scholarly journals First Report of Vidalia Onion (Allium cepa) Naturally Infected with Tomato spotted wilt virus and Iris yellow spot virus (Family Bunyaviridae, Genus Tospovirus) in Georgia

Plant Disease ◽  
2004 ◽  
Vol 88 (11) ◽  
pp. 1285-1285 ◽  
Author(s):  
S. W. Mullis ◽  
D. B. Langston ◽  
R. D. Gitaitis ◽  
J. L. Sherwood ◽  
A. C. Csinos ◽  
...  
Keyword(s):  
Tomato Spotted Wilt Virus ◽  
Thrips Tabaci ◽  
Iris Yellow Spot Virus ◽  
Yellow Spot ◽  
Unknown Etiology ◽  
Enzyme Linked Immunosorbent Assay ◽  
Rt Pcr ◽  
Spot Virus ◽  
Tomato Spotted Wilt ◽  
Wilt Virus

Vidalia onion is an important crop in Georgia's agriculture with worldwide recognition as a specialty vegetable. Vidalia onions are shortday, Granex-type sweet onions grown within a specific area of southeastern Georgia. Tomato spotted wilt virus (TSWV) has been endemic to Georgia crops for the past decade, but has gone undetected in Vidalia onions. Tobacco thrips (Frankliniella fusca) and Western flower thrips (Frankliniella occidentalis) are the primary vectors for TSWV in this region, and a number of plant species serve as reproductive reservoirs for the vector or virus. Iris yellow spot virus (IYSV), an emerging tospovirus that is potentially a devastating pathogen of onion, has been reported in many locations in the western United States (2,4). Thrips tabaci is the known vector for IYSV, but it is unknown if noncrop plants play a role in its epidemiology in Georgia. During October 2003, a small (n = 12) sampling of onions with chlorosis and dieback of unknown etiology from the Vidalia region was screened for a variety of viruses, and TSWV and IYSV infections were serologically detected. Since that time, leaf and bulb tissues from 4,424 onion samples were screened for TSWV and IYSV using double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA) with commercial kits (Agdia Inc., Elkhart, IN). Samples were collected from 53 locations in the Vidalia region during the growing season between November 2003 and March 2004. Plants exhibiting stress, such as tip dieback, necrotic lesions, chlorosis or environmental damage were selected. Of these, 306 were positive for TSWV and 396 were positive for IYSV using positive threshold absorbance of three times the average plus two standard deviations of healthy negative onion controls. Positive serological findings of the onion tissues were verified by immunocapture-reverse transcription-polymerase chain reaction (IC-RT-PCR) for TSWV (3) and RT-PCR for IYSV (1). In both instances, a region of the viral nucleocapsid (N) gene was amplified. The PCR products were analyzed with gel electrophoresis with an ethidium bromide stain in 0.8% agarose. Eighty-six percent (n = 263) of the TSWV ELISA-positive samples exhibited the expected 774-bp product and 55 percent (n = 217) of the IYSV ELISA-positive samples exhibited the expected 962-bp product. The reduced success of the IYSV verification could be attributed to the age and deteriorated condition of the samples at the time of amplification. Thrips tabaci were obtained from onion seedbeds and cull piles within the early sampling (n = 84) and screened for TSWV by the use of an indirect-ELISA to the nonstructural (NSs) protein of TSWV. Of the thrips sampled, 25 were positive in ELISA. While the incidence of IYSV and TSWV in the Vidalia onion crop has been documented, more research is needed to illuminate their potential danger to Vidalia onions. References: (1) I. Cortês et al. Phytopathology 88:1276, 1998. (2) L. J. du Toit et al. Plant Dis. 88:222, 2004. (3) R. K. Jain et al. Plant Dis. 82:900, 1998. (4) J. W. Moyer et al. (Abstr.) Phytopathology 93(suppl.):S115, 2003.

scholarly journals Lisianthus Leaf Necrosis: A New Disease of Lisianthus Caused by Iris yellow spot virus

