Natural resistance to Alfalfa mosaic virus in different lupin species

Plants of nine different species of lupin (Lupinus spp.) were challenged with Alfalfa mosaic virus (AMV) in glasshouse experiments. No infection of Lupinus cosentinii was detected following sap or graft inoculation. Lupinus albus and Lupinus pilosus were not infected by sap inoculation. However, on graft inoculation, L. albus sometimes responded with localised necrosis just below the graft union without further systemic movement, and L. pilosus responded once with severe systemic necrosis. In Lupinus atlanticus, Lupinus digitatus and Lupinus mutabilis, sap inoculation induced necrotic local lesions in inoculated leaves without subsequent systemic infection, while graft inoculation often caused necrosis just below the graft union without further systemic movement. Lupinus angustifolius, Lupinus hispanicus and Lupinus luteus developed systemic susceptible responses when sap-inoculated. AMV caused milder symptoms than Cucumber mosaic virus in L. angustifolius, while mixed infection with both viruses caused more severe symptoms than either virus alone. In addition, AMV was transmitted through seed to seedlings (0.8%) in a seed sample of L. angustifolius.