蔬菜及花卉立枯絲核菌（Rhizoctonia solani）對FRAC C類殺菌劑之感受性分析

Sensitivity Distribution of Rhizoctonia solani, Isolated from Vegetables and Ornamentals, to FRAC Group C Fungicides and Mixtures

李敏郎(Meen-Lang Lee)

《臺灣農藥科學》 13期 (2022/12) Pp. 1-17

https://doi.org/10.6671/TPS.202212_(13).01

摘要

本研究探討臺灣蔬菜及花卉等13種植物上所分離之15株立枯絲核菌 （Rhizoctonia solani）菌株，對FRAC C類及其混合劑等22種殺菌劑之感受性分佈情形，據此分析立枯絲核菌對同群作用機制殺菌劑是否存在交叉抗藥性，並檢視現行登記之殺菌劑劑量產生抗藥性之相對風險。供試菌株對C2類賽氟滅與福多寧，以及C3類百克敏最敏感，其EC_(50)分別為0.13±0.09、0.22±0.11及0.18±0.19 mg/L，C5類扶吉胺之EC_(50)為0.37±0.55 mg/L，而C4類殺菌劑EC_(50)均超過1,000 mg/L；在混合劑部份，亞托環克座及三氟得克利抑制菌絲生長的效果最佳，其EC_(50)分別為0.07±0.03及0.08±0.07 mg/L，其主要抑制作用來自G1類環克座及得克利。本研究首次應用集群分析（cluster analysis）方式，分析立枯絲核菌是否具備群內交叉抗藥性，結果顯示在不同群標的部位間不存在交叉抗藥性。另也首次應用列聯性分析（contingency analysis）方式，探討立枯絲核菌對現行登記殺菌劑劑量之相對抗藥性風險，結果顯示C2+M5混合劑之抗藥性風險最低，登記之最高劑量均可抑制供試菌株之菌絲生長，其次為C3+G1及C2+C3混合劑，其抗藥性風險值分別為10.0%及13.3%；單劑部份，C4及C3群則有100%及91.67%抗藥性風險，其概度比檢定與皮爾森卡方檢定之χ^2統計值分別為193.424及161.829，P值均小於0.001（N=329），綜言之，福多寧、四氯福多寧、四氯托敏及得克利之抗藥性風險最低，其次為亞托環克座、白克列及白列克收欣，均有6.67%抗藥性風險，而安美速、賽座滅、亞托敏、克收欣及三氟敏均為100%抗藥性風險。本研究首次以集群分析探討R. solani交叉抗藥性，以及應用列聯性分析探討R. solani相對抗藥性風險。

關鍵字

立枯絲核菌 ； 呼吸作用抑制劑 ； 感受性 ； 集群分析 ； 交叉抗藥性 ； 關聯性分析 ； 相對風險

並列摘要

This study investigated the sensitivity distribution of 15 Rhizoctonia solani isolates to 22 FRAC group C fungicides and mixtures. Isolates collected from 13 vegetable and ornamental species in central Taiwan and were found to be very sensitive to thifluzamide (FRAC group C, Subgroup C2), flutolanil (C2), pyraclostrobin (C3) and fluazinam (C5), with EC_(50) values of 0.13±0.09, 0.22±0.11, 0.18±0.19, and 0.37±0.55 mg/L, respectively. Isolates were not sensitive to subgroup C4 fungicides (EC_(50) values greater than 1,000 mg/L). Among group C mixtures, azoxystrobin + cyproconazole and trifloxystrobin + tebuconazole showed superior inhibitory effects, with EC_(50) values of 0.07±0.03 and 0.08±0.07 mg/L, respectively. The inhibitory effects of these mixtures were primarily conferred from the FRAC group G, subgroup G1 fungicides, cyproconazole and tebuconazole. In addition, we analyzed the cross-resistance of fungicides as well as the relative risk of R. solani isolates developing resistance to fungicides. Specially, we performed a cluster analysis to determine the cross-resistance of R. solani to fungicides that target the same sites. Results revealed that there is no cross-resistance between different targeted sites among FRAC group C fungicides. Finally, we performed a contingency analysis to assess the relative risk of R. solani developing resistance to currently-registered fungicides. We found that the C2+M5 mixture posed the lowest risk of fungicide resistance, followed by C3+G1 and C2+C3 mixtures, which had resistance risk values of 10.0% and 13.3%, respectively. For the single active ingredient considered in the study, a likelihood ratio test and the Pearson's chi-squared test respectively yielded χ^2 values of 193.424 and 161.829, and P values less than 0.001 (N=329). In summary, flutolanil, flutolanil + chlorothalonil, chlorothalonil + azoxystrobin and tebuconazole showed the lowest risk of resistance, followed by azoxystrobin + cyproconazole, boscalid and boscalid + kresoxim-methyl, which had a 6.67% risk of resistance. In contrast, amisulbrom, cyazofamid, azoxystrobin, kresoxim-methyl and trifloxystrobin all had 100% risk of resistance. This is the first study to (1) apply cluster analysis in determining the cross-resistance of R. solani and (2) apply a contingency analysis in assessing the relative risk fungicide resistance in R. solani.

並列關鍵字

Rhizoctonia solani ； respiration inhibitor ； sensitivity ； cluster analysis ； cross-resistance ； contingency analysis ； relative risk