Selective media for detection and quantification of Brazilian Ralstonia solanacearum isolates in soil

Meios seletivos para a detecção e a quantificação de isolados brasileiros de Ralstonia solanacearum no solo

ABSTRACT

The efficacy of five selective media described in the literature for the detection of Ralstonia solanacearum in soil was evaluated using isolates from different regions of Brazil. The selective media were evaluated regarding their sensitivity, target-pathogen repression index, capacity for suppressing contaminating microorganisms and recovery rate of the pathogen in soil. No bacterial growth was observed at the concentrations tested for FSM and SM-1 media. Some isolates grew on the PCCG medium with the addition of antimicrobial agents, but only at concentrations of 10⁶ cfu/mL. For the SM and SMSA-E media, adequate sensitivity for the detection of R. solanacearum in soil was observed, enabling detection at a concentration of approximately 10³ cfu/gram of soil. SMSA-E (Selective Medium South Africa - Elphinstone) was found to be the most effective in suppressing the growth of contaminating microorganisms, resulting in the lowest rate of repression of R. solanacearum and the highest recovery rate of the bacterium in the soil.

Keywords:
bacterial wilt; culture medium; diagnosis; SMSA-E.