Complete genome sequences of two novel Ralstonia jumbo phages isolated from leaf litter compost.

Two Ralstonia phages, FLC1-1B and FLC4-3B, were isolated from leaf litter compost, using Ralstonia pseudosolanacearum, which is a causal agent of bacterial wilt disease, as a host. The genomic DNA sequences of FLC1-1B and FLC4-3B were determined and found to be 290,008 bp and 291,257 bp in length, respectively, and they were therefore classified as jumbo phages. However, they did not show high similarity to any jumbo phage genomic sequence in the NCBI nt database. The closest hit in a BLAST search was the jumbo phage ripduovirus RP12, with only 35% coverage and 77% sequence identity, whereas the FLC1-1B and FLC4-3B sequences were 99.0% identical. Based on these findings, FLC1-1B and FLC4-3B should be classified as members of a new genus in the order Caudoviricetes. FLC4-3B was found to suppress wilt disease in tomato plants, suggesting that it has potential as a biocontrol agent for managing R. pseudosolanacearum infections.