Department of Plant Pathology, University of Georgia, Athens, GA.
Plant Dis. 2019 Jun;103(6):1293-1301. doi: 10.1094/PDIS-09-18-1534-RE. Epub 2019 Apr 17.
Epidemiological field studies utilizing disease monitoring, spore trapping, and trap plants were conducted on rabbiteye blueberry () between 2014 and 2017 to shed light on the epidemiology of Exobasidium leaf and fruit spot, an emerging disease in the southeastern United States caused by the fungus . Wash plating of field-collected blueberry tissue from the late dormant season through bud expansion showed that the pathogen overwintered epiphytically on blueberry plants in the field, most likely in its yeast-like conidial stage. Agrichemical applications during the dormant season altered epiphytic populations of the pathogen, which correlated directly with leaf spot incidence later in the spring. Disease monitoring of field plants and weekly exposure of potted trap plants revealed that young leaves at the mouse-ear stage were most susceptible to infection, that disease incidence on leaves progressed monocyclically, and that infection periods were associated with rainfall variables such as the number of days per week with ≥1.0 mm of rain or cumulative weekly rainfall. Weekly spore trapping with an Andersen sampler showed that airborne inoculum was detected only after sporulating leaf lesions producing basidiospores were present in the field, suggesting that the primary inoculum is not airborne. The first symptoms on young, green fruit were observed soon after petal fall (requiring removal of the waxy fruit layer to visualize lesions), and visible disease progress on fruit was delayed by 1 to 3 weeks relative to that on leaves. Fruit infection of field plants and trap plants occurred before airborne propagules were detected by spore trapping and before sporulating leaf lesions were present in the field. Hence, this study showed that fruit infections are initiated by the same initial inoculum as leaf infections but it was not possible to conclusively exclude the possibility of a contribution of basidiospore inoculum from leaf lesions to disease progress on later developing fruit. This is one of only a few studies addressing the epidemiology and disease cycle of an sp. in a pathosystem where artificial inoculation has not been possible to date.
2014 年至 2017 年，对兔眼蓝莓（）进行了疾病监测、孢子诱捕和诱捕植物的流行病学实地研究，以阐明叶斑和果实斑点的流行病学，这是美国东南部一种新兴疾病，由真菌引起。从休眠后期到芽期扩展，对田间采集的蓝莓组织进行的洗涤平板显示，病原体在田间的蓝莓植物上以附生方式越冬，最有可能处于其酵母状分生孢子阶段。休眠季节的农用化学品应用改变了病原体的附生种群，这与春季晚些时候叶斑病的发病率直接相关。田间植物的疾病监测和每周暴露于盆栽诱捕植物表明，鼠耳状的幼叶最易感染，叶片上的病害发病率呈单循环进展，感染期与降雨变量有关，如每周有≥1.0 毫米降雨或每周累计降雨量的天数。每周用安德森采样器进行的孢子诱捕表明，仅在田间出现产孢叶斑病斑后才检测到气传接种体，表明主要接种体不是气传的。在花瓣落下后不久（需要去除蜡质果层才能观察到病变），就观察到幼果上的最初症状，与叶片相比，果实上的可见病害进展延迟 1 至 3 周。在田间植物和诱捕植物上发现果实感染之前，通过孢子诱捕检测到气传繁殖体，并且在田间出现产孢叶斑病斑之前。因此，本研究表明，果实感染是由与叶片感染相同的初始接种体引发的，但不能排除来自叶斑病斑的担子孢子接种体对后期发育果实病害进展的贡献。这是为数不多的几篇研究之一，涉及到人工接种迄今尚未可能的病理系统中 的流行病学和病害循环。
