Candidate Causal Organisms for Apple Replant Disease in the United Kingdom
Candidate Causal Organisms for Apple Replant Disease in the United Kingdom
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DOI：
10.1094/pbiomes-11-18-0050-r
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
E. Tilston;G. Deakin;Julie M. Bennett;T. Passey;N. Harrison;Flora J. M. O’Brien;F. Fernández-Fernández-F.-Fernández-Fernández-1401161427;Xiangming Xu
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文献类型：
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作者：
E. Tilston;G. Deakin;Julie M. Bennett;T. Passey;N. Harrison;Flora J. M. O’Brien;F. Fernández-Fernández-F.-Fernández-Fernández-1401161427;Xiangming Xu
在同一地区连续种植苹果，会导致生长力下降和随后的作物损失，即苹果再植病（ARD）综合征。一些土壤传播的植物病原体，包括镰刀菌、镰刀菌和柱头carpon等，经常被认为是ARD的候选致病生物。此外，根损线虫的存在和有益菌群的缺乏被认为会加剧或减轻植物病原体的影响。这些提出的因果和辅助因素的重要性似乎因地点而异。为了减少空间变异，我们采用了空间明确的采样策略，从邻近的健康和假定的ARD树对中收集根际土壤样本，以确定ARD的候选致病生物。利用基于扩增子的元条形码技术获得土壤样品中细菌、真菌、卵菌和线虫的群落水平谱。利用qPCR调整原始序列reads数据，估计每个样品中的细菌和真菌总生物量。结果表明，提高根际生物多样性本身并不能改善ARD。我们鉴定了25个细菌操作分类单位（OTU）， 16个真菌OTU， 18个卵菌OTU和一个线虫OTU组，它们在健康树和推定的ARD树之间具有不同的丰度。所有25种细菌OTUs在ARD症状树样品中的丰度均低于健康树样品。一个AMF OTU在ARD症状树样本中丰度较低。在ARD症状树样品中，13种真菌OTUs丰度较高，但都不是已知的植物病原体；但至少有一种Pythium OTU（可能是中间的Pythium）是引起ARD的候选者。一种线虫OTU的丰度在ARD症状树样品中比在健康树样品中高得多。结果表明，除了使用广谱熏蒸剂外，ARD的复杂性可能需要综合使用多种管理策略，由于ARD致病因子在不同地点的重要性不同，这些措施的成功程度在不同地点之间差异很大。
Continuous planting of apple in the same area leads to reduced growth vigor and subsequent crop losses, i.e., apple replant disease (ARD) syndrome. Several soilborne plant pathogens including Pythium, Fusarium, and Cylindrocarpon spp. are often proposed as candidate causal organisms for ARD. In addition, the presence of root lesion nematodes and the lack of beneficial groups of bacteria are believed to exacerbate or ameliorate the effects of the plant pathogens. The importance of these proposed causal and auxiliary agents seems to vary with site. Using a spatially explicit sampling strategy to minimize spatial variability we collected rhizosphere soil samples from neighboring pairs of healthy and putative ARD trees to identify candidate causal organisms of ARD. Amplicon-based metabarcoding was used to obtain community-level profiles of the bacteria, fungi, oomycetes and nematodes in the soil samples. Total bacterial and fungal biomass in each sample was estimated using qPCR to adjust the raw sequence reads data. The results suggested that ARD is not ameliorated by enhanced rhizosphere biodiversity per se. We identified 25 bacterial operational taxonomic units (OTUs), 16 fungal OTUs, 18 oomycetes OTUs, and one nematode OTU group with differential abundance between healthy and putative ARD trees. All 25 bacterial OTUs had lower abundance in samples from ARD symptomatic trees than from healthy trees. One AMF OTU had lower abundance in samples from ARD symptomatic trees. None of 13 fungal OTUs that had higher abundance in samples from ARD symptomatic trees is a known plant pathogen; but at least one Pythium OTU (probably Pythium intermedium) is a candidate for causing ARD. The abundance of one nematode OTU was much higher in samples from ARD symptomatic trees than in healthy trees. The results suggest that, apart from the use of broad spectrum fumigants, the complexity of ARD may necessitate the combined use of multiple management strategies with the success of these measures expected to vary considerably between sites because of the varying importance of ARD causal agents among sites.