Plant Disease ◽  
2000 ◽  
Vol 84 (11) ◽  
pp. 1185-1189 ◽  
Author(s):  
A. Kritzman ◽  
H. Beckelman ◽  
S. Alexandrov ◽  
J. Cohen ◽  
M. Lampel ◽  
...  
Keyword(s):  
Polyclonal Antibodies ◽  
Iris Yellow Spot Virus ◽  
Yellow Spot ◽  
Enzyme Linked Immunosorbent Assay ◽  
Rt Pcr ◽  
Spot Virus ◽  
Systemic Necrosis ◽  
Nucleocapsid Gene ◽  
Pcr Product ◽  
Wilt Virus

Unusual viral symptoms were seen on lisianthus (Eustoma russellianum) grown in the Besor area in Israel. Symptoms included necrotic spots and rings on leaves and systemic necrosis. Preliminary analyses suggested that the disease was caused by a tospovirus. Virus particles typical of a tospovirus were observed with electron microscopy in samples taken only from symptomatic leaves. Double-antibody sandwich enzyme-linked immunosorbent assay tests of leaf sap, extracted from lisianthus and mechanically inoculated indicator plants, gave a strong positive reaction to Iris yellow spot virus (IYSV). Polyclonal antibodies prepared against IYSV enabled specific detection of the virus in crude sap from infected plants. Western blot analysis showed that IYSV was serologically distinct from Tomato spotted wilt virus (TSWV). Primers specific to the nucleocapsid gene of IYSV were used in a reverse transcription-polymerase chain reaction assay (RT-PCR) to verify the presence of IYSV. RT-PCR gave an expected PCR product of approximately 850 bp. The sequence of the cloned nucleocapsid gene confirmed the identity of IYSV, thus confirming IYSV infection of lisianthus. This is the first report of IYSV infection in dicotyledons.

scholarly journals Wild Allium spp. as Natural Hosts of Iris yellow spot virus

Plant Disease ◽  
2006 ◽  
Vol 90 (3) ◽  
pp. 378-378 ◽  
Author(s):  
H. R. Pappu ◽  
B. C. Hellier ◽  
F. M. Dugan
Keyword(s):  
Natural Infection ◽  
The State ◽  
Thrips Tabaci ◽  
Iris Yellow Spot Virus ◽  
Yellow Spot ◽  
N Gene ◽  
Enzyme Linked Immunosorbent Assay ◽  
Rt Pcr ◽  
Spot Virus ◽  
Sequence Comparisons

The incidence of Iris yellow spot virus (IYSV) of genus Tospovirus, family Bunyaviridae in a commercial onion crop was first confirmed in Washington state during 2003 (1). First found in Adams County, IYSV has rapidly spread to all onion-producing counties in the state, affecting seed and bulb crops. The USDA-ARS Western Regional Plant Introduction Station (WRPIS) collects, maintains, and distributes various Allium (garlic and onion) accessions. As part of the regeneration process, accessions are grown under field conditions at the WRPIS farms in two locations: Pullman and Central Ferry, WA. Symptoms indicative of viral infection, now known to be caused by IYSV, first appeared in field-grown accessions in 1999. In June 2005, leaf and scape tissues were collected from WRPIS accessions of wild onions (Allium pskemense, A. vavilovii, and A. altaicum) in Central Ferry that had symptoms indicative of IYSV infection (2). IYSV infection was confirmed using enzyme-linked immunosorbent assay with a commercially available kit (Agdia Inc., Elkhart, IN). Virus infection was further verified using reverse transcription-polymerase chain reaction (RT-PCR) with primers derived from the small (S) RNA of IYSV. The primers flanked the IYSV N gene (5′-TAA AAC AAA CAT TCA AAC AA-3′ and 5′-CTC TTA AAC ACA TTT AAC AAG CAC-3′). RT-PCR gave a PCR product of expected size (≈1.2 kb). The DNA amplicon was cloned and sequenced. Nucleotide sequence comparisons with known IYSV N gene sequences showed 95 to 98% sequence identity. The prevalence of the vector, onion thrips (Thrips tabaci), combined with the widespread incidence of IYSV in seed and bulb production areas of the state may have resulted in natural infection of wild relatives of cultivated onion. The potential role of wild Allium spp. in IYSV epidemiology remains to be determined. Information on the extent of IYSV infection of onion germplasm would be useful in identifying potential sources of host plant resistance to IYSV. References: (1) L. J. du Toit et al. Plant Dis. 88:222, 2004. (2) B. Hellier et al. APSnet Image of the Week. Online publication, iw000049.asp, 2004.

