Isolation and pathogenicity of Ralstonia solanacearum in tomato and potential of phage BHDTSo81 against the pathogen

The bacterial wilt disease in tomato caused by Ralstonia solanacearum results in harvest losses of up to 90% and significant economic loss to farmers. In this study, 11 R. solanacearum strains were isolated in the largest tomato-growing province in Vietnam. These strains belonged to 3 different groups, and 9/11 strains showed different disease rates in experimental tomato plants. A BHDTSo81 phage specific to R. solanacearum was isolated from a soil sample. Morphological analysis indicated that BHDTSo81 had podovirus morphology and was classified into the Autographiviridae family. The latent period and burst size of BHDTSo81 were calculated to be approximately 145 min and 8.6 +/- 1.8 virions per infected cell, respectively. In a test of 26 bacterial strains, BHDTSo81 infected 7/11 R. solanacearum strains, while none of the other bacteria tested were susceptible to the phages. R. solanacearum was also challenged in vitro and was inactivated by BHDTSo81 for 40 h in broth. The genome of BHDTSo81 is 41,296 bp long with a total GC content of 63% and contains 46 predicted protein-encoding CDSs (coding sequences). No virulence factor or antibiotic resistance gene was found in the genome. Thus, the initial characteristics of phage BHDTSo81 indicate its potential utility as a control agent against R. solanacearum.