First Report of Asiatic Brown Rot Caused by Monilinia polystroma on Peach in Italy

Monilinia spp. are well-known pathogens causing brown rot of fruit trees in many fruit production areas worldwide. In Italy, three Monilinia species are particularly significant with regard to fruit trees, causing blossom and twig blight and brown rot in fruits: Monilinia laxa (Aderhold and Ruhland) Honey, M. fructicola (Winter) Honey, and M. fructigena (Aderhold and Ruhland). In 2009, a new species, M. polystroma, was distinguished from M. fructigena based on morphological and molecular characteristics in Europe (3). M. polystroma is not known to occur in Italy and to date has been reported from the Czech Republic (1), Hungary (3), Poland (4), Serbia (5), and Switzerland (2). In July 2013, during a survey for fungal postharvest pathogens, stored peaches (Prunus persica (L.) Batsch) belonging to different cultivars showing brown rot symptoms were observed in the Emilia Romagna and Sardinia regions of Italy. Typical decay spots were circular and brown, tending toward black, and 5% of peaches presented a large number of yellowish or buff-colored stromata and firm decayed tissues, the symptoms originated by M. polystroma. The pathogen was isolated on V8 agar (V8A) and culture plates were incubated at 25°C in darkness for 5 days. A conidial suspension was spread on malt extract agar (MEA) and single spores were selected. M. polystroma colonies grown on potato dexstrose agar (PDA) were yellowish in color. Irregular black stromatal crusts occurred on the edges of the colonies after 10 to 12 days of incubation and on the margin was present sporogenous tissue slightly elevated above the colony surface, color buff/pale luteous (1). The conidia were one-celled, ovoid or limoniform, smooth and hyaline, and 12 to 20 × 8 to 12 μm in distilled water when grown on V8A at 22°C. The ribosomal ITS1-5.8S-ITS2 region was PCR-amplified from genomic DNA obtained from mycelium using primers ITS1 and ITS4. A BLAST search in GenBank revealed the highest similarity (99%) to M. polystroma sequences (GenBank Accession No. GU067539). Pathogenicity was confirmed using surface-sterilized mature 'Red Heaven' peaches. The fruits were wounded (2 × 2 × 2 mm) twice with a sterile needle and inoculated with 2-mm plugs of 7-day-old mycelia from fungal colony margins. The sample unit was represented by 10 fruits. Control fruits were inoculated with PDA. After 7 days of incubation at 20°C in plastic containers with high humidity, typical symptoms of brown rot developed on both the wounds of all