First Report of Iris yellow spot virus on Garlic in India

Garlic (Allium sativum) is a spice crop of prime importance in India as well as other parts of the world. Iris yellow spot virus (IYSV; genus Tospovirus, family Bunyaviridae) is an important pathogen of onion bulb and seed crops in many parts of the world (3). The virus is also known to infect garlic and other Allium spp. (2–4). IYSV infection of garlic was reported from Reunion Island (4) and the United States (1). In February 2010, straw-colored, spindle-shaped spots with poorly defined ends were observed on the leaves of a garlic crop at the research farm of the Directorate of Onion and Garlic Research in the Pune District of Maharashtra State, India, 105 days after planting. The spots coalesced to form larger patches on the leaves, suggesting possible IYSV infection. Symptoms were visible on older leaves and more prevalent on cv. G-41, G-282, AC50, AC200, AC283, and Godavari than on other cultivars. The incidence of symptomatic plants was estimated at 5% for G-41 and AC-200, 8% for G-282 and AC283, and 10% for AC50. Leaves were sampled from 40 symptomatic plants per cultivar with each sample composited from young, middle, and older (basal) leaves of the plant. Samples were assayed by double-antibody sandwich-ELISA (Loewe Biochemica GmbH, Sauerlach, Germany) and each tested positive for the virus. Total RNA was extracted from the leaves of ELISA-positive plants using the RNAeasy Plant Mini kit (Qiagen GmbH, Hilden, Germany) and tested by reverse transcription-PCR assay using primers IYSV-F (5′-TCAGAAATCGAGAAACTT-3′) and IYSV-R (5′-TAATTATATCTATCTTTCTTGG-3′) (2) designed to amplify 797 bp of the nucleocapsid (N) gene of IYSV. Amplicons of expected size were obtained and cloned into a pDrive vector (Qiagen GmbH). The recombinant clone was sequenced (GenBank Accession No. HM173691). Sequence comparisons showed 98 to 100% nt identity with other IYSV N gene sequences in GenBank (Nos. EU310294 and EU310286). A phylogenetic analysis of the deduced amino acid sequences of the N gene showed that the garlic isolate of IYSV grouped most closely with onion IYSV isolates from India (GenBank Nos. EU310294, EU310286, EU310300, and EU310296). To our knowledge, this is the first report of natural infection of garlic by IYSV in India. Additional surveys and evaluations are needed to obtain a better understanding of the potential impact of IYSV on garlic production in India. References: (1) S. Bag et al. Plant Dis. 93:839, 2009. (2) A. Bulajic et al. Plant Dis. 93:976, 2009. (3) D. Gent et al. Plant Dis. 90:1468, 2006. (4) I. Robène-Soustrade et al. Plant Pathol. 55:288, 2006.

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First Report of Natural Infection of Garlic with Iris yellow spot virus in the United States

Plant Disease ◽

10.1094/pdis-93-8-0839a ◽

2009 ◽

Vol 93 (8) ◽

pp. 839-839 ◽

Cited By ~ 5

Author(s):

S. Bag ◽

P. Rogers ◽

R. Watson ◽

H. R. Pappu

Keyword(s):

