ISHS Acta Horticulturae 309: XV International Symposium on Fruit Tree Diseases
EARLY DETECTION OF APPLE SCAR SKIN GROUP VIROIDS FROM IMPORTED PEAR GERMPLASM |
| Authors: | S.S. Hurtt, E.V. Podleckis, A. Hadidi, L.M. Ibrahim |
| Abstract:
A dot blot molecular hybridization procedure was developed to rapidly detect members of the apple scar skin viroid (ASSV) group in imported pear germplasm. Bark chips of imported accessions were grafted below dormant buds of the susceptible pear ‘Nouveau Poiteau’ on pear seedling rootstocks. Six weeks after forcing, the ‘Nouveau Poiteau’ shoots were cut off 2–3 nodes above the graft to force a second flush of growth. Nucleic acid or crude sap extracts of petiole and midrib tissue from the shoots were analyzed by dot blot molecular hybridization with an SP6-generated 32P-labeled cRNA probe for apple scar skin (ASSV) type viroids. Extracts from inoculated ‘Nouveau Poiteau’ were compared with those from the tissues of imported, orchard-grown germplasm and graft-inoculated, orchard-grown ‘Lord Lambourne’ apples. Viroids were reliably detected in graft-inoculated ‘Nouveau Poiteau’ by dot blot hybridization. Comparisons of bioassays for common pome fruit viruses (pear ring pattern mosaic, pear vein yellows and apple stem grooving viruses) and dot blot assays for ASSV group viroids showed that accessions infected with the viroids were not always coinfected with any or all of the aforementioned viruses. The ‘Nouveau Poiteau’ graft-inoculation and cRNA probe hybridization procedure provides a rapid method for testing imported pear germplasm for viroids in as little as eight weeks after it enters the quarantine program. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
