Incidence Of Tomato Spotted Wilt Virus Research Articles

Field Screening for Tomato Spotted Wilt and White Mold (Stem Rot) Resistance among Peanut Genotypes

White mold (WM), stem rot, and southern blight are common names for the same soilborne peanut (Arachis hypogaea L.) disease caused by Athelia rolfsii (Curzi) C. C. Tu & Kimbr. = Sclerotium rolfsii Sacc. Tomato spotted wilt is a systemic foliar peanut disease caused by Tomato spotted wilt virus (TSWV). The objective of this study was to screen several currently available peanut genotypes (cultivars and breeding lines) for combined general field resistance to both of these diseases. Results from these field tests showed significant differences (P≤0.05) among the peanut genotypes evaluated for combined resistance to both WM and TSWV. The overall three-year (2018-20) average found that ‘Georgia-12Y’ had among the lowest percent incidence of mid-season TSWV, mid-late season TSWV+WM, late-season WM+TSWV, WM after digging, and the highest pod yield compared to other runner-type peanut cultivars. FloRun ‘331’ was found to have comparable WM resistance as Georgia-12Y, however it was also found to be susceptible to TSWV. ‘Georgia-14N’ was found to have moderate TSWV and WM resistance similar to ‘Georgia-07W’, and it also has a high-level of root-knot nematode (RKN) resistance.

Genotypic, Temporal, and Tissue-type Effects on the Incidence of Tomato spotted wilt virus in Peanut (Arachis hypogaea L.)

Spotted wilt, caused by Tomato spotted wilt virus (TSWV), is one of the major diseases affecting peanut production in the southeastern United States. Growers use integrated disease management to control spotted wilt; however, disease resistance of a cultivar is the most important factor for managing this disease. This research evaluated genotypic, temporal, and tissue-type effects on the incidence of TSWV on each of four peanut cultivars. Four different types of tissues (leaf, root crown, old leaf and young leaf) were collected from each of four peanut cultivars (Florida-EPTM ‘113’, Florida-07, Georgia Green and Georgia Valencia) at five time points during the growing season. Immunoassays were conducted to detect viral presence. The incidence of TSWV infection increased over time during the growing season. Root crown tissue had higher infection than other types of tissue. Florida-EPTM ‘113’ had the lowest infection incidence. Compared to Florida-EPTM ‘113’, Florida-07 was seven times more likely to be infected by TSWV, while Georgia Green and Georgia Valencia possessed even higher probability, 18 times and 21 times higher, respectively. Florida-EPTM ‘113’ had significantly reduced TSWV infection likely due to slowing movement of the virus throughout the plant.

Epidemiology of tomato spotted wilt virus in Chrysanthemum morifolium in South Korea and its management using a soil-dwelling predatory mite (Stratiolaelaps scimitus) and essential oils

Tomato spotted wilt virus (TSWV) is one of most destructive viruses in vegetable and ornamental crop production worldwide. A greenhouse survey to determine the incidence of TSWV in Chrysanthemummorifolium Ramat. was conducted during the 2018 and 2019 growing seasons in South Korea. TSWV was detected using a double antibody sandwich-enzyme-linked immunosorbent assay, and positive results were confirmed using reverse transcription-polymerase chain reaction (RT-PCR). A total of 1569 chrysanthemum plants (70.77 %) tested positive for TSWV among 2217 symptomatic chrysanthemum plants collected from 16 greenhouses. In addition, 116 thrips (72.96 %; Frankliniella occidentalis Pergande) that contained TSWV were identified using RT-PCR from a total of 159 thrips collected from the greenhouses during the survey. A high incidence of viruliferous thrips may have played a role in TSWV occurrence in the chrysanthemum greenhouse. To develop a novel approach for thrips management, the effectiveness of a soil-dwelling predatory mite (Stratiolaelaps scimitus Berlese) and 45 essential oils (as bio-insecticides applied via foliar treatment) was assayed. Four essential oils (cinnamon oil, cinnamon bark oil, oregano oil, and thyme oil) were shown to be significantly toxic to eggs, larvae, and adults of F. occidentalis. For the combined treatment, individuals of S. scimitus (60/m2) were placed on the soil in the chrysanthemum greenhouses. Then, a mixture of the four essential oils was applied as foliar treatment at 4-day intervals. A very low incidence of thrips emerged as adults from the soil (1.2–8.5 %) in the combined treatment in the chrysanthemum greenhouses when surveyed twice per month, compared with the non-treated control or when conventional insecticide sprays were applied. The incidence of TSWV (0.93 %) in chrysanthemum treated with S. scimitus in conjunction with the mixture of four essential oils decreased significantly compared with that treated with chemical insecticides (32.05 %) and in the non-treated controls (84.85 %). Our findings contribute to the development of novel strategies to control TSWV disease in chrysanthemum plants; notably, the control of F. occidentalis using eco-friendly insecticides appears promising.

