Two isolates of Rhizoctonia solani AG11 were isolated from sugar beet seedlings from South-west Poland. Both isolates gave C2 reactions in anastomose pairings with the tester isolates of AG11. The membership of both isolates to AG11 was confirmed by analysis of pectic isozyme profiles, and by verification that the internal transcribed spacer sequences of both isolates matched the references in the GenBank database. Both AG11 isolates formed white-beige to creamy-colored mycelium with wide concentric zonation. One of them formed light-colored sclerotia. The average daily rate of hyphal growth at 21 °C was 22.8 mm and 22.6 mm on PDA. They were mildly pathogenic to sugar beet seedlings due to the mycelial and secondary metabolites’ activity. The sensitivity to fungicides typically used in sugar beet protection was different for each isolate; one of them (isolate ID11) was less sensitive to thiram than the other (isolate ID3). This article discusses the worldwide occurrence of R. solani AG11, expands the currently known host range, shows its broad world distribution in regions of moderate climate, and confirms the isolates’ low frequency.

两种枯萎病菌从波兰西南部的甜菜幼苗中分离出AG11。两种分离物均与AG11的测试分离物以吻合的形式进行C2反应。通过对果胶同工酶谱的分析，并通过验证两个分离株的内部转录间隔区序列与GenBank数据库中的参考序列相匹配，证实了这两个分离株均属于AG11。这两个AG11分离物均形成了白色至浅米色至奶油色菌丝体，并具有宽的同心区域。其中之一形成浅色菌核。在PDA上，21°C的菌丝平均日生长速率为22.8 mm和22.6 mm。由于其菌丝和次生代谢产物的活性，它们对甜菜幼苗有轻度的致病性。每个分离株对甜菜保护中通常使用的杀菌剂的敏感性不同。其中一个（隔离号ID11）比其他（隔离号ID3）对thiram的敏感性低。本文讨论了世界范围内发生的R. solani AG11扩大了目前已知的寄主范围，显示了其在中等气候区域的广泛世界分布，并确认了分离株的低频率。