CHARACTERIZATION OF GRAPEVINE RUGOSE WOOD DISEASE SOURCES FROM ITALY

A collection of 27 sources of grapevine rugose wood (RW) disease from a viticultural. region in northern Italy was analyzed by graft-inocula ting vines of three selective Vitis indicators (V. rupestris cv. St. G eorge, V. berlandieri x V. riparia cv. Kober 5BB, and hybrid cv. LN 33 ). On the basis of stem reactivity, different groups were identified a mong the selected RW inoculum sources: nine isolates induced pitting o nly on cv. St. George, whereas four induced grooving only on cv. Kober 5BB. These two groups were classified as isolates of rupestris stem p itting and Kober stem grooving. Three of the remaining isolates induce d wood abnormalities on cvs. LN 33 and Kober 5BB, seven induced wood a bnormalities on cvs. St. George and Kober 5BB, and four induced sympto ms on all three indicators. These groups may represent RW sources with various disease combinations. RW-affected grapevine clones used as in oculum sources also were tested for virus infections by enzyme-linked immunosorbent assay (ELISA). ELISA revealed the presence of grapevine fleck virus, grapevine leafroll-associated closterovirus I and 3, and grapevine trichovirus A. These viruses infected most of the selected R W sources. However, eight of the latter were ELISA-negative. The findi ngs are discussed, and the biological and etiological complexity of th e RW phenomena in grapevine is confirmed.