Efficacy of Some Probiotic Bacteria on Erwinia amylovora the Causal Agent of Fire Blight

Fire blight, caused by Erwinia amylovora bacteria, is one of the well-known plant diseases in the world including major diseases of the fruit trees, especially apples and pears. In recent years, due to chemical nature of the pesticides damaging human health and environment, the importance of biological control is considered as alternative measure to manage plant diseases. To investigate the possibility of biological control of the pathogens, healthy foliar samples of apple, pear, and quince trees were collected from different regions of Kerman Province, Iran, and then, biocontrol activity of antagonist agents was evaluated under laboratory conditions. On the basis of the results, some of the antagonists could decrease the symptoms of the disease by 14.28-79.59%. Laboratory evaluation included investigating the disease severity in immature pears, biocontrol activity of antagonist agents in the plate assay, inhibitory siderophore production, biofilm formation capacity, drought stress tolerance, and silver nanoparticle synthesis capability, which showed that these antagonist agents could potentially control the disease. Among the 9 well-performed antagonistic isolates from apples and pears, Vr87 isolate was selected. The studies were confirmed by amplifying part of 16S rDNA region of the isolate, using specific primers. By comparing the results on the NCBI website, the selected isolate was identified as Enterobacter sp. genus. Among all selected isolates as successful factors in controlling fire blight pathogen, including isolated isolates and isolates in the collection of Vali-e-Asr University, Bacillus subtilis strain BsVRU1 in the Vali-e-Asr University collection, with 73.5% inhibition, had higher inhibitory power than the other antagonist isolates against the pathogen of fire blight disease.