United States ◽

Natural Infection ◽

Sandwich Elisa ◽

The United States ◽

Iris Yellow Spot Virus ◽

Yellow Spot ◽

N Gene ◽

Spot Virus ◽

Sequence Comparisons ◽

First Report

Iris yellow spot virus (IYSV; family Bunyaviridae, genus Tospovirus) is an important constraint to onion bulb and seed production in several onion-growing regions of the United States (1,3). While garlic (Allium sativum) was reported to be infected with IYSV in Réunion Island (4), there have been no confirmed reports of natural infection of garlic in the United States. Garlic plants showing near-diamond-shaped lesions were found in August of 2008 in Marion County, Oregon. The 0.4046-ha (1-acre) field plot consisted of various true-seeded garlic varieties and was adjacent to three onion fields that showed IYSV symptoms. Symptoms were observed on 5% of the garlic plants with most of the symptomatic plants displaying small and diffuse straw-colored spots. Seven of these symptomatic plants were selected for testing. Of these, two showed characteristic diamond-shaped, elongated, straw-colored lesions on garlic scapes. However, the lesions were more diffuse with less-defined edges compared with the characteristic diamond-shaped lesions that are often associated with IYSV infection (1). All symptomatic plants were positive for IYSV by double-antibody sandwich-ELISA with a commercially available kit (Agdia Inc., Elkhart, IN). To verify IYSV infection, total nucleic acid extracts from the symptomatic parts of the leaves were prepared and tested for the presence of IYSV by reverse transcription (RT)-PCR with primers 5′-TAAAACAAACATTCAAACAA-3′ and 5′-CTCTTAAACACATTTAACAAGCAC-3′, which flank the nucleocapsid (N) gene coded by the small RNA of IYSV (2). An approximate 1.1-kb amplicon was obtained from all symptomatic plants and cloned and sequenced. Nucleotide sequence comparisons using BLAST showed that a consensus of three clones derived from the amplicon from garlic (No. FJ514257) was 85 to 99% identical with IYSV sequences available in GenBank (Nos. AF001387, AB180918, and AB286063), confirming the identity of IYSV. To our knowledge, this is the first report of natural infection of IYSV infection of garlic in the United States. Additional surveys and testing are needed to obtain a better understanding of IYSV incidence in garlic to evaluate its impact on garlic production. References: (1) D. Gent et al. Plant Dis. 90:1468, 2006. (2) H. R. Pappu et al. Arch. Virol. 151:1015, 2006. (3) H. R. Pappu et al. Virus Res. 141:219, 2009. (4) I. Robène-Soustrade et al. Plant Pathol. 55:288, 2006.

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First Report of Iris yellow spot virus in Commercial Leek (Allium porrum) in Spain

Plant Disease ◽

10.1094/pdis-91-10-1365b ◽

2007 ◽

Vol 91 (10) ◽

pp. 1365-1365 ◽

Cited By ~ 5

Author(s):

C. Córdoba-Sellés ◽

C. Cebrián-Mico ◽

A. Alfaro-Fernández ◽

M. J. Muñoz-Yerbes ◽

C. Jordá-Gutiérrez

Keyword(s):

Natural Infection ◽

The United States ◽

Iris Yellow Spot Virus ◽

Yellow Spot ◽

N Gene ◽

Nucleotide Sequence Analysis ◽

Allium Porrum ◽

Rt Pcr ◽

Spot Virus ◽

First Report

Iris yellow spot virus (IYSV; family Bunyaviridae, genus Tospovirus) has a wide host range, with onion (Allium cepa L.) being one of the most economically important hosts. The first report of IYSV in Spain was from Albacete in 2003 (1) followed by the Canary Islands in 2005. In November of 2006, disease symptoms suspected to be caused by IYSV were observed on the central and outer leaves of commercial leeks plants (cvs. Asthow, Edison, and Shelton) from Alicante, Spain. Symptoms consisted of dry, white-to-straw-colored, spindle-shaped, irregular chlorotic and necrotic lesions on the leaves. Tissue from symptomatic leaves was sampled and analyzed by a double-antibody sandwich (DAS)-ELISA with specific polyclonal antibodies against Onion yellow dwarf virus (OYDV), Leek yellow stripe virus (LYSV) (Biorad Phyto-Diagnostics, Marnes-La Coquette, France), IYSV, and Tomato spotted wilt virus (TSWV) (Loewe Biochemica, Sauerlach, Germany). Five of seven leek samples belonging to the three cultivars tested were positive for IYSV. All samples were negative for the other viruses tested. The presence of IYSV was verified in the positive samples by reverse transcription (RT)-PCR using primers derived from the nucleocapsid (N) gene of IYSV (1). RT-PCR gave a PCR amplicon of expected size (approximately 790 bp) from symptomatic leek plants. The product of one of the positive leek samples was purified and sequenced (GenBank Accession No. EF427447). Nucleotide sequence analysis confirmed the identity of the amplicon as that of the IYSV N gene. Sequence comparisons showed 99% identity with the sequence of the IYSV Spanish isolate available in GenBank (Accession No. EF419888). Thrips tabaci is the primary vector of IYSV. Although the vector is present in Spain, the efficiency of the Mediterranean ecotype in transmitting the virus is not known. Leek has been reported to be a host of IYSV in countries such as the Netherlands, Reunion Island, Australia, and the United States (2). To our knowledge, this is the first report of natural infection of leek with IYSV in Spain. References: (1) C. Córdoba-Sellés et al. Plant Dis. 89:1243, 2005. (2) H. F. Schwartz et al. Plant Dis. 91:113, 2007.

