Nagle Annemarie M, Long Robert P, Madden Laurence V, Bonello Pierluigi
Department of Plant Pathology, The Ohio State University, Columbus, OH 43210.
United States Department of Agriculture Forest Service, Northern Research Station, Delaware, OH 43015.
Plant Dis. 2010 Aug;94(8):1026-1034. doi: 10.1094/PDIS-94-8-1026.
A decline syndrome and widespread mortality of mature white oak tree (Quercus alba) associated with wet and low-lying areas has been recently observed in southern Ohio forests. Previous studies have isolated Phytophthora cinnamomi from white oak rhizospheres. In 2008 and 2009, P. cinnamomi population densities in two healthy and two declining white oak stands at Scioto Trail State Forest were quantified and potential roles of three environmental drivers of Phytophthora spp.-induced decline were assessed: soil texture, soil moisture, and topography. Significantly higher P. cinnamomi propagule densities were found in declining stands in both years but propagule densities were not associated with soil moisture content. Trends in population densities were not correlated with soil moisture or topographic position within field sites. There was a positive, exponential relationship between overall P. cinnamomi population levels and soil moisture on a seasonal scale in 2008 but not 2009. Sites with greater soil clay content were associated with greater decline. Effects of P. cinnamomi inoculum and periodic flooding on root health of 1-year-old potted white oak trees grown in native soil mixes in the greenhouse were examined. Root systems of potted oak were significantly damaged by soil inoculation with P. cinnamomi, especially under flooding conditions. Results of these studies support the hypothesis that P. cinnamomi is a contributing agent to white oak decline in southern Ohio.
最近在俄亥俄州南部森林中观察到，成熟白橡树（Quercus alba）出现衰退综合征并在潮湿低洼地区广泛死亡。此前的研究已从白橡树根际分离出肉桂疫霉。2008年和2009年，对Scioto Trail州立森林中两个健康和两个衰退的白橡树林分中的肉桂疫霉种群密度进行了量化，并评估了疫霉属引起衰退的三个环境驱动因素的潜在作用：土壤质地、土壤湿度和地形。在这两年中，衰退林分中的肉桂疫霉繁殖体密度均显著更高，但繁殖体密度与土壤含水量无关。种群密度趋势与田间场地内的土壤湿度或地形位置无关。2008年在季节尺度上，肉桂疫霉总体种群水平与土壤湿度之间存在正指数关系，但2009年没有。土壤粘土含量较高的场地与更大程度的衰退有关。研究了肉桂疫霉接种物和周期性洪水对温室中在原生土壤混合物中生长的1年生盆栽白橡树根系健康的影响。用肉桂疫霉对盆栽橡树的土壤进行接种会显著损害其根系，尤其是在洪水条件下。这些研究结果支持了肉桂疫霉是俄亥俄州南部白橡树衰退的一个促成因素这一假设。
