New potential bacterial antagonists for the biocontrol of charcoal rot disease (Macrophomina phaseolina) on strawberry in Spain. Biocontrol bacteria for Macrophomina phaseolina in strawberry plants

The effectiveness of antagonistic bacteria to control Macrophomina phaseolina was evaluated under in vitro, infection chamber, greenhouse and field conditions. A total of 176 bacteria, isolated from Arthrocaulon macrostachyum rhizosphere of the Lebrija marsh, were screened for their antagonistic potential against M. phaseolina by dual culture assay. Of them, 14 most promising strains were molecularly identified by the 16S rDNA sequencing. These strains were tested for in vitro hydrolytic enzymes and HCN pro-duction, and biocontrol on infection chamber against M. phaseolina in strawberry plants. All the 14 strains produced, at least, one hydrolytic enzymatic activity and one of them, identified as Bacillus frigoritolerans (Hvs8), showed the lowest records of disease incidence (20 %) and severity (0.4) on strawberry plants. With these results, greenhouse and field trials were carried out on strawberry plants with the Hvs8 strain. In the greenhouse assays, Hvs8 strain increased root dry mass by 30 %, over the control. In the field trials, all the production and fruit quality parameters showed no significant differences between Hvs8 treatment and non-treated control, but plant mortality and plant mortality associated to M. phaseolina decreased by more than 24 % and 65 % respectively