Lichtemberg Paulo S F, Luo Yong, Morales Rafael G, Muehlmann-Fischer Juliana M, Michailides Themis J, May De Mio Louise L
First, second, and fifth authors: Department of Plant Pathology, University of California, Davis and Kearney Agricultural Research and Extension Center, 9240 S Riverbend Ave., Parlier, CA 93648; third and sixth authors: Department of Plant Pathology, Universidade Federal do Paraná, Curitiba, PR, 80035-050, Brazil; and fourth author: Department of Genetics, Universidade Federal do Paraná, Curitiba, PR, 81531-990, Brazil.
Phytopathology. 2017 Dec;107(12):1507-1514. doi: 10.1094/PHYTO-02-17-0050-R. Epub 2017 Sep 19.
The ascomycete Monilinia fructicola is the causal agent of brown rot of stone fruit in Brazil, causing major pre- and postharvest losses. For many years, the demethylation inhibitor (DMI) fungicide tebuconazole has been used as the most effective active ingredient for controlling brown rot and, as a result, strains of M. fructicola resistant to this ingredient have emerged in many Brazilian states producing stone fruit. The aim of this study was to investigate the mechanisms associated with the resistance of M. fructicola to DMI tebuconazole. By sequencing the M. fructicola CYP51 (MfCYP51) gene, encoding the azole target sterol 14α-demethylase, a mutation was identified at the nucleotide position 1,492, causing the amino acid substitution from glycine to serine at the codon position 461, associated with reduced tebuconazole sensitivity. In addition, it was observed that MfCYP51 gene expression could play a secondary role in DMI fungicide resistance of M. fructicola strains in Brazil. However, for the specific isolate found to exhibit elevated expression levels of MfCYP51, no insertions that would trigger gene expression were found. Based on the point mutation associated with tebuconazole resistance, an allele-specific polymerase chain reaction method was developed to quickly identify resistant genotypes within the Brazilian population. This is the first report determining molecular mechanisms for DMI resistance identification for M. fructicola isolates from Brazil. This information provides an important advancement for risk assessment of DMI fungicides used to manage brown rot of stone fruit.
子囊菌果生链核盘菌是巴西核果褐腐病的病原菌，会导致严重的采前和采后损失。多年来，脱甲基抑制剂（DMI）杀菌剂戊唑醇一直作为防治褐腐病最有效的活性成分使用，结果，在巴西许多生产核果的州出现了对该成分具有抗性的果生链核盘菌菌株。本研究的目的是调查果生链核盘菌对DMI戊唑醇产生抗性的相关机制。通过对编码唑类靶标甾醇14α-脱甲基酶的果生链核盘菌CYP51（MfCYP51）基因进行测序，在核苷酸位置1492处发现一个突变，导致密码子位置461处的氨基酸由甘氨酸替换为丝氨酸，这与戊唑醇敏感性降低有关。此外，观察到MfCYP51基因表达在巴西果生链核盘菌菌株对DMI杀菌剂的抗性中可能起次要作用。然而，对于发现MfCYP51表达水平升高的特定分离株，未发现会触发基因表达的插入序列。基于与戊唑醇抗性相关的点突变，开发了一种等位基因特异性聚合酶链反应方法，以快速鉴定巴西种群中的抗性基因型。这是第一份确定巴西果生链核盘菌分离株对DMI抗性鉴定分子机制的报告。该信息为用于防治核果褐腐病的DMI杀菌剂的风险评估提供了重要进展。
