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Molecular Plant Pathology

Natural Spread and Molecular Analysis of Grapevine Leafroll-Associated Virus 3 in Australia. N. Habili, Cooperative Research Center for Viticulture and CSIRO Division of Horticulture, GPO Box 350, Adelaide, South Australia 5001; C. F. Fazeli(2), A. Ewart(3), R. Hamilton(4), R. Cirami(5), P. Saldarelli(6), A. Minafra(7), and M. A. Rezaian(8). (2)(8)Cooperative Research Center for Viticulture and CSIRO Division of Horticulture, GPO Box 350, Adelaide, South Australia 5001; (3)Mountadam Winery, Eden Valley, South Australia 5235; (4)Primary Industries South Australia, GPO Box 1671, Adelaide, South Australia 5001; (5)P.O. Box 122, Greenock, South Australia 5360; (6)(7)Dipartimento di Protezione delle Piante, Universita degli Studi and Centro di Studio del CNR sui Virus e le Virosi delle Colture Mediterranee, Via Amendola 165/A, 70126 Bari, Italy. Phytopathology 85:1418-1422. Accepted for publication 22 August 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/Phyto-85-1418.

Natural spread of grapevine leafroll disease was observed in a Pinot Noir clonal evaluation trial in South Australia. The trial consisted of 13 clones with the spread apparently initiated from 3 leafroll-infected clones: Antav 543, Geisenheim 20, and Bourgogne H199A. The occurrence of grapevine leafroll-associated virus 3 (GLRaV-3) was suspected. All 104 vines in the trial were tested by enzyme-linked immunosorbent assay using antibody to GLRaV-3 and by slot blot hybridization analysis using double-stranded RNA as target and labeled GLRaV-3–specific cDNA as probe. Both tests linked GLRaV-3 with the disease spread and detected the infection prior to the onset of symptoms. A cDNA clone from an Italian isolate of GLRaV-3 hybridized in Northern blots with three major dsRNAs of 19.5, 1.9, and 0.9 kbp extracted from leafroll-infected vines. The cloned cDNA insert of approximately 1 kbp was sequenced, and a set of primers designed based on the sequence was used to obtain a corresponding polymerase chain reaction product from the Antav 543 isolate grown in Australia. The nucleotide sequence of the cDNA clones from the two isolates of GLRaV-3 showed 99.5% identity and contained an open reading frame (ORF) encoding a putative protein with a molecular mass of 20.4 kDa with no significant homology to known protein sequences. This ORF was mapped near the 3'-end of the plus strand viral genome and had a 3'-untranslated AU-rich region of approximately 347 nucleotide residues.