Isolation and Toxicity of Xanthomonas spp. in Tomato and Potential of Phage L2.1 against the Pathogen

Abstract

The bacterial spot caused by Xanthomonas spp. is one of the most common diseases in tomato. In this study, 7 Xanthomonas spp. strains were isolated in Lam Dong province, the largest tomato-growing area in Vietnam. All of these strains showed different disease rates in experimental tomato plants. A L2.1 phage specific to Xanthomonas spp. was isolated from a tomato field. Morphological analysis indicated that L2.1 had podovirus morphology and was classified into the Tectiviridae family. The latent period and burst size of L2.1 were calculated to be approximately 95 min and 4.5 ± 0.27 virions per infected cell. In a test of 13 bacterial strains, L2.1 infected 7/7 Xanthomonas spp. strains, while none of the other bacteria tested were susceptible to the phages. Xanthomonas spp. was also challenged in vitro and was inactivated by L2.1 for 25-27 h in broth at different concentration ratios of phage to bacteria of 0.01, 0.1 and 1.0. Initial characterization of phage L2.1 indicates its potential utility as a biotherapeutic agent against bacterial spot in tomato.