DisplayTitle

Iris yellow spot virus in Onion in Chile

Iris yellow spot virus (IYSV) (genus Tospovirus, family Bunyaviridae) has become endemic in several parts of the world. Between 2000 and 2004, the virus was reported from several states in the United States and the most recent report was from Georgia (2). In South America, IYSV was first reported from Brazil (3). Symptoms indicative of IYSV infection (1), such as diamond-shaped and irregular chlorotic and necrotic lesions, were observed during 2004 and 2005 in onion fields in Colina and Tiltil (Chacabuco Province) and Rengo (Cachapoal Province) located in central Chile. In the sampled fields, as much as 50% of the crop showed symptoms. In all three locations, the crop was destined for bulb production and the cultivar was a long-day Valenciana-type. Approximately 50 and 5 ha in Chacabuco and Cachapoal provinces, respectively, were surveyed. Symptomatic plants were collected and tested in the laboratory for confirmation of IYSV infection. A commercially available IYSV-specific enzyme-linked immunosorbent assay kit was used (Adgen Limited, Ayr, Scotland, UK) that confirmed the samples were infected with IYSV. Total nucleic acids were extracted, and using primers flanking the nucleoprotein (NP) gene of IYSV, reverse transcription-polymerase chain reaction was used to verify virus identity. Primer sequences were 5′-TAA AAC AAA CAT TCA AAC AA-3′ and 5′-CTC TTA AAC ACA TTT AAC AAG CAC-3′. The resulting 1.2-kb DNA amplicons from five samples were cloned and sequenced (GenBank Accession No. DQ150107). Nucleotide sequence comparisons with known IYSV NP gene sequences showed 95 to 98% identity, confirming the virus as IYSV. The presence of IYSV in Brazil and now in Chile indicates its potential to become established in onion crops in the region.

References: (1) L. J. du Toit et al. APSnet Image of the Week. http://apsnet.org/online/archive/2003/IW000030.asp, 2003. (2) S. W. Mullis et al. Plant Dis. 88:1285, 2004. (3) L. Pozzer et al. Plant Dis. 83:345, 1999.