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Natural Infection of Iris yellow spot virus in Twoscale Saltbush (Atriplex micrantha) Growing in Utah

Plant Disease ◽

10.1094/pdis-93-4-0430c ◽

2009 ◽

Vol 93 (4) ◽

pp. 430-430 ◽

Cited By ~ 7

Author(s):

C. K. Evans ◽

S. Bag ◽

E. Frank ◽

J. R. Reeve ◽

C. Ransom ◽

...

Keyword(s):

Natural Infection ◽

Sandwich Elisa ◽

The United States ◽

Iris Yellow Spot Virus ◽

Yellow Spot ◽

N Gene ◽

Nucleotide Sequence Analysis ◽

Jefferson County ◽

Spot Virus ◽

Sequence Identity

Iris yellow spot virus (IYSV; family Bunyaviridae, genus Tospovirus) continues to be an economically important pathogen affecting onion bulb and seed production in several parts of the world and the United States (1). Several weeds were reported naturally infected with IYSV (1,2,4). Leaves of Atriplex micrantha Ledeb. (synonym A. heterosperma Bunge) were collected from naturally occurring plants in a weed trial conducted in commercial onions grown in Box Elder County, UT on 24 September 2008. Leaves displayed a range of symptoms including spotting, chlorosis, and necrosis. Symptomatic leaves were preferentially selected for subsequent diagnostic analyses. Samples were positive for IYSV when tested by double-antibody sandwich-ELISA using a commercially available kit (Agdia Inc., Elkhart, IN). For further confirmation, total nucleic acid extracts from the symptomatic parts of the leaves were prepared and tested for the presence of IYSV by reverse transcription-PCR with primers specific to the nucleocapsid (N) gene coded by the small (S)-RNA of IYSV. The forward and reverse primer pair, 5′-TCAGAAATCGAGAAACTT-3′ and 5′-CACCAATGTCTTCAACAATCTT-3′, respectively, amplifies a 751-nt fragment of the N gene (3). An amplicon of expected size was obtained, cloned, and sequenced. The nucleotide sequence analysis and comparison with known IYSV S-RNA sequences showed that the sequence of the amplicon from A. micrantha (GenBank Accession No. FJ493541) shared more than 84% nt sequence identity with the corresponding region of IYSV isolates available in GenBank, confirming the IYSV infection of the new host weed. The highest sequence identity (98%) was with an IYSV isolate from Jefferson County, OR (GenBank Accession No. DQ233479). To our knowledge, this is the first report of IYSV infection of A. micrantha under natural conditions. The role of A. micrantha and other weeds in IYSV epidemiology needs further investigation. References: (1) D. Gent et al. Plant Dis. 90:1468, 2006. (2) C. Nischwitz et al. Plant Dis. 91:1518, 2007. (3) H. R. Pappu et al. Arch. Virol. 151:1015, 2006. (4) R. Sampangi et al. Plant Dis. 91:1683, 2007.

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First Report of Iris yellow spot virus in Commercial Leek (Allium porrum) in the United States

Plant Disease ◽

10.1094/pd-91-0113b ◽

2007 ◽

Vol 91 (1) ◽

pp. 113-113 ◽

Cited By ~ 5

Author(s):

H. F. Schwartz ◽

K. Otto ◽

H. R. Pappu

Keyword(s):

