RHIZOSPHERIC BACTERIA FOR THE MANAGEMENT OF CITRUS DISEASES

MICHAVILA, GABRIELA; ADLER CONRADO; LAMI, MARÍA JESUS; ZENOFF, ANA; DE CRISTOBAL RE ; VINCENT, PAULA

Mendoza

Congreso; SAIB; 2012

The rhizospheric soil is the region in intimate contact with plant roots. The bacteria that inhabit the rhizosphere and have the ability to cause a positive effect on plants are called Plant Growth Promoting Rhizobacteria (PGPR). In general, biological control mechanisms and growth promotion by bacterial strains are based on microbial metabolites that adversely affect pathogens or induce systemic resistance in the plant. Our laboratory addressed a search for secondary metabolites from rhizospheric bacteria with antibiotic action on plant pathogens. Isolates were obtained from citrus rhizosphere. Among the selected microorganisms we identified strains belonging to the Pseudomonas and Bacillus bacterial genera. We studied biochemical markers associated with growth promotion i.e. siderophore production and synthesis of indole acetic acid (IAA). We also analyzed in-vitro the antibiotic capacity of these isolates and found that certain isolates showed activity against the plant pathogens Xanthomonas citri pv. citri and Pseudomonas syringae. The active compound was purified and identified as Pyochelin. We demonstrated that this siderophore has both in-vitro and in vivo activity against Xanthomonas spp. Since Xanthomonas citri pv. citri is the causative agent of citrus canker, these results indicate a promising role of Pyochelin as a biocontrol agent against this disease.