scholarly journals Increase of Tospoviral Diversity in Brazil with the Identification of Two New Tospovirus Species, One from Chrysanthemum and One from Zucchini

1999 ◽  
Vol 89 (9) ◽  
pp. 823-830 ◽  
Author(s):  
I. C. Bezerra ◽  
R. de O. Resende ◽  
L. Pozzer ◽  
T. Nagata ◽  
R. Kormelink ◽  
...  
Keyword(s):  
Yellow Spot ◽  
Enzyme Linked Immunosorbent Assay ◽  
Broad Host Range ◽  
Spot Virus ◽  
Chlorotic Spot ◽  
Molecular Features ◽  
Tomato Spotted Wilt ◽  
Tospovirus Species ◽  
Stem Necrosis ◽  
Wilt Virus

During a survey conducted in several different regions of Brazil, two unique tospoviruses were isolated and characterized, one from chrysanthemum and the other from zucchini. The chrysanthemum virus displayed a broad host range, whereas the virus from zucchini was restricted mainly to the family Cucurbitaceae. Double-antibody sandwich-enzyme-linked immunosorbent assay and western immunoblot analyses demonstrated that both viruses were serologically distinct from all reported tospovirus species including the recently proposed peanut yellow spot virus and iris yellow spot virus (IYSV) species. The nucleotide sequences of the nucleocapsid (N) genes of both viruses contain 780 nucleotides encoding for deduced proteins of 260 amino acids. The N proteins of these two viruses displayed amino acid sequence similarities with the previously described tospovirus species ranging from 20 to 75%, but they were more closely related to each other (80%). Based on the biological and molecular features, these viruses are proposed as two new tospovirus species, designated chrysanthemum stem necrosis virus (CSNV) and zucchini lethal chlorosis virus (ZLCV). With the identification of CSNV and ZLCV, in addition to tomato spotted wilt virus, groundnut ring spot virus, tomato chlorotic spot virus, and IYSV, Brazil harbors the broadest spectrum of tospovirus species reported.

scholarly journals Caracterização do Tomato chlorotic spot virus isolado de jiló no Vale do Paraíba, Estado de São Paulo

2002 ◽  
Vol 27 (3) ◽  
pp. 285-291 ◽  
Author(s):  
MARCELO EIRAS ◽  
ALEXANDRE L. R. CHAVES ◽  
ADDOLORATA COLARICCIO ◽  
RICARDO HARAKAVA ◽  
JANSEN DE ARAUJO ◽  
...  
Keyword(s):  
Tomato Spotted Wilt Virus ◽  
Sao Paulo ◽  
Ringspot Virus ◽  
São Paulo ◽  
Rt Pcr ◽  
Spot Virus ◽  
Chlorotic Spot ◽  
Tomato Spotted Wilt ◽  
Wilt Virus ◽  
Das Elisa