United States ◽

The United States ◽

Iris Yellow Spot Virus ◽

Yellow Spot ◽

N Gene ◽

Allium Porrum ◽

Rt Pcr ◽

Spot Virus ◽

Disease Symptoms ◽

First Report

Iris yellow spot virus (IYSV; family Bunyaviridae, genus Tospovirus) has a wide host range, with onion (Allium cepa L.) being one of the most economically important hosts. IYSV has been widely reported from this species throughout most onion-production regions of the United States and many areas of the world in recent years. A relative of onion, leek (Allium porrum L.), has been reported to be a host of IYSV in countries such as the Netherlands, Reunion Island, and Australia (1,4). A related tospovirus, Tomato spotted wilt virus (TSWV), was recently reported causing necrotic lesions and extended bleaching of leaf tips of leek in Georgia (2). In September of 2006, disease symptoms suspected to be caused by IYSV were observed on central and outer leaves of plants in a 2.6-ha section of commercial leeks being grown from seed (cvs. Tadorna and King Richard). The leek plants were adjacent to a 3.1-ha section of seeded onion (cv. Exacta) that had been harvested 2 weeks earlier. Twenty-five to thirty percent of unharvested onion plants next to the leek section also exhibited IYSV-type disease symptoms generally on the central leaves. Both Allium spp. were seeded 5 months earlier and grown under certified organic, pivot-irrigated conditions in Larimer County in northern Colorado. Disease symptoms on leek and onion leaves appeared as dry, white-to-straw-colored, spindle- or diamond-shaped lesions that ranged in size from 5 to 10 × 25 to 50 mm or larger depending on lesion age. Lesion centers, especially on leek, often had green centers with concentric rings of alternating green and straw-colored tissue. Green tissue near necrotic lesions of a single symptomatic leaf from 10 plants each of leek and onion was sampled and analyzed using a double-antibody sandwich (DAS)-ELISA (Agdia, Inc., Elkhart, IN). Five of ten leek and nine of ten onion samples were positive for IYSV. Using reverse transcription (RT)-PCR and primers specific to the small RNA of IYSV (5′-TAA AAC AAA CAT TCA AAC AA-3′ and 5′-CTC TTA AAC ACA TTT AAC AAG CAC-3′), the complete nucleocapsid (N) gene was amplified from symptomatic leek plants and then sequenced (3). Comparisons with IYSV N gene sequences available in the GenBank confirmed the identity of the virus as IYSV. Leek samples were negative for TSWV when tested by RT-PCR with TSWV-specific primers. In addition, three specimens of the presumed thrips vector recovered from five IYSV-infected leek plants were identified as Thrips tabaci (L. A. Mahaffey and W. S. Cranshaw, personal communication). Earlier in the season, T. tabaci was observed in the nearby planting of onion that also exhibited IYSV in September. To our knowledge, this is the first report of natural infection of commercial leek with IYSV in the United States. The incidence of plants (25 to 30%) with foliar lesions on multiple leaves and stunting of 5% of infected plants in both leek cultivars suggests that IYSV could seriously reduce leek stem development and marketability. References: (1) I. Cortes et al. Phytopathology 88:1276, 1998. (2) C. Nischwitz et al. Plant Dis. 90:525, 2006. (3) H. R. Pappu et al. Arch. Virol. 151:1015, 2006. (4) T. N. Smith et al. Plant Dis. 90:729, 2006.

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First Report of Onion (Allium cepa) Naturally Infected with Iris yellow spot virus in Peru

Plant Disease ◽

10.1094/pd-90-0377a ◽

2006 ◽

Vol 90 (3) ◽

pp. 377-377 ◽

Cited By ~ 8

Author(s):

S. W. Mullis ◽

R. D. Gitaitis ◽

C. Nischwitz ◽

A. S. Csinos ◽

Z. C. Rafael Mallaupoma ◽

...

Keyword(s):

The United States ◽

Thrips Tabaci ◽

Iris Yellow Spot Virus ◽

Yellow Spot ◽

N Gene ◽

Enzyme Linked Immunosorbent Assay ◽

Spot Virus ◽

First Report ◽

The Impact ◽

Das Elisa

Onions have become an important export crop for Peru during the last few years. The onions produced for export are primarily short-day onions and include Grano- or Granex-type sweet onions. The first of two growing seasons for onion in Peru occurs from February/March until September/October and the second occurs from September/October to December/January. Iris yellow spot virus (IYSV [family Bunyaviridae, genus Tospovirus]), primarily transmitted by onion thrips (Thrips tabaci), has been reported in many countries during recent years, including the United States (1,2). In South America, the virus was reported in Brazil during 1999 (3) and most recently in Chile during 2005 (4). During 2003, an investigation of necrotic lesions and dieback in onions grown near the towns of Supe and Ica, Peru led to the discovery of IYSV in this region. Of 25 samples of symptomatic plants collected from five different fields near Supe, 19 tested strongly positive and an additional three tested weakly positive for IYSV using double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA) (Agdia Inc., Elkhart, IN). None of the samples tested positive for Tomato spotted wilt virus (TSWV). A number of onions with necrosis and dieback symptoms were also observed during 2004 and 2005. During September 2005, 25 plants with symptoms suspected to be caused by IYSV or TSWV in the Supe and Casma valleys were collected and screened for both viruses using DAS-ELISA. All plants screened were positive for IYSV. There was no serological indication of TSWV infection in these samples. The positive samples were blotted onto FTA cards (Whatman Inc., U.K.) to bind the viral RNA for preservation and processed according to the manufacturer's protocols. The presence of IYSV was verified by reverse transcription-polymerase chain reaction (RTPCR) using (5′-TCAGAAATCGAGAAACTT-3′) and (5′-TAATTATATCTATCTTTCTTGG-3′) as forward and reverse primers (1), respectively. The primers amplify the nucleocapsid (N) gene of IYSV, and the RT-PCR products from this reaction were analyzed with gel electrophoresis with an ethidium bromide stain in 0.8% agarose to verify the presence of this amplicon in the samples. Subsequent to the September 2005 sampling, 72 additional samples from regions in northern and southern Peru were analyzed in the same manner. The amplicons obtained were cloned, sequenced, and compared with known IYSV isolates for further verification. Onions have become a significant export crop for Peru, and more research is needed to determine the impact of IYSV on the Peruvian onion export crop. To our knowledge, this is the first report of IYSV in onion in Peru. References: (1) L. du Toit et al. Plant Dis. 88:222, 2004. (2) S. W. Mullis et al. Plant Dis. 88:1285, 2004. (3) L. Pozzer et al. Plant Dis. 83:345, 1999. (4) M. Rosales et al. Plant Dis. 89:1245, 2005.

