College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China.
Plant Dis. 2019 Sep;103(9):2385-2391. doi: 10.1094/PDIS-01-19-0153-RE. Epub 2019 Jul 16.
Stimulatory effects of low doses of fungicides on the virulence of phytopathogens have profound implications for applications of fungicides. The present study demonstrated that carbendazim sprayed at 0.001 to 0.03 μg/ml had stimulatory effects on the virulence of mycelia of , and the maximum percent stimulations were 15.5 and 21.4% for isolates HB459 and HB536, respectively. Potato dextrose agar (PDA) amended with carbendazim at 0.01, 0.02, and 0.05 μg/ml inhibited mycelial growth of isolate HB536 by 0.8, 10.0, and 30.6%, respectively. However, after the inhibited mycelia were inoculated on cucumber leaves, virulence increased by 10.1, 12.9, and 10.8%, respectively. With respect to sclerotial production, carbendazim at 0.005 and 0.02 μg/ml in PDA significantly ( < 0.05) increased, while at 0.1 μg/ml significantly ( < 0.05) reduced the sclerotial number and weight of both isolates compared with nontreated controls. Conidia germination percentages slightly yet statistically significantly ( < 0.05) increased after being inoculated on PDA amended with carbendazim at 0.001 and 0.005 μg/ml. Carbendazim at 0.001∼0.02 μg/ml, either sprayed on cucumber leaves or cosuspended with conidia, exerted significantly ( < 0.05) stimulatory effects on the virulence of conidia. Mechanism studies showed that sublethal doses of carbendazim did not increase the expression levels of pathogenicity-related pectin methylesterase gene , endopolygalacturonase gene , cutinase gene , xylanase gene , or NADPH oxidase gene .
低剂量杀菌剂对植物病原菌毒力的刺激作用对杀菌剂的应用有深远的影响。本研究表明， 0.001 至 0.03 μg/ml 的多菌灵喷雾对 HB459 和 HB536 分离株的菌丝毒力有刺激作用，最大刺激率分别为 15.5%和 21.4%。在含 0.01、0.02 和 0.05 μg/ml 多菌灵的马铃薯葡萄糖琼脂（PDA）上，HB536 分离株的菌丝生长分别被抑制了 0.8%、10.0%和 30.6%。然而，当受抑制的菌丝接种到黄瓜叶片上时，毒力分别增加了 10.1%、12.9%和 10.8%。就产菌核而言，0.005 和 0.02 μg/ml 的多菌灵在 PDA 中显著（<0.05）增加，而 0.1 μg/ml 的多菌灵显著（<0.05）减少了两个分离株的菌核数量和重量，与未处理对照相比。与未处理对照相比，将孢子接种在添加了 0.001 和 0.005 μg/ml 多菌灵的 PDA 上后，孢子的萌发率略有但统计学上显著（<0.05）增加。0.001∼0.02 μg/ml 的多菌灵，无论是喷洒在黄瓜叶片上还是与孢子共悬浮，都对 孢子的毒力有显著（<0.05）的刺激作用。机制研究表明，亚致死剂量的多菌灵不会增加致病相关果胶甲酯酶基因、内切多聚半乳糖醛酸酶基因、角质酶基因、木聚糖酶基因或 NADPH 氧化酶基因的表达水平。