FIRST REPORT OF TOMATO SPOTTED WILT VIRUS INFECTING PUMPKIN IN CHINA

In August 2015, symptomatic pumpkin (Cucurbita moschata Duch.) plants were observed in Linyi, Shandong province, China. Plants exhibited symptoms of leaf mottling, crinkling and mosaic which appeared similar to symptoms caused by Tomato spotted wilt virus (TSWV) (Karavina et al., 2016). Twenty field samples, two symptomatic and 18 asymptomatic, were collected. A high incidence of thrips (Thrips palmi) was also observed in the field and on the sampling plants. Given the symptoms observed and the prevalence of thrips, TSWV infection was suspected. Total RNA was extracted from symptomatic and asymptomatic plants and analyzed by RT-PCR using specific primer pair TSWV-F1 (5’-CACACTAAGCAAGCACA-3’)/TSWV-R1 (5’-TCAGTCTTACAAATCATC-3’), designed for this study, corresponding to a highly conserved region including the complete nucleocapsid protein (N) gene. Fragments of the expected size (976 bp) were amplified from the symptomatic but not from the asymptomatic samples, and one of them was cloned and sequenced (KX185153). No other viruses were detected. The incidence of TSWV in the four acres pumpkin field surveyed was 0.45%. Sequence comparisons revealed that the N gene of this isolate shared the highest nucleotide identity of 99.9% with an isolate of TSWV from an asparagus lettuce sample from China (KP330473) indicating the pumpkin plants were infected with TSWV. Phylogenetic analysis showed that this isolate and other isolates from China clustered together with those from South Korea and Japan as a separate group. TSWV (genus Tospovirus, family Bunyaviridae) has an extensive host range (Cho et al., 1987) of which tomato, pepper, peanut and tobacco are common susceptible host crops. TSWV has been reported to infect tomato, tobacco and other plants (Dong et al., 2010) in China. To our knowledge, this is the first report of TSWV infecting pumpkin in China.

Identification of two plant viruses using partial purification and mass spectrometry

Serological and PCR techniques failed to detect Tomato spotted wilt virus (TSWV) infecting stunted tomato plants exhibiting leaf curling, purpling and crumpling. In contrast, Mass Spectrometry rapidly identified peptides generated from a ~28kD protein cut from PAGE gels as TSWV N-protein within 5 days. The results indicate that the incidence of TSWV may be underestimated in the field. Cocksfoot mild mosaic virus (CMMV) was identified infecting Bromus diandrus using serological techniques. Peptides from a ~25kD protein failed to identify with any protein on GenBank until a CMMV sequence was published. The use of Mass Spectrometry as an adjunct for virus detection and identification is briefly discussed.

Stem Rot (White Mold) and Tomato Spotted Wilt Resistance among Peanut Genotypes

ABSTRACT Stem rot, also known as white mold (WM), caused by Sclerotium rolfsii Sacc., and tomato spotted wilt, caused by Tomato spotted wilt virus (TSWV), are two major disease problems in Georgia peanut (Arachis hypogaea L.) production. Current fungicides for stem rot control are very effective but expensive, and insecticides usually have little effect on TSWV, which is transmitted by thrips. Consequently, the objective of this study was to evaluate different peanut genotypes for resistance to both of these pathogens. Field test evaluations were conducted for four consecutive years (2010-13) at a site on the agronomy research farm near the Coastal Plain Experiment Station which has a long history of continuous peanut production and a high incidence of stem rot (WM) and TSWV. Results from these field tests showed significant differences among the peanut genotypes evaluated for combined resistance to both diseases. Several genotypes showed low TSWV incidence at mid-season and mid-to-late season. However by late season and after digging, the best combination of stem rot (WM) and TSWV disease resistance and highest consistent yield over years was in the runner-type peanut cultivar ‘Georgia-12Y’, along with ‘York’, ‘Georgia-07W’, and ‘Georgia-10T’.

