Phytopathology. 2002 Nov;92(11):1152-9. doi: 10.1094/PHYTO.2002.92.11.1152.
ABSTRACT The Karnal bunt pathogen, Tilletia indica, is heterothallic and depends on encounters on wheat spikes between airborne secondary sporidia of different mating types for successful infection and reproduction. This life history characteristic results in reduced reproductive success for lower population densities. Such destabilizing density dependence at low population levels has been described for a range of animals and plants and is often termed an Allee effect. Our objective was to characterize how the Allee effect might reduce the invasive potential of this economically important pathogen. We developed a simple population model of T. indica that incorporates an Allee effect by calculating the probability of infection for different numbers of secondary sporidia in the infection court. An Allee effect is predicted to be important at the frontier of an invasion, for establishment of new foci by a small population of teliospores, and when the environment is nonconducive for the production of secondary sporidia. Using estimated model parameter values, we demonstrated a theoretical threshold population size below which populations of T. indica were predicted to decline rather than increase. This threshold will vary from season to season as a function of weather variables and their effect on the reproductive potential of T. indica. Deployment of partial resistance or use of fungicides may be more useful if they push population levels below this threshold.
卡纳尔腥黑穗病菌（Tilletia indica）是异宗配合的，依赖于空气中不同交配型的次级分生孢子在小麦穗上相遇，才能成功感染和繁殖。这种生活史特征导致较低种群密度下的繁殖成功率降低。这种在低种群水平下的不稳定密度依赖性已在多种动植物中得到描述，通常被称为阿利效应。我们的目标是描述阿利效应如何降低这种具有重要经济意义的病原体的入侵潜力。我们开发了一个简单的 T. indica 种群模型，通过计算感染法庭中不同数量的次级分生孢子的感染概率来纳入阿利效应。阿利效应预计在入侵的前沿、由少量冬孢子建立新焦点以及环境不利于次级分生孢子产生时很重要。使用估计的模型参数值，我们证明了理论上的种群大小阈值，低于该阈值，T. indica 的种群预计会减少而不是增加。这个阈值将随着天气变量及其对 T. indica 生殖潜力的影响而在季节之间变化。如果局部抗性的部署或杀菌剂的使用将种群水平推低至这个阈值以下，可能会更有用。
