Biological and serological diversity of a potyvirus infecting maize in the Mediterranean area

Summary — Several years ago we reported the occurrence of potyvirus infecting maize in southern France and in Spain and Italy, the most prevalent virus being maize dwarf mosaic virus (MDMV) strain A. MDMV is present on dent and sweet corn mainly in areas where Johnson grass (Sorghum halepense L), the reservoir host, is abundant. The aim of our work was to obtain a good and reliable diagnostic method and to start to study the biodiversity of MDMV. We have obtained a good specific antiserum directed against the capsid protein of the virus. In 1991, we started a collec-tion now made up of more than 100 isolates from southern France, the northern part of Italy and some areas of north-ern Spain. The molecular weights of the capsid protein of all the isolates were determined by the immunoblot method. We have been able to classify the isolates in different groups. The behaviour of the isolates belonging to each group defined by Western blot was analysed by mechanical inoculation on several maize inbred lines. We have thus demon-strated a biodiversity in MDMV. This situation is important for the breeder and allows a better understanding of the behaviour of inbred lines of maize in different areas. maize dwarf mosaic virus A (MDMV-A) / Zea mays L = maize / biodiversity Résumé — Diversité biologique et sérologique des potyvirus infectant le maïs en zone méditerranéenne. Le potyvirus dominant sur maïs dans la moitié sud de la France et la partie nord de l’Espagne et de l’Italie est le virus de la mosaïque nanisante du maïs souche A (MDMV-A). Ce virus est présent principalement en production de maïs dou