Foliar virulence of Phytophthora infestans isolates to two Solanum betaceum cultivars, Red and Yellow, was characterized using a detached leaf assay. Six P. infestans sensu lato isolates from S. betaceum belonging to at least two different populations were included (representing the EC-3 clonal lineage and a population that was not previously reported). Three isolates from potato (representing the EC-1 clonal lineage) were included in order to determine their ability to attack S. betaceum cultivars and whether there was difference in virulence between these and isolates from S. betaceum. Significant variation for virulence parameters was found between isolates, isolate-origins, and cultivars. Infection frequency, sporulation intensity, and incubation period allowed differentiation of EC-1 isolates from S. betaceum isolates. Isolates infecting both cultivars exhibited significantly higher values of infection frequency and sporulation intensity and lower latent period values. Cv. Red showed significantly higher values for area under the lesion expansion curve (AULEC), and final lesion size (FLS) and lower values for incubation period (IP) in comparison with cv. Yellow. These results demonstrated that there are two separate populations of P. infestans attacking S. betaceum each with specific virulence towards two different cultivars of Solanum betaceum.
detached leaves assay; EC-1 clonal lineage; EC-3 clonal lineage; late blight; tree tomato
