College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
Pestic Biochem Physiol. 2018 Jan;144:27-35. doi: 10.1016/j.pestbp.2017.10.010. Epub 2017 Oct 28.
In the current study, sensitivity distribution of Sclerotinia sclerotiorum populations to fluazinam was determined using 103 strains collected from the fields of Jiangsu Province of China in 2016-2017 and the resistance risk of fluazinam was assessed. The average EC (50% effective concentration) values and MIC (minimum inhibitory concentration) values of 103 S. sclerotiorum strains against fluazinam were 0.0073±0.0045μg/ml and <0.3μg/ml for mycelial growth, respectively. Nine mutants with low resistance level were obtained from wild type sensitive strains exposed on PDA medium amended with fluazinam and the resistance was stable after their ten transfers on PDA without the fungicide. Compared with the parental strains, the nine fluazinam-resistant mutants decreased in mycelial growth, sclerotial production, pathogenicity and were more sensitive to 0.7M NaCl. In addition, cell membrane permeability of resistant mutants was higher than that of their parental strains. Cross resistance assay showed that there was no cross-resistance between fluazinam and fludioxonil, dimetachlone, prochloraz, tebuconazole, azoxystrobin, or procymidone in S. sclerotiorum. The above results indicated that there was a low resistance risk for fluazinam in S. sclerotiorum. However, the sensitivity of all fluazinam-resistant mutants to fludioxonil decreased. Sequencing alignment results showed that there were no mutations in the two-component histidine kinase gene (Shk1) of the resistant mutants and the expression levels of Shk1 of three resistant mutants were significantly up-regulated while others were almost the same as their parental strains. These results will contribute to evaluating the resistance risk of fluazinam for management of diseases caused by S. sclerotiorum and further increase our understanding about the mode of action of fluazinam.
在本研究中，使用 2016-2017 年从中国江苏省田间采集的 103 株菌，测定了核盘菌种群对氟啶胺的敏感性分布，并评估了氟啶胺的抗风险。103 株核盘菌对氟啶胺的平均 EC（50%有效浓度）值和 MIC（最小抑菌浓度）值分别为 0.0073±0.0045μg/ml 和<0.3μg/ml，用于菌丝生长。从野生敏感菌株在添加氟啶胺的 PDA 培养基上暴露获得了 9 株低抗水平的突变体，在没有杀菌剂的 PDA 上连续传代 10 次后，抗性稳定。与亲本菌株相比，9 株氟啶胺抗性突变体的菌丝生长、菌核产生、致病性降低，对 0.7M NaCl 更为敏感。此外，抗性突变体的细胞膜通透性高于亲本菌株。交叉抗性测定表明，核盘菌对氟啶胺与 fludioxonil、二甲噻草酮、丙环唑、戊唑醇、肟菌酯或咯菌腈之间没有交叉抗性。上述结果表明，核盘菌对氟啶胺的抗风险较低。然而，所有氟啶胺抗性突变体对 fludioxonil 的敏感性都降低了。测序比对结果表明，抗性突变体中不存在双组分组氨酸激酶基因（Shk1）的突变，3 个抗性突变体的 Shk1 表达水平显著上调，而其他突变体与亲本菌株几乎相同。这些结果将有助于评估氟啶胺对核盘菌引起的病害的抗风险，并进一步提高我们对氟啶胺作用模式的认识。
