During a new cataloging of the herbaria of library “Leonardo Angeloni” at CREA-CI of Caserta (South of Italy), a dry leaf of Nicotiana tabacum (var. Burley) stored in a herbarium dated 1934, was noticed for the presence of typical symptoms of Peronospora tabacina. This plant pathogenic fungus, causal agent of blue mold disease, was unknown at that time to the cataloguers, since the first report on tobacco is dated 1958 in Europe and 1960 in Italy. The genomic DNA was extracted from the symptomatic regions of the diseased dry leaf and used as template in PCR reactions with specific primers for the internal transcribed spacers, comprising the 5.8S rDNA gene (ITS1–5.8-ITS2), of P. tabacina. Sequence analysis of PCR products confirmed the presence of the pathogen on the herbarium leaf, providing evidence on the presence of P. tabacina in Europe in 1934, 24 years before the first report. This work emphasizes the usefulness of herbarium specimens to study genetic, ecological and epidemiological aspects of fungal plant diseases through the years.
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