Identification of some molecular traits in fluorescent pseudomonads with antifungal activity

We assessed a collection of 47 fluorescent Pseudomonas spp., some with known biological control activity against certain soil-borne phytopathogenic fungi such as, Macrophomina phaseolina, Rhizoctonia solani, Phytophthora nicotianae var. parasitica, Pythium sp. and Fusarium sp. in vitro and the potential to produce known secondary metabolites such as, siderophore, HCN and protease. The results indicated that 66%, 40.42%, 63.82%, 48.94% and 27.65% of strains revealed antagonistic activity against R. solani, M. phaseolina, Pythium sp., P. nicotianae and Fusarium sp., respectively. Among the 47 strains, 76.59%, 97.87% and 17% produced protease, siderophore and HCN, respectively. In this survey, the detection of phlD and phlA genes was evaluated with a PCR-based assay. We detected phlD in strains P-5, P-32, P-47, and phlA in strains P-5, P-18, P-34 and P-35. Strain CHA0 was used as positive control for the detection of both genes. Overall, there was no obvious link between inhibition of fungal growth in vitro and production of the antifungal metabolites or existence of phlD and phlA genes. Characterization of fluorescent pseudomonads with potential to produce of 2, 4-diacetylphloroglucinol will further enhance our knowledge of their function in the suppression of root diseases.