ISHS Acta Horticulturae 193: XIII International Symposium on Fruit Tree Virus Diseases
FURTHER INFORMATIONS ABOUT A NEW VIRUS ISOLATED FROM PEACH IN HUNGARY |
| Authors: | C. KERLAN, D. THOMAS, A. CAVALIER, O. COLLIN |
| Abstract:
In 1974, severe Sharka-like symptoms were observed on a peach tree in an orchard in Hungary. First attempts were carried out to identify the causing agent and it appeared that the infectious agent was not Plum Pox Virus, but a virus with isometric particles sedimenting as one single component and containing a single nucleic acid. No serological relationships were found between this virus and 17 other ones. So it was assumed that it could be a new virus. In this paper, we report further characterization of some properties of the particles. Purified suspensions were obtained from fresh leaves of Chenopodium quinoa by a procedure previously described using clarification by ammonium sulfate, PEG precipitation and two cycles of high speed centrifugation on sucrose gradients. The protein composition of the isolated particles was analyzed by SDS polyacrylamide gel electrophoresis. A major component having a molecular weight of 33 000 Da was clearly detected after gel staining with Coomassie blue. Suspensions of virus particles were observed by electron microscopy after negative staining with a 2 p.cent solution of uranyl acetate. Precise measurements of the size of the particles confirm our first results, i.e. a diameter of 33,3 + 0,2 nm (n = 52); on some pictures, subunits of about 8 nm were clearly seen on the particles. In order to obtain further informations about the virion structure, we have used the polyethylene glycol staining carbon film technique. This technique provides an useful method for inducing crystallization of the particles into regular packed monolayers. Virus suspensions tended to produce hexagonally packed particles in two dimensionnal sheets. Analysis by optical diffraction of virus crystals shows hexagonal lattice with a first order at 34 nm-1, which is in close agreement with the measured size of the virion particle. The optical diffraction pattern extends to a 4th order corresponding to 8.5 nm, size of the structural subunits. | |
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