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United States Department of Agriculture

Agricultural Research Service

Title: First Molecular Evidence of the Occurrence of a Pea Mosaic Strain of Bean Yellow Mosaic Virus in Verbena X Hybrida

Authors
item GUARAGNA, MARY ANN
item JORDAN, RAMON
item Putnam, Melodie - OREGON STATE UNIVERSITY

Submitted to: Acta Horticulture Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 16, 2005
Publication Date: October 31, 2006
Citation: Guaragna, M.A., Jordan, R.L., Putnam, M. 2006. First molecular evidence of the occurrence of a pea mosaic strain of Bean yellow mosaic virus in Verbena x hybrida. Acta Horticulture. 722:305-312.

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. 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 transmitted mechanically to Nicotiana benthamiana from infected verbena plants by sap inoculation. Total RNA extractions from infected verbena and tobacco leaves were used in molecular assays to clone and then sequence the 3' terminus of this unknown potyvirus. The cloned nucleotide and putative coat protein amino acid (CP) sequences from the infected verbena and tobacco plants were compared to the corresponding regions of other potyviruses. Amino acid comparison of the CP and non-coding regions of the verbena potyvirus showed very high identity to four pea mosaic strains (PMV) of Bean yellow mosaic virus (BYMV) (95-98%), but only 85-89% identity to 20 other strains of BYMV, and 74-76% identity with six strains of Clover yellow vein virus (CYVV), and only 50-64% identity with 28 other potyviruses. Further serological analysis with our panel of BYMV-specific, BYMV-subgroup, and potyvirus cross-reactive monoclonal antibodies confirmed that the verbena potyvirus isolate was a pea mosaic strain of BYMV. Nineteen other viruses have been reported to infect verbena. To our knowledge this is the first confirmed report of BYMV-pea mosaic strain in Verbena. This information should help verbena growers and producers develop virus-free materials.

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. 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 transmitted mechanically to Nicotiana benthamiana from infected verbena plants by sap inoculation. Further serological analysis with our panel of Bean yellow mosaic virus (BYMV)-specific, BYMV-subgroup, and potyvirus cross-reactive monoclonal antibodies suggested that the verbena potyvirus might be a member of the BYMV subgroup. Total RNA extractions from infected verbena and tobacco leaves were used in RT-PCR assays with generic potyvirus-specific primers, which amplify highly conserved 700bp or 1600bp fragments from the 3' terminus of most potyviruses. This region includes the potyviral coat protein (CP) and the 3' non-coding region (3'NCR). The PCR amplified fragments were cloned using standard 'TA cloning' procedures and sequenced using dye-terminator chemistry. 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 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. 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. These and other phylogenetic analysis of the CP and 3'NCR sequences of PMV, BYMV, CYVV and other potyviruses confirmed the designation of the verbena potyvirus isolate as a pea mosaic strain of BYMV. Nineteen other viruses have been reported to infect verbena. To our knowledge this is the first confirmed report of BYMV-pea mosaic strain in Verbena.

Last Modified: 9/10/2014