Molecular Variability of the Fusarium solani Species Complex Associated with Fusarium Wilt of Melon in Iran

Species of the Fusarium solani species complex (FSSC) are responsible for the Fusarium wilt disease of melon (Cucumis melo), a major disease of this crop in Iran. According to a recent taxonomic revision of Fusarium based primarily on multilocus phylogenetic analysis, Neocosmospora, a genus distinct from Fusarium sensu stricto, has been proposed to accommodate the FSSC. This study characterized 25 representative FSSC isolates from melon collected in 2009–2011 during a field survey carried out in five provinces of Iran. Pathogenicity assays showed the isolates were pathogenic on different varieties of melon and other cucurbits, including cucumber, watermelon, zucchini, pumpkin, and bottle gourd. Based on morphological characteristics and phylogenetic analysis of three genetic regions, including nrDNA internal transcribed spacer (ITS), 28S nrDNA large subunit (LSU) and translation elongation factor 1-alpha (tef1), Neocosmospora falciformis (syn. F. falciforme), N. keratoplastica (syn. F. keratoplasticum), N. pisi (syn. F. vanettenii), and Neocosmospora sp. were identified among the Iranian FSSC isolates. The N. falciformis isolates were the most numerous. This is the first report of N. pisi causing wilt and root rot disease in melon. Iranian FSSC isolates from different regions in the country shared the same multilocus haplotypes suggesting a long-distance dispersal of FSSC, probably through seeds.