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  • Author or Editor: J.M. Halbrendt x
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The ability of 32P-labeled transcribed cRNA probes to detect tomato ringspot virus (TmRSV) RNA in nucleic acid extracts from roots, bark, and leaves of nectarine (Prunus persica [L.] Batsch) trees with the Prunus stem-pitting disease was assessed and compared with detection of TmRSV antigen by enzyme-linked immunosorbent assay (ELISA) in the same tissues. Neither TmRSV-specific nucleic acid nor antigen was detected in nectarine leaf tissue. ELISA detected TmRSV antigen in root extracts from 71% of the diseased trees, while dot hybridization detected virus-specific nucleic acid in 18% of the same samples. However, ELISA detected TmRSV antigen in only 47% of bark extracts; whereas TmRSV-specific nucleic acid was detected in 100% of the bark extracts from samples collected at or near the soil line. When nucleic acid extracts from bark were prepared from various locations on diseased trees and tested for TmRSV-specific nucleic acid by dot hybridization, there was an almost perfect correlation between the presence of stem-pitting symptoms and the detection of TmRSV nucleic acid. Detection of TmRSV RNA from the bark tissue of rootstock suckers from TmRSV-infected `Delicious'/MM.lO6 apple (Malus × domestica Borkh.) trees was unsuccessful using dot hybridization. The viral RNA, however, was usually detected in either leaf or root tissue of these same trees.

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Rooted cuttings of `Halford' and `Redhaven' peaches [Prunus persica (L.) Batsch] and `Stanley' (Prunus domestica L.) and `Marianna 2624' (P. cerasifera × P. munsoniana) plums were planted in soil containing ≈38 tomato ringspot virus-(TomRSV) infested nematodes (Xiphinema americanum sensu lato Cobb) per 100 cc. Test- and control-plant sap extracts were made from root and leaf tissues after 10, 22, and 34 weeks. Aliquots of these samples were assayed by mechanical inoculation to Chenopodium quinoa Willd. Total nucleic-acid extracts prepared from the remainder of each sample were analyzed by dot blot hybridization using a cRNA probe for TomRSV. The bioassay identified one `Stanley' and two `Redhaven' infected plants. Hybridization results indicated that two of two `Stanley', three of three `Halford', five of five `Redhaven', and zero of six `Marianna 2624' were infected. Our results demonstrate the sensitivity of molecular hybridization for TomRSV detection in Prunus and substantiate the TomRSV resistance of `Marianna 2624'.

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