전남 지역의 토마토반점위조바이러스병 발생 양상

Crop Protection Division, National Academy of Agricultural Science, Suwon 441-707, Korea(Received on October 9, 2013; Revised on November 4, 2013; Accepted on November 7, 2013)Tomato spotted wilt virus (TSWV) was occurred at 8 areas including Naju, Suncheon, Younggwang, Youngam,and Shinan in Jeonnam province and the crops of Younggwang were severely damaged by TSWV. The hotpepper (Capsicum annuum), bell pepper (Capsicum annuum va .r angulosum) and tomato (Solanumlycopersicon) in greenhouse and hot pepper in open field were infected by TSWV. Especially, hot pepper wasseverely damaged by TSWV infection. The survey data indicated that 1.1 −30% in the nursery field at Naju,Suncheon, and Jangheung were infected by TSWV. Plants were infected by TSWV from early June toAugust. However, TSWV-infected seedlings from nursery fields showed the disease symptoms from May aftertransplanting. In pepper greenhouses, Frankliniella occidentalis was more dominant insect vector thanFrankliniella intonsa. But in open field, the population of insect vector was opposed to greenhouse. Inaddition, the removal of weeds was able to delay the incidence of TSWV via side-window of greenhouse inWinter. Taken together, the control of weed and insect vector nearby side-window of greenhouse is importantto prevent TSWV infection of plants.Keywords : Frankliniella occidentalis, Hot pepper, Tomato spotted wilt virus

Effect of cyantraniliprole on feeding behavior and virus transmission of Frankliniella fusca and Frankliniella occidentalis (Thysanoptera: Thripidae) on Capsicum annuum

The anthranilic diamide insecticide cyantraniliprole was previously shown to reduce transmission of Tomato spotted wilt virus (TSWV) to pepper, Capsicum annuum, by Frankliniella fusca but not Frankliniella occidentalis. This study examines the effects of cyantraniliprole and imidacloprid on thrips feeding using electrical penetration graphing (EPG), and on TSWV transmission in field cage studies. Some antifeedant responses were observed in the EPG studies when thrips fed on cyantraniliprole- and imidacloprid-treated plants; however, these responses were variable between species and among the 2, 6, and 10 day post-treatment time intervals during which feeding behavior was observed. Cyantraniliprole significantly reduced the probability of TSWV infection when spread by F. fusca in field-grown pepper when viruliferous thrips were released 7 days but not when released at 14 days after the insecticide treatment in one of 2 field trials. In the second trial cyantraniliprole significantly reduced the probability of infection when F. fusca were released 14 days but not 7 days after treatment. In both years, imidacloprid prevented or significantly reduced transmission of TSWV by F. fusca in field-grown pepper when viruliferous thrips were released 7 days and 14 after treatment. In one of two years, cyantraniliprole significantly reduced the incidence of TSWV in field-grown pepper that was spread by F. occidentalis when viruliferous thrips were released 7 days after the insecticide treatment, but not 14 days after the treatment. Imidacloprid did not reduce the incidence of TSWV in field-grown pepper when viruliferous F. occidentalis were released. Although these studies demonstrate that probing behavior of these thrips species is altered on cyantraniliprole-treated pepper plants, results of field cage studies did not consistently show a reduction in incidence of TSWV-infected plants.

