Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Calle Profesor Albareda 1, 18008, Granada, Spain.
Departamento de Protección de Cultivos, Instituto de Agricultura Sostenible, CSIC, Campus 'Alameda del Obispo' s/n, Avd. Menéndez Pidal s/n, 14004, Córdoba, Spain.
Microbiome. 2020 Feb 1;8(1):11. doi: 10.1186/s40168-020-0787-2.
Verticillium wilt of olive (VWO) is caused by the soilborne fungal pathogen Verticillium dahliae. One of the best VWO management measures is the use of tolerant/resistant olive cultivars. Knowledge on the olive-associated microbiome and its potential relationship with tolerance to biotic constraints is almost null. The aims of this work are (1) to describe the structure, functionality, and co-occurrence interactions of the belowground (root endosphere and rhizosphere) microbial communities of two olive cultivars qualified as tolerant (Frantoio) and susceptible (Picual) to VWO, and (2) to assess whether these communities contribute to their differential disease susceptibility level.
Minor differences in alpha and beta diversities of root-associated microbiota were detected between olive cultivars regardless of whether they were inoculated or not with the defoliating pathotype of V. dahliae. Nevertheless, significant differences were found in taxonomic composition of non-inoculated plants' communities, "Frantoio" showing a higher abundance of beneficial genera in contrast to "Picual" that exhibited major abundance of potential deleterious genera. Upon inoculation with V. dahliae, significant changes at taxonomic level were found mostly in Picual plants. Relevant topological alterations were observed in microbial communities' co-occurrence interactions after inoculation, both at structural and functional level, and in the positive/negative edges ratio. In the root endosphere, Frantoio communities switched to highly connected and low modularized networks, while Picual communities showed a sharply different behavior. In the rhizosphere, V. dahliae only irrupted in the microbial networks of Picual plants.
The belowground microbial communities of the two olive cultivars are very similar and pathogen introduction did not provoke significant alterations in their structure and functionality. However, notable differences were found in their networks in response to the inoculation. This phenomenon was more evident in the root endosphere communities. Thus, a correlation between modifications in the microbial networks of this microhabitat and susceptibility/tolerance to a soilborne pathogen was found. Moreover, V. dahliae irruption in the Picual microbial networks suggests a stronger impact on the belowground microbial communities of this cultivar upon inoculation. Our results suggest that changes in the co-occurrence interactions may explain, at least partially, the differential VWO susceptibility of the tested olive cultivars. Video abstract.
油橄榄维管束萎蔫病（VWO）是由土壤病原菌大丽轮枝菌引起的。VWO 管理的最佳措施之一是使用具有耐受性/抗性的橄榄品种。关于橄榄相关微生物组及其与生物胁迫耐受性的潜在关系的知识几乎为零。本研究的目的是：（1）描述两种被认为对 VWO 具有耐受性（Frantoio）和易感性（Picual）的橄榄品种的地下（根内和根际）微生物群落的结构、功能和共现相互作用；（2）评估这些群落是否有助于其不同的疾病易感性水平。
无论是否接种大丽轮枝菌致萎型，橄榄品种的根相关微生物群落的α和β多样性差异较小。然而，在未接种植物群落的分类组成上存在显著差异，“Frantoio”表现出有益属的丰度较高，而“Picual”则表现出潜在有害属的丰度较高。接种大丽轮枝菌后，在 Picual 植株中发现了在分类水平上的显著变化。在接种后，在微生物群落的共现相互作用的结构和功能水平上，以及在正/负边缘比上，都观察到了相关的拓扑变化。在根内，Frantoio 群落转变为高度连接和低模块化的网络，而 Picual 群落表现出截然不同的行为。在根际中，大丽轮枝菌仅在 Picual 植株的微生物网络中爆发。
两种橄榄品种的地下微生物群落非常相似，病原菌的引入并没有引起其结构和功能的显著改变。然而，在接种后，它们的网络中存在明显的差异。这种现象在根内微生物群落中更为明显。因此，发现了这个微生境的微生物网络的变化与对土壤病原菌的易感性/耐受性之间存在相关性。此外，大丽轮枝菌在 Picual 微生物网络中的爆发表明，在接种后，该品种的地下微生物群落受到更大的影响。我们的研究结果表明，共现相互作用的变化可能至少部分解释了所测试的橄榄品种对 VWO 的不同敏感性。
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