Tasmanian Institute of Agriculture, College of Sciences and Engineering, University of Tasmania, Burnie, Tasmania 7320, Australia.
Tasmanian Institute of Agriculture, University of Tasmania, Sandy Bay, Tasmania 7005.
Phytopathology. 2023 Oct;113(10):1946-1958. doi: 10.1094/PHYTO-10-22-0385-R. Epub 2023 Nov 10.
Emergence of pathogens with decreased sensitivity to succinate dehydrogenase inhibitor fungicides is a global agronomical issue. Analysis of isolates ( = 173), which cause tan spot of pyrethrum (), collected prior to (2004 to 2005) and after (2009, 2010, 2012, and 2014) the commercial implementation of boscalid in Tasmanian pyrethrum fields identified that insensitivity developed over time and has become widespread. To evaluate temporal change, isolates were characterized for frequency of mutations in the succinate dehydrogenase (Sdh) B, C, and D subunits associated with boscalid resistance, mating type, and SSR genotype. All isolates from 2004 and 2005 exhibited wild-type (WT) Sdh alleles. Seven known Sdh substitutions were identified in isolates collected from 2009 to 2014. In 2009, 60.7% had Sdh substitutions associated with boscalid resistance in . The frequency of WT isolates decreased over time, with no WT isolates identified in 2014. The frequency of the SdhB-H277Y genotype increased from 10.7 to 77.8% between 2009 and 2014. Genotypic evidence suggested that a shift in the population structure occurred between 2005 and 2009, with decreases in gene diversity (; 0.51 to 0.34), genotypic evenness (E; 0.96 to 0.67), genotypic diversity (G; 9.3 to 6.8), and allele frequencies. No evidence was obtained to support the rapid spread of Sdh genotypes by clonal expansion of the population. Thus, insensitivity to boscalid has developed and become widespread within a diverse population within 4 years of usage. These results suggest that can disperse insensitivity through repeated frequent mutation, sexual recombination, or a combination of both.
病原菌对琥珀酸脱氢酶抑制剂类杀菌剂敏感性降低的现象是一个全球性的农业问题。对 2004 年至 2005 年（商业推广巴斯夫利之前）和 2009 年、2010 年、2012 年和 2014 年（商业推广巴斯夫利之后）在塔斯马尼亚除虫菊上采集的 173 个导致除虫菊叶斑病的分离株进行分析后发现，随着时间的推移，这些分离株的不敏感性逐渐增强且变得广泛存在。为了评估时间变化，对这些分离株的琥珀酸脱氢酶（Sdh）B、C 和 D 亚基与巴斯夫利抗药性相关的突变频率、交配型和 SSR 基因型进行了特征描述。2004 年和 2005 年采集的所有分离株均表现为野生型（WT）Sdh 等位基因。在 2009 年至 2014 年采集的分离株中鉴定出 7 种已知的 Sdh 取代。2009 年，60.7%的分离株具有与 中的巴斯夫利抗药性相关的 Sdh 取代。随着时间的推移，WT 分离株的频率逐渐降低，2014 年未发现 WT 分离株。SdhB-H277Y 基因型的频率从 2009 年的 10.7%增加到 2014 年的 77.8%。基因型证据表明，2005 年至 2009 年间种群结构发生了变化，基因多样性（H；0.51 至 0.34）、基因型均匀度（E；0.96 至 0.67）、基因型多样性（G；9.3 至 6.8）和等位基因频率均降低。没有证据表明种群的克隆扩张导致 Sdh 基因型迅速传播。因此，在巴斯夫利使用 4 年内，该药剂对病原菌的敏感性已降低且变得广泛存在于一个多样化的种群中。这些结果表明，除虫菊可以通过反复频繁的突变、有性重组或两者的结合来传播抗药性。
