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Arcenio Gutierrez-Estrada, Emma Zavaleta-Mejl̀a, and Gustavo Mora-Aguilera

Viruses associated to eight Alstroemeria varieties and the relationship of thrips density and environmental factors with Tomato Spotted Wilt (TSW) intensity as well as the TSW effect on yield were studied in `Rosario' in Central Mèxico. Using hosts range the viruses detected were Tomato Spotted Wilt Tospovirus (TSWV), Impatiens Necrotic Spot Tospovirus (INSV), Alstroemeria Mosaic Potyvirus (AlMV), Alstroemeria Streak Potyvirus (ASV), Arabis Mosaic Nepovirus (ArMV), and Cucumber Mosaic Cucumovirus (CMV). With serology it was confirmed the presence of TSWV in `Jubilee', `Rosario', and `Regina' varieties; INSV in `Anabel', `Jubilee', and `Red Sunset'; and AlMV in `Rosario', `Red Sunset', `Rosita', `Yellow King', `Jubilee'. and `Rojo Sangria'. TSWV and AlMV were found coinfecting `Rosario' plants. Five percent of plants were serologically positive to TSWV in the first flower harvest (25 Jan.-5 Apr.), 10% in the second (12 Ap.-21 June), and third (5 July-13 Sept.), and 18% in the last harvest (23 Sept.-6 Dec.). The highest peak density of thrips (520 to 630 individuals per sticky trap) were registered when the maximum temperature was higher than 35 °C and the relative humidity was between 40% to 60%. However, such peak density was not correlated with a significant increase of TSW incidence. Number and quality of inflorescences and the stem growth rate were significantly higher (P = 0.05) in plots with asymptomatic plants than that with plants showing putative symptoms of TSW.

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Arcenio Gutièrrez-Estrada, Emma Zavaleta-Mejl̀a, and Gustavo Mora-Aguilera

Viruses associated to eight Alstroemeria varieties and the relationship of thrips density and environmental factors with Tomato Spotted Wilt (TSW) intensity as well as the TSW effect on yield were studied in `Rosario' in Central Mexico. Using hosts range the viruses detected were Tomato Spotted Wilt Tospovirus (TSWV), Impatiens Necrotic Spot Tospovirus (INSV), Alstroemeria Mosaic Potyvirus (AlMV), Alstroemeria Streak Potyvirus (ASV), Arabis Mosaic Nepovirus (ArMV) and Cucumber Mosaic Cucumovirus (CMV). With serology, the presence of TSWV was confirmed in `Jubilee', `Rosario', and `Regina'; INSV in `Anabel', `Jubilee', and `Red Sunset'; and AlMV in `Rosario', `Red Sunset', `Rosita', `Yellow King', `Jubilee', and `Rojo Sangria'. TSWV and AlMV were found coinfecting `Rosario' plants. Five percent of plants were serologically positive to TSWV in the first flower harvest (25 Jan.-5 Apr.), 10% in the second (12 Apr.-21 June), and third (5 July-13 Sept.) and 18% in the last harvest (24 Sept.-6 Dec.). The highest peak density of thrips (520 to 630 individuals per sticky trap) were registered when the maximum temperature was higher than 35 °C and the relative humidity was between 40% to 60%. However, such peak density was not correlated with a significant increase of TSW incidence. Number and quality of inflorescences and the stem growth rate were significantly higher (P = 0.05) in plots with asymptomatic plants than that with plants showing putative symptoms of TSW.

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S.J. Scott, M. Stevens, and R.C. Gergerich

Three methods to inoculate Lycopersicon esculentum 'VF Pink' seedlings with tomato spotted wilt virus (TSWV) were compared. Treatments were 1) two inoculations by hand (rubbing leaves with a sterile cotton swab), 2) a single inoculation using a paint sprayer at 3.56 × 105 N· m-2, and 3) two spray inoculations. All three methods were effective (>95% infection) under moderate temperatures in the spring, but hand inoculation was not effective under hot