Potential of Moroccan isolates of plant growth promoting streptomycetes for biocontrol of the root rot disease of pea plants caused by the oomycete pathogen Aphanomyces euteiches.

Abstract

ABSTRACT We report in this study the evaluation of Moroccan plant growth promoting (PGP) Streptomyces spp. capacities to control pea root rot caused by Aphanomyces euteiches. Actinobacteria isolates were tested against A. euteiches under greenhouse conditions. Individual treatments of pea plants cultivated in either perlite or soil with three isolates reduced significantly disease symptom index (DSI) and increased plant growth parameters compared to untreated controls. A phylogenetic tree analysis based on 16S rDNA sequences showed that our isolates belongs to Streptomyces genus. In order to analyse the plant growth promoting capacities of the isolates, the production of indole-3-acetic acid was analysed by HPLC under different culture conditions (different pH values, tryptophan concentrations). Only OB22b and AC2B3(1) had the ability to produce IAA. However, only isolate AC2B3(1) showed a PGP effect on pea plants indicating that growth promotion. Our PGP Strepromyces spp. isolates OB22b and AC2B3(1) showed a good capacity to act as biocontrol agents to protect pea plant against A. euteiches. In Morocco, this is the first study to use some Streptomyces spp. strains against A. euteiches on pea plants. The study can have impact on legumes protection and sustainability production.