Effect of gamma irradiation on Pseudomonas syringae pv. tomato DC3000

Abstract

Gamma irradiation (GI) was evaluated for its in vitro and in vivo antibacterial activity against bacterial specks of tomato, Pseudomonas syringae pv. tomato (Pst). GI showed complete inactivation of Pst DC3000, especially at a dose of 200 Gy in vitro. Gamma-irradiated bacterial cells were found to (1) have spilled cytoplasmic contents, (2) display a damage on the surface of the cells, (3) have reduced membrane integrity, and (4) have fragmented genomic DNA, all in a dosedependent manner. Consistent with the in vitro assay, a low dose of 150 Gy showed sufficient antibacterial activity on tomato seedlings. The present study suggested that the GI of bacterial cells results in substantial damage of the cell membrane, and that, along with DNA fragmentation, results in dose-dependent cell inactivation. These findings suggest that GI has potential as an antibacterial approach to reduce the severity of the bacterial speck disease of tomato.