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Outbreak of Iris yellow spot virus in Onion Seed Crops in Central Oregon

Plant Disease ◽

10.1094/pd-89-0105c ◽

2005 ◽

Vol 89 (1) ◽

pp. 105-105 ◽

Cited By ~ 14

Author(s):

F. J. Crowe ◽

H. R. Pappu

Keyword(s):

United States ◽

The United States ◽

Iris Yellow Spot Virus ◽

Yellow Spot ◽

N Gene ◽

Rt Pcr ◽

Spot Virus ◽

Seed Crop ◽

Onion Seed ◽

Seed Crops

Iris yellow spot virus (IYSV) of the genus Tospovirus, family Bunyaviridae is considered an emerging or reemerging pathogen affecting onions in the United States. The virus has been endemic to the Treasure Valley of southern Idaho for more than a decade (4). Reports of its further spread came from several states in the region, most recently from New Mexico and Washington (1,3). During the 2004 growing season, a few onion seed crops near Madras (Jefferson County) in central Oregon showed symptoms suggestive of IYSV infection, including characteristic diamond-shaped scape lesions (2). By July, scapes in one-half of a 4-ha field were 100% symptomatic and 95% lodged, leading to nearly total crop failure; in the other half, scapes were 30 to 40% symptomatic and 15% lodged, with symptoms and lodging increasing weekly at 8 weeks before harvest. The half of this crop with greater incidence was immediately adjacent to a field where very limited IYSV-like symptoms were noticed in a 2002–2003 onion seed crop that was harvested in mid-August 2003, after the highly symptomatic 2003–2004 onion seed crop was planted next to it in early July 2003. Both crops were planted from true seed. In another onion seed crop located 1,000 m away, IYSV-like symptoms were abundant around the field edges in July and through the field in August 2004, with approximately 5% lodging by mid-August. A small number of plants with IYSV-like symptoms were present in a few more distant fields, but not in most onion seed fields in central Oregon. Symptomatic plants were collected and tested in the laboratory for confirmation of IYSV infection. IYSV was confirmed using enzyme-linked immunosorbent assay (ELISA) with a commercially available antiserum (Agdia Inc., Elkhart, IN). Total nucleic acids were extracted, and using primers specific to the nucleocapsid (N) gene of IYSV (3), reverse transcription-polymerase chain reaction (RT-PCR) was done. RT-PCR gave DNA amplicons of the expected size. The DNA amplicons were cloned and sequenced. Nucleotide sequence comparisons with known IYSV N gene sequences confirmed virus identity. The rapid spread of IYSV in the Pacific Northwest and its severity of incidence often leading to 100% incidence is a cause for concern for onion growers and industry. Efforts to identify management practices to reduce its impact have to be undertaken on a regional basis because of its widespread occurrence across several states in the northwestern United States. References: (1) R. Creamer et al. Plant Dis. 88:1049, 2004 (2) L. J. du Toit et al. APSnet image of the week. On-line publication: http://apsnet.org/online/archive/ 2003/IW000030.asp , 2003. (3) L. J. du Toit et al. Plant Dis. 88:222, 2004. (4) J. M. Hall et al. Plant Dis. 77:952, 1993.