2010년 우리나라 주요 작물 바이러스병 발생 상황

2010년 농업현장의 농업인 등이 임상진단 요청한 시료 중 채소류는 고추 등 8개 작물이었으며 이중 토마토가 31.8%, 수박 21.4%, 고추 19.5%로 바이러스병으로 인한 피해가 많은 작물이었다. 과수류는 사과 등 4작물이었으며, 포도가 63.6%, 사과 33.0%로서 임상진단 요청시료의 대부분을 차지하였다. 화훼류는 국화 등 6개 작물이었으며, 튜립 60.0%, 선인장이 20.0%로 바이러스 피해가 발생하고 있었다. 바이러스 감염시료를 분석한 결과 고추와 토마토는 CMV, BBWV2 등 6종의 바이러스가 감염되었으며, 수박은 MNSV, CMV 등 5종의 바이러스가 감염되었다. 포도는 GFkV 등 6종의 바이러스가 감염되었다. 바이러스 종류별 감염은 CMV가 8종의 채소류 중 6종의 채소류와 튜립에 감염되었다. 2010년 농업현장에서 임상진단한 시료에 감염된 바이러스는 32종이었으며, 바이로이드는 4종이었다. 토마토황화잎말림바이러스(TYLCV)는 2010년 전북 부안 등 6개 도 18개 시 군에 신규로 발생되어 2008년 처음 발생된 이후 총 58개 시 군으로 확산되었다. 토마토원형반점바이러스(TSWV)는 2010년 전북진안, 제주도의 제주 지역에서 신규로 발생하였으며, 2004년 안양 관양동 지역에 대 발생한 이후 25개 시 군에 확산되었으나, 경북 및 충북 지역에서는 현재까지 발생하지 않았다. 토마토덤불위축바이러스(TBSV)는 2010년 경남진주 지역에 신규로 발생하여 2004년 경남 사천지역에 처음 발생한 이후 경남 충북 지역의 5개 시 군에 발생 하였다. The kinds of crop requested from agricultural actual places of famers, Agricultural extension services and so forth was 8 including red pepper for vegetables, 4 including apple for fruit trees and 6 including chrysanthemum for flowers in 2010. The important vegetables in clinical diagnosis of viral diseases were tomato, watermelon and red pepper having the requested rate of 31.8%, 21.4% and 19.5%, respectively. On fruit trees, grape and apple were most common with the requested rate of 63.6% and 33.0%, orderly. On floral crops, tulip and cactus were damaged by viral diseases with the requested rate of 60.0% and 20.0%, orderly. On peppers and tomatoes, six viruses including Cucumber mosaic virus (CMV) and Broad bean wilt virus 2 (BBWV2) infected. Five viruses including Melon necrotic spot virus (MNSV) and CMV were identified from watermelons. On grapes, six viruses including Grapevine fleck virus (GFkV) infected. CMV was identified from six vegetables including pepper out of 8 kinds of vegetables and tulip plant. Total agents of virus and viroid species were 32 and 4 species, respectively, in 2010. Tomato yellow leaf curl disease by Tomato yellow leaf curl virus and Tobacco yellow leaf curl virus was occurred newly at 18 Si/Gun areas including Buan, Jeonbuk province in 2010 and the total areas were increased up to 58 Si/Gun from the first incidence in 2008. Tomato spotted wilt virus (TSWV) occurred newly at two areas of Jinan, Jeonbuk and Jeju in Jeju province in 2010, and the incidence areas were expanded to 25 Si/Gun areas from severe occurrence at Anyang area in 2004. No incidence of TSWV was recorded only in Gyeongbuk and Chungbuk province. Tomato bushy stunt virus occurred newly at Jinju, Gyeongnam, and it had the total incidence areas of 5 Si/Gun after first observation at Sacheon, Gyeongnam in 2004.

Evaluation of Tempera Paints to Reduce Occurrence of Tomato Spotted Wilt Virus

Thrips occur in lower numbers on certain colors of flowers and with the use of certain reflective mulches. A series of experiments was conducted to evaluate the potential of foliar application of selected colors of tempera paints on tomato [Solanum lycopersicum L. (syn.: Lycopersicon esculentum Mill.)] plants as an alternative to plastic mulches for reducing numbers of thrips and incidence of tomato spotted wilt virus (TSWV). Two preliminary greenhouse experiments were conducted in Winter/early Spring 2005 and Fall 2005 to evaluate possible adverse effects of selected tempera paints on growth and early yield of tomato in Auburn, Alabama. Brilliant red, cerise, crimson, jazz orange, or purple tempera paint was applied weekly to foliage of container-grown plants until first harvest. Paint treatments did not significantly reduce plant height in comparison with nontreated plants in either the winter/early spring or fall experiment; fruit yield was reduced on plants treated with purple paint in the spring experiment and all paint colors (except cerise) in the fall experiment. Four subsequent field experiments were conducted in 2006 and 2007 in Shorter and Auburn, Alabama, to evaluate the effects of the same foliar-applied paints on tomato yield, occurrence of thrips, and incidence of TSWV. Plants sprayed with jazz orange paint exhibited reduced yield of marketable fruit in only one of the four crops; otherwise, total weight of marketable fruit from paint-treated plants showed no significant reduction compared with nontreated plants. There was an indication of reduction in thrips numbers on painted plants when evaluated prebloom but not postbloom. Paint treatments did not significantly reduce occurrence of TSWV.

