Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691.
Phytopathology. 2012 Sep;102(9):867-77. doi: 10.1094/PHYTO-11-11-0323.
A multilevel analysis of heterogeneity of disease incidence was conducted based on observations of Fusarium head blight (caused by Fusarium graminearum) in Ohio during the 2002-11 growing seasons. Sampling consisted of counting the number of diseased and healthy wheat spikes per 0.3 m of row at 10 sites (about 30 m apart) in a total of 67 to 159 sampled fields in 12 to 32 sampled counties per year. Incidence was then determined as the proportion of diseased spikes at each site. Spatial heterogeneity of incidence among counties, fields within counties, and sites within fields and counties was characterized by fitting a generalized linear mixed model to the data, using a complementary log-log link function, with the assumption that the disease status of spikes was binomially distributed conditional on the effects of county, field, and site. Based on the estimated variance terms, there was highly significant spatial heterogeneity among counties and among fields within counties each year; magnitude of the estimated variances was similar for counties and fields. The lowest level of heterogeneity was among sites within fields, and the site variance was either 0 or not significantly greater than 0 in 3 of the 10 years. Based on the variances, the intracluster correlation of disease status of spikes within sites indicated that spikes from the same site were somewhat more likely to share the same disease status relative to spikes from other sites, fields, or counties. The estimated best linear unbiased predictor (EBLUP) for each county was determined, showing large differences across the state in disease incidence (as represented by the link function of the estimated probability that a spike was diseased) but no consistency between years for the different counties. The effects of geographical location, corn and wheat acreage per county, and environmental conditions on the EBLUP for each county were not significant in the majority of years.
基于 2002-11 年俄亥俄州镰孢穗枯病（由禾谷镰刀菌引起）的观测数据，采用多层次分析法对病害发生率的异质性进行了分析。采样方法为在 10 个地点（每个地点约 30m 远，每县 12-32 个采样点）的每 0.3m 行长的行内计数感病和健康小麦穗数。然后将每个地点的感病穗率作为发病率。各县、各县内各田块和各田块内各采样点间发病率的空间异质性，采用广义线性混合模型进行拟合，数据采用互补对数函数连接，假设穗部病害状态在条件为县、田块和采样点效应的情况下服从二项分布。根据估计的方差项，每年各县间和各县内各田块间的空间异质性均具有高度显著意义；各县和各田块间估计方差的大小相似。各田块内各采样点间的异质性最小，在 10 年中的 3 年，采样点方差为 0 或不显著大于 0。根据方差，各采样点内穗部病害状态的组内相关表明，同一采样点的穗部更有可能具有相同的病害状态，而不是来自其他采样点、田块或县的穗部。确定了每个县的最佳线性无偏预测值（EBLUP），表明全州各县的病害发生率存在很大差异（表现为估计的穗部感病概率的连接函数），但各县间多年来没有一致性。在大多数年份，地理位置、各县的玉米和小麦种植面积以及环境条件对各县 EBLUP 的影响并不显著。
