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United States Department of Agriculture

Agricultural Research Service

Title: First Report of Iris yellow spot virus on Onion and Leek in Western Oregon

Authors
item Gent, David
item Martin, Robert
item Ocamb, C - OREGON STATE UNIVERSITY

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 15, 2007
Publication Date: April 30, 2007
Citation: Gent, D.H., Martin, R.R., Ocamb, C.M. 2007. First Report of Iris yellow spot virus on Onion and Leek in Western Oregon. Plant Disease. V91: P 468.

Interpretive Summary: Onion and leek are grown on approximately 600 ha in western Oregon annually for bulb and seed production. Plants with elongated to diamond-shaped, straw-colored lesions characteristic of those caused by Iris yellow spot virus (IYSV) were observed on onion bulb crops and onion and leek seed crops in western Oregon in surveys carried out in July and August of 2006. The virus was detected by two different methods, confirming the presence of IYSV in the symptomatic plants. In the Pacific Northwest region of the U.S., IYSV has been confirmed in the semi-arid regions of central Oregon, central Washington, and the Treasure Valley of eastern Oregon and southwest Idaho. To our knowledge, this is the first report of the disease on a host crop in the mild, maritime region west of the Cascade Mountain Range, and the first report of IYSV on leek seed crops in the U.S. The presence of IYSV in this region may have implications for the iris and other ornamental bulb industries in western Oregon and western Washington. This report underscores the need for further research to determine the impact of the disease on allium crops and other hosts, and development of effective management programs for IYSV and the onion thrips vector.

Technical Abstract: Onion (Allium cepa) and leek (Allium porrum) are grown on approximately 600 ha in western Oregon annually for bulb and seed production. Plants with elongated to diamond-shaped, straw-colored lesions characteristic of those caused by Iris yellow spot virus (IYSV) were observed on onion bulb crops and onion and leek seed crops in western Oregon in surveys carried out in July and August of 2006. The presence of IYSV was confirmed from symptomatic leaves and scapes by enzyme-linked immunosorbant assay (ELISA) using antiserum specific to IYSV. RNA was extracted from symptomatic areas of onion leaves and scapes, and a portion of the nucleocapsid gene was amplified by reverse transcription-polymerase chain reaction. The amplicons were sequenced and found to share over 99% nucleotide and amino acid sequence identity with an onion isolate of IYSV from the Imperial Valley of California (GenBank accession DQ233475). In the Pacific Northwest region of the U.S., IYSV has been confirmed in the semi-arid regions of central Oregon, central Washington, and the Treasure Valley of eastern Oregon and southwest Idaho. To our knowledge, this is the first report of the disease on a host crop in the mild, maritime region west of the Cascade Mountain Range, and the first report of IYSV on leek seed crops in the U.S. The presence of IYSV in this region may have implications for the iris and other ornamental bulb industries in western Oregon and western Washington. This report underscores the need for further research to determine the impact of the disease on allium crops and other hosts, and development of effective management programs for IYSV and the vector, Thrips tabaci.

Last Modified: 11/25/2014
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