ISHS Acta Horticulturae 193: XIII International Symposium on Fruit Tree Virus Diseases
SEED TRANSMISSION OF APPLE MOSAIC VIRUS IN HAZELNUT |
| Authors: | H.R. Cameron, M. Thompson |
| Abstract:
Mosaic-like symptoms have been attributed to common apple mosaic virus (ApMV) in numerous woody plants. While sap transmission has been reported for tulare apple mosaic (TApMV) the only known transmission of ApMV has been by grafting. Observers have noticed an occasional apple seedling with mosaic symptoms, but with the exception of the tomato ringspot virus, it has been generally accepted that apple viruses are not seed transmitted. As a result, seedling rootstocks are commonly used as understock of virus apple indexed trees. In 1980 and 1981 two 'Negret' hazelnut trees (Coryleus avallena) that were expressing mosaic symptoms were used as either male or female parents in 21 crosses. Seedlings with mosaic-like symptoms appeared in the progeny of eight of these crosses. By 1984 20 seedlings out of 923 (2%) had expressed mosaic symptoms. Nine of these 20 seedlings were ApMV positive by ELISA. Mosaic symptoms occurred in seedlings from crosses where ApMV-infected trees were the male or female parent. In 1985, pollen was collected from the two ApMV infected 'Negret' trees and two symptomless 'Negret' trees. ELISA procedures were used to compare the virus content of the 4 pollen samples with known TApMV and ApMV infected and healthy Catharanthus roseus. The four trees and healthy Catharanthus were negative for Tulare ApMV. The two symptomless trees and the healthy Catharanthus were also negative for ApMV. In contrast, both of the mosaic infected trees and the ApMV-infected Catharanthus extracts gave ELISA readings in excess of 10 times background. These results prove seed transmission of ApMV in hazelnut trees and suggest that the occasional occurrence of mosaic symptoms on apple seedlings may also be due to seed transmission. Until this is confirmed, tree fruit certification programs should not use unindexed apple seedlings as rootstock under virus indexed scion wood. | |
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