ISHS Acta Horticulturae 130: XII International Symposium on Fruit Tree Virus Diseases
SURVEY FOR TOMATO RINGSPOT VIRUS IN APPLE ORCHARDS IN EASTERN NEW YORK |
| Authors: | D.A. Rosenberger, D. Gonsalves, J.N. Cummins, M.B. Harrison |
| Abstract:
Graft-union symptoms of apple union necrosis and decline (AUND) were observed in 22 orchards involving seven cultivars on MM. 106 rootstock. Orchard observations suggested diseased trees in some cases were more prevalent in parts of the orchard subject to drought or oxygen stress. Tomato ringspot virus (TmRSV) was detected by the enzyme-linked immunosorbent assay (ELISA) in both the scions and MM. 106 rootstocks of 'Empire' and 'Rome Beauty' trees but only in the rootstocks of affected 'Delicious' and 'Spartan' trees. TmRSV was also detected in bark and leaf tissue from M.26 rootstocks in two orchards and from one M.7a rootstock. Disorganized wood tissues and trees broken at the graft unions were observed in six orchards with 'Empire', 'McIntosh', 'Cortland', 'Delicious', or 'Golden Delicious' on M.26 rootstocks, but the ELISA failed to detect TmRSV in the M.26 stumps of five recently-broken trees. In four intensively surveyed Delicious/MM.106 orchards, TmRSV was detected in the rootstock bark samples from 159 of 309 trees indexed and in 41 of 70 dandelion samples (three plants per sample). There was a high, but not perfect, correlation between TmRSV detection in MM. 106 rootstocks and presence of graft-union symptoms. Mean numbers of Xiphinema nematodes per 100 cc of soil in 169 samples collected from beneath indexed trees and in sodded row middles were 84 and 181, respectively. Potential explanations for differences in AUND incidence throughout New York State and the possible role of plant stress in disease development are discussed. | |
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