Garrett K A, Zúñiga L N, Roncal E, Forbes G A, Mundt C C, Su Z, Nelson R J
Department of Plant Pathology, 4024 Throckmorton Plant Sciences Center, Kansas State University, Manhattan, Kansas 66506, USA.
Ecol Appl. 2009 Oct;19(7):1868-83. doi: 10.1890/08-0942.1.
The effects of host biodiversity on disease risk may vary greatly depending on host population structure and climatic conditions. Agricultural diseases such as potato late blight, caused by Phytophthora infestans, provide the opportunity to study the effects of intraspecific host diversity that is relatively well-defined in terms of disease resistance phenotypes and may have functional impacts on disease levels. When these systems are present across a climatic gradient, it is also possible to study how season length and conduciveness of the environment to disease may influence the effects of host diversity on disease risk. We developed a simple model of epidemic progress to evaluate the effects on disease risk of season length, environmental disease conduciveness, and host functional divergence for mixtures of a susceptible host and a host with some resistance. Differences in disease levels for the susceptible vs. resistant genotypes shifted over time, with the divergence in disease levels first increasing and then decreasing. Disease reductions from host diversity were greatest for high host divergence and combinations of environmental disease conduciveness and season length that led to moderate disease severity. We also compared the effects of host functional divergence on potato late-blight risk in Ecuador (long seasons), two sites in Peru (intermediate seasons) in El Niño and La Niña years, and the United States (short seasons). There was some evidence for greater disease risk reduction from host diversity where seasons were shorter, probably because of lower regional inoculum loads. There was strong evidence for greater disease reduction when host functional divergence was greater. These results indicate that consideration of season length, environmental conduciveness to disease, and host functional divergence can help to explain the variability in disease response to host diversity.
宿主生物多样性对疾病风险的影响可能因宿主种群结构和气候条件的不同而有很大差异。由致病疫霉引起的马铃薯晚疫病等农业病害，为研究种内宿主多样性的影响提供了契机，这种多样性在抗病表型方面相对明确，可能对病害水平产生功能性影响。当这些系统存在于一个气候梯度上时，还可以研究季节长度和环境对病害的适宜程度如何影响宿主多样性对疾病风险的作用。我们开发了一个流行病进展的简单模型，以评估季节长度、环境病害适宜程度以及易感宿主与具有一定抗性的宿主混合时宿主功能差异对疾病风险的影响。易感基因型和抗性基因型的病害水平差异随时间变化，病害水平差异先增大后减小。对于高宿主差异以及导致中等病害严重程度的环境病害适宜程度和季节长度组合，宿主多样性带来的病害减少最为显著。我们还比较了宿主功能差异对厄瓜多尔（生长季节长）、秘鲁两个地点（生长季节中等）在厄尔尼诺年和拉尼娜年以及美国（生长季节短）马铃薯晚疫病风险的影响。有证据表明，在生长季节较短的地区，宿主多样性降低病害风险的效果更明显，这可能是因为区域接种量较低。有强有力的证据表明，宿主功能差异越大，病害减少越显著。这些结果表明，考虑季节长度、环境对病害的适宜程度以及宿主功能差异有助于解释病害对宿主多样性反应的变异性。
