Necrotic ring spot and prune dwarf viruses in Prunus and in herbaceous indicators

Abstract

SUMMARYWhen scions from sweet cherry trees with tatter‐leaf disease were used to infect a range of Prunus species they induced necrotic leaf spot and stunt in peach, prune dwarf in Italian Prune and necrotic leaf spot and yellows in sour cherry. Inoculum prepared from such infected sweet cherry leaves caused two types of lesions on inoculated cucumber cotyledons from which single‐lesion cultures yielded two viruses differing in physical properties and herbaceous host ranges.One of these viruses reacted with antiserum prepared against a North American isolate of necrotic ring spot virus and, when returned from cucumber to Prunus, it caused tatter‐leaf in sweet cherry, necrotic leaf spot in peach and sour cherry, and no symptoms in Italian Prune. The other virus, which reacted with antiserum prepared against a North American isolate of prune dwarf virus, caused prune dwarf in Italian Prune, stunt in peach and only slight leaf necrosis in sweet cherry. Sour cherry trees developed yellows only when infected with both viruses, but in sweet and sour cherry infection with one virus reduced the severity of the necrotic shock symptoms induced by the other.