Twelve virus isolates from pea, broad bean, red clover and yellow lupin have been compared with the B25 strain of bean yellow mosaic virus (BYMV-B25), the E198 strain of pea mosaic virus (PMV-E198) and the pea necrosis virus (El 78), which were described earlier (Bos, 1970).On the basis of host ranges, symptoms and bean and pea varietal reactions most isolates could be classified into three groups, representatives of which did not differ appreciably serologically. These groups were considered to be typical bean yellow mosaic virus isolates (E212, L1, B25), pea yellow mosaic strain isolates of BYMV (E198, E204, Kow28) and pea necrosis strain isolates of BYMV (E197, E199, E221). From these results and from a survey of literature it is concluded that PMV is only a strain of BYMV.The pea necrosis virus (EI78), described earlier as a distinct entity, is still considered a different virus. A severe pea necrosis isolate (Kow14) resembled E178 in many respects and was also more distantly related serologically to the BYMV isolates tested. Four other virus isolates from pea and broad bean (E196, Vfl 5, Vf18 and Vf30) could not yet be identified. Lettuce mosaic virus (LMV) was found to be serologically rather closely related to BYMV.Results of cross-protection tests were erratic, and particle length measurements were no help in differentiating the strains and viruses studied.
A new carlavirus, apparently omnipresent in shallot (Allium ascalonicum) without causing symptoms, is described as shallot latent virus. It has also been detected in naturally infected onion (A. cepa) Dilution end-point was 104-10s, thermal inactivation at ca. 80~ and ageing in vitro 8 11 days. Purification by molecular sieving on Sephadex G-200 followed by equilibrium density-gradient centrifuging in CsCI was successful. Sedimentation coefficient was 147.5 S, buoyant density 1.313 g/cm 3 and molecular mass of protein snbunits 23 200 dalton. With the antiserum (titre 1024) distant serological relationships to some carlaviruses were determined. No inclusion bodies were observed with the light microscope. With the electron microscope a high concentration of straight or slightly curved particles with a normal length of 650 to 652 nm could easily be detected in crude sap and in purified preparations.
A standard pea necrosis virus isolate (PNV-E178) and two isolates resembling PNV (Kowl4 and E242) were fully compared with bean yellow mosaic virus type strain B25 (BYMV-B25). PNV-E178 and PNV-like isolates Kowl4 and E242 resembled each other and the earlier described pea necrosis strain of BYMV in their reaction on pea, but differed from BYMV strains studied so far in inclusion bodies, and in their reaction in cucumber.Serologically, PNV isolates E 178 and E242 were closely related to each other and both showed a more distant relationship to BYMV-B25. PNu isolate Kowl4 was serologically intermediate between PNV and BYMV-B25, but was hardly infectious to Phaseolus beans.E242 and, to a lesser extent, also Kowl4 were considered strains of the pea necrosis virus, which is closely related to BYMV, but apparently not more so than bean common mosaic virus, pea seedborne mosaic virus, clover yellow vein virus and some other members of the potyvirus group.The lack of well-definable borderlines between the different taxonomic entities unavoidably leads to problems in diagnosing (identifying) intermediate isolates.
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