Biological Control of Phytophthora Drechsleri the Causal Agent of Pistachio Gummosis by Bacillus Subtilis (VRU1 Strain) in Green House Condition

Introduction: Plant probiotic bacteria are a group of microorganisms that enhance plant growth and protect plants against many diseases by several mechanisms; they can also be used as biofertilizers. Materials and Methods: In this study, the ability of Bacillus subtilis strains (VRU1 and BS-VRU) to produce siderophore, IAA, and some enzymes, such as cellulase, lipase, protease, as well as their potential biocontrol against Phytophthora drechsleri, the causal agent of crown and root rot in pistachios, were evaluated in vitro. In addition, the effects of these bacterial strains on growth parameters, such as fresh and dry weights of shoots and roots, plant height, as well as the biocontrol of P. drechsleri were investigated under greenhouse conditions. Results: According to the results of this study, two strains were able to produce siderophore, IAA, lipase, cellulas, and protease. Greenhouse results showed that both strains of B. subtilis increased growth parameters significantly in inoculated plants compared to the control. In addition, the results obtained showed that these bacterial strains decreased the mortality rate of pistachio seedlings, with the highest and lowest reductions having been 75% and 50% in VRU1 and BS-VRU, respectively. Conclusion: According to the results, pistachio gummosis could be controlled by Bacillus subtillis bacteria. In addition, B. subtilis VRU1 and BS-VRU showed high efficacy in the suppression of diseases through several biocontrol mechanisms.