Chemical management of dollar spot in turf may lead to the development of Sclerotinia homoeocarpa populations with reduced fungicide sensitivity. The objective of this study was to investigate resistance of S. homoeocarpa isolates to triazole fungicides and to test cross-resistance among three triazole fungicides. A total of 66 isolates of S. homoeocarpa were collected from 15 golf courses across Korea, and tested via in vitro sensitivity assay against hexaconazole, propiconazole and tebuconazole. EC₅₀ values of the isolates to these fungicides were distributed in the range of 0.001-1.1 a. i. μg ml^-1. Based on the EC₅₀ values, twelve representative strains were selected as sensitive isolates including control and insensitive isolates with respect to each fungicide. At a concentration of 0.1 a. i. μg ml^-1 for all fungicides, the selected strains were distinguished as sensitive or resistant isolates with the mycelial growth inhibition rate of 50% as the criterion. The EC₅₀ values of resistant strains exposed to hexaconazole, propiconazole and tebuconazole were 20-50 times, 50-70 times, and 77 times greater, respectively, than that of the control strains. Two isolates of S. homoeocarpa S0-41 and Sh14-2-1 showed sensitivity toward all the fungicides used, while two other isolates Sh7-5-1 and Sh2-1-1 showed resistance to all fungicides. Each isolate showed similar resistance to the three types of triazole fungicides, whereby cross-resistance of isolates was confirmed in the present study; all three triazole fungicide combinations displayed significant correlation coefficients equivalent to or greater than 0.8.

中文翻译：

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三唑类杀菌剂在韩国高尔夫球场中对核盘菌的敏感性。

草坪中美元斑的化学处理可能导致杀菌剂敏感性降低的高果核盘菌种群的发展。这项研究的目的是调查高果链球菌分离株对三唑类杀菌剂的耐药性，并测试三种三唑类杀菌剂之间的交叉耐药性。从韩国的15个高尔夫球场中收集了共66株高果链球菌，并通过体外敏感性测定对六孔唑，丙环唑和戊唑醇进行了测试。分离物对这些杀真菌剂的EC ₅₀值分布在0.001-1.1aiμgml ^-1的范围内。基于EC ₅₀值，选择十二种代表性菌株作为敏感菌株，包括对每种杀菌剂的对照和不敏感菌株。所有杀菌剂的浓度为0.1 aiμgml ^-1时，以50％的菌丝体生长抑制率为标准，将所选菌株区分为敏感或耐药菌株。暴露于己康唑，丙环唑和戊唑醇的抗性菌株的EC ₅₀值分别比对照菌株高20-50倍，50-70倍和77倍。高果链球菌的两个分离株S0-41和Sh14-2-1对所有使用的杀菌剂均表现出敏感性，而另外两个分离株Sh7-5-1和Sh2-1-1对所有杀菌剂均表现出抗性。每个分离株对三种类型的三唑类杀菌剂均显示出相似的抗性，从而在本研究中证实了分离株的交叉抗性。所有三种三唑杀菌剂组合均显示出等于或大于0.8的显着相关系数。