EVIDENCE THAT VIRUS TRANSLOCATION AND VIRUS-INFECTION OF NON-WOUNDED CELLS ARE ASSOCIATED WITH TRANSMISSIBILITY BY LEAF-FEEDING BEETLES

Two experimental systems were used to study the translocation of virus particles in plants and translocation followed by infection of non-wounded plant cells. Translocation of virus particles in cut plant stems occurred with the beetle-transmissible viruses southern bean mosaic, bean pod mottle and cowpea severe mosaic, but not with sunn hemp mosaic and tobacco ringspot viruses, which are not transmitted by beetles. When purified viruses were injected below sections of steam-killed stems, only the beetle-transmissible viruses were translocated and infected non-wounded tissue above the steam-killed area. However, sunn hemp mosaic, tobacco ringspot and bean yellow mosaic viruses, which are not transmitted by beetles, did not infect plants above killed portions of the stem. These results suggest that both translocation of virus particles in the xylem of plants and establishment of infection in non-wounded tissue are key properties of viruses that are transmitted by beetles.