Genetic variability in differently conserved genomic regions of Diaporthe helianthi isolates of different geographic origin

Diaporthe helianthi, the causal agent of sunflower stem canker, a serious pathogen of sunflower in Europe, is sporadically recorded in Italy. A comparison of pathogen populations from different countries can be performed in order to detect genetically different biotypes. Our approach was turned to study molecular variability in genomic coding and non coding regions among D.helianthi isolates from different geographic origin. A set of isolates from different countries have been used to evaluate genomic variability in endo-polygalacturonase (endo-PG) genic portions and IGS region of rDNA. A PCR analysis with Fusarium moniliforme endo-PG degenerated primers produced variable amplification profiles between isolates in relation to their geographic origin. French and Yugoslavian isolates (countries where the pathogen is most aggressive) showed conserved patterns, while Italian isolates showed highly variable patterns. Primers for speciation studies in filamentous ascomycetes were used for the amplification of a portion of IGS region of rDNA. Amplification products were purified and sequenced in both directions. Phylogenetic analysis separated the isolates into two main clusters: i) all isolate from France and Yugoslavia; ii) all isolates from Italy. This investigation pointed out a good correlation between data obtained by the two different molecular approaches in order to detect intraspecific genetic variability in D.helianthi.