Diseases of broad bean (Vicia faba L. major) and green pea (Pisum sativum L.) in Tasmania caused by subterranean clover red leaf virus.
Evidence is presented, from investigations that included transmission tests with 4 species of aphids, that a disease of broad bean (Vicia faba) that is common in Tasmania and was thought to be caused by subterranean clover stunt virus (SCSV) is in fact caused by subterranean clover red leaf virus (SCRLV). The symptoms in bean are similar to those caused in Europe by bean leaf roll virus (BLRV). The virus occurred as commonly in pea crops as in broad bean, causing a top yellowing. SCRLV was transmitted to subterranean clover (Trifolium subterraneum) test seedlings from affected broad bean plants by its known vector Aulacorthum solani (Kalt.) but not by Aphis craccivora Koch (the main vector of SCSV), Macrosiphum euphorbiae (Thos.) (an inefficient vector of SCRLV) or Myzus persicae (Sulz.) (an inefficient vector of SCSV.). The disease was reproduced in broad bean with SCRLV in controlled aphid transmission tests. SCSV caused symptoms in broad bean and pea that were similar to those induced by SCRLV, but SCSV was rarely found infecting pea and bean crops in Tasmania. The effects of infection by SCRLV on yield of broad bean were severe. Large numbers of Aulacorthum solani were found overwintering on white clover in 1976, and these were found to carry SCRLV. Since white clover was highly infected with the virus and is the predominant legume in pastures of the Tasmanian vegetable-growing regions, it provides a large reservoir for aphid infestation and virus infection.<new para>ADDITIONAL ABSTRACT:<new para>A leaf-roll disease of broad bean, similar to that induced by bean leaf roll virus (BLRV) in Europe, is common in Tasmania and was shown to be caused by subterranean clover red leaf virus. Effects of infection on yield were severe, as further pod set was markedly reduced after symptoms of infection developed. There was some variation among cv. in their response to infection. The virus occurred as commonly in green pea crops as in broad bean. In pea it caused a top yellowing, but most commercially grown pea cv. had some tolerance.