Characterization and Pathogenicity ofColletotrichum gloeosporioidesandC. karstiiCausing Preharvest Disease onCitrus sinensisin Italy

During the period from 2010 to 2013 preharvest symptoms were detected on different cultivars of sweet orange in six orchards in Catania, Siracusa and Enna provinces, Southern Italy. A total of 56 monosporic fungal isolates were obtained, and among these, 44 were identified as Colletotrichum gloeosporioides and 12 as C . karstii through morphological and molecular analysis. PCR with primers ITS 1 and ITS 4, primers Tub GF 1 and Tub GR specific for β ‐tubulin gene, primers GDF ‐ GDR , specific for Glyceraldehyde‐3‐phosphate dehydrogenase ( GAPDH ) gene, were used to confirm the identification of Colletotrichum isolates from citrus. The ITS 1‐5.8S‐ ITS 2 region, a portion of approximately 500 bp of β ‐tubulin gene and a fragment of 220 bp of GAPDH gene of the isolates were sequenced and analysed with the BLAST n program. Koch's postulates were fulfilled by pathogenicity tests carried out on fruit of ‘Tarocco Scirè’ and ‘Tarocco Nucellare’ with representative isolates of C . gloeosporioides and C . karstii . Field surveys and pathogenicity tests revealed significant differences in fruit susceptibility between ‘Tarocco Scirè’ and ‘Tarocco Nucellare’ and in virulence between the fungal species. To our knowledge, this is the first report on the emergence of Colletotrichum spp. causing anthracnose in preharvest conditions.