M. Pourjafari - Department of Plant Protection, Faculty of Agriculture, Vali –e- Asr University of Rafsanjan, Islamic Republic of Iran.
R. Saberi Riseh - Department of Plant Protection, Faculty of Agriculture, Vali –e- Asr University of Rafsanjan, Islamic Republic of Iran.
P. Khodaygan - Department of Plant Protection, Faculty of Agriculture, Vali –e- Asr University of Rafsanjan, Islamic Republic of Iran.
A. Hosseinipour - Department of Plant Pathology, Faculty of Agriculture, Bahonar University of Kerman, Islamic Republic of Iran.
M. Moradi - Pistachio Research Center, Agricultural Research, Education and Extension Organization, Rafsanjan, Islamic Republic of Iran.

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 ۱۴.۲۸-۷۹.۵۹%. 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 ۹ well-performed antagonistic isolates from apples and pears, Vr۸۷ isolate was selected. The studies were confirmed by amplifying part of ۱۶S 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 BsVRU۱ in the Vali-e-Asr University collection, with ۷۳.۵% inhibition, had higher inhibitory power than the other antagonist isolates against the pathogen of fire blight disease.

Bacillus subtilis, Biological control, Biosynthesis, Drought stress, Silver nanoparticle.