Metataxonomic analysis of endophytic bacteria of blackberry (Rubus ulmifolius Schott) across tissues and environmental conditions.

(1) Background: Endophytic bacteria represent an important component of plant wellness. They have been widely studied for their involvement in plant development and enhancement of stress tolerance. In this work, the endophytic communities of roots, stems, and leaves of blackberry (Rubus ulmifolius Schott) were studied in three different niches: natural, riverside, and human-impacted niches. (2) Results: The microbiome composition revealed that Sphingomonadaceae was the most abundant family in all samples, accounting for 9.4-45.8%. In contrast, other families seem to be linked to a specific tissue or niche. Families Microbacteriaceae and Hymenobacteraceae increased their presence in stem and leaf samples, while Burkholderiaceae abundance was important in riverside samples. Alpha and beta diversity analyses showed that root samples were the most diverse, and they gathered together in the same cluster, apart from the rest of the samples. (3) Conclusions: The analysis of the microbiome of R. ulmifolius plants revealed that the composition was essentially the same in different niches; the differences were primarily influenced by plant tissue factors with a core genome dominated by Sphingomonadaceae. Additionally, it was observed that R. ulmifolius can select its own microbiome, and this remains constant in all tissues evaluated regardless the niche of sampling.

Ferranicluibacter rubi gen. nov., sp. nov., a new member of family Rhizobiaceae isolated from stems of elmleaf blackberry (Rubus ulmifolius Schott) in Northwest Spain.

Strain CRRU44T was isolated from the stems of Rubus ulmifolius plants growing in Salamanca (Spain). The phylogenetic analysis of the 16S rRNA gene sequence places this strain within the family Rhizobiaceae showing that it is equidistant to the type species of several genera from this family with similarity values ranging from 91.0 to 96.3 %. Strain CRRU44T formed a divergent lineage which clustered with Endobacterium cereale RZME27T, Neorhizobium galegae HAMBI540T and Pseudorhizobium pelagicum R1-200B4T. The phylogenomic analysis showed that strain CRRU44T was equal to or more distant from the remaining genera of the family Rhizobiaceae than other genera among them. The calculated average nucleotide identity based on blast and average amino acid identity values with respect to the type species of all genera from the family Rhizobiaceae were lower than 78.5 and 76.5 %, respectively, which are the currently cut-off values proposed to differentiate genera within this family. All these results together with those from phenotypic and chemotaxonomic analyses support that strain CRRU44T represents a novel species of a novel genus within the family Rhizobiaceae, for which the name Ferranicluibacter rubi gen. nov., sp. nov. is proposed (type strain CRRU44T=CECT 30117T=LMG 31822T).

Mechanisms of Action of Microbial Biocontrol Agents against Botrytis cinerea.

Botrytis cinerea is a phytopathogenic fungus responsible for economic losses from USD 10 to 100 billion worldwide. It affects more than 1400 plant species, thus becoming one of the main threats to the agriculture systems. The application of fungicides has for years been an efficient way to control this disease. However, fungicides have negative environmental consequences that have changed popular opinion and clarified the need for more sustainable solutions. Biopesticides are products formulated based on microorganisms (bacteria or fungi) with antifungal activity through various mechanisms. This review gathers the most important mechanisms of antifungal activities and the microorganisms that possess them. Among the different modes of action, there are included the production of diffusible molecules, both antimicrobial molecules and siderophores; production of volatile organic compounds; production of hydrolytic enzymes; and other mechanisms, such as the competition and induction of systemic resistance, triggering an interaction at different levels and inhibition based on complex systems for the production of molecules and regulation of crop biology. Such a variety of mechanisms results in a powerful weapon against B. cinerea; some of them have been tested and are already used in the agricultural production with satisfactory results.