Os tospovírus são responsáveis por perdas significativas em diversas culturas, principalmente solanáceas. No município de São José dos Campos (SP), plantas de jiló (Solanum gilo) apresentando sintomas de mosaico, bolhosidades, nanismo e queda acentuada da produção foram coletadas para análise. Visando a caracterização do agente causador dos sintomas, testes biológicos, elétrono microscópicos, sorológicos e moleculares foram realizados. Através de inoculação mecânica em plantas indicadoras das famílias Amaranthaceae, Chenopodiaceae e Solanaceae obtiveram-se resultados típicos aos esperados para tospovírus. Ao microscópio eletrônico de transmissão, observaram-se, em contrastação negativa, partículas pleomórficas com diâmetro entre 80 e 110 nm e em cortes ultra-finos partículas presentes em vesículas do retículo endoplasmático. Através de DAS-ELISA, identificou-se o Tomato chlorotic spot virus (TCSV). A partir de RNA total extraído de folhas infetadas, amplificaram-se, via RT-PCR, fragmentos correspondentes ao gene da proteína do capsídeo (cp) os quais foram seqüenciados e comparados com outros depositados no "GenBank". A homologia de nucleotídeos e aminoácidos deduzidos foi respectivamente de 99 e 95% quando comparada com seqüências de isolados de TCSV. A comparação com as outras espécies do gênero Tospovirus apresentou valores de homologia entre 72 e 84%. Estes resultados confirmam a identidade deste vírus como pertencente à espécie TCSV, que é predominante no Estado de São Paulo e importante patógeno de outras plantas cultivadas. Além disso, variedades de jiló quando inoculadas foram susceptíveis tanto ao TCSV como às espécies Tomato spotted wilt virus (TSWV) e Groundnut ringspot virus (GRSV).

Comparison of ELISA and RT-PCR assays for the detection of Tomato spotted wilt virus in peanut

2009 ◽  
Vol 36 (2) ◽  
pp. 133-137 ◽  
Author(s):  
P. M. Dang ◽  
D. L. Rowland ◽  
W. H. Faircloth
Keyword(s):  
Tomato Spotted Wilt Virus ◽  
Enzyme Linked Immunosorbent Assay ◽  
Infection Rates ◽  
Rt Pcr ◽  
Chi Square ◽  
Tomato Spotted Wilt ◽  
Significant Difference ◽  
Pcr Assays ◽  
Chi Square Analysis ◽  
Wilt Virus

Abstract Diagnosis of Tomato spotted wilt virus (TSWV) in peanut can be accomplished by enzyme-linked immunosorbent assay (ELISA) or reverse transcription polymerase chain reaction (RT-PCR) but there has been no report of a direct comparison of the success of the two assays in evaluating infection rates of field-grown peanut. We collected peanut root samples from field-grown plants, 76 in 2006 and 48 in 2007, and tested these samples by both ELISA and RT-PCR assays for the presence of TSWV. Out of 124 samples, 50 (40.3%) and 57 (46.0%) were positive for TSWV by ELISA and RT-PCR respectively. In 13.7% of these samples, ELISA and RT-PCR differed in their results. However, Chi square analysis showed no significant difference between the results for these two assays. This result supports the conclusion that ELISA and RT-PCR are comparable for detecting TSWV infection rates in field-grown peanuts.

scholarly journals First Report of Tomato spotted wilt virus in Blackberry Lily in North America

Plant Disease ◽  
2003 ◽  
Vol 87 (1) ◽  
pp. 102-102 ◽  
Author(s):  
S. Adkins ◽  
L. Breman ◽  
C. A. Baker ◽  
S. Wilson
Keyword(s):  
North America ◽  
Tomato Spotted Wilt Virus ◽  
Amino Acid Sequences ◽  
South Florida ◽  
N Gene ◽  
Enzyme Linked Immunosorbent Assay ◽  
Rt Pcr ◽  
First Report ◽  
Tomato Spotted Wilt ◽  
Wilt Virus

