Phytopathology. 2003 Apr;93(4):502-12. doi: 10.1094/PHYTO.2003.93.4.502.
ABSTRACT Citrus sudden death (CSD), a new disease of unknown etiology that affects sweet orange grafted on Rangpur lime, was visually monitored for 14 months in 41 groves in Brazil. Ordinary runs analysis of CSD-symptomatic trees indicated a departure from randomness of symptomatic trees status among immediately adjacent trees mainly within rows. The binomial index of dispersion (D) and the intraclass correlation (k) for various quadrat sizes suggested aggregation of CSD-symptomatic trees for almost all plots within the quadrat sizes tested. Estimated parameters of the binary form of Taylor's power law provided an overall measure of aggregation of CSD-symptomatic trees for all quadrat sizes tested. Aggregation in each plot was dependent on disease incidence. Spatial autocorrelation analysis of proximity patterns suggested that aggregation often existed among quadrats of various sizes up to three lag distances; however, significant lag positions discontinuous from main proximity patterns were rare, indicating a lack of spatial association among discrete foci. Some asymmetry was also detected for some spatial autocorrelation proximity patterns, indicating that within-row versus across-row distributions are not necessarily equivalent. These results were interpreted to mean that the cause of the disease was most likely biotic and its dissemination was common within a local area of influence that extended to approximately six trees in all directions, including adjacent trees. Where asymmetry was indicated, this area of influence was somewhat elliptical. Longer-distance patterns were not detected within the confines of the plot sizes tested. Annual rates of CSD progress based on the Gompertz model ranged from 0.37 to 2.02. Numerous similarities were found between the spatial patterns of CSD and Citrus tristeza virus (CTV) described in the literature, both in the presence of the aphid vector, Toxoptera citricida. CSD differs from CTV in that symptoms occur in sweet orange grafted on Rangpur lime. Based on the symptoms of CSD and on its spatial and temporal patterns, our hypothesis is that CSD may be caused by a similar but undescribed pathogen such as a virus and probably vectored by insects such as aphids by similar spatial processes to those affecting CTV.
摘要 柑橘猝死病（CSD）是一种新的病因不明的疾病，影响甜橙嫁接到莱姆上。在巴西的 41 个果园中，对其进行了为期 14 个月的视觉监测。对 CSD 症状树的普通运行分析表明，主要在行间，临近的症状树状态的随机性发生偏离。各种大小的方格离散度（D）和内类相关（k）的二项式指标表明，CSD 症状树几乎在所有测试的方格大小内都呈聚集状态。泰勒幂律的二项式形式的估计参数为所有测试方格大小的 CSD 症状树的聚集提供了总体度量。每个地块的聚集取决于疾病的发病率。邻近模式的空间自相关分析表明，在各种大小的方格中，聚集通常存在于三个滞后距离以内；然而，显著的滞后位置与主要邻近模式不连续是罕见的，表明离散焦点之间缺乏空间关联。对于一些空间自相关邻近模式，也检测到一些不对称，表明行间与跨行间的分布不一定相等。这些结果表明，疾病的原因很可能是生物的，其传播在一个局部影响区域内很常见，在所有方向上大约扩展到六棵树，包括相邻的树。在表明存在不对称的地方，这个影响区域有点椭圆形。在测试的地块大小范围内没有检测到更长距离的模式。基于 Gompertz 模型的 CSD 进展年度率范围为 0.37 至 2.02。在蚜虫媒介 Toxoptera citricida 的存在下，CSD 的空间模式与文献中描述的柑橘衰退病毒（CTV）有许多相似之处。CSD 与 CTV 的不同之处在于，症状发生在甜橙嫁接到莱姆上。基于 CSD 的症状及其时空模式，我们的假设是 CSD 可能是由一种类似但未被描述的病原体引起的，例如病毒，并且可能通过类似影响 CTV 的昆虫（如蚜虫）来传播。
