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United States Department of Agriculture

Agricultural Research Service

Title: First Report of Bean Yellow Mosaic Virus (Pea Mosaic Strain) in Verbena X Hybrida

Authors
item Guaragna, Mary Ann
item Jordan, Ramon
item Putnam, Melodie - OREGON STATE UNIV, OREGON

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 6, 2004
Publication Date: April 21, 2004
Citation: Guaragna, M.A., Jordan, R.L., Putnam, M.L. 2004. First report of bean yellow mosaic virus (pea mosaic strain) in verbena x hybrida. Plant Disease. 88(5):574.

Interpretive Summary: Verbena x hybrida is an ornamental annual used in rock gardens, as an edging plant, and in hanging baskets. It comes in a variety of colors and grows approximately 6 to 10 inches tall. Viral diseases have been and remain a major threat to the production and quality of the crop. Although viruses alone do not typically kill the plant, they can cause economic loss by reducing plant quality. More than nineteen viruses have been detected in naturally-infected verbena. In the spring of 2002, verbena 'Lavender Shades' plants from California showing leaf mosaic symptoms tested positive for an unknown potyvirus using our potyvirus broad spectrum reacting PTY-1 monoclonal antibody. Total RNA preparations from infected verbena leaves were used in RNA cloning assays using generic potyvirus-specific primers, which amplify various highly conserved fragments from the 3' terminus of most potyviruses. The cloned nucleotide and putative coat protein amino acid sequences from the infected verbena plants were compared to the corresponding regions of other potyviruses. Pairwise comparisons of the verbena potyvirus with available potyviral sequences indicated high identities to bean yellow mosaic virus, specifically pea mosaic strains. Further serological analysis with our panel of BYMV-specific, BYMV-subgroup, and potyvirus cross-reactive monoclonal antibodies confirmed the designation of the verbena potyvirus isolate as a pea mosaic strain of BYMV. To our knowledge this is the first confirmed report of BYMV-pea mosaic strain in Verbena. This information will be useful to nurseries in their screening assays to detect and control this virus in the parent propagation stock lines and subsequently in the large scale plant production phases.

Technical Abstract: Verbena x hybrida is an ornamental annual used in rock gardens, as an edging plant, and in hanging baskets. It comes in a variety of colors and grows approximately 6 to 10 inches tall. In the spring of 2002, verbena 'Lavender Shades' plants from California showing leaf mosaic symptoms tested positive for potyvirus in an antigen-coated plate ELISA using our potyvirus broad spectrum reacting PTY-1 monoclonal as the detecting antibody. The virus was then mechanically transmitted to Nicotiana benthamiana from infected verbena plants by sap inoculation. Total RNA preparations from infected verbena and tobacco leaves were used in RT-PCR assays with generic potyvirus-specific primers, which amplify various highly conserved 700bp or 1600bp fragments from the 3' terminus of most potyviruses. This region includes the 3' non-coding region (3'NCR) and the potyviral coat protein (CP). The PCR amplified fragments were subsequently cloned using standard 'TA cloning' procedures and sequenced using dye-terminator chemistry. Diversity of the CP sequences of potyviruses occurs predominately at the N-terminal regions while the C-terminal half is more highly conserved. All of the molecular data compiled to date has shown that the sequences of the capsid protein and 3' NCR are the most useful regions of the potyviral genome for taxonomic analysis and that the 3'-terminal region may be used as a reliable criterion in distinguishing the strains of a virus from distinct potyviruses. The cloned nucleotide and putative coat protein amino acid sequences from the infected verbena and tobacco plants were compared to the corresponding regions of other potyviruses. Amino acid comparison of the CP region of the verbena potyvirus showed 95-96 % identity to four pea mosaic strains (PMV) of Bean yellow mosaic virus (BYMV), 85-89 % identity to 20 other strains of BYMV, 74-76% identity with six strains of Clover yellow vein virus (CYVV), and only 50-64% identity with 28 other potyviruses. Pairwise comparisons among and between the CP sequences of PMV, BYMV, CYVV and other potyviruses revealed identities of 92-99% for BYMV::BYMV, PMV::PMV, and CYVV::CYVV; 84-89% for BYMV::PMV, 69-78% for BYMV::CYVV and PMV::CYVV, and 50-64% for all other potyvirus combinations. Additionally, similar pairwise analysis of the 3'NCR of the verbena potyvirus showed 98-99% identity to PMV strains, 81-94% to other BYMVs, 68-75% to CYVVs, and 52-64% with other potyviruses. Other 3'NCR pairwise comparisons generally revealed the same identity trend as described for the CP. Further serological analysis with our panel of BYMV-specific, BYMV-subgroup, and potyvirus cross-reactive monoclonal antibodies confirmed the designation of the verbena potyvirus isolate as a pea mosaic strain of BYMV. To our knowledge this is the first confirmed report of BYMV-pea mosaic strain in Verbena.

Last Modified: 10/22/2014