro and increased lysis of zoospores. Dose of 2 mg L^-1 of dimethomorph was sufficient to inhibit mycelial growth and sporangial production of P. cubensis on leaf disks, 5 mg L^-1 was enough to lyse zoospores of P. cubensis, and 25 mg L^-1 was required to inhibit sporangial production on detached leaves. In whole plant tests, dimethomorph exhibited strong protective and curative activity. Dimethomorph when applied at a dose of 300 mg L^-1 for 1, 3, 5, 7 days before inoculation exhibited 100% efficacy on disease control. On the other hand, efficacies of 67.1 and 31.5% were obtained when the same dose of dimethomorph was applied for 1 and 3 days after inoculation, respectively. So dimethomorph had persistence effect on leaves for 7 days at least and exhibited strong protective and curative activity. Bioassay analyses showed that dimethomorph could be translocated in the xylem system, redistributed in the leaf, and penetrated from the upper surface to the lower surface of the leaf but could not be translocated in phloem system or transferred from the roots to leaves of cucumber plants in sufficient amounts for disease control. The biocharacteristics of dimethomorph make it well suitable for integration of a control programme against downy mildew disease on cucumber and as a component to delay other peronosporomycetes fungicide-resistance development.展开更多
[Objective] The paper was to clarify the sensitivity and resistance of Pseudoperonospora cubensis to cymoxanil.[Method] A total of 69 strains were collected from 13 major cucumber producing areas in eight provinces an...[Objective] The paper was to clarify the sensitivity and resistance of Pseudoperonospora cubensis to cymoxanil.[Method] A total of 69 strains were collected from 13 major cucumber producing areas in eight provinces and cities of Guangdong, Hubei, Jiangsu, Shandong, Beijing, Liaoning, Jilin and Heilongjiang from 2012 to 2016, and their sensitivity and resistance to cymoxanil was determined using leaf disc floating method.[Result] The EC50 of cymoxanil to P. cubensis were 0.006 8-0.134 1 μg/mL and the average EC50 was 0.062 4 μg/mL. The sensitivity of P. cubensis to cymoxanil presented a single-peak curve, which was approximately normal distribution, and no strains with decreased sensitivity were found. The average EC50 (0.062 4 μg/mL) could be used as the sensitivity baseline of P. cubensis to cymoxanil. Among the 69 strains, 16 were low-resistance strains, accounting for 23.19% of the total strains;53 were sensitive strains, accounting for 76.81%, which were dominant populations;and no medium-resistance and high resistance strains were found. The resistance of P. cubensis to cymoxanil ranged from 0.11 to 2.15 times, and the average resistant level was 1.00 times.[Conclusion] Cymoxanil showed strong inhibitory effect against P. cubensis.展开更多
Pseudoperonospora cubensis(Berk.& M.A.Curtis)Rostovzev,the causal agent of cucumber downy mildew,is an obligate parasitic fungus.Up to now it can not be preserved on culture medium.In this study,the sporangia of P...Pseudoperonospora cubensis(Berk.& M.A.Curtis)Rostovzev,the causal agent of cucumber downy mildew,is an obligate parasitic fungus.Up to now it can not be preserved on culture medium.In this study,the sporangia of P.cubensis were preserved in protective substances of 10% dimethyl sulfoxide plus 5% skim milk,10% dimethyl sulfoxide plus 10% skim milk,sterilized water and leaves in vitro,and stored at-20℃,-70℃,and preliminary freezing at-20℃ for 24 h prior to-70℃ respectively.The results showed that the sporangia preserved in 10% dimethyl sulfoxide plus 5% skim milk,preliminary freezing at-20℃ for 24 h prior to-70℃ were still highly pathogenic after 12 months preservation.The percentage of germination of sporangia,incidence and disease index were 46%,50.0% and 40.0 respectively 9 d after inoculation.This method solved the problem of P.cubensis preservation.展开更多
基金Supported by Science and Technology Project of Educational Commission of Shandong Province of China( J07WJ48)~~
文摘[ Objectlve] The paper was to compare the induced resistance of several chemicals on cucumber against Pseudoperonospora cubensis [ Method ] When the cucumber seedlings grew to 4-leaf stage, the second true leaf was treated with salicylic acid, oxalate, chitosan, calcium nitrate and Na2HPO4, the activity of protective enzymes in the third leaf was determined after 7 d. At the same time, inoculation test was also conducted after induced treatment, and the disease condi- tion was coumed. [ Result ] These chemical treatments promoted protective enzyme activities （POD, SOD, PAL, PPO） in different degree, improved the ultra-weak luminescence, and reduced the disease index of cucumber leaves. [ Conclusion] Five chemical treatments expressed good effects on induced resistance. Among the treatments, oxalate had the best induced effect, followed by salicylic acid, chitosan, Na2 HPO4 and calcium nitrate.
