in vitro BIOLOGICAL EFFECTIVENESS OF ACTINOMYCETES UPON THE CAUSAL AGENT OF HALO BLIGHT OF COMMON BEAN

Abstract

The development of inoculants based on soil microorganisms for use as biological control agents of plant pathogens is a strategy that may reduce the use of agrochemicals, particularly for controlling diseases caused by pathogenic bacteria such as Pseudomonas syringae pv. phaseolicola (Psph). This study evaluated the in vitro inhibitory effectiveness of 80 actinomycete strains isolated from agricultural soils against the causal agent of halo blight in bean (Psph) and selected the highest antibacterial activity (ABA). To estimate the effectiveness of isolates as potential agents for the biological control of Psph, in vitro antibacterial activity was evaluated by direct confrontation against Psph strain 1448A on PDA culture medium (pH 7). The experiment was established in a completely randomized design, with 81 treatments (80 actinomycetes confronted with Psph and a control comprising only the phytopathogenic bacteria), with three replications. The recorded response variable was the inhibition growth area of Pseudomonas syringae (IAPS) determined by an ordinal inhibition scale. Statistical analysis by Kruskal -Wallis reported significant differences between actinomycetes strains on ABA, and five of them inhibited absolutely bacterial growth. The results suggest the potential of actinomycetes as biocontrol agents for bean halo blight caused by Psph.