Evaluation of native bacteria and manganese phosphite for alternative control of charcoal root rot of soybean

SIMONETTI E; PIN VISO N; MONTECCHIA M; ZILLI CG; BALESTRASSE KB; CARMONA M

MICROBIOLOGICAL RESEARCH

ELSEVIER GMBH

Año: 2015

0944-5013

Plant growth promoting rhizobacteria (PGPR) are potential agents to control plant pathogens and theircombined use with biopesticides such as phosphites may constitute a novel strategy to incorporate indisease management programs. In the present study, 11 bacterial isolates were selected on the basis oftheir antagonistic activity against Macrophomina phaseolina in dual-culture tests, and their plant growthpromoting traits. Selected isolates were characterised on the basis of auxin and siderophore production,phosphate solubilisation and rep-PCR genomic fingerprinting. Two of these isolates, identified as Pseudomonasfluorescens 9 and Bacillus subtilis 54, were further evaluated for their inhibitory capacity againstM. phaseolina using in vitro (on soybean seeds) and in vivo (greenhouse assay) tests. Both bacteria wereapplied individually as well as in combined treatment with manganese phosphite as seed treatments.Damage severity on soybean seeds was significantly reduced, compared with the untreated control, byboth bacterial strains; however, the individual application of phosphite showed to be least effective incontrolling M. phaseolina. Interestingly, the phosphite treatment improved its performance under greenhouseconditions compared to the results from the in vitro assays. In the greenhouse trials, the greatestreductions in disease severity were achieved when strain P. fluorescens 9 was applied singly or whenstrain B. subtilis 54 was combined with manganese phosphite, achieving 82% of control in both cases.This work is the first to report the control of M. phaseolina using combined treatment with PGPR andphosphite under greenhouse conditions.