Abstract
The rhizosphere-associated microbiome has diverse functions that support plant growth and health, varying among plant species, vegetation growth stages and environmental habitats. This microbiome includes a group of bacteria denominated plant growth-promoting rhizobacteria (PGPR) which can colonize plant roots. Certain PGPR isolates improve the ability of plants to adapt to a stressful environment. In this study, we collected and characterised the rhizosphere-associated bacteria, or epiphytic rhizobacteria, from Malbec and Cabernet-Sauvignon vineyards from the main wine-producing provinces of Argentina to analyse their potential use as biologic fertilisers and/or as pathogen-control agents. A total of 170 bacterial isolates were obtained, distributed into eleven different genera and classified into three phyla, Proteobacteria, Actinobacteria and Firmicutes. The in vitro analysis for plant-growth-promoting (PGP) activities demonstrated that a significant number of bacterial isolates had one or more of these traits. The Pseudomonas was the genus with the highest number of isolates and PGP activities, followed by the Arthrobacter, Serratia, Bacillus andPantoea. We observed that bacterial isolates identified as Bacillus exhibited a remarkable production of hydrolytic enzymes related to biocontrol activities. Biocontrol trials from the Bacillus collection revealed that at least five isolates were able to inhibit the fungal growth of Botrytis cinerea and Alternaria alternata. The results obtained suggest the biological potential of each isolate and the relevance of proceeding to greenhouse and field assays to obtain long-term environmentally compatible bio-products for vineyard management.
Highlights
Associations of microorganisms with plants range from mutually beneficial to commensalistic or pathogenic (Kogel et al, 2006; Newton et al, 2010)
Plant growth-promoting rhizobacteria (PGPR) include a wide variety of rhizospheric and endophytic bacteria which benefit from the nutrients secreted by the plant root and beneficially influence the plant directly or indirectly, resulting in a stimulation of its growth (Bloemberg and Lugtenberg, 2001; Compant et al, 2005)
An investigation undertaken in Argentina by Salomon et al (2016) demonstrated that plant bacterisation with rhizobacteria isolated from grapevine cv
Summary
Associations of microorganisms with plants range from mutually beneficial to commensalistic or pathogenic (Kogel et al, 2006; Newton et al, 2010). The soil zone adhered directly to the plant root system has a high diversity of these microorganisms known as rhizospheric microorganisms. Plant growth-promoting rhizobacteria (PGPR) include a wide variety of rhizospheric and endophytic bacteria which benefit from the nutrients secreted by the plant root and beneficially influence the plant directly or indirectly, resulting in a stimulation of its growth (Bloemberg and Lugtenberg, 2001; Compant et al, 2005). Rhizobacteria isolated from grapevines have been demonstrated to possess different beneficial effects These effects have been attributed to nutrient acquisition (Baldan et al, 2015), secondary metabolites (Ait Barka et al, 2006; Rolli et al, 2015) and the ability to induce and/or increase the plant tolerance against different abiotic and biotic stresses (Calvo-Garrido et al, 2018). A stimulating effect of the nitrogenfixing strain Azospirillum brasilense Sp245 on nursery propagation of rootstocks and during the vegetative development of young grapevine plants was observed in the field (Bartolini et al, 2017)
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