NINE VIRUSES ISOLATED FROM PELARGONIUM IN THE UNITED KINGDOM

Cucumber mosaic virus and arabis mosaic virus occur in plants which have been grown in the open and are not specific to pelargonium.

Pelargonium leaf curl, is also transmitted in the open, probably through the soil, and is also spread by vegetative propagation because symptoms are masked at high temperatures.

Two American viruses have now been recorded in U.K. Tomato ringspot was discovered in 1969 in cvs. of the Irene group, especially cv. Treasure Chest. Spread to other cvs. has not been recorded. Tobacco ringspot virus was isolated in 1979 from cv. Charlotte imported from U.S.A. It may also be present in other cvs. as it appears to be symptomless.

Pelargonium ringspot, is quite widespread in older cvs. and infects both P. peltatum and P. zonale. It causes ringspots in P. peltatum but line patterns in P. zonale. Three further viruses infect only P. zonale. Pelargonium flower-break is almost symptomless, inducing flower-break in only a few cvs. Pelargonium ring pattern is quite common in older varieties causing ring patterns in the leaves in spring. Pelargonium line pattern (1583 isolate) was first isolated in W. Germany and also occurs in Yugoslavia. It causes line patterns in pelargonium.

All these viruses are distinct and serologically unrelated. Most of them occur in low concentrations in pelargonium and may be difficult to isolate and identify in this host. All can be cultured in Nicotiana clevelandii and assayed in Chenopodium quinoa. All can be identified by serological tests (including ELISA and immune electron microscopy) in N. clevelandii sap, but not in sap of pelargoniums.

These viruses often occur in mixtures and identification from the symptoms in pelargonium is almost impossible.

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