Abstract

The aim of this work was to select and characterize native Cuban fluorescent Pseudomonas from the rhizosphere of Oryza sativa with in vitro and in vivo antagonistic activity against Pyricularia oryzae. A total of 200 isolates were recovered with the typical growth and cultural characteristics of fluorescent Pseudomonas. The results showed that 12.5% of total isolates were capable of inhibiting mycelial growth, with different levels of inhibition between strains. Six of them (AI03, AI05, AI08, AJ01, AJ13 and AJ29) were able to reduce disease severity and incidence in vivo whereas only four (AI05, AJ13, AJ01 and AI08) showed efficient control of P. oryzae in greenhouse conditions. Pseudomonas fluorescens AI05 and Pseudomonas putida AJ13 were able to inhibit in vitro the mycelial growth of P. oryzae and to reduce symptom severity of Pyricularia infection. The production of lytic enzymes, siderophores, hydrogen cyanide (HCN), as well as the detection of genes encoding antibiotics and bacterial motility were also assessed for both strains. They were able to fix nitrogen, produce indolic compounds and to solubilize Pi. These results demonstrate the potential use of P. fluorescens AI05 and P. putida AJ13 as a biocontrol agent for the protection of rice plants from P. oryzae infection.

Key words: Biocontrol, rice blast, Pyricularia, Pseudomonas, plant growth-promoting bacteria.