Screening of epiphytic rhizosphere-associated bacteria in argentinian malbec and cabernet-sauvignon vineyards for potential use as biological fertilisers and pathogen-control agents

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 pathogencontrol 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 and Pantoea. 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.