Biological control of gray mold of three cultivar of strawberry using Bacillus strains

In this research, the ability of Bacillus strains in suppression of mycelial growth and conidial germination of B. cinerea against Botrytis fruit rot of strawberry were evaluated in three cultivars of strawberry including Quineliza, Paros and Kurdistan. Results indicated that among 32 strains of Bacillus, ten strains showed strong inhibitory effects against B. cinerea using the plate assay and they are selected for further studies. Antagonistic effects of Bacillus stains against the disease were evaluated through dual-culture, volatile and extracellular compounds using plate assays. Results indicated that all Bacillus strains could reduce the mycelial growth of pathogen, but this ability is varied in different Bacillus strains. Growth inhibition percent of pathogen in dual-culture, volatile and extracellular compounds tests were ranged 30.5-67.1, 27.5-86.2 and 41-82, respectively. In addition, inhibition of mycelial growth and conidial germination of B. cinerea by Bacillus strains were observed on strawberry fruits. Disease severity of Botrytis fruit rot of strawberry was significantly reduced (p≤0.05) by Bacillus strains as compared with untreated control. Our results shows that Bacillus strains have a good potential to control Botrytis fruit rot of strawberry. This research suggests that volatile and extracellular compounds of Bacillus spp. are promising biofumigants for controlling of Botrytis fruit rot of strawberry. Therefore, it is needed to evaluate their efficiency under field conditions.