Abstract
This paper describes the properties of burdock yellows virus, BdYV (formerly ‘Bd-F’ by Inouye and Mitsuhata, 1971), and its serological relationship to three other closteroviruses.
BdYV induced no apparent symptoms or only faint marginal chlorosis in older leaves of infected burdock, Arctium lappa. BdYV was transmitted by the aphid, Dactynotus gobonis, in a semi-persistent manner to Callistephus chinensis, Chrysanthemum carinatum and Nicotiana clevelandii, but by sap inoculation to only N. clevelandii. The thermal inactivation point of BdYV was between 45 and 50 C and longevity in vitro was 1-2days (20 C). Ultraviolet absorption spectrum of purified preparations of BdYV was characteristic of nucleoprotein spectrum with an A 260/280 ratio of 1.73. Particles of BdYV were flexuous rods, 1700-1750×12nm, with a helical arrangement (3.6nm pitch) of the protein subunits. In ultrathin sections of infected N. clevelandii leaves, banded aggregates of virus particles as well as the characteristic vesicular structures were found in phloem cells. Necrosis of some phloem cells were also observed.
In SDS-immunodiffusion tests with three other closteroviruses, carnation necrotic fleck (CNFV), citrus tristeza (CTV) and wheat yellow leaf (WYLV) viruses, single precipitin lines were formed in homologous antiserum-antigen combinations. BdYV produced clear precipitin line in agar gel containing 0.5% SDS, whereas the other three viruses produced in 0.1% SDS agar gel. In microprecipitin tests, positive serological relationship was observed between CNFV and WYLV.
