Abstract：
Emergence of pathogens with decreased sensitivity to succinate dehydrogenase inhibitor fungicides is a global agronomical issue. Analysis of Didymella tanaceti isolates (n = 173), which cause tan spot of pyrethrum (Tanacetum cinerariifolium), 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 D. tanaceti. 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 (uh; 0.51 to 0.34), genotypic evenness (E5; 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 D. tanaceti can disperse insensitivity through repeated frequent mutation, sexual recombination, or a combination of both.
摘要：
对琥珀酸脱氢酶抑制剂杀真菌剂的敏感性降低的病原体的出现是全球性的农艺问题。丁氏菌分离株的分析(n=173)，导致除虫菊的棕褐色斑点（Tanacetumcinerariifolium），在塔斯马尼亚除虫菊田的商业实施之前（2004-2005年）和之后（2009年，2010年，2012年和2014年）收集的，发现不敏感随着时间的推移而发展，并已变得普遍。为了评估时间变化，分离株被表征为琥珀酸脱氢酶（Sdh）B的突变频率，C和D亚基与啶酰菌胺抗性相关，交配型和SSR基因型。2004年和2005年的所有分离株都表现出野生型(WT)Sdh等位基因。在2009年至2014年收集的分离物中鉴定出七个已知的Sdh取代。2009年，有60.7％的人在坦西D.tanaceti中出现了Sdh置换，这些置换与bocalid抗性相关。WT分离株的频率随着时间的推移而下降，2014年没有发现WT分离株。SdhB-H277Y基因型的频率在2009-2014年间从10.7%增加到77.8%。基因型证据表明，2005年至2009年之间发生了人口结构的转变，基因多样性下降（呃;0.51至0.34），基因型均匀度（E5；0.96至0.67），基因型多样性（G;9.3至6.8）和等位基因频率。没有证据支持通过克隆扩展种群来快速传播Sdh基因型。因此，在使用后的4年内，对啶酰菌胺的不敏感性已经发展并在不同的人群中变得普遍。这些结果表明D.tanaceti可以通过反复频繁的突变来分散不敏感，性重组或两者的结合。
