López-Escudero F J, Blanco-López M A
Departamento de Agronomía, ETSIAM, Universidad de Córdoba, Apdo. 3048, 14080, Córdoba, Spain.
Plant Dis. 2007 Nov;91(11):1372-1378. doi: 10.1094/PDIS-91-11-1372.
An experiment was conducted in microplots which were artificially infested with a defoliating isolate of Verticillium dahliae using seven different treatments of inoculum densities ranging from 0 to 10 microsclerotia per gram of soil (ppg). The experiment was conducted in Andalucía (southern Spain), and the susceptible Spanish olive cv. Picual was used to determine the relationship between pathogen inoculum density and the progress of Verticillium wilt of olive (VWO). The inoculum, produced on a sodium pectate cellophane medium, was found to efficiently infect olive trees. Symptoms first appeared 30 weeks after the trees were transplanted into infested soil. Periods of increasing disease incidence in the following seasons and years were mainly during spring and autumn, particularly in the second year after planting. Olive trees exhibited a high susceptibility to the defoliating pathotype of the pathogen, even at very low inoculum levels; in fact, diseased plants were encountered throughout the experiment regardless of the inoculum density treatment. Inoculum densities greater than 3 ppg in the soil resulted in final disease incidence greater than 50% for the trees after 2.5 years. Therefore, these inoculum densities must be considered very high for olive trees. There were no differences in final disease incidence, mean symptom severity, or area under the disease progress curve between plots infested with 10 or 3.33 ppg, whereas other treatments exhibited lower values for each of these disease parameters. The temporal variations of disease incidence and severity were highly correlated for the higher inoculum density treatments, with r values ranging from 0.92 to 0.84 for disease incidence and from 0.93 to 0.88 for severity. However, r was slightly lower for the treatments involving lower inoculum densities of the pathogen in microplots. The slopes of the linear regression curves were statistically different for nearly all the inoculum density treatments. Positive correlation was found between the initial inoculum density and final disease incidence values after the study period that was accurately explained by mathematical models. The results suggest that susceptible olive cultivars should not be planted in soils infested with virulent defoliating pathotypes of V. dahliae. Results also clarify that inoculum density levels obtained from field soil analyses can be used for establishing a risk prediction system with a view to controlling VWO in olive tree plantations.
在人工接种大丽轮枝菌落叶分离株的微小区中进行了一项实验，采用了七种不同的接种密度处理，范围从每克土壤0至10个微菌核（ppg）。该实验在安达卢西亚（西班牙南部）进行，使用了易感的西班牙油橄榄品种皮夸尔来确定病原菌接种密度与油橄榄黄萎病（VWO）病情发展之间的关系。在果胶酸钠玻璃纸培养基上产生的接种物被发现能有效感染油橄榄树。症状在树木移植到受侵染土壤30周后首次出现。在接下来的季节和年份中，病情发病率增加的时期主要在春季和秋季，特别是在种植后的第二年。油橄榄树对病原菌的落叶型表现出高度易感性，即使在接种水平非常低的情况下也是如此；事实上，在整个实验过程中，无论接种密度处理如何，都发现了患病植株。土壤中接种密度大于3 ppg会导致2.5年后树木的最终发病率大于50%。因此，对于油橄榄树来说，这些接种密度必须被视为非常高。接种10或3.33 ppg的小区之间在最终发病率、平均症状严重程度或病情发展曲线下面积方面没有差异，而其他处理在这些病害参数中的每一个都表现出较低的值。对于较高接种密度处理，病情发病率和严重程度的时间变化高度相关，病情发病率的r值范围从0.92至0.84，严重程度的r值范围从0.93至0.88。然而，对于微小区中病原菌接种密度较低的处理，r值略低。几乎所有接种密度处理的线性回归曲线斜率在统计学上都不同。在研究期后，初始接种密度与最终发病率值之间发现了正相关，这可以通过数学模型准确解释。结果表明，易感油橄榄品种不应种植在受大丽轮枝菌强毒落叶型侵染的土壤中。结果还表明，从田间土壤分析获得的接种密度水平可用于建立一个风险预测系统，以控制油橄榄种植园中的VWO。
