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Molecular Plant Pathology

Nucleotide Sequences of the 3 Regions of Two Major Viruses from Mosaic-Diseased Garlic: Molecular Evidence of Mixed Infection by a Potyvirus and a Carlavirus. Takayuki Nagakubo, Biotechnology Laboratory, Takarazuka Research Center, Sumitomo Chemical Co. Ltd., 4-2-1, Takatsukasa, Takarazuka, Hyogo 665, Japan; Mika Kubo, and Kenji Oeda. Biotechnology Laboratory, Takarazuka Research Center, Sumitomo Chemical Co. Ltd., 4-2-1, Takatsukasa, Takarazuka, Hyogo 665, Japan. Phytopathology 84:640-645. Accepted for publication 28 February 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/Phyto-84-640.

Garlic viruses from 289 mosaic-diseased garlic plants, cultivar Howaito-roppen, were purified, and two different flexuous, rod-shaped viruses, one with a 33-kDa coat protein (CP) and the other with a 36-kDa CP, appeared to be the most common. We determined the partial amino acid sequences of these two CPs and obtained cDNA clones. The 1,413 nucleotides of the 3 region of garlic virus 1 had a genome structure conserved in carlaviruses: a coding region for the 36-kDa CP and the 3 open reading frame (ORF) for a 14.2-kDa putative protein followed by 51 nucleotides of the 3 noncoding region. Phylogenetic comparison of the CP sequences between this virus and known carlaviruses and potexviruses suggested that the virus belongs to the carlavirus group. The 1,974 nucleotides of the 3 terminal region of garlic virus 2 has one large ORF, 597 nucleotides of the 3 noncoding region, and a genome structure characteristic of the Potyviridae. The ORF codes for the C terminal 1/3 region of nuclear inclusion protein b (NIb) and the full length of the 33-kDa CP, which have high homologies to NIb and CP of known potyviruses. Comparison of the amino acid sequence at the NIb-CP junction revealed phylogenetic conservation of S/A residues at the P1 position as well as the F/L/H residues at the P2 position.

Additional keywords: garlic latent virus, garlic mosaic virus, NIa protease, 3 palindrome.