Everhart S E, Scherm H
First and second authors: Department of Plant Pathology, University of Georgia, Athens, GA 30602.
Phytopathology. 2015 Apr;105(4):542-9. doi: 10.1094/PHYTO-03-14-0088-R.
The purpose of this study was to determine the fine-scale genetic structure of populations of the brown rot pathogen Monilinia fructicola within individual peach tree canopies to better understand within-tree plant pathogen diversity and to complement previous work on spatiotemporal development of brown rot disease at the canopy level. Across 3 years in a total of six trees, we monitored disease development, collected isolates from every M. fructicola symptom during the course of the season, and created high-resolution three-dimensional maps of all symptom and isolate locations within individual canopies using an electromagnetic digitizer. Each canopy population (65 to 173 isolates per tree) was characterized using a set of 13 microsatellite markers and analyzed for evidence of spatial genetic autocorrelation among isolates during the epidemic phase of the disease. Results showed high genetic diversity (average uh=0.529) and high genotypic diversity (average D=0.928) within canopies. The percentage of unique multilocus genotypes within trees was greater for blossom blight isolates (78.2%) than for fruit rot isolates (51.3%), indicating a greater contribution of clonal reproduction during the preharvest epidemic. For fruit rot isolates, between 54.2 and 81.7% of isolates were contained in one to four dominant clonal genotypes per tree having at least 10 members. All six fruit rot populations showed positive and significant spatial genetic autocorrelation for distance classes between 0.37 and 1.48 m. Despite high levels of within-tree pathogen diversity, the contribution of locally available inoculum combined with short-distance dispersal is likely the main factor generating clonal population foci and associated spatial genetic clustering within trees.
本研究的目的是确定褐腐病菌（Monilinia fructicola）在单个桃树树冠内种群的精细尺度遗传结构，以更好地了解树内植物病原体的多样性，并补充先前关于树冠水平褐腐病时空发展的研究。在总共六棵树的三年时间里，我们监测了病害发展情况，在季节过程中从每个褐腐病菌症状处收集分离株，并使用电磁数字化仪创建了单个树冠内所有症状和分离株位置的高分辨率三维地图。每个树冠种群（每棵树65至173个分离株）使用一组13个微卫星标记进行表征，并分析病害流行阶段分离株之间空间遗传自相关的证据。结果表明，树冠内具有高遗传多样性（平均uh = 0.529）和高基因型多样性（平均D = 0.928）。树内独特多位点基因型的百分比在花腐分离株（78.2%）中比在果腐分离株（51.3%）中更高，这表明在收获前流行期间克隆繁殖的贡献更大。对于果腐分离株，每棵树中54.2%至81.7%的分离株包含在一至四个至少有10个成员的优势克隆基因型中。所有六个果腐种群在0.37至1.48米的距离类别上均显示出正的且显著的空间遗传自相关。尽管树内病原体多样性水平较高，但本地可用接种物与短距离传播的结合可能是在树内产生克隆种群聚集点和相关空间遗传聚类的主要因素。