Effect of Imazapic and 2,4-DB on Peanut Yield, Grade, and Seed Germination

Abstract Recurrent problems with peanut seed germination and stand establishment have raised concerns about the potential effects of herbicides on peanut seed quality. Field trials were conducted in south Georgia in 2005 and 2006 to evaluate the effects of imazapic and 2,4-DB on peanut yield, grade, incidence of tomato spotted wilt virus (TSWV), and seed germination. Imazapic at 71 g ai ha−1, applied at 30 and 40 days after planting (DAP), and 2,4-DB at 270 g ai ha−1, applied at 75 or 90 DAP, had no effect on peanut yield, grade, incidence of TSWV, and seed germination when averaged over two locations (Dawson and Tifton) and three cultivars (Georgia Green, Georgia-01R, and C-99R). Normal cultivar yield variations were observed; however, Georgia-01R had reduced standard (25 C) and cold (15 C) germination when compared to the other cultivars.

채소류의 토마토 반점 위조 바이러스 발생과 병징 (I)

토마토 반점위조 바이러스(Tomato spotted wilt virus; TSWV)가 2004년 경기도 안양지역에서 토마토, 고추 등을 포함한 14개 채소 작물에서 발생하였다. TSWV검정은 지표식물 검정, IC/RT-PCR, VC/RT-PCR 및 Total RNA를 이용한 RT-PCR방법을 이용하였으며, TSWV가 발생한 작물의 종류는 토마토, 방울 토마토, 고추, 시금치, 치커리, 적치커리, 적겨자, 용설채, 트레비소, 감자, 들깨, 참깨, 호박, 쌈추 이었다. 포장에서의 발생율은 토마토, 고추 등 주요 작물에서 <TEX>$30\%$</TEX>에서 <TEX>$100\%$</TEX> 발생하였으며,병징은 대부분 전형적인 원형반점이었으며, 괴저, 위조 및 심한 모자이크 병징으로 진전되었다. TSWV가 발생한 포장에서 채집한 꽃노랑 총채벌레(Frankliniella occidentalis)를 IC/RT-PCR 검정한 결과 감염율이 <TEX>$90\%$</TEX>이었다. Tomato spotted wilt virus (TSWV) occurred abruptly with a high incidence rate in 14 vegetable crops in Anyang area, Gyunggido in 2004. TSWV was identified by the symptoms on the indicator plants, immunocaptured reverse transcription-polymerase chain reaction (IC/RT-PCR), virion captured (VC)RT-PCR and RT-PCR using total RNA from the infected plants. Vegetable crops infected with TSWV included table tomato, cherry tomato, red pepper, lettuce, chicory, red leaf chicory, red mustard, dragon tongue, treviso, potato, perilla, sesame, pumpkin, and ssamchoo (hybrid of oriental cabbage and cabbage). The incidence of TSWV in fields ranged from 30 to <TEX>$100\%$</TEX>. TSWV usually produced necrosis, wilt and/or severe mosaic with typical single or double ring spots on the leaves. TSWV could be detected in Frankliniella occidentalis collected from the crops in the fields with <TEX>$90\%$</TEX> rate by IC/RT-PCR.

Utilizing immunoassays to determine systemic tomato spotted wilt virus infection for elucidating field resistance in peanut

Tomato spotted wilt disease was compared in three peanut cultivars, SunOleic 95R, Southern Runner (S. Runner) and DP-1, at two planting dates (April and May) and row spacings (7.6 and 15.2 cm) in a 2-year study in Florida. Tomato spotted wilt virus (TSWV) was detected directly using an enzyme-linked immuno-sorbent assay (ELISA) in both leaf and root crown tissues throughout the growing season to determine the timing and percentage of infected plants. Under low disease pressure, in harvested samples, more April-planted peanuts were infected with TSWV than May-planted. TSWV infection was not affected by plant spacings regardless of disease pressure. Under low disease pressure, from 60 days after planting (DAP), the most susceptible cultivar, SunOleic 95R, had a significantly higher percentage of plants with TSWV compared to the more resistant cultivars. Under high disease pressure, TSWV infection was detected earlier (30 DAP), and there was a clear separation of cultivars, with SunOleic 95R showing the highest infection (75%) followed by S. Runner (55%) and then DP-1 (20%). A higher incidence of TSWV in root crowns compared to leaves was observed for all cultivars. A delayed accumulation of TSWV in a cultivar was a reliable indicator of resistance. The field resistance manifested by peanut may be due to factors that decrease TSWV systemic spread resulting in slower TSWV accumulation in root crowns.

