Moyo Providence, Cook Glynnis, Basson Elaine, Steyn Chanel, Bester Rachelle, Olivier Charmaine, Fourie Paul H
Citrus Research International, Nelspruit 1200, South Africa.
Department of Genetics, Stellenbosch University, Stellenbosch 7600, South Africa.
Plant Dis. 2022 May;106(5):1374-1380. doi: 10.1094/PDIS-07-21-1459-RE. Epub 2022 Apr 6.
Citrus black spot (CBS), caused by , is an economically important disease, which is effectively controlled by repeated fungicide applications to protect fruit from infection. Systemic fungicides such as benzimidazoles are widely used for controlling CBS in South Africa, but the molecular mechanisms of benzimidazole resistance in . had not been investigated. Analysis of the nucleotide sequence of the β-tubulin gene in . revealed mutations inducing three amino acid replacements in benzimidazole-resistant isolates when compared with those of sensitive strains. Amino acid replacements in benzimidazole-resistant isolates included the change of glutamic acid to either alanine or lysine at codon 198 of the β-tubulin gene and the change from phenylalanine to tyrosine at codon 200. All three mutations were previously implicated in benzimidazole resistance in several fungal pathogens. A PCR assay was designed to amplify a portion of the β-tubulin gene, which is subsequently sequenced to identify benzimidazole resistance in . . This PCR and sequence assay was found to be a more rapid and reliable method for detecting resistance compared with the fungicide-amended plate tests and is valuable for monitoring the occurrence of benzimidazole-resistant . and for assessment of the need for alternative CBS management practices.
柑橘黑点病（CBS）由[未提及的病原体]引起，是一种具有重要经济影响的病害，通过反复施用杀菌剂保护果实免受感染可有效控制该病。在南非，苯并咪唑类等内吸性杀菌剂被广泛用于防治柑橘黑点病，但[未提及的病原体]对苯并咪唑产生抗性的分子机制尚未得到研究。对[未提及的病原体]β-微管蛋白基因的核苷酸序列分析表明，与敏感菌株相比，抗苯并咪唑分离株中的突变导致三个氨基酸替换。抗苯并咪唑分离株中的氨基酸替换包括β-微管蛋白基因第198位密码子处谷氨酸变为丙氨酸或赖氨酸，以及第200位密码子处苯丙氨酸变为酪氨酸。这三个突变先前在几种真菌病原体对苯并咪唑的抗性中均有涉及。设计了一种PCR检测方法，用于扩增β-微管蛋白基因的一部分，随后对其进行测序以鉴定[未提及的病原体]对苯并咪唑的抗性。与杀菌剂改良平板试验相比，这种PCR和测序检测方法被发现是一种检测抗性更快速、可靠的方法，对于监测抗苯并咪唑[未提及的病原体]的发生以及评估是否需要采用替代的柑橘黑点病管理措施具有重要价值。
