First report of Elsinoe leaf and fruit spot and Elsinoe pyri on apple in Denmark
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An apple disease, known as “Topaz spot” in northern Europe (Trapman and Jansonius, 2008) has since year 2000 become widespread in Danish organic apple orchards (Malus domestica). Characteristic symptoms are small spots (black on fruits, brown on leaves) having a silvery-grey cen- tre. The associated pathogen has not previously been identi- fied, but symptoms are identical to those described for el- sinoe leaf and fruit spot (ELFS) caused by the ascomycete, Elsinoe pyri (Scheper et al., 2013). In 2012, DNA from fruit skin of apples was purified from two cultivars, Pigeon fra Juellinge and Rifbjerg Skarlagen Pearmain growing near Copenhagen that showed severe symptoms of Topaz spot. Fungal DNA was analyzed by pyrosequencing using PCR primers targeting the ITS2 region of ascomycetes (Louarn et al., 2012). Several fungal species were identified, but only a single DNA sequence of 182 bp was found to show con- sistent and specific accumulation in all symptomatic skin samples (n=6). A BLAST search revealed 100% identity only to sequences of E. pyri (isolates from New Zealand, GenBank accession Nos. KC626006, KC626007). Two inde- pendent fungal isolates with morphology identical to E. pyri (Scheper et al., 2013) were recovered by inoculating Topaz- spot infected fruit skin onto potato dextrose agar. Sequenc- ing of the ITS1-5.8S-ITS2 region revealed two identical 628 bp sequences (GenBank KC928079, KC928080) with 99% sequence identity to the previously published sequences of E. pyri. Our findings suggest that Topaz spot is identical to ELFS and show that the pathogen, E. pyri, is hereby re- ported in Denmark and in Scandinavia for the first time.