DETECTION OF PRUNUS NECROTIC RINGSPOT VIRUS (PNRV) AND PRUNE DWARF VIRUS (PDV) ISOLATES ON WOODY INDICATORS AND WITH ELISA IN HUNGARY

Fifteen PNRV and 25 PDV isolates, inoculated in 1989 and expressing typical symptoms at visual evaluation in the following year, were used as virus sources for further comparative assays. In July 1990, these isolates were inoculated onto Prunus serrulata var. Shirofugen, onto 5 plants of Prunus avium and onto GF 305 seedling. At the end of June 1991, leaves of the maintenance host for the isolates were tested by ELISA. Evaluation of Shirofugen trees was performed at the end of September, 1991. Symptoms on P. avium and GF 305 seedlings were read in spring, 1992. The maintenance hosts of the isolates were tested by ELISA using dormant and forced buds in March 1993.

Results of woody indexing revealed that of the 40 virus isolates tested, 3, 6 and 7 isolates could not be detected on Shirofugen, P. avium and GF 305 indicators, respectively. In all cases at least one of the 3 indicator species showed symptoms, however.

No positive results were obtained by ELISA with 3 isolates in 1992. Thirteen and 12 of the 40 virus isolates could not be detected in dormant buds and in forced buds, respectively, but only 5 isolates were negative in both forced and dormant buds.

Consequently, all three woody indicator species should be used for indexing, while ELISA is recommended at least twice a year (late winter and during summer) to increase the reliability of testing.

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