Evaluation of rhizobacterial isolates from Argentina, Uruguay and Chile for plant growth-promoting characteristics and antagonistic activity towards Rhizoctonia sp. and Macrophomina sp. in vitro

Abstract

This study was conducted over 3 years in soils of Uruguay and Chile and two years in soils of Argentina. 686 bacterial isolates were phenotypically characterized by testing in relation to the presence of plant growth promoting properties: phosphate solubilization, production of siderophores, starch hydrolysis, production of exopolysaccharides and biological control of Macrophomina phaseolina and Rhizoctonia spp. In all samples analyzed, the number of Gram-positive bacteria exceeded that of Gram negative. Ten bacterial isolates were selected for their plant growth promoting properties and API Test and 16S rRNA gene (rDNA). Six of these isolates belong to the genus Pseudomonas, three to the genus Bacillus and one to Janibacter. This is the first report of a strain from the genus Janibacter with promising plant growth-promoting attributes. The results obtained allow us to improve the microbial germplasm of plant growth promoting bacteria from soils of Chile, Argentina and Uruguay with a view to their potential use in the formulation of mixed inoculants that promote the growth of alfalfa.