Biodiversity and ITS-RFLP Characterisation of Aspergillus Section Nigri Isolates in Grapes from Four Traditional Grape-Producing Areas in Greece

A study on the occurrence of Aspergillus section Nigri species on grapes from four traditional grape-producing areas in Greece during the 2011/2012 vintage, and their capability to produce OTA was conducted. One hundred and twenty-eight black aspergilli isolates were characterised at the species level initially by the use of morphological criteria in accordance with appropriate keys, followed by molecular characterisation performed with Polymerase Chain Reaction–Restriction Fragment Length Polymorphism (PCR-RFLP) of the 5.8 ribosomal RNA gene Internal Transcribed Spacer region (5.8 rRNA ITS). Restriction enzyme digestion of the ITS amplicons using the HhaI, HinfI and RsaI, endonucleases distinguished eleven different patterns of restriction fragment length polymorphism (RFLP), four for each of the HhaI and RsaI digests and three for HinfI. From a total number of 128 individual isolates, 124 were classified into four Aspergillus species corresponding to A. carbonarius, A. tubingensis, A. japonicus and A. ibericus, and the remaining 4 were classified as members of the A. niger aggregate. A. carbonarius and A. tubingensis being the main representative species were equally counted, with higher geographical representation of the former in southern and the latter in northern regions, respectively. All isolates were tested for their ochratoxigenic potential by use of High Performance Liquid Chromatography (HPLC) and Enzyme Linked Immuno Sorbent Assay (ELISA), resulting in significant interspecies differences in OTA production

Risk assessment of the occurrence of black aspergilli on grapes grown in an alpine region under a climate change scenario

Members of the Aspergillus section Nigri, also known as black aspergilli, are responsible for the ochratoxin A (OTA) and fumonisins contamination of wine. The presence of black aspergilli in vineyards has been investigated extensively in warm climates, in which the incidence of these aspergilli on grapes and levels of OTA contamination of wines are commonly high. However, a detailed description of black aspergilli populations is needed in wine-producing cool regions to establish a baseline in view of the strengthening of temperature increase and in case of summer rainfall decrease. With this in mind, we isolated and characterized black aspergilli from grapes grown in an alpine region in Northern Italy (Trentino) during a 3-year sampling. Black aspergilli were isolated from around 10 % of the grape berries and most of the isolates were classified as A. niger, A. tubingensis and A. uvarum. A. carbonarius was isolated only once. OTA production was detected only in the A. carbonarius isolate and in one A. niger. Most of A. niger isolates were able to produce fumonisins. The presence of mycotoxins biosynthesis genes was assessed in A. niger isolates. An15g07920, a polyketide synthase (PKS) gene involved in OTA biosynthesis, was detected by PCR only in the single ochratoxigenic isolate. This strong correlation was not observed for anfum1, anfum6 and anfum8, three genes included in the A. niger fumonisin biosynthesis gene cluster, which were detected in different A. niger isolates not able to produce fumonisins. Projections of mean daily temperatures and monthly rainfall indicate that the presence of black aspergilli on grapes grown in vineyards of these valleys will probably increase in the future