Résumé
Pathogenic micro-organisms of crops can be responsible for epidemics with a high socio-economic impact. Herbaria in natural history collections are sources of information for studying these epidemics: they cover the last 200 years, including the last wave of major agricultural changes, and complement the data from modern samples. More generally, museum collections of biological samples are becoming an increasingly important source for reconstructing the evolutionary history of life. The exploration of a herbarium takes into account the date and place of sample collection, and the existence of visible symptoms. The analysis of exploitable sequences from the sample, following the extraction of nucleic acids (DNA or siRNA), is subject to specific constraints. Theories on the domestication of plants for agriculture generally hypothesize that it enabled the initial emergence of specialized pathogens causing diseases with a significant socio-economic impact.