USDA-ARS-SEFTNRL, Byron, GA 31008.
Division of Biometrics, Department of Agronomy, National Chung Hsing University, Taichung, Taiwan.
Plant Dis. 2019 Nov;103(11):2865-2876. doi: 10.1094/PDIS-11-18-1950-RE. Epub 2019 Aug 29.
The most destructive disease of pecan in the southeastern United States is scab, caused by . Incidence (I)-severity (S) relationships have not previously been characterized in this pathosystem, but incidence measures can save time and should have higher accuracy compared with estimates of severity. Ten scab-susceptible cultivars and seedling trees were assessed for I and S of scab on fruit (1,972 trees) and foliage (compound leaves and leaflets, 1,129 trees) between 2010 and 2014. Samples were assessed on a tree basis, and sample size ranged from 10 to 100 specimens per tree. The range in mean I and S was different depending on the organ (fruit I = 0 to 100%, S = 0 to 100%; compound leaves and leaflets, I = 0 to 100%, S = 0-10.1%, respectively). However, mean I could be 100% at a mean S < 2.0% for fruit, compound leaves, and leaflets. Both I and S data were transformed by complementary log-log prior to linear regression analysis. A linear regression model described the relationship between transformed I and S per tree for fruit ( ≤ 0.0001, R = 0.61), compound leaves ( ≤ 0.0001, R = 0.82), and leaflets ( ≤ 0.0001, R = 0.91) for all cultivars. The regression analysis showed significant effects of cultivar and year on the relationship between I and S; therefore, separate analyses were performed for each cultivar and year. Back-transformed predicted severity values showed that the differences among cultivars and years were negligible at severity <80%, and were generally numerically small at severity >80%. The observation that low severity persists until a high incidence of scab is achieved may limit the ability of incidence data to clearly differentiate treatment effects, even when based on the CLL transformation. But if found to be effective, and if used, it would reduce the labor requirements and result in more accurate data being obtained, as incidence estimates do not tend to suffer from the same subjective biases as do visual estimates of severity.
美国东南部对山核桃破坏性最大的疾病是疮痂病，由 引起。在这个病理系统中，发病率（I）-严重度（S）关系以前没有被描述过，但发病率的测量可以节省时间，并且与严重度的估计相比应该具有更高的准确性。2010 年至 2014 年，对 10 个疮痂病易感品种和实生树的果实（1972 棵树）和叶片（复叶和小叶，1129 棵树）的疮痂病发病率（I）和严重度（S）进行了评估。样品是按树为基础进行评估的，每个树的样本大小从 10 到 100 个标本不等。由于器官的不同，平均 I 和 S 的范围也不同（果实 I = 0 到 100%，S = 0 到 100%；复叶和小叶，I = 0 到 100%，S = 0-10.1%）。然而，在平均 S < 2.0%的情况下，果实、复叶和小叶的平均 I 可以达到 100%。在进行线性回归分析之前，I 和 S 数据都通过互补对数转换。对于所有品种，树间的 I 和 S 的线性回归模型描述了果实（≤0.0001，R = 0.61）、复叶（≤0.0001，R = 0.82）和小叶（≤0.0001，R = 0.91）的转换后 I 和 S 之间的关系。回归分析表明，品种和年份对 I 和 S 之间的关系有显著影响；因此，对每个品种和年份分别进行了分析。反变换后的预测严重度值表明，在严重度 <80%时，品种和年份之间的差异可以忽略不计，而在严重度 >80%时，差异通常在数值上很小。在达到高疮痂病发病率之前，低严重度持续存在的现象可能会限制发病率数据清楚地区分处理效果的能力，即使是基于 CLL 变换。但是，如果发现有效，并且如果使用，它将减少劳动力需求，并获得更准确的数据，因为发病率的估计不会像严重度的视觉估计那样受到同样的主观偏见的影响。
