Incidence and diversity of the fungal genera Aspergillus and Penicillium in Portuguese almonds and chestnuts Paula Rodrigues & Armando Venâncio & Nelson Lima Accepted: 22 May 2013 / Published online: 14 June 2013 # KNPV 2013 Abstract Almonds (Prunus dulcis (Miller) D.A. Webb) and European (sweet) chestnuts (Castanea sativa Miller) are of great economic and social impact in Mediterranean countries, and in some areas they consti- tute the main income of rural populations. Despite all efforts to control fungal contamination, toxigenic fungi are ubiquitous in nature and occur regularly in world- wide food supplies, and these nuts are no exception. This work aimed to provide knowledge on the general mycobiota of Portuguese almonds and chestnuts, and its evolution from field to the end of storage. For this matter, 45 field chestnut samples and 36 almond sam- ples (30 field samples and six storage samples) were collected in Trás-os-Montes, Portugal. All fungi belong- ing to genus Aspergillus were isolated and identified to the section level. Fungi representative of other genera were identified to the genus level. In the field, chestnuts were mainly contaminated with the genera Fusarium, Cladosporium, Alternaria and Penicillium, and the ge- nus Aspergillus was only rarely found, whereas almonds were more contaminated with Aspergillus. In almonds, Aspergillus incidence increased significantly from field to the end of storage, but diversity decreased, with potentially toxigenic isolates belonging to sections Flavi and Nigri becoming more significant and wide- spread throughout storage. These fungi were determined to be moderately associated, which can be indicative of mycotoxin co-contamination problems if adequate stor- age conditions are not secured. Keywords Aspergillus . Penicillium . Field fungi Storage fungi . Fungal association Introduction Almonds (Prunus dulcis (Miller) D.A. Webb, synonym Amygdalus communis L.) and European (sweet) chest- nuts (Castanea sativa Miller) are of great economic and social impact in Mediterranean countries, and in Portugal they constitute the main income of rural popu- lations. Portugal has a typical Mediterranean climate, generally characterised by long periods of high temper- atures and moderate-to-scarce rainfall. Almonds are ex- tremely dry nuts produced under highly stressful envi- ronmental conditions, in regions where the maturation and harvest period corresponds to a hot and dry summer. On the other hand, chestnuts are produced under more cold and humid conditions. Under such conditions, tree nuts, and mostly almonds, are known to be targets of Eur J Plant Pathol (2013) 137:197–209 DOI 10.1007/s10658-013-0233-4 P. Rodrigues (*) CIMO/School of Agriculture of the Polytechnic Institute of Bragança, Campus de Santa Apolónia, 5301-855 Bragança, Portugal e-mail: prodrigues@ipb.pt A. Venâncio : N. Lima IBB–Institute for Biotechnology and Bioengineering, Centre for Biological Engineering, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal A. Venâncio e-mail: avenan@deb.uminho.pt N. Lima e-mail: nelson@ie.uminho.pt