Further studies on turnip yellow mosaic tymovirus isolates from an endemic Australian Cardamine

Native and introduced species of Cardamine and other brassicas were collected from various parts of south-eastern Australia and tested for sap-transmitted viruses. Isolates of turnip yellow mosaic virus (TYMV-Cd) were obtained from a robust sward-forming (SF) species, C. lilacina , that is an endemic species and restricted to the high glacial cirques of the Kosciusko alpine area. At two sites (Blue Lake and Club Lake) 22% of the plants were infected. An undescribed species of flightless pill beetle, Pedilophorus (Byrrhidae), was found on the C. lilacina SF plants. They preferred feeding on leaf discs infected with TYMV-Cd rather than on virus-free leaf discs and transmitted the virus for 48 h to seedlings of C. lilacina SF (2.5%) or Chinese cabbage (10%).
The pattern of distribution of TYMV-Cd and its close association with Pedilophorus suggested that it is not a recent migrant to the area. The possible time of its arrival is discussed.
A carlavirus was isolated from up to 4% of three other native highland Cardamine species.