Severns Paul M, Estep Laura K, Sackett Kathryn E, Mundt Christopher C
Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, USA.
Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, USA ; Connecticut Agricultural Experimental Station, Department of Entomology, University of Connecticut, New Haven, Connecticut, USA.
J Appl Ecol. 2014 Dec 1;51(6):1622-1630. doi: 10.1111/1365-2664.12326.
Disease epidemics typically begin as an outbreak of a relatively small, spatially explicit population of infected individuals (focus), in which disease prevalence increases and rapidly spreads into the uninfected, at-risk population. Studies of epidemic spread typically address factors influencing disease spread through the at-risk population, but the initial outbreak may strongly influence spread of the subsequent epidemic.We initiated wheat stripe rust f. sp. epidemics to assess the influence of the focus on final disease prevalence when the degree of disease susceptibility differed between the at-risk and focus populations.When the focus/at-risk plantings consisted of partially genetic resistant and susceptible cultivars, final disease prevalence was statistically indistinguishable from epidemics produced by the focus cultivar in monoculture. In these experimental epidemics, disease prevalence was not influenced by the transition into an at-risk population that differed in disease susceptibility. Instead, the focus appeared to exert a dominant influence on the subsequent epidemic.Final disease prevalence was not consistently attributable to either the focus or the at-risk population when focus/at-risk populations were planted in a factorial set-up with a mixture (~28% susceptible and 72% resistant) and susceptible individuals. In these experimental epidemics, spatial heterogeneity in disease susceptibility within the at-risk population appeared to counter the dominant influence of the focus.Cessation of spore production from the focus (through fungicide/glyphosate application) after 1.3 generations of stripe rust spread did not reduce final disease prevalence, indicating that the focus influence on disease spread is established early in the epidemic. Our experiments indicated that outbreak conditions can be highly influential on epidemic spread, even when disease resistance in the at-risk population is greater than that of the focus. Disease control treatments administered shortly after the initial outbreak within the focus may either prevent an epidemic from occurring or reduce its severity.
疾病流行通常始于一小群空间明确的受感染个体（疫点）的爆发，在这个群体中疾病患病率上升，并迅速传播到未受感染的高危人群中。对流行病传播的研究通常关注影响疾病在高危人群中传播的因素，但最初的爆发可能会对后续流行病的传播产生强烈影响。我们引发了小麦条锈病菌的流行，以评估当高危人群和疫点人群的疾病易感性不同时，疫点对最终疾病患病率的影响。当疫点/高危种植区由部分遗传抗性和易感品种组成时，最终疾病患病率在统计学上与单一栽培的疫点品种引发的流行病没有区别。在这些实验性流行病中，疾病患病率不受向疾病易感性不同的高危人群转变的影响。相反，疫点似乎对后续流行病产生了主导影响。当疫点/高危人群以因子设计种植，包含混合物（约28%易感和72%抗性）和易感个体时，最终疾病患病率并不总是可归因于疫点或高危人群。在这些实验性流行病中，高危人群中疾病易感性的空间异质性似乎抵消了疫点的主导影响。在条锈病传播1.3代后，停止疫点的孢子产生（通过施用杀菌剂/草甘膦）并没有降低最终疾病患病率，这表明疫点对疾病传播的影响在流行病早期就已确立。我们的实验表明，即使高危人群的抗病性大于疫点，爆发条件对流行病传播也可能有很大影响。在疫点内最初爆发后不久进行的疾病控制处理可能会阻止流行病的发生或降低其严重程度。
