Introduction:

The plants harbor a microbiome that includes plant growth-promoting bacteria, which can act as biological agents that antagonize the growth of phytopathogens, diminishing or eliminating their harmful effects in plants. In this work, the presence and association of the phlD and hcnC antifungal genes with the production of siderophores (Fe chelating agents) in bacteria isolated from the endosphere and rhizosphere of blackberry plants (Rubus fruticosus L.) was evaluated.

Method:

In total, 410 bacterial isolates associated with blackberry plants (Rubus fruticosus L.), from the rhizosphere (205) and endosphere (205) were analyzed for the detection of the phlD and hcnC antimicrobial genes by polymerase chain reaction and subsequent sequencing. The search of the genes was carried out only in siderophore producing strains, using the CAS medium (Chromium Azurol) for its production. Of the strains selected, antagonism bioassays were carried out against the plant pathogens Botrytis cinerea, Fusarium oxysporum, F. solani and Rhizoctonia solani.

Results:

The results showed that from the 410 bacterial isolates analyzed here (50% endophytes and 50% rhizospheric), it was confirmed that 70 strains were siderophores-producing (24 from rhizosphere and 46 endophytes). It was observed that 70% (49/70) of the siderophore producing strains present either one or two of the phlD or hcnC genes. The nucleotide sequences of the phlD and hcnC genes showed high identity to homologous genes to species Pseudomonas sp., P. fluorescens, P. chlororaphis, P. protegens, P. putida and P. brassicacearum. The abundance of the hcnC gene was also higher in the endophytic and rhizospheric isolates (36/70), with respect to the phlD gene (13/70). Greater detection of phlD or hcnC genes was found in strains isolated from the endosphere (43/70), compared with those of rhizospheric origin (6/70). Finally, a high ratio was observed between the production of siderophores, the presence of genes phlD and hcnC with the antagonistic activity towards important phytopathogenic fungi, like Botrytis cinerea, Fusarium oxysporum, Fusarium solani and Rhizoctonia solani.

Conclusion:

These results showed the potential to identify quickly, efficiently and at low cost, mechanisms of antagonism towards phytopatogens in bacteria associated with blackberry plants (Rubus fruticosus L.), such as siderophore production.

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