Fusarium oxysporum f. sp. echeveriae, a novel forma specialis causing crown and stem rot of Echeveria agavoides

analysis based on the ITS region confirmed the pathogen as Fusarium oxysporum. In order to identify the forma specialis, thirteen isolates obtained from infected tissues were used for phylogenetic analysis based on four polygalacturonase genes (Pg1, Pg5, Pgx1 and Pgx4) together with the translation elongation factor 1-alpha (EF-1alpha) gene. Sequences generated in this study were aligned with other formae speciales of Fusarium oxysporum from GenBank to construct phylogenetic trees. Eleven isolates of a new forma specialis, Fusarium oxysporum f. sp. crassulae described on Crassula ovata, were added to the analysis based on Pg5 and Pgx1 genes. The results obtained for each genomic region showed that the isolates derived from E. agavoides are in a unique group well separated from other formae speciales already described. The first report of F. oxysporum on E. agavoides together with the results obtained in this study suggest a new forma specialis, here named F. oxysporum f. sp. echeveriae.