Phytopathology. 1999 Jan;89(1):84-91. doi: 10.1094/PHYTO.1999.89.1.84.
ABSTRACT Using a combination of experimentation and mathematical modeling, the effects of initial (particulate) inoculum density on the dynamics of disease resulting from primary and secondary infection of wheat by the take-all fungus, Gaeumannomyces graminis var. tritici, were tested. A relatively high inoculum density generated a disease progress curve that rose monotonically toward an asymptote. Reducing the initial inoculum density resulted in a curve that initially was monotonic, rising to a plateau, but which increased sigmoidally to an asymptotic level of disease thereafter. Changes in the infectivity of particulate inoculum over time were examined in a separate experiment. Using a model that incorporated terms for primary and secondary infection, inoculum decay, and host growth, we showed that both disease progress curves were consistent with consecutive phases dominated, respectively, by primary and secondary infection. We examined the spread of disease from a low particulate inoculum density on seminal and adventitious root systems separately. Although seminal roots were affected by consecutive phases of primary and secondary infection, adventitious roots were affected only by secondary infection. We showed that the characteristic features of disease progress in controlled experiments were consistent with field data from crops of winter wheat. We concluded that there is an initial phase of primary infection by G. graminis var. tritici on winter wheat as seminal roots grow through the soil and encounter inoculum, but the rate of primary infection slows progressively as inoculum decays. After the initial phase, there is an acceleration in the rate of secondary infection on both seminal and adventitious roots that is stimulated by the increase in the availability of infected tissue as a source of inoculum and the availability of susceptible tissue for infection.
摘要 本研究采用实验和数学建模相结合的方法，测试了初侵染（颗粒）接种密度对禾顶囊壳菌（Gaeumannomyces graminis var. tritici）初次侵染和再次侵染小麦引起病害动态的影响。较高的初始接种密度会导致病害进展曲线呈单调上升趋势，逐渐逼近渐近线。而降低初始接种密度则会导致曲线呈单调上升趋势，达到一个平台期，但随后会呈指数增长，达到渐近水平的病害。在另一个实验中，我们研究了颗粒接种物随时间的感染力变化。通过一个包含初次侵染和再次侵染、接种物衰减和宿主生长的模型，我们发现这两种病害进展曲线都与分别由初次侵染和再次侵染主导的连续阶段一致。我们分别研究了低颗粒接种密度在主根和不定根系统上的病害传播。尽管主根受到初次侵染和再次侵染的连续阶段的影响，但不定根仅受到再次侵染的影响。我们表明，控制实验中病害进展的特征与来自冬小麦作物的田间数据一致。我们得出结论，在冬小麦主根穿过土壤并接触接种物时，禾顶囊壳菌会经历一个初始的初次侵染阶段，但随着接种物的衰减，初次侵染的速度会逐渐减缓。在初始阶段之后，在主根和不定根上会加速再次侵染，这是由受感染组织作为接种物来源的可用性增加以及易感组织的可用性增加所刺激的。
