A coding region in Diaporthe helianthi reveals genetic variability among isolates of different geographic origin

A set of Diaporthe helianthi isolates collected in different geographic areas was studied in order to examine whether different genetic biotypes could be responsible for epidemiological differences shown by sunflower stem canker. D. helianthi causes serious losses in France and in former Yugoslavia, while the pathogen is only sporadically recorded in Italy in spite of conducive pedoclimatic conditions. Variability of a D. helianthi coding genomic region, evaluated by means of polymerase chain reaction (PCR), Southern blot hybridisation and restriction fragments length polymorphism (RFLP), showed a conserved homogeneous pattern shared by French and Yugoslavian isolates compared with the heterogeneous pattern of Italian isolates. These results are consistent with other investigations (IGS and ITS region variability) performed on the same set of isolates, allowing a correlation between D. helianthi biotypes, their geographic origin and sunflower stem canker epidemiology.