广西烟草棒孢霉病菌对10种杀菌剂的敏感性及对QoIs类杀菌剂的耐药性

Sensitivity of Corynespora tabacco to 10 fungicides and resistance to QoIs fungicides in Guangxi

[目的]近年来由多主棒孢霉病菌引起的烟草棒孢霉叶斑病在广西烟区危害日益加重。为筛选出防治烟草棒孢霉叶斑病的优良杀菌剂,并针对棒孢霉病原菌对甲氧基丙烯酸酯类(QoIs)杀菌剂的耐药性进行初步探究。[方法]采用菌丝生长速率法测定10种杀菌剂对来自广西贺州、百色、河池3个烟区8株烟草棒孢霉病菌菌株的生物活性;扩增并分析了多主棒孢霉细胞色素b基因(Cytb)部分序列,以期探寻该病原菌对QoIs类的2种杀菌剂敏感性下降的分子机制。[结果]供试杀菌剂对烟草棒孢霉病菌菌丝生长均有不同程度的抑制,杀菌剂效果比较好的是咪鲜胺、氟啶胺和吡噻菌胺,EC50值分别为(0.049±0.027)、(0.063±0.045)、(0.286±0.077)mg/L。[结论]广西烟草棒孢霉叶斑病防治中杀菌剂应优先选用咪鲜胺、氟啶胺。广西烟区烟草棒孢霉病菌群体对QoIs类杀菌剂产生很高的耐药性,因此田间生产中不推荐再使用该类杀菌剂防治烟草棒孢霉叶斑病。且经试验发现多主棒孢霉抗性菌株与抗性相关的位点未出现Cytb基因突变。上述结果可为烟草棒孢霉叶斑病的有效防治提供依据,同时可为探寻烟草棒孢霉病菌对甲氧基丙烯酸酯类(QoIs)杀菌剂敏感性下降的分子机制提供参考。

[Aims]In recent years,the harm of tobacco Corynespora leaf spot caused by Corynespora cassiicola has become more and more serious in Guangxi tobacco growing areas.This study aims to screen out fungicides for controlling this disease,and preliminarily explore the drug resistance of C.cassiicola to QoIs fungicides.[Methods]The indoor virulence of 10 fungicides to 8 C.cassiicola strains from Hezhou,Baise and Hechi in Guangxi was determined by mycelial growth rate method.The partial sequences of cytochrome b gene(Cytb)of C.cassiicola were amplified and analyzed in order to explore the molecular mechanism of the decline of sensitivity of two fungicides of QoIs.[Results]The tested fungicides inhibited the mycelial growth of C.cassiicola in varying degrees.The better fungicides were prochloraz,fluazinam and penthiopyrad,with EC50values of(0.049±0.027),(0.063±0.045)and(0.286±0.077)mg/L respectively.[Conclusions]Prochloraz and haloperidol should be the priority fungicides for the control of tobacco Corynespora leaf spot in Guangxi.The population of tobacco Corynespora in Guangxi tobacco area has high resistance to QoIs fungicides,so it is not recommended to use this kind of fungicides to control tobacco Corynespora leaf spot in field production.It was found that there was no Cytb gene mutation in the sites related to the resistance of C.cassiicola resistant strains.The above results can provide a basis for the effective control of tobacco Corynespora leaf spot,and provide a reference for exploring the molecular mechanism of the decline of the sensitivity of tobacco Corynespora to QoIs fungicides.