Phytopathology. 1999 Aug;89(8):653-9. doi: 10.1094/PHYTO.1999.89.8.653.
ABSTRACT The effects of temperature and duration of wetness (relative humidity >/=95%) on infection of three peanut cultivars by Cercospora arachidicola were determined under controlled conditions. Plants of the Spanish cv. Spanco and the runner cvs. Florunner and Okrun were exposed to constant temperatures of 18 to 30 degrees C during 12-h periods of wetness each day that totaled 12 to 84 h following inoculation of leaves with conidia. Severity of disease, measured by either lesion density (number per leaf) or lesion size (diameter), was greatest for 'Spanco', intermediate for 'Florunner', and lowest for 'Okrun' in each of two experiments. Lesion density was evaluated further because it was an indicator of both the occurrence and degree of infection. Nonlinear regression analysis was employed to evaluate the combined effects of temperature (T) and wetness duration (W) on lesion density (Y). In the regression model, the Weibull function characterized the monotonic increase of Y with respect to W, while a hyperbolic function characterized the unimodal response of Y with respect to T. Parameters for the intrinsic rate of change with respect to W (b), the intrinsic rate of change with respect to T (f), the optimal value of T (g), and the upper limit (e) when T is optimum (T = g) were estimated for each cultivar and experiment. The effect of cultivar was characterized primarily by differences in the upper limit parameter e. In each experiment, e was greatest for 'Spanco', intermediate for 'Florunner', and least for 'Okrun'. The effect of cultivar on b followed a pattern similar to that for e in experiment 1, but not in experiment 2. Differences among cultivars for estimates of f and g were small and inconsistent. Estimates for g were precise for each cultivar and experiment and fell within the range of 22.3 to 23.2 degrees C. Cultivar responses to T and W were further evaluated using data pooled over the two experiments. Parameter e was estimated for each cultivar, but common values of b, f, and g were estimated. At e = 22.8 degrees C, lesion density approached an upper limit of 96, 17, and 6 lesions per leaf for the cvs. Spanco, Florunner, and Okrun, respectively. These fitted values approximated the observed values of 86, 25, and 9 lesions per leaf for the respective cultivars. Cultivars varied in their response to W at a given T. At 22.8 degrees C, one lesion per leaf was expected following 26, 30, and 36 h of wetness for 'Spanco', 'Florunner', and 'Okrun', respectively. If temperature was increased to 28 degrees C, one lesion per leaf was expected following 36, 44, and 54 h of wetness for the respective cultivars.
摘要 在控制条件下，测定了温度和湿度持续时间（相对湿度> = 95%）对 3 个花生品种被尾孢菌感染的影响。在每天 12 小时的湿期内，西班牙 cv. Spanco 和 runner cv. Florunner 和 Okrun 的植株暴露在 18 至 30 摄氏度的恒定温度下，接种叶片后，湿期总时长为 12 至 84 小时。在两次实验中，“Spanco”的病害严重程度最大，“Florunner”居中，“Okrun”最小，用病变密度（每叶的数量）或病变大小（直径）来衡量。在进一步评估病变密度时，因为它是感染发生和程度的指标。采用非线性回归分析评估温度（T）和湿度持续时间（W）对病变密度（Y）的综合影响。在回归模型中，Weibull 函数描述了 Y 随 W 的单调增加，而双曲函数描述了 Y 随 T 的单峰响应。对于每个品种和实验，分别估计了与 W 相关的内禀增长率（b）、与 T 相关的内禀增长率（f）、T 的最佳值（g）和 T 最优时的上限（e）（T = g）。品种的影响主要由上限参数 e 的差异决定。在每次实验中，“Spanco”的 e 值最大，“Florunner”的 e 值居中，“Okrun”的 e 值最小。品种对 b 的影响模式与实验 1 中的 e 相似，但在实验 2 中并非如此。品种间对 f 和 g 的估计值差异较小且不一致。g 的估计值对于每个品种和实验都很精确，落在 22.3 至 23.2 摄氏度的范围内。使用两次实验的数据进一步评估了品种对 T 和 W 的反应。为每个品种估计了参数 e，但估计了 b、f 和 g 的公共值。在 e = 22.8°C 时，Spanco、Florunner 和 Okrun 的叶片病变密度分别接近 96、17 和 6 个病变的上限。这些拟合值接近各自品种的 86、25 和 9 个病变的观察值。品种在给定 T 下对 W 的反应不同。在 22.8°C 时，预计 Spanco、Florunner 和 Okrun 的叶片每片分别出现 26、30 和 36 小时的湿期后会出现 1 个病变。如果温度升高到 28°C，预计每个品种的叶片分别出现 36、44 和 54 小时的湿期后会出现 1 个病变。
