柑橘黑斑病菌与柚黑斑病菌对苯并咪唑类杀菌剂的抗性及其分子机制

Resistance and its molecular mechanism of Phyllosticta citricarpa and Phyllosticta citriasiana to benzimidazole fungicide

为了对柑橘黑斑病和柚黑斑病提出更科学的化学防治方法,该文研究了柑橘黑斑病菌和柚黑斑病菌对杀菌剂多菌灵的抗性频率、抗性水平及其抗性分子机制。结果表明:在江西114个柑橘黑斑病菌株中发现了2个多菌灵抗性菌株,抗性频率为1.75%,抗性系数分别为5333.6和379.2;在四川32个柑橘黑斑病菌株中发现了1个多菌灵抗性菌株,抗性频率为3.13%,抗性系数为303.3;在浙江23个菌株和重庆3个菌株中没有出现抗性菌株。在广东收集的54个柚黑斑病菌株中发现了1个抗性菌株,抗性频率为1.85%,抗性系数为13719.5;在广西和福建分别收集的34个柚黑斑病菌株中没有发现抗性菌株。柑橘黑斑病菌和柚黑斑病菌对甲基硫菌灵和多菌灵存在正交互抗性,对嘧菌酯和多菌灵无交互抗性。因此,建议多菌灵可继续在柑橘黑斑病和柚黑斑病防治中使用,鉴于高抗菌株已出现,使用时应与其他作用机制的杀菌剂轮换使用。本实验还发现,柑橘黑斑病菌存在2种抗苯并咪唑类的分子机制,即β-微管蛋白基因上第198位氨基酸位点由谷氨酸突变为赖氨酸(抗性系数为5333.6的菌株)和第200位氨基酸位点由苯丙氨酸突变为酪氨酸(抗性系数为379.2的菌株);而柚黑斑病菌抗苯并咪唑类的分子机制则与β-微管蛋白基因第198位氨基酸由谷氨酸突变为丙氨酸有关。

In order to control citrus black spot(CBS,Phyllosticta citricarpa)and pummelo black spot(PBS,Phyllosticta citriasiana)effectively,we evaluated the resistance frequency,resistance level and their molecular mechanisms of these two pathogen populations collected from seven provinces of China to the fungicide carbendazim.The results showed that two carbendazim-resistant(Cab-R)isolates were found from the Jiangxi subpopulation of P.citricarpa out of 114 strains.The resistant frequency was 1.75%,and their coefficient of resistance were 5333.6 and 379.2,respectively.One Cab-R strain with coefficient of resistance of 303.3 was found in the Sichuan subpopulation of P.citricarpa out of 32 strains,and the resistant frequency was 3.13%.However,none of the Cab-R isolates was detected from the Zhejiang(23 strains)and the Chongqing(3 strains)subpopulations.For P.citriasiana,one Cab-R strain,whose coefficient of resistance was 13719.5,was obtained in the Guangdong subpopulation(54 strains in total),and the resistant frequency was 1.85%.None of the Cab-R strains was found in the Guangxi(34 strains)and the Fujian(34 strains)subpopulations.In addition,there was a positive cross-resistance between thiophanate-methyl and carbendazim in P.citricarpa and P.citriasiana,while there was no cross-resistance between azoxystrobin and carbendazim.Based on the results obtained,we suggest that the fungicide carbendazim can still be used in controlling CBS and PBS in the fields,but the rotation of the fungicides with different antifungal mechanisms is necessary given the existence of high-resistant strains.Finally,the two molecular mechanisms of carbendazim-resistance of P.citricarpa were found.One was a mutation at the amino acid(aa)198 ofβ-tubulin gene,in which the glutamic acid changed to lysine(the strain with a coefficient of resistance of 5333.6),and the other one was a mutation at the aa 200 of β-tubulin gene,in which the phenylalanine changed tyrosine(the strain with a coefficient of resistance of 379.2).However,the molecular mechanism of the carbendazim-resistance of P.citriasiana was a mutation at the aa 198 in the β-tubulin gene,in which the glutamic acid changed to alanine.