TOMATO YIELD AND SPOTTED WILT VIRUS INCIDENCE AMONG CULTIVARS IN A MISSISSIPPI TRIAL

Mississippi's two largest tomato-growing areas are in Smith and George Counties. The Truck Crops Branch Experiment Station in Crystal Springs is the closest vegetable research site to Smith County but does not share the same soil type. Tomato spotted wilt virus (TSWV) reduces fruit yield and marketability, and its incidence appears to be increasing in the state. The objectives of this trial were 1) to determine fruit yield and TSWV incidence in tomatoes (Lycopersicon esculentum) grown in central Mississippi, and 2) compare yield and relative yield among cultivars and between locations. Tomato seedlings were transplanted to the field in April 2004 in Smith and Copiah County plots. Production practices included raised beds, black plastic mulch, drip irrigation, and fertilizer applied pre-plant and as side-dressings based on soil test and regionally recommended practices. TSWV incidence was recorded in each plot in Smith Co. in June 2004. In both locations, `Amelia' and `Mountain Spring' were among the top yielding entries. In Smith, the top entries also included `BHN 543' and two commercial experimental entries. In Copiah, `Florida 47 R', `Biltmore', `Mountain Fresh', and `BHN 543' also produced high marketable yields. `Florida 47R', `Bush Celebrity', and `Mountain Fresh' were among the poorest yielding varieties in Smith County. Incidence of TSWV was not formally rated in Copiah. In Smith, percent symptomatic plants per plot were negatively correlated with yield. Symptoms were found on entries reportedly resistant or tolerant to TSWV.

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.

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.

A survey for viruses and a viroid in Tasmanian pyrethrum crops

In early 2003, 4-year-old pyrethrum crops in north-west Tasmania were surveyed for the presence of Tomato spotted wilt virus (TSWV), Beet western yellows virus (BWYV), Cucumber mosaic virus (CMV), Tomato aspermy virus (TAV), various members of the genera Potyvirus and Carlavirus, and Chrysanthemum stunt viroid (CSVd). Of these, only TSWV was detected by enzyme linked immunosorbent assay and infection confirmed by reverse transcription polymerase chain reaction. Most (18/21) of the crops planted in 1999 contained plants symptomlessly infected with TSWV, with a mean incidence of 2.6% (range 0–11.3%). In comparison, less than half of 1-year-old crops were affected by TSWV and the mean incidence of infection was only 0.1% (range 0–0.5%). Examination of the spatial distribution of TSWV infected crops (irrespective of age) showed crops in the Central Coast region had a significantly higher mean incidence of TSWV (3.1%) than those in the Devonport (0.2%) and Burnie/Wynyard (0.2%) regions.

Resistance to Tomato spotted wilt virus and Root‐Knot Nematode in Peanut Interspecific Breeding Lines

The peanut root‐knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1] and Tomato spotted wilt virus (TSWV), genus Tospovirus, are economically significant pathogens of peanut (Arachis hypogaea L.) in the USA. Peanut cultivars are available that have resistance to either the peanut root‐knot nematode (PRN) or TSWV, but no cultivars are available that have resistance to both pathogens. The objective of this research was to identify peanut breeding lines that have resistance to both pathogens. We crossed interspecific peanut germplasm with two cultivars that are susceptible to both PRN and TSWV. Progenies were examined in a greenhouse screening system to measure resistance to PRN. Subsequently, this material was evaluated for resistance to TSWV in field plots. Ten breeding lines were identified which exhibited a reduction in nematode reproduction in comparison to the nematode susceptible check ‘Georgia Green’. These breeding lines also exhibited a reduction in incidence of TSWV in comparison to the TSWV susceptible check ‘COAN’. When grown in a field with pressure from both pathogens, these breeding lines had higher yield than cultivars with resistance to only one pathogen. This is the first report of peanut germplasm with resistance to both TSWV and the peanut root‐knot nematode and the first report of resistance to TSWV in interspecific peanut germplasm.

First Report of Tomato spotted wilt virus on Soybean in Iran.

