First report of Gibberella avenacea causing wet apple core rot in Italy.

Abstract

Gibberella avenacea R.J. Cook, [syn. Fusarium avenaceum (Fr.) Sacc.] is a widely distributed plant pathogen and the causal agent of wet apple core rot (wACR), a disease that develops inside the fruits and remains undetected until they are eaten (Sorensen et al., 2009). In 2012, wACR symptoms were observed in apples cv. Golden Delicious from a southern Italian orchard. Diseased carpel tissues were colonized by a white mycelium, whereas the surrounding mesocarp tissues showed a light-brown wet rot. Single spore cultures were grown on PDA slants and carnation leaf agar (CLA) plates. On PDA slants, after 14 days at alternating day/night temperatures of 25/20°C and a 12 h photoperiod, the fungus formed abundant floccose white mycelium with pale orange sporodochia and released a greyish-rose pigment in the agar. Macroconidia formed on CLA were 40-80!3.5-4 "m, slightly falcate, thin-walled, usually 5 septate, with a tapering apical cell. Microconidia and chlamydospores were absent. Based on these morphological characters the fungus was identified as G. avenacea. For molecular confirmation, DNA was extracted from the fungal mycelium (Sanzani et al., 2012), its internal transcribed spacer regions ITS1 and ITS2, including the 5.8S gene, were amplified using the universal primers ITS5/ITS4 (White et al., 1990) and sequenced (GenBank KC342826). BLAST analysis of the 424 bp amplicon showed 100% identity with other G. avenacea/F. avenaceum ITS sequences from database. This is the first report of G. avenacea as causal agent of wACR in Italy. G. avenacea infections constitute an economical problem for growers and a safety issue due to the potential production of mycotoxins such as moniliformin and enniatins (Sorensen et al., 2009).