Properties of a new isolate of grapevine leafroll-associated virus 2

A new isolate of grapevine leafroll-associated virus 2 (GLRaV-2-H4) was rec overed by mechanically inoculating herbaceous hosts with concentrated tissu e extracts from a North American accession of Vitis rupestris. Contrary to the Semillon isolate of GLRaV-2, isolate H4 elicited necrotic local lesions in Nicotiana clevelandii and infected systemically N. occidentalis inducin g very severe symptoms. The migration rate of dissociated capsid protein of GLRaV-2-H4 in SDS-PAGE differed slightly from that of GLRaV-2-Sem. The coa t protein sequence of GLRaV-2-H4 differed by about 12 % at the nucleotide l evel from capsid proteins of the other two GLRaV-2 isolates that have been sequenced to date. No serological differences could be detected. Isolate H4 is a biological variant of GLRaV-2, which can be distinguished from other mechanically transmitted isolates of the same virus because of differences in type and reactions of the herbaceous host range and in molecular traits of the coat protein cistron.