Biocontrol bacterial communities associated with diseased peanut (Arachis hypogaea L.) plants

In the present study, the isolation and characterization of endophytic and epiphytic biocontrol bacteria from peanut plants affected with white mold and root rot are described. Two hundred and sixty three isolates were selected from diseased plants and biocontrol traits analyzed were antibiosis against Sclerotinia minor and Fusarium solani, siderophore production and similarities in carbon source utilization between bacteria and fungi. Diversity and sequence analysis of potential biocontrol bacteria were developed. It was observed that 34% of the 263 isolates were able to inhibit the growth of at least one of the two fungi tested and 47% showed siderophore production in CAS medium. Analysis of nutritional similarity index demonstrated that both fungi were capable to growth in all carbon compounds assayed and that 20% of bacteria showed NOI values equal or above 0.9. Genetic diversity analysis by BOX–PCR indicated that culturable epiphytic and endophytic bacteria associated with peanut are highly diverse. The 16S rDNA sequences of the most remarkable isolates, indicated as potential biocontrol agents according to all the screenings performed and belonging to different BOX profiles showed that they were 99% identical to Bacillus amyloliquefaciens. Comparisons analysis was performed with results previously obtained from a similar study done in the bacterial community isolated from healthy peanut plants from the same producing area. Results obtained suggest that presence of fungal pathogens in peanut ecosystem would be acting as a selective factor in the peanut plant associated bacterial communities. It was concluded from this study that peanut soils in Cordoba harbor bacteria with major biocontrol properties which represent a potential source of new strains that could be used as biological inoculants in agriculture.