Twenty-eight potato cultivars were evaluated for resistance to bacterial wilt caused by Ralstonia solanacearum, race 1, biovar I, from May to August, 1998, at Embrapa Hortaliças. The trial was carried out in a naturally infested field in a randomised complete block design with three replications and six plants per plot of 2.4 m². 'Cruza 148' and 'Achat' (resistant), and 'Bintje' (susceptible) were used as controls. Disease incidence was assessed for eight weeks starting 22 days after planting, when the first symptoms were observed. The areas under the disease progress curves (AUDPC) were calculated and the cluster analysis performed using the unweighted pair-group method by arithmetic averages (UPGMA) and simple Euclidian distance coefficient. Five clusters of resistance/susceptibility levels were defined. 'Cruza 148', 'Cruza 148 mutant', 'Araucaria' and 'Granola' had the lowest levels of disease and belonged to cluster 1 (AUDPC values from 0.00 up to 256.90). These cultivars also had the highest commercial (tubers >50mm diameter) and total yields (13.3 and 25.1 t/ha; 10.4 and 21.9 t/ha; 11.4 and 18.8 t/ha, and 14.6 and 16.4 t/ha, respectively). Negative significant correlations (P<0.01) were found between AUDPC and commercial yield (r = - 0.76) and AUDPC and total yield (r = - 0.83).
Solanum tuberosum; Pseudomonas solanacearum; bacterial wilt; resistance
