بررسی اثر باکتری بیمارگر حشرات Bacillus thuringiensis در بیوکنترل بیماری پژمردگی فوزاریومی گوجه فرنگی

The enteropathogenic bacterium Bacillus thuringiensis belongs to Bacillus cereus group. This bacterium is ubiquitous and widely used as bioinsecticide for the control of many agricultural pests. Also, some studies have reported that B. thuringiensis was able to colonize the root and increase of legumes nodulation. In this study, sampling was carried out in order to isolate plant growth-promoting (PGP) and biocontrol bacteria from tomato rhizosphere. Tomato seeds were treatment with bacterium suspension to evaluate the PGP effect of B. thuringiensis on seed germination in vitro and greenhouse condition. Furthermore, the ability of this strain to produce various metabolites like siderophore, HCN, auxin and phosphate solublization were examined. All tests were performed in completely randomize design with three replicates. This strain increased the germination rate of tomato seeds compared to untreated control. The results of the pot experiment showed that this strain promoted tomato root and shoot length, as well as fresh and dry weight of root and shoot compared to control. The ability to produce siderophore, auxin and ability to dissolve mineral phosphate have been proven in this isolate. Moreover, antifungal activity in dual culture and volatile compounds assay showed that, this strain can inhibit the mycelial growth of the Fusarium oxysporum fsp. lycopersici up to 67 and 54 % respectively. Also tomato root treatment with B. thuringiensis can suppress the wilt symptoms compare to control, significantly. For molecular investigation, total DNA was extracted using Kiagen Kit and the whole genome was sequenced using the Iliuminia Hiseq technology in Cornell University. After obtaining the nucleotide sequence, its quality was controlled by FastQC software and annotated with RAST database .Then the sequencing data was compared with deposited sequence in GenBank via BLAST available at NCBI and SEED websites. Results showed that, this strain has 99.8% similarity with B. thuringiensis bt185. In conclusion, this strain of B. thuringiensis has potential to be introduce as a multifunctional biocontrol agent.