OCCURENCE OF TWO SAP-TRANSMISSIBLE VIRUSES IN WALNUTS

From walnut trees growing in Apulia (southern Italy) and showing foliar discolorations of various kinds, i.e. yellowish ringspots and line patterns or a bright chrome yellow mottle, two mechanically transmissible viruses were recovered. One of these viruses (walnut ringspot virus = WRSV) was purified and partially characterized. It proved to be a multicomponent entity with two nucleoproteins sedimenting at different rates and containing 39 and 43% of single-stranded RNA, respectively. The mol. wt. of two RNA species was about 2.0 – 2.1 and 2.5x10⁶ daltons.

The protein coat was composed of a single polypeptide with mol. wt. of about 54,000. WRSV was not serologically related to any of 26 isometric viruses including 12 members of NEPO virus group. Whether or not WRSV is related to the virus associated with walnut yellow mosaic has not been ascertained.