Potential use of bacterial strain in the genus Serratia to biocontrol fungal pathogens associated with defoliation on Pinus patula

Pathogenic fungi that cause defoliation in different pine species, including Pinus patula, have been reported. The most common practice for controlling these pathogens is the use of fungicides, which have adverse environmental consequences. The objective of this study was to evaluate an alternative for pathogen control without affecting the ecosystem. Bacteria with antifungal activity obtained from forest soil were isolated and biochemically and molecularly identified for evaluation in biocontrol assays of fungi associated with defoliation under laboratory and field conditions. Two species of the genus Serratia, Serratia grimesii and S. proteamaculans, were identified as bacteria with antifungal activity. In vitro biocontrol was achieved by reducing the mycelium growth of fungi associated with diseased needles of P. patula: Alternaria alternata, Annulohypoxylon stygium, Botryosphaeria dothidea, Curvularia lunata, C. pseudobrachyspora, C. spicifera, C. trifolii, Daldinia sp., Daldinia eschscholtzii, Diplodia sapinea, Lophodermium indianum, and Myrmaecium rubricosum. The fungi in P. patula (Annulohypoxylon stygium and Daldinia eschscholtzii) decreased their damage by 82% and 77%, respectively, in the presence of Serratia under humid chamber conditions. In addition, the incidence of lesions (IL) and Disease Severity Index (%DSI) were significantly reduced under natural conditions. The results showed that biocontrol with bacteria of the genus Serratia is an alternative for the management of health in Pinus patula trees.