Abstract:
Eighty one isolates of Ralstonia solanacearum-like bacteria on triphenyl tetrazolium chloride
(TTC) medium were collected from different Solanaceae crops (i.e. potato, tomato and pepper
plants and potato tubers) at various sites in Ethiopia. Of these, 62 strains were identified as
R. solanacearum based on their cultural characteristics on TTC medium, tomato pathogenicity
bioassay, carbon source utilisation patterns and a specific PCR-based assay. By Hayward’s
classification method, based on carbon source utilisation, 19 of the 62 R. solanacearum strains
were identified as biovar I and 43 strains were identified as biovar II. The biovar I strains
exhibited a high growth rate at high temperatures (37 °C). Whereas the growth rate of biovar II
strains was greatest at lower temperatures (22 °C). Biovar I strains had broader host range than
biovar II strains, which were limited to potato, tomato, and eggplant. To our knowledge, this is
the first report of R. solanacearum biovar I in Ethiopia. The existence of biovar I strains in
Ethiopia raises concerns because they have a broader host range than biovar II strains.
