The Host Status Of Coffee (Coffea arabica) To Ralstonia solanacearum Phylotype I Isolates

The Solanaceae and Rubiaceae families have close phylogenetic relationship, being members of the same Asterid clade of Eudicots. Species of the Solanaceae family are among the most important hosts for Ralstonia solanacearum (Rs), the causal agent of the bacterial wilt disease. In the present work, we investigated the potential host status of the genus Coffea to a diverse collection of Rs isolates. Pathogenicity tests were carried out under greenhouse conditions with nine Rs isolates from distinct geographic areas and host plants. Seedlings of three coffee (Coffea arabica) cultivars were inoculated via root dipping into a bacterial suspension. Plants of all cultivars were infected with three out of nine Rs isolates. Xylem vessels were colonized and plants developed typical wilt symptoms, although milder when compared with tomato seedlings used as controls. All isolates pathogenic to coffee were classified as phylotype I (previously race 1/biovar3). This finding, together with the remarkable pathogen plasticity, the reallocation of the coffee agricultural frontier to warm climate areas, and the current global warming trend are major driving forces of a stronger selection pressure towards Rs isolates pathogenic to coffee trees under natural conditions.