Root colonization of cultivated plants inoculated with Ralstonia solanacearum biovar 1, 2 and 3

Abstract

Bacterial wilt caused by Ralstonia solanacearum is considered the main plant disease of bacterial origin in the world, where hundreds of plant species in more than 50 botanical families are host plants. Root colonization of lettuce (Lactuca sativa), rice (Oryza sativa), spring onion (Allium fistulosum), pea (Pisum sativum), cucumber (Cucumis sativus), and soybean (Glycine max) by six isolates of Ralstonia solanacearum (Rs) biovars 1, 2 and 3 was evaluated under greenhouse conditions. Bacterial strains resistant to streptomycin, rifampicin and chloranfenicol were used. Root colonization was evaluated 45 days after inoculation by counting bacteria in root extracts of culture media with antibiotics. Pea plants hosted all six isolates, but only the isolate biovar 3 was pathogenic to this species. High populations of four isolates of the three biovars were found on soybean, and cucumber hosted high population of only two isolates (biovars 1 and 3). Pea was a non-susceptible host for Rs, except for one pathogenic isolate. Rice hosted very low populations of all isolates, while lettuce and spring onion did not host any isolates. These results showed the ability of Rs to colonize and survive on different plant roots as rhizobacteria.