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© 2008 Plant Management Network.
Accepted for publication 7 March 2008. Published 10 June 2008.


Iris yellow spot virus on Shallot and Onion in France


Odile Huchette, Magnus Kahl Seeds, INH-STPH, 2 rue Le Nôtre, 49045 Angers Cedex 01, France; Christèle Bellamy, Dijon Céréales / R&D Oignon, INRA Dijon-Bretenière, BP 86510, 21065 Dijon Cedex, France; Rodolphe Filomenko, Blandine Pouleau, and Sam Seddas, SEDIAG SAS, 3, Boulevard de Beauregard, 21600 Longvic, France; and Hanu R. Pappu, Department of Plant Pathology, Washington State University, Pullman 99164-6430


Corresponding author: Hanu R. Pappu.  hrp@wsu.edu


Huchette, O., Bellamy, C., Filomenko, R., Pouleau, B., Seddas, S., and Pappu, H.R. 2008. Iris yellow spot virus on shallot and onion in France. Online. Plant Health Progress doi:10.1094/PHP-2008-0610-01-BR.


Iris yellow spot virus (IYSV; family Bunyaviridae, genus Tospovirus) is an economically important viral pathogen of onion (Allium cepa L.) (1). The virus has been reported from several countries in the world in recent years and in Europe, the virus was reported from the Netherlands, Slovenia, Italy, and more recently from Spain [reviewed in (1)]. France ranks fifth in onion production in the European Union, with most of the production consisting of yellow, long-day onion for storage or processing located in the north. At the southeastern limit of this production area is Burgundy (Fig. 1), where the first symptoms of IYSV were suspected on onion in July 2002. Symptoms observed in research plots located at INRA Dijon, Bretenière, France (Fig. 1), include elongated to diamond-shaped light green to necrotic lesions and straw-colored necrotic areas along the leaf margins with extensive spreading along the leaf leading to total necrosis starting near the leaf tip (Fig. 2). Severely affected plants had prematurely dried leaves and produced bulbs of reduced-size with large necks. Similar symptoms suggestive of IYSV infection have been observed each year, but the severity of the necrotic lesions and dried leaves varied from year to year. Symptomatic plants from the above location were tested beginning in June 2005 using a double antibody sandwich-enzyme linked immunosorbent assay kit (SEDIAG, France). Onion plants were found positive for IYSV in ELISA. However, further verification of IYSV infection could not be done at that time. Symptomatic plants continued to persist during field evaluation of onion varieties in 2006 and 2007. Symptomatic leaves from onions were sampled at INRA Dijon in June 2007. Additionally, leaves of shallot (A. cepa L. Aggregatum group) grown in the same location were also collected, as they showed symptoms suggestive of IYSV infection. Symptoms on shallot were slightly different from those observed on onion: numerous necrotic, stroke-shaped lesions covered the shallot leaves (Fig. 3).


 

Fig. 1. Map of France with locations where IYSV was detected in shallot and onion.

 


   
 
 

Fig. 2. Symptoms of Iris yellow spot virus infection on onion plants observed at INRA Dijon, Bretenières, France: infected plants (left); and close up of lesions on leaves (right). Symptoms include elongated to diamond-shaped light green to necrotic lesions and straw-colored necrotic areas along the leaf margins with extensive spreading along the leaf leading to total necrosis starting near the leaf tip.

 

 

Fig. 3. Symptoms (numerous necrotic, stroke-shaped lesions) of Iris yellow spot virus infection on shallot leaves observed in plots of INRA Dijon, Bretenières, France.

   

The IYSV infection of both shallot and onion samples collected in 2007 were confirmed by reverse transcription-polymerase chain reaction (RT-PCR) following cloning and sequencing the amplicons. Total nucleic acids were prepared from symptomatic tissue and primers specific to the small (S) RNA of IYSV (5'-TAA AAC AAA CAT TCA AAC AA-3' and 5'-CTC TTA AAC ACA TTT AAC AAG CAC-3') were used to amplify ca. 1.2 kb region of the S-RNA that flanked the complete nucleocapsid (N) gene (2). The amplicon was cloned and sequenced. Sequence analysis showed that the N gene of the French isolate was 822 bp long and shared 92 to 95% nucleotide sequence homology with known IYSV N gene sequences available in the GenBank confirming the presence of IYSV in shallot and onion in France.

IYSV was also detected in symptomatic onion leaf samples that were collected in July 2007 in a field 5 km from INRA Dijon, and in a field near Angers, in the Pays de la Loire area of France (Fig. 1). This suggests that IYSV is present in different areas of France. The impact of the IYSV on onion and shallot in the different production areas of France remains to be seen.


Literature Cited

1. Gent, D., du Toit, L. J., Fichtner, S. F., Krishna Mohan, S., Pappu, H. R., and Schwartz, H. F. 2006. Iris yellow spot virus: An emerging threat to onion bulb and seed production. Plant Dis. 90:1468-1480.

2. Pappu, H. R., du Toit, L. J., Schwartz, H. F., and Mohan, K. 2006. Sequence diversity of the Nucleoprotein gene of Iris yellow spot virus (genus Tospovirus, family Bunyaviridae) isolates from the western region of the United States. Arch. Virol. 151:1015-1023.