A virus complex of subterranean clover

Abstract

A study was made of subterranean clover plants from areas of New South Wales where clovers were not re-establishing. Eight field isolates of diseased plants were collected in central and southern New South Wales and in the Australian Capital Territory. Mixed infections of strains of subterranean clover stunt virus (SCSV) and a bean yellow mosaic virus (BYMV) were transmitted from the isolates.

Four species of aphids, Aphis cvaccivora (Koch), A. gossypii (Glov.), Macrosighum euphorbiae (Thomas), and Myzus persicae (Sulz.), transmitted strains of SCSV and the BYMV and a mixture of these to a number of legumes.

Four stable strains of SCSV were separated after a large number of transfers and selections. BYMV was isolated by mechanical inoculation. One Australian cultivar, four Mediterranean introductions, and one intersubspecific hybrid of subterranean clovers were highly resistant to two strains of SCSV and to BYMV.

Mixed infection with SCSV and BYMV and infection with one severe strain of SCSV seriously reduced pod formation and seeding in peas and canning beans as well as in subterranean clover.