Blackberry lily (Belamcanda chinensis (L.) DC.) is an herbaceous perennial in the Iridaceae characterized by purple-spotted orange flowers followed by persistent clusters of black fruit. In July 2002, virus-like symptoms including chlorotic ringspots and ring patterns were observed on blackberry lily leaves on 2 of 10 plants in a south Florida ornamental demonstration garden. Inclusion body morphology suggested the presence of a Tospovirus. Tomato spotted wilt virus (TSWV) was specifically identified by serological testing using enzyme-linked immunosorbent assay (Agdia, Elkhart, IN). Sequence analysis of a nucleocapsid (N) protein gene fragment amplified by reverse transcription-polymerase chain reaction (RT-PCR) with primers TSWV723 and TSWV722 (1) from total RNA confirmed the diagnosis. Nucleotide and deduced amino acid sequences of a 579 base pair region of the RT-PCR product were 95 to 99% and 95 to 100% identical, respectively, to TSWV N-gene sequences in GenBank. Since these 2-year-old plants were grown on-site from seed, they were likely inoculated by thrips from a nearby source. Together with a previous observation of TSWV in north Florida nursery stock (L. Breman, unpublished), this represents, to our knowledge, the first report of TSWV infection of blackberry lily in North America although TSWV was observed in plants of this species in Japan 25 years ago (2). References: (1) S. Adkins, and E. N. Rosskopf. Plant Dis. 86:1310, 2002. (2) T. Yamamoto and K.-I. Ohata. Bull. Shikoku Agric. Exp. Stn. 30:39, 1977.

scholarly journals Tomato spotted wilt virus Identified in Desert Rose in Florida

Plant Disease ◽  
2005 ◽  
Vol 89 (5) ◽  
pp. 526-526 ◽  
Author(s):  
S. Adkins ◽  
C. A. Baker
Keyword(s):  
Tomato Spotted Wilt Virus ◽  
The United States ◽  
N Gene ◽  
Enzyme Linked Immunosorbent Assay ◽  
Insect Vector ◽  
Rt Pcr ◽  
Tomato Spotted Wilt ◽  
Wilt Virus ◽  
Symptomatic Plant ◽  
Das Elisa

Desert rose (Adenium obesum (Forssk.) Roem. & Schult), a member of the family Apocynaceae, is characterized by fleshy stems and leaves and colorful flowers. This exotic ornamental, originally from southeast Africa, is propagated vegetatively and is a perennial in warm climates. Virus-like foliar symptoms, including chlorotic ring and line patterns, were observed in the fall of 2004 on one of five stock plants being maintained in a greenhouse in Fort Pierce, FL. Inclusion body morphology suggested the presence of a Tospovirus in the symptomatic plant, and Tomato spotted wilt virus (TSWV) was specifically identified in this plant using a commercially available double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA; Agdia, Elkhart, IN). TSWV was not detected in symptomless desert rose plants nor was Impatiens necrotic spot virus detected in any of the plants using DAS-ELISA. Graft transmission of TSWV to other desert rose plants was successful. Sequence analysis of a nucleocapsid (N) protein gene fragment amplified by reverse transcription-polymerase chain reaction (RT-PCR) with primers TSWV723 and TSWV722 (1) from total RNA of the symptomatic plant confirmed the diagnosis. Nucleotide and deduced amino acid sequences of a 579-bp region of the RT-PCR product were 95 to 99% and 95 to 100% identical, respectively, to TSWV N-gene sequences in GenBank. No product was amplified from symptomless plants. Since these 3-year-old plants were grown on-site from seed and only expressed symptoms 2 months following damage to the greenhouse by hurricanes Frances and Jeanne, it is likely that viruliferous thrips were introduced from local vegetable or ornamental production areas during or following the storms. To our knowledge, this is the first report of TSWV infection of desert rose in Florida, although TSWV was observed in this plant in Europe approximately 10 years ago (3,4). Because of the wide distribution of TSWV in the United States, the increasing popularity of desert rose, and the recent identification of Cucumber mosaic virus in this host (2), attention to sanitation and insect vector management is merited during desert rose propagation and production. References: (1) S. Adkins and E. N. Rosskopf. Plant Dis. 86:1310, 2002. (2) C. A. Baker et al. Plant Dis. 87:1007, 2003. (3) J. Mertelik et al. Acta Hortic. 432:368, 1996. (4) J. Th. J. Verhoeven and J. W. Roenhorst. Acta Hortic. 377:175, 1994.