During the summers of 1999 and 2000, 3,110 soybean (Glycine max) leaf samples were randomly collected from soybean fields in the Ardebil, Goletan, Khuzestan, Lorestan, and Mazandaran provinces of Iran. Tomato spotted wilt virus (TSWV) was detected in leaf samples by TSWV-specific polyclonal antibody (As-0526 and As-0580, DSMZ, Braunschweig, Germany) in double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). Mechanical inoculation of 26 plant species (10 plants per species) and cultivars with extracts of positive leaf samples produced necrotic local lesions in Beta vulgaris, Chenopodium quinoa, C. amaranticolor, Gomphrena globosa, Phaseolus vulgaris cv. Talash, Vicia faba, and Vigna unguiculata cv. Mashad; produced systemic chlorosis followed by necrosis in Datura stramonium, D. metel, Nicotiana rustica, N. tabacum cv. Samsun, N. glutinosa, N. bentamiana, and Glycine max cv. Hill; and produced chlorosis, stunting, and bud necrosis in Arachis hypogaea (peanut). Plants developing these symptoms following mechanical inoculation with extracts from original soybean leaves were positive in ELISA for TSWV. ELISA results indicate that the overall incidence of TSWV on soybean in the five provinces was 5.4%. TSWV has been reported in potato (2) and tomato (1) from Iran, but to our knowledge, this is the first report of the occurrence of TSWV on soybean in Iran.

Influence of intercropping system on insect pests and viral diseases of tomato, Lycopersicon esculentum Mill.

Studies to assess the effects of intercropping in tomato under irrigated and rainfed conditions for the management of key pests at Regional Research Station, Paiyur, TamilNadu. Agricultural University, TamilNadu during 1998-2000. Experiments were conducted in a factorial randomized block design using intercrops viz, clusterbean, green gram and mustard and two rounds. of spraying with NSKE 5% and monocrotophos 0.07%, once on 30th day after transplanting and second at the time of maximum flowering and fruit set. The results revealed that tomato intercropped with mustard at 2:1 ratio had recorded reduced incidence of whitefly and thrips population and fruit borer damage as well in two different field studies. Natural incidence of tomato spotted wilt virus (TSWV) and leaf curl virus (LCV) diseases. were noticed on the rainfed tomato crop raised during August-September, 1999 planting season. The incidence of TSWV and LCV diseases were less under intercropped tomatoes than sole crop tomato and this was significantly low on the mustard intercropped plots. Nearly 30% of plants were lost due to these diseases in the tomato sole crop plots and this loss in plant population was nearly 45-60% more than the mustard intercropped plots. The combined yield of undamaged and damaged fruits was 16.319 t ha and 16.028 t ha for the sole tomato and mustard intercropped tomato under irrigated condition. However, under rainfed condition due to the severe incidence of viral diseases, an yield of 5.832 tha was recorded in sole crop while it was 8.527 t ha in mustard intercropped plots. The undamaged fruit yield recorded was 15.00 and 7.810 tha for the mustard intercropped plots, whereas it was 13.386 and 4.833 t ha for sole crop tomato under irrigated and rainfed conditions respectively. The mustard intercropping had given an additional net return of Rs.7080 and Rs.12400 because of reduced pest infestation under irrigated and rainfed conditions respectively.

027 Tomato Plant Size and Fruit Yield as Affected by the Date of Symptom Appearance of Tomato Spotted Wilt Virus

Tomato spotted wilt virus (TSWV) can cause serious damage to tomato, pepper, lettuce, and other crops. The virus is transmitted by several species of thrips. The objective of this study was to determine the effect of the time (t, days after transplanting) when TSWV symptoms first appeared on tomato plant size and fruit yield. Tomato (`Florida-47') plants were drip-irrigated and planted over black plastic mulch. The experiment was carried out in Tifton, Ga., during Spring 1999. High populations of thrips were detected since early stages of plant development, which resulted in a high incidence of TSWV. Plant fresh weight was significantly higher (r2 = 0.632, n = 216) the later in plant development TSWV symptoms first appeared (i.e., with increasing t values). Total fruit production of individual plant linearly increased with increasing t values (r2 = 0.664, n = 216). As with total fruit production, fruit marketable yield was also higher with increasing t values; however, marketable yield was significantly reduced even when plants were infected later in the season (t &gt; 55 days after transplanting). Our results suggest that it is important to keep tomato plants free from TSWV as long as possible. This applies to both developing and developed plants.