Annual variation in strains of barley yellow dwarf virus in Manitoba, and the occurrence of greenbug-specific isolates

Abstract

Seventeen isolates of the aphid-borne barley yellow dwarf virus (BYDV), collected in southern Manitoba in 1966, were transmitted from oats to oats most efficiently by Rhopalosiphum padi. They were transmitted also by Macrosiphum avenae and all but two were transmitted by Schizaphis graminum and Acyrthosiphon dirhodum. Most of these isolates were not transmitted by R. maidis.Only 3 of 25 isolates collected in 1967 were transmitted by the five species of aphids in a pattern similar to that of the isolates collected in 1966. Twenty of the remainder were transmitted with a moderate to high degree of specificity by R. maidis, R. padi, or S. graminum. Two of the latter isolates were transmitted only by S. graminum. When the transmissibility of one of the isolates, for which S. graminum was the most efficient vector, was examined more critically, both the relative and the specific efficiency of the three vectors varied with the age of the infection in the source plants, though S. graminum was always the most efficient vector.