Diagnosis of tobacco rattle virus (TRV) and other viruses in weed and rotation crops in potato fields

The methodology for the detection of tobacco rattle virus (TRV) and for the incidence of TRV and other viruses was determined in weed species associated with potatoes. Symptoms onNicotiana tabacum L. cv. ‘Samsun NN’and Phaseolus vulgaris L. cv. ‘Bountiful’ were used to detect the viruses. Identity was confirmed by comparison with symptoms produced on plants by standard cultures of TRV and potato virus X (PVX), by electron microscopy, and by serology.Portulaca oleracea L.,Solatium sarachoides Sendt., andAmaranthus retroflexus L. were hosts of TRV; the latter two also carried PVX. Most TRV carriers were found adjacent to infected potatoes. The roots of naturally infectedS. sarachoides contained the highest concentration of TRV encountered in these studies. Mechanical inoculation of TRV to A.retroflexus andS. sarachoides produced variable symptoms that included red spots on the former and chlorosis and stunting on the latter. TRV moved systematically in both species. Assay methods for detection were adequate but low concentrations of TRV limited the usefulness of electron microscopy and serology.