A loss of fungicide efficacy, particularly for carbendazim, was noted in soybean fields in Thailand and was considered to be due to the development of Colletotrichum truncatum resistance. The carbendazim sensitivity of C. truncatum populations isolated from various soybean fields in Thailand was thus evaluated with in vitro sensitivity assays and molecular characterization of mutations in the sequences of the s₂‐tubulin (TUB2) gene that confer carbendazim resistance in the pathogen. Among 52 isolates, 46 isolates were classified as highly resistant (HR) to carbendazim (EC₅₀ > 1,000 µg/ml). All HR isolates grew on PDA amended with carbendazim at 1,000 µg/ml. Six isolates were classified as carbendazim sensitive (S) (EC₅₀ < 1 µg/ml). Mycelial growth on PDA amended with 1 µg/ml carbendazim was inhibited by over 50% compared with growth on PDA alone. When a partial TUB2 gene from the isolates was amplified and analysed using predicted amino acid sequences, an alteration from glutamic acid to alanine at codon 198 (E198A) was found in 45 HR isolates for which the EC₅₀ was higher than 2000 µg/ml. This mutation resulted from a nucleotide substitution from adenine to cytosine (GAG → GCG). The other HR isolate, CtPhS_1, with EC₅₀ of 1,127 µg/ml, had an alteration at codon 200 (F200Y) (TTC → TAC).

中文翻译：

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泰国大豆炭疽病抗多菌灵分离株的检测与分子表征

在泰国的大豆田中注意到杀菌剂效力的丧失，尤其是多菌灵，这被认为是由于截头孢菌抗性的发展。因此，通过体外敏感性测定和 s2-微管蛋白 (TUB2) 基因序列突变的分子表征，评估了从泰国不同大豆田中分离的 C. truncatum 种群的多菌灵敏感性，这些突变赋予病原体对多菌灵的抗性。在 52 个分离株中，46 个分离株被归类为对多菌灵高度耐药（HR）（EC₅₀ > 1,000 µg/ml）。所有 HR 分离物都在 PDA 上生长，用 1,000 µg/ml 的多菌灵修正。六个分离株被归类为对多菌灵敏感（S）（EC 50 < 1 µg/ml）。与单独在 PDA 上的生长相比，用 1 µg/ml 多菌灵修正的 PDA 上的菌丝生长被抑制了 50% 以上。当使用预测的氨基酸序列扩增和分析来自分离株的部分 TUB2 基因时，在 45 个 HR 分离株中发现密码子 198 (E198A) 从谷氨酸变为丙氨酸，EC₅₀ 高于 2000 µg/ml。这种突变是由从腺嘌呤到胞嘧啶的核苷酸取代（GAG → GCG）引起的。另一种 HR 分离物 CtPhS_1，EC ₅₀ 为 1,127 µg/ml，在密码子 200 (F200Y) 处发生改变（TTC → TAC）。这种突变是由从腺嘌呤到胞嘧啶的核苷酸取代（GAG → GCG）引起的。另一种 HR 分离物 CtPhS_1，EC ₅₀ 为 1,127 µg/ml，在密码子 200 (F200Y) 处发生改变（TTC → TAC）。这种突变是由从腺嘌呤到胞嘧啶的核苷酸取代（GAG → GCG）引起的。另一种 HR 分离物 CtPhS_1，EC ₅₀ 为 1,127 µg/ml，在密码子 200 (F200Y) 处发生改变（TTC → TAC）。