Three aphid vectors of faba bean (Vicia faba) viruses in northern New South Wales and occurrence ofAcyrthosiphon pisum-transmitted isolates ofSoybean dwarf virus

Abstract

Aphid-transmitted virus diseases are a constraint on production of faba bean (Vicia faba) and other cool season grain legumes in northern New South Wales (NSW), Australia. A field study in 2004 identified potentially important aphid vectors of viruses that infect faba bean. Individual alatae were trapped on vertical nets in four field situations and placed immediately on bioassay plants (faba bean seedlings) to identify viruses transmitted in persistent and non-persistent manners. Viruses were identified by nine virus-specific tissue blot immunoassays (TBIAs). Out of a total of 447 individual alatae comprising 14 species, 10 individuals comprising three aphid species transmitted a virus: five Acyrthosiphon pisum (two that transmitted Bean leafroll virus, two Bean yellow mosaic virus, and one Soybean dwarf virus, SbDV), four Aphis craccivora (all Beet western yellows virus, BWYV), and one Myzus persicae (BWYV). No transmissions were detected for the other 11 aphid species, including the faba bean colonising species Acyrthosiphon kondoi, although virus-like symptoms were observed in some cases. None of the alatae transmitted Subterranean clover stunt virus, Alfalfa mosaic virus, Cucumber mosaic virus, Pea seed-borne mosaic virus, or Turnip mosaic virus. In separate tests in which acquisition fed apterae were used to inoculate faba bean, A. pisum was able to transmit four additional isolates of SbDV from chickpea or subterranean clover from Queensland, Tasmania, and NSW. The potential importance of A. pisum, A. craccivora, and M. persicae as vectors is discussed. Of these, A. pisum appears the most likely to cause crop losses in faba bean based on propensity as a vector, numbers trapped, efficient colonisation, and severity of virus isolates transmitted.