Department of Plant Pathology, University of California-Davis, Kearney Agricultural Research and Extension Center, Parlier, CA, USA.
University of California - Cooperative Extension, Yuba City, CA, USA.
J Appl Microbiol. 2020 Nov;129(5):1337-1348. doi: 10.1111/jam.14702. Epub 2020 Jun 9.
A real-time quantitative PCR (qPCR) assay was established to quantify the inoculum densities in the air and rainwater for six canker-causing pathogen groups in prune and walnut orchards in California.
The previously published DNA primers to target six pathogen groups including Botryosphaeria dothidea, Cytospora spp., Diplodia spp., Lasiodiplodia spp., Neofusicoccum spp. and Phomopsis spp. were used in a qPCR assay. Air samples from Burkard spore traps and rain samples from special rain collector devices were collected periodically from various prune and walnut orchards. Using the qPCR approach, we were able to quantify the concentrations of these pathogen groups in rainwater and air samples and study the dynamics of pathogen inoculum in orchards showing severe canker potential. Phomopsis spp. and Diplodia spp. were not found in all rain samples in prune orchards, although they were detected in the 2016 in the walnut orchard. The other four pathogen groups were quantified at varying concentrations in the prune and walnut orchards. Cytospora spp. in some cases showed higher concentrations in the rainwater in prune orchards.
The rainy season during winter and early spring is a highly risky period of time for infection by the pathogens when the inoculum of these pathogens can easily spread by air and rain water, thus serving as an important inoculum source for disease initiation. The different studied pathogen groups showed different concentrations during the growing season, indicating the complexity of the components of canker-causing species in various tree crops.
This study showed the applicability of the qPCR assay in the quantification of inoculum in tree orchards to help reveal the mechanisms of canker disease epidemics and to help design disease management strategies.
建立实时荧光定量 PCR（qPCR）检测方法，用于定量加利福尼亚州李树和核桃园中六种溃疡病病原菌在空气和雨水中的接种体密度。
本研究使用先前发表的针对六种病原菌群的 DNA 引物，包括 Botryosphaeria dothidea、Cytospora spp.、Diplodia spp.、Lasiodiplodia spp.、Neofusicoccum spp. 和 Phomopsis spp.，进行 qPCR 检测。使用 Burkard 孢子捕捉器收集空气样本，使用特殊雨水收集器收集雨水样本，定期从不同的李树和核桃园中采集。使用 qPCR 方法，我们能够定量分析雨水中和空气样本中这些病原菌群的浓度，并研究具有严重溃疡病潜力的果园中病原菌接种体的动态变化。Phomopsis spp. 和 Diplodia spp. 并非在李树园中所有雨水样本中均被检出，尽管它们在 2016 年的核桃园中被检测到。其他四个病原菌群在李树和核桃园中以不同浓度被定量。在一些情况下，Cytospora spp. 在李树园的雨水中浓度更高。
冬季和早春的雨季是病原菌感染的高风险期，此时这些病原菌的接种体很容易通过空气和雨水传播，因此成为疾病起始的重要接种体来源。不同研究的病原菌群在生长季节表现出不同的浓度，这表明各种树木作物溃疡病病原菌的组成非常复杂。
本研究表明 qPCR 检测方法可用于定量果园中的接种体，有助于揭示溃疡病流行的机制，并帮助设计疾病管理策略。
