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ARS Home » Pacific West Area » Pullman, Washington » Plant Germplasm Introduction and Testing Research » Research » Publications at this Location » Publication #221456
Title: Evaluation of the National Plant Germplasm System's Garlic Collection for Seven Viruses

Author
item PAPPU, HANU - PLANT PATHOLOGY, WSU
item Hellier, Barbara
item Dugan, Frank

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2008
Publication Date: 9/19/2008
Citation: Pappu, H., Hellier, B.C., Dugan, F.M. 2008. Evaluation of the National Plant Germplasm System's Garlic Collection for Seven Viruses. Plant Health Progress doi:10.1094/PHP-2008-0919-01-RS.

Interpretive Summary: The collection of cultivars of garlic (mostly Allium sativum, with some A. longicuspis) located with the USDA-ARS Western Regional Plant Introduction Station (WRPIS) represents one of the largest collections of garlic world wide. Garlic is known world wide as a host for several viruses, which vary in impact on the host cultivar depending on both virus and host. We have noticed symptomatic garlic accessions over several seasons, and in 2005-2006, using modern molecular diagnostic techniques, we embarked on a systematic survey of the collection for important garlic viruses: Garlic common latent virus (GCLV), Iris yellow spot virus (IYSV), Leek yellow stripe virus (LYSV), Onion yellow dwarf virus (OYDV), Shallot latent virus (SLV), and Tobacco rattle virus (TRV). Of these, we found GCLV, LYSV or OYDV, with some plants showing mixed infections of OYDV and GCLV. The most prevalent virus was OYDV (accounting for 60% of infected material), followed by GCLV (25%) and LYSV (15%). Incidence of symptomatic plants ranged from less than 10% to 100% in individual accessions. Survey results can be used for location of potential sources of resistance to viral infection.

Technical Abstract: The garlic (Allium sativum L.and A. longicuspis Regel.) germplasm maintained by the USDA-ARS Western Regional Plant Introduction Station (WRPIS) was screened for viruses. Over 200 accessions were rated for the incidence of symptomatic plants in July 2005 and June 2006. Symptoms indicative of virus infection were noticed in a majority of the accessions, while some appeared to be symptom-free. Incidence of symptomatic plants ranged from less than 10% to 100% in individual accessions. Leaf tissue from representative symptomatic plants from several accessions was collected for laboratory testing. Enzyme-linked immunosorbent assay (ELISA) was first used to determine the identity of the viruses involved. Each sample was tested separately for the following viruses that are known to infect garlic and onions: Garlic common latent virus (GCLV), Iris yellow spot virus (IYSV), Leek yellow stripe virus (LYSV), Onion yellow dwarf virus (OYDV), Shallot latent virus (SLV), and Tobacco rattle virus (TRV). Samples that were found ELISA-positive were verified by reverse transcription-polymerase chain reaction followed by cloning and sequencing of the amplicons. Results showed that the accessions were predominantly infected with GCLV, LYSV or OYDV with some plants showing mixed infections of OYDV and GCLV. The most prevalent virus was OYDV (60%), followed by GCLV (25%) and LYSV (15%). None of the plants tested were positive for IYSV, SLV or TRV. A few accessions remained uninfected, indicating a differential response to viral infection and potential sources of genetic resistance in the garlic germplasm.