scholarly journals Iris yellow spot virus: A New Onion Disease in Spain

Plant Disease ◽  
2005 ◽  
Vol 89 (11) ◽  
pp. 1243-1243 ◽  
Author(s):  
C. Córdoba-Sellés ◽  
L. Martínez-Priego ◽  
R. Muńoz-Gómez ◽  
C. Jordá-Gutiérrez
Keyword(s):  
Plant Protection ◽  
Iris Yellow Spot Virus ◽  
Yellow Spot ◽  
Enzyme Linked Immunosorbent Assay ◽  
Rt Pcr ◽  
Pcr Assay ◽  
Spot Virus ◽  
Nucleocapsid Gene ◽  
Pcr Product ◽  
Mediterranean Plant

So far, only three viral diseases have been identified in onion crops grown in Spain. These are Tomato spotted wilt virus (TSWV), Onion yellow dwarf virus (OYDV), and Leek yellow stripe virus (LYSV). In September 2003, unusual virus-like symptoms including straw-colored, dry, tan, diamond-shaped lesions on the leaves and stalks, sometimes with necrotic lesions, curled leaves, and bulbs of reduced size, were observed on several onion plants (Allium cepa L.) in commercial fields in Albacete, Spain. Severely affected plants eventually died. To verify the identity of the disease found in the Spanish onions, double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) was performed on leaf extracts of symptomatic onions using specific polyclonal antibodies against OYDV, LYSV, Cucumber mosaic virus (CMV) (Biorad Phyto-Diagnostics, Marnes-La Coquette, France), Iris yellow spot virus (IYSV), and TSWV (Loewe Biochemica, Sauerlach, Germany). All samples of infected onion tissue were positive for IYSV and negative for the other viruses tested. To confirm the ELISA results, viral RNA was extracted from five of the ELISA-positive onion samples, a healthy onion plant, and a positive control for IYSV (DSMZ, Braunschweig. Germany). The extracted RNA was used in a One-Step reverse transcription-polymerase chain reaction (RT-PCR) assay using SuperScript Platinum Taq (Invitrogen Life Technologies, Barcelona, Spain) in the presence of the IYSV1S and IYSV1A primers for the nucleocapsid gene of IYSV (1). The RT-PCR assay produced an amplicon of the expected size of 790 bp. No amplification products were observed when healthy plants or a water control were used as templates in the RT-PCR reaction. To establish the authenticity of the virus from onion, the PCR products were purified (High Pure PCR Product Purification Kit, Roche Diagnostics, Mannheim, Germany), sequenced, and the nucleotide sequences obtained were analyzed and compared with the published sequences in GenBank. The PCR product was 97% identical to the sequence of the IYSV nucleocapsid gene (Genbank Accession No. AB121026). IYSV, an emerging tospovirus that is potentially a devastating pathogen of onion, has been reported in many locations in Brazil, Japan, the Netherlands, Israel, Australia, the western United States, Slovenia, and Iran (2). IYSV is included in the European and Mediterranean Plant Protection Organization alert list of viruses (2), and to our knowledge, this is the first report of IYSV in Spain. This tospovirus is transmitted in a propagative manner by Thrips tabaci. Although the vector is present in large populations in the onion-growing areas in Spain, the efficiency of the Mediterranean ecotype in transmitting IYSV is not known. References: (1) B. A. Coutts et al. Australas. Plant Pathol. 32:555, 2003. (2) European and Mediterranean Plant Protection Organization. EPPO on-line publication at www.eppo.org/QUARANTINE/Alert_List/Viruses/irysxx.html .

scholarly journals Serological and Molecular Assays for Rapid and Sensitive Detection of Iris yellow spot virus Infection of Bulb and Seed Onion Crops

