Xu Z, Gleason M L, Mueller D S, Esker P D, Bradley C A, Buck J W, Benson D M, Dixon P M, Monteiro J E B A
Department of Plant Pathology, Iowa State University, Ames 50011.
Department of Plant Pathology, North Dakota State University, Fargo 58105.
Plant Dis. 2008 May;92(5):719-724. doi: 10.1094/PDIS-92-5-0719.
Previously known only from the southern United States, hosta petiole rot recently appeared in the northern United States. Sclerotium rolfsii var. delphinii is believed to be the predominant petiole rot pathogen in the northern United States, whereas S. rolfsii is most prevalent in the southern United States. In order to test the hypothesis that different tolerance to climate extremes affects the geographic distribution of these fungi, the survival of S. rolfsii and S. rolfsii var. delphinii in the northern and southeastern United States was investigated. At each of four locations, nylon screen bags containing sclerotia were placed on the surface of bare soil and at 20-cm depth. Sclerotia were recovered six times from November 2005 to July 2006 in North Dakota and Iowa, and from December 2005 to August 2006 in North Carolina and Georgia. Survival was estimated by quantifying percentage of sclerotium survival on carrot agar. Sclerotia of S. rolfsii var. delphinii survived until at least late July in all four states. In contrast, no S. rolfsii sclerotia survived until June in North Dakota or Iowa, whereas 18.5% survived until August in North Carolina and 10.3% survived in Georgia. The results suggest that inability to tolerate low temperature extremes limits the northern range of S. rolfsii.
玉簪叶柄腐烂病此前仅在美国南部有记载，最近在美国北部也出现了。罗尔夫小核菌德尔菲变种被认为是美国北部主要的叶柄腐烂病原菌，而罗尔夫小核菌在美国南部最为普遍。为了验证不同的极端气候耐受性影响这些真菌地理分布的假说，对罗尔夫小核菌和罗尔夫小核菌德尔菲变种在美国北部和东南部的存活情况进行了调查。在四个地点的每一处，将装有菌核的尼龙筛袋放置在裸土表面和20厘米深处。2005年11月至2006年7月在北达科他州和爱荷华州，以及2005年12月至2006年8月在北卡罗来纳州和佐治亚州，对菌核进行了六次回收。通过量化胡萝卜琼脂上菌核的存活百分比来估计存活率。罗尔夫小核菌德尔菲变种的菌核在所有四个州至少存活到7月下旬。相比之下，北达科他州或爱荷华州没有罗尔夫小核菌菌核存活到6月，而在北卡罗来纳州18.5%的菌核存活到8月，在佐治亚州10.3%的菌核存活。结果表明，无法耐受极端低温限制了罗尔夫小核菌在北部的分布范围。
