|Major virus diseases of Vitis, where they originated from?|
G. P. MARTELLI (1), G. P. Martelli (1). (1) University Aldo Moro, Bari, Bari, , Italy
Grapevines host more than 60 viruses, 25 of which are involved in the etiology of three major virus diseases: infectious degeneration/decline, leafroll and rugose wood. Except for decline, these diseases have a worldwide distribution which makes the identification of their site of origin an arduous exercise. Hints to this aim can be found in historical sources (bibliography, artworks, herbaria) and in the knowlege of disease ecology. Grapevine decline, the American counterpart of the European infectious degeneration, is largely confined to USA and Canada, is induced by American nepovirures (ToRSV, TRSV, PRMV), and is vectored by American <i>Xiphinema </i>species. Its North American origin contrasts with that of the other aforesaid disorders, which appear to have their roots in the Old World. The GFLV-induced fanleaf disease is the most relevant component of infectious degeneration, a nepoviral disease (ArMV, TBRV, SLRSV, RpRSV) restricted to continental Europe, and transmitted by local vectors. As to leafroll, early reddening of grape leaves is descrbed in old French and Italian literature, while the disease and some of its agents (GLRaV-1, GLRaV-3) were found in own-rooted vines from phylloxera-free countries with a millennial viticultural history. A comparable situation exists for rugose wood, a disease first described in Italy, whose symptoms and related agents (GVA, GVB) were found in countries with a long history of own-rooted grape cultivation.