Plant Disease ◽  
2008 ◽  
Vol 92 (4) ◽  
pp. 588-594 ◽  
Author(s):  
H. R. Pappu ◽  
I. M. Rosales ◽  
K. L. Druffel
Keyword(s):  
Real Time ◽  
Rapid Detection ◽  
The United States ◽  
Iris Yellow Spot Virus ◽  
Yellow Spot ◽  
Sensitive Detection ◽  
Detection Methods ◽  
Enzyme Linked Immunosorbent Assay ◽  
Rt Pcr ◽  
Spot Virus

Iris yellow spot virus (IYSV) has spread rapidly in the United States and has become an important economic constraint to the production of both bulb and seed onion crops. Symptoms caused by IYSV may be confused with those caused by other fungal and bacterial pathogens and virus-specific, reliable, sensitive, and rapid detection methods would improve the diagnosis. Antiserum was produced to Escherichia coli-expressed nucleocapsid protein of IYSV and an indirect format of the enzyme-linked immunosorbent assay (ELISA) was developed. IYSV could be detected in onion tissue at dilutions of up to 1:1,000. An IYSV-specific primer pair was designed and used in a real-time reverse-transcription polymerase chain reaction (RT-PCR) assay for the rapid detection of IYSV. Compared with standard RT-PCR, real-time RT-PCR was more rapid and sensitive. A commercially available RNA extraction kit and a total nucleic acid extraction method were compared for the quality of the templates obtained for use in real-time RT-PCR and there was no difference in limits of detection. Availability of ELISA- and PCR-based rapid and sensitive detection methods would facilitate accurate virus diagnosis and aid in better understanding of the epidemiology of the disease and in development of management strategies.

scholarly journals Evaluation of Lisianthus as an Indicator Host for Iris yellow spot virus

Plant Disease ◽  
2011 ◽  
Vol 95 (12) ◽  
pp. 1520-1527 ◽  
Author(s):  
Rajagopalbabu Srinivasan ◽  
Stan Diffie ◽  
Sivamani Sundaraj ◽  
Stephen W. Mullis ◽  
David Riley ◽  
...  
Keyword(s):  
Transmission Rate ◽  
Thrips Tabaci ◽  
Iris Yellow Spot Virus ◽  
Yellow Spot ◽  
Effect Of Temperature ◽  
Enzyme Linked Immunosorbent Assay ◽  
Mechanical Transmission ◽  
Symptom Expression ◽  
Spot Virus ◽  
Temperature Regimes

Iris yellow spot virus (IYSV) can severely affect onion production. IYSV is transmitted by the onion thrips, Thrips tabaci. However, information on IYSV–thrips–onion interactions is limited due to the difficulty associated with infecting onion plants experimentally. Lisianthus (Eustoma russellianum) was used as an indicator host to study mechanical transmission of IYSV, IYSV transmission by T. tabaci, IYSV distribution in the host plant, and the effect of temperature on IYSV symptom expression. Mechanical inoculation tests from IYSV-infected onion plants to noninfected lisianthus plants resulted in a mean transmission rate of 82.5 ± 6.9% (mean ± standard error), and from IYSV-infected lisianthus plants to noninfected lisianthus plants resulted in a mean transmission rate of 89.2 ± 7.1%. T. tabaci adults transmitted IYSV at a rate of 80.0 ± 8.3% from infected onion plants to noninfected lisianthus plants. To assess IYSV distribution in infected lisianthus plants, leaf sections, stems, and roots were tested by enzyme-linked immunosorbent assay (ELISA). All the plant parts tested positive for IYSV, but not on every plant assayed. Alternating night and day temperatures of 18 and 23°C, 25 and 30°C, and 30 and 37°C were evaluated for the effects on IYSV symptom expression. More severe symptoms developed on inoculated plants incubated at the 18 and 23°C or 25 and 30°C temperature regimes than at the 30 and 37°C regime, and symptoms were observed earliest on plants incubated at the 25 and 30°C temperature regime compared to the other temperature regimes.

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