Genotyping the oldest potato blight specimen from Belgian mycologist Marie-Anne Libert

Marie-Anne Libert, a Belgian mycologist was working on the cryptogamic flora of Malmedy when the first potato late blight outbreaks reached the European continent in 1845. Libert, an educated and self-trained mycologist, began collecting samples of the pathogen from infected potato fields. She examined them microscopically and was the first person to provide the name Botrytis vastatrix to the pathogen now known as Phytophthora infestans (Mont.) de Bary. She published a description of her observations in a letter to the editor of the Gazette de Liège in Belgium in August of 1845. A preserved specimen from her work was retrieved from the Herbarium of the Botanic Garden (BR), Meise. We extracted DNA from the sample and conducted multilocus sequencing of mitochondrial genes and microsatellite (SSR) genotyping. Libert's sample was identified as a FAM-1 SSR genotype and was identical to outbreak samples collected in France in 1845. Minimum spanning networks revealed a large cluster of identical multilocus genotypes (MLG's) of FAM-1 that spanned from 1845 to 1883. Several unique MLGs were observed in samples from tomato and black nightshade. Our work represents the genotyping of the oldest potato late blight sample from the famine era in Europe.