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

Plant Disease ◽

10.1094/pdis-91-4-0468a ◽

2007 ◽

Vol 91 (4) ◽

pp. 468-468 ◽

Cited By ~ 5

Author(s):

D. H. Gent ◽

R. R. Martin ◽

C. M. Ocamb

Keyword(s):

United States ◽

Disease Incidence ◽

The United States ◽

Yellow Spot ◽

Onion Bulb ◽

Spot Virus ◽

First Report ◽

Seed Crop ◽

Onion Seed ◽

Seed Crops

Onion (Allium cepa) and leek (Allium porrum) are grown on approximately 600 ha in western Oregon annually for bulb and seed production. During July and August of 2006, surveys of onion bulb crops and onion and leek seed crops in western Oregon found plants with symptoms of elongated to diamond-shaped, straw-colored lesions characteristic of those caused by Iris yellow spot virus (IYSV) (1–4). Symptomatic plants were collected from fields of an onion bulb crop, an onion seed crop, and two leek seed crops located in Marion County. The onion bulb crop had been planted in the spring of 2006, and the onion and leek seed crops had been planted in the fall of 2005, all direct seeded. Cultivar names were not provided for proprietary purposes. Symptomatic plants in the onion bulb crop and leek seed crop generally were found near the borders of the field. Disease incidence was less than 5% and yield losses in these crops appeared to be negligible. In the onion seed crop, symptomatic plants were found throughout the field and disease incidence was approximately 20%. Approximately 1% of the onion plants in this field had large necrotic lesions that caused the seed stalks (scapes) to lodge. The presence of IYSV was confirmed from symptomatic leaves and scapes by ELISA (Agdia Inc., Elkhart, IN) 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-PCR. The amplicons were sequenced and found to share more than 99% nucleotide and amino acid sequence identity with an onion isolate of IYSV from the Imperial Valley of California (GenBank Accession No. DQ233475). In the Pacific Northwest region of the United States, IYSV has been confirmed in the semi-arid regions of central Oregon (1), central Washington (2), and the Treasure Valley of eastern Oregon and southwest Idaho (3). 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 United States, which complements a simultaneous report of IYSV on commercial leek in Colorado. The presence of IYSV 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 the development of effective management programs for IYSV and the vector, Thrips tabaci. References: (1) F. J. Crowe and H. R. Pappu. Plant Dis. 89:105, 2005. (2) L. J. du Toit et al. Plant Dis. 88:222, 2004. (3) J. M. Hall et al. Plant Dis. 77:952, 1993. (4) H. F. Schwartz et al. Plant Dis. 91:113, 2007.

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First Report of Iris yellow spot virus in Onion in Mauritius

Plant Disease ◽

10.1094/pdis-10-09-0645 ◽

2010 ◽

Vol 94 (11) ◽

pp. 1373-1373 ◽

Cited By ~ 5

Author(s):

K. Lobin ◽

A. Saison ◽

B. Hostachy ◽

S. P. Benimadhu ◽

H. R. Pappu

Keyword(s):