基金funded by BASF (China)CorporationNational 973 Program of China(2006CB101907)863 Program of China(2008AA10Z414).
文摘Dimethomorph is a fungicide with high activity against Peronosporomycetes plant pathogens. The present study showed that dimethomorph is effective on controlling the oomycete fungal pathogen Pseudoperonospora cubensis causing downy mildew on cucumber. The fungicide did not affect zoospores discharge from sporangia of P. cubensis, but it strongly inhibited mycelial growth and sporangial production in vitro and increased lysis of zoospores. Dose of 2 mg L^-1 of dimethomorph was sufficient to inhibit mycelial growth and sporangial production of P. cubensis on leaf disks, 5 mg L^-1 was enough to lyse zoospores of P. cubensis, and 25 mg L^-1 was required to inhibit sporangial production on detached leaves. In whole plant tests, dimethomorph exhibited strong protective and curative activity. Dimethomorph when applied at a dose of 300 mg L^-1 for 1, 3, 5, 7 days before inoculation exhibited 100% efficacy on disease control. On the other hand, efficacies of 67.1 and 31.5% were obtained when the same dose of dimethomorph was applied for 1 and 3 days after inoculation, respectively. So dimethomorph had persistence effect on leaves for 7 days at least and exhibited strong protective and curative activity. Bioassay analyses showed that dimethomorph could be translocated in the xylem system, redistributed in the leaf, and penetrated from the upper surface to the lower surface of the leaf but could not be translocated in phloem system or transferred from the roots to leaves of cucumber plants in sufficient amounts for disease control. The biocharacteristics of dimethomorph make it well suitable for integration of a control programme against downy mildew disease on cucumber and as a component to delay other peronosporomycetes fungicide-resistance development.
基金Supported by Northeast Agricultural University Student SIPT ProjectNational Natural Science Foundation of Heilongjiang Province(ZD2016003)
文摘[Objective] The paper was to clarify the sensitivity and resistance of Pseudoperonospora cubensis to cymoxanil.[Method] A total of 69 strains were collected from 13 major cucumber producing areas in eight provinces and cities of Guangdong, Hubei, Jiangsu, Shandong, Beijing, Liaoning, Jilin and Heilongjiang from 2012 to 2016, and their sensitivity and resistance to cymoxanil was determined using leaf disc floating method.[Result] The EC50 of cymoxanil to P. cubensis were 0.006 8-0.134 1 μg/mL and the average EC50 was 0.062 4 μg/mL. The sensitivity of P. cubensis to cymoxanil presented a single-peak curve, which was approximately normal distribution, and no strains with decreased sensitivity were found. The average EC50 (0.062 4 μg/mL) could be used as the sensitivity baseline of P. cubensis to cymoxanil. Among the 69 strains, 16 were low-resistance strains, accounting for 23.19% of the total strains;53 were sensitive strains, accounting for 76.81%, which were dominant populations;and no medium-resistance and high resistance strains were found. The resistance of P. cubensis to cymoxanil ranged from 0.11 to 2.15 times, and the average resistant level was 1.00 times.[Conclusion] Cymoxanil showed strong inhibitory effect against P. cubensis.
文摘Pseudoperonospora cubensis(Berk.& M.A.Curtis)Rostovzev,the causal agent of cucumber downy mildew,is an obligate parasitic fungus.Up to now it can not be preserved on culture medium.In this study,the sporangia of P.cubensis were preserved in protective substances of 10% dimethyl sulfoxide plus 5% skim milk,10% dimethyl sulfoxide plus 10% skim milk,sterilized water and leaves in vitro,and stored at-20℃,-70℃,and preliminary freezing at-20℃ for 24 h prior to-70℃ respectively.The results showed that the sporangia preserved in 10% dimethyl sulfoxide plus 5% skim milk,preliminary freezing at-20℃ for 24 h prior to-70℃ were still highly pathogenic after 12 months preservation.The percentage of germination of sporangia,incidence and disease index were 46%,50.0% and 40.0 respectively 9 d after inoculation.This method solved the problem of P.cubensis preservation.
