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Effect of Repetitive Applications of the Biocontrol Bacterium Pseudomonas putida 06909-rif/nal on Citrus Soil Microbial Communities

The effects of repetitive applications of Pseudomonas putida 06909-rif/nal on the resident microbial communities within a citrus orchard were studied with fatty acid methyl-ester (FAME) profiles and ribosomal intergenic spacer analysis. The data set from FAME was large and very complex, requiring 23 factors from principal component analysis to explain 91% of variability in the data. Spatial and temporal effects on variation within microbial communities were much greater than the effects of either yearly applications of Pseudomonas putida 06909-rif/nal, weekly repetitive applications of Pseudomonas putida 06909-rif/nal, or yearly applications of the fungicide metalaxyl and the nematicide phenamiphos. Multivariate analysis of covariance showed much of the variability between treatments could be accounted for by populations of Pseudomonas putida 06909-rif/nal. Soil fatty acids that showed significant changes between treatments were not related to fatty acids found in Pseudomonas putida 06909-rif/nal, suggesting applications of Pseudomonas putida 06909-rif/nal altered the soil microbial community.