Disease Incidence ◽

Consensus Sequence ◽

Thrips Tabaci ◽

Iris Yellow Spot Virus ◽

Yellow Spot ◽

N Gene ◽

Spot Virus ◽

Viral Pathogen ◽

First Report ◽

Das Elisa

Iris yellow spot virus (IYSV; family Bunyaviridae, genus Tospovirus) transmitted by thrips (Thrips tabaci Lindeman) is an economically important viral pathogen of bulb and seed onion (Allium cepa) crops in many onion-growing areas of the world (2,3). In Africa, IYSV has been reported in Reunion (4) and South Africa (1). In June 2008, diamond-shaped lesions that are typical of IYSV were observed on onion seed scapes in an onion plot of 0.25 ha at Reduit in the central part of Mauritius. Disease incidence was 80% with a severity of 50 to 75% of the scape surface area. Lodging was observed in 25% of the symptomatic plants. Twenty-two symptomatic plants were tested and found to be positive for IYSV when tested by double antibody sandwich (DAS)-ELISA with a commercially available kit (Agdia Inc., Elkhart, IN). The presence of the virus was confirmed by reverse transcription (RT)-PCR tests with primers 917L: 5′-TAAAACTTAACTAACACAAA-3′ and 56U: 5′-TCCTAAGTATTCACCAT-3′ as forward and reverse primers, respectively, for specific sequences flanking the CP gene. Another set of primers specific to the small (S) RNA of IYSV (5′-TAAAACAAACATTCAAACAA-3′ and 5′-CTCTTAAACACATTT AACAAGCAC-3′) produced an amplicon of approximately 1.2 kb that includes the 772-bp nucleocapsid (N) gene. The 1.2-kb amplicon was cloned and four clones were sequenced and consensus sequence was used for comparisons. Sequence analysis showed that the N gene of the IYSV isolate from Mauritius (GenBank Accession No. HM218822) shared the highest nucleotide sequence identity (99%) with several known IYSV N gene sequences (Accession Nos. FJ785835 and AM900393) available in the GenBank, confirming the presence of IYSV in the onion crops in Mauritius. A survey was subsequently carried out from July to November 2008 in major onion-growing localities at La Marie, Henrietta, Reduit, and Plaine Sophie (center); Bassin, La Ferme, and La Chaumiere (west); Grand Sable, Petit Sable, and Plaisance (south, southeast); and Belle Mare, Trou d'Eau Douce, and Palmar (east) to monitor the distribution of the disease on the island. Symptomatic samples with diamond-to-irregularly shaped lesions were observed and 155 symptomatic and 35 nonsymptomatic samples were collected and screened by DAS-ELISA for IYSV and Tomato spotted wilt virus (TSWV), another tospovirus reported to infect onion elsewhere. Sixty-six percent of the symptomatic samples screened (102 of 155) tested positive for IYSV. No IYSV was detected in the symptomless samples. There was no serological indication of TSWV infection in the samples. Samples that tested positive for IYSV were collected from Belle mare, Palmar, and Trou d'eau douce in the east and La Ferme in the west. Cultivars infected were Gandiole, Local Red, and Veronique. No IYSV was detected in the bulbs. The vector, T. tabaci, was observed in infected onion parcels surveyed and is known to occur in all onion-producing areas of the island. To our knowledge, this is the first report of IYSV in onion in Mauritius. Further surveys and monitoring of IYSV incidence, along with its impact on the yield, need to be established. References: (1) L. J. du Toit et al. Plant Dis. 91:1203, 2007. (2) D. H. Gent et al. Plant Dis. 88:446, 2004. (3) H. R. Pappu et al. Virus Res. 141:219, 2009. (4) I. Robène-Soustrade et al. Plant Pathol. 55:288, 2006.

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First Report of Iris yellow spot virus on Onion in New York

Plant Disease ◽

10.1094/pdis-91-3-0327a ◽

2007 ◽

Vol 91 (3) ◽

pp. 327-327 ◽

Cited By ~ 13

Author(s):

C. A. Hoepting ◽

H. F. Schwartz ◽

H. R. Pappu

Keyword(s):

United States ◽

New York ◽

Iris Yellow Spot Virus ◽

Yellow Spot ◽

N Gene ◽

Nucleotide Sequence Analysis ◽

Rt Pcr ◽

Onion Thrips ◽

Spot Virus ◽

First Report

Iris yellow spot virus (IYSV [family Bunyaviridae, genus Tospovirus]), a potentially devastating disease of onion vectored by onion thrips (Thrips tabaci Lindeman), has been reported from most states in the western United States where significant onion production occurs, with the most recent report from Texas (1). In June 2006, volunteer onion (Allium cepa) plants in Orleans County, New York (Elba muckland) were found to have symptoms indicative of IYSV infection. The scapes (seed stalks) of the volunteer onions found at the edge of a cull pile from a 2005 onion crop exhibited diamond-shaped lesions, each with a distinct green center and a double yellow border. Approximately 25 of 100 plants of red and yellow onion cultivars exhibited characteristic IYSV lesions. The cull pile was composed primarily of locally grown onions, although a few of the bulbs were grown from imported bare-root transplants imported from Arizona. Symptomatic plants tested positive for IYSV using IYSV-specific antiserum from Agdia Inc. (Elkhart, IN) in a double-antibody sandwich-ELISA. The presence of IYSV was verified by reverse transcription (RT)-PCR using primers derived from the small RNA of IYSV (S-RNA). The primers flanked the IYSV nucleocapsid (N) gene (5′-TAA AAC AAA CAT TCA AAC AA-3′ and 5′-CTC TTA AAC ACA TTT AAC AAG CAC-3′ (3). RT-PCR assays produced a PCR amplicon of expected size (approximately 1.2 kb) and the product was cloned and sequenced. Nucleotide sequence analysis confirmed the identity of the amplicon as that of the IYSV S-RNA. Sequence comparisons showed 95 to 98% identity with known IYSV N gene sequences available in GenBank. The virus is poorly transmitted to onion by mechanical inoculation and we did not have access to a noninfested colony of the onion thrips vector to transfer the virus from these samples to noninfected onions. No asymptomatic plants were tested. Among the onion-growing states in the eastern United States, IYSV has previously only been reported from Georgia (2). To our knowledge, this is the first report of IYSV in New York and the greater northeastern United States. The finding of this disease in New York confirms further spread of the virus within North America and the need for research to develop more effective management options to reduce the impact of IYSV on onion crops. References: (1) M. Miller et al. Plant Dis. 90:1359, 2006. (2) S. W. Mullis et al. Plant Dis. 90:377, 2006. (3) H. R. Pappu et al. Arch. Virol. 151:1015, 2006.

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Green Foxtail (Setaria viridis), A Naturally Infected Grass Host of Iris yellow spot virus in Utah

Plant Disease ◽

10.1094/pdis-93-6-0670c ◽

2009 ◽

Vol 93 (6) ◽

pp. 670-670 ◽

Cited By ~ 11

Author(s):

C. K. Evans ◽

S. Bag ◽

E. Frank ◽

J. Reeve ◽

C. Ransom ◽

...

Keyword(s):

Nucleotide Sequence ◽

Iris Yellow Spot Virus ◽

Yellow Spot ◽

N Gene ◽

Grass Species ◽

Setaria Viridis ◽

Onion Thrips ◽

Spot Virus ◽

First Report ◽

Green Foxtail

Iris yellow spot virus (IYSV; family Bunyaviridae, genus Tospovirus) is a serious virus pathogen in onion bulb and seed crops in the United States and several parts of the world (1). The virus is exclusively transmitted by onion thrips (Thrips tabaci). Besides onion and other susceptible crops such as garlic, leek, chives, and several ornamentals, weeds could be serving as potential reservoir sources of virus inoculum. There are reports of several weeds found naturally infected with IYSV (1,2,4). However, there is no report of IYSV infection of a grass species. Leaves of green foxtail (Setaria viridis (L.) Beauv.) were collected from two naturally occurring plants approximately 30 m apart in a weed trial conducted in commercial onions grown in Box Elder County, UT on 24 September 2008. Notes of IYSV symptoms on green foxtail were made only on the two grass plants sampled. Density of green foxtail in the weed trial was low and was not recorded. Leaves on both plants displayed a range of symptoms that included streaking, purpling, and chlorotic and necrotic lesions along leaf margins oriented along the axis of longitudinal venation. Samples were positive for IYSV by double-antibody sandwich-ELISA with a commercially available kit (Agdia Inc., Elkhart, IN). ELISA values of the grass samples were 2.64 and 2.23 for each plant sampled. Negative and positive control readings were 0.24 and 4.33, respectively. All absorbance readings were made at 405 nm. To provide a contrast of the grass data in context to the onion field where the weed trial was located, final visual assessments of onions in the field were made on 4 September 2009. Approximately 300 onion plants were assessed for incidence and severity of disease. Incidence of the disease among onions was 100% and the severity of iris yellow spot on leaves was 20 lesions per leaf. The average ELISA value over 30 individual onions arbitrarily sampled from the field on the same day was 3.50, and the ELISA values among the samples ranged from 1.37 to 4.38. The negative and positive controls were 0.19 and 4.40, respectively. To further verify the presence of IYSV in the grass specimen, reverse transcription-PCR was performed on total nucleic acid extracts obtained from the symptomatic parts of the leaves. Primers specific to the nucleocapsid (N) gene coded by the small (S)-RNA of IYSV were used (3). The forward and reverse primer pairs, 5′-TCAGAAATCGAGAAACTT-3′ and 5′-CACCAATGTCTTCAACAATCTT-3′, respectively, amplify a 751-nt fragment of the N gene (3). An amplicon of expected size was obtained, cloned, and sequenced. The nucleotide sequence analysis and comparison with known IYSV S-RNA sequences showed that the amplicon from foxtail (GenBank Accession No. FJ652594) samples had the highest nucleotide sequence identity (98%) with the corresponding region of an IYSV isolate from Jefferson County, OR (GenBank Accession No. DQ233479). To our knowledge, this is the first report of natural infection of a grass species by IYSV and the first report of a Tospovirus infecting a grass species. The data suggests grasses may serve as a new host reservoir for IYSV. The increasing number of weed hosts of IYSV warrants further study on the role of these weeds as hosts for onion thrips and in IYSV epidemiology. References: (1) D. Gent et al. Plant Dis. 90:1468, 2006. (2) C. Nischwitz et al. Plant Dis. 91:1518, 2007. (3) H. R. Pappu et al. Arch. Virol. 151:1015, 2006. (4) R. Sampangi et al. Plant Dis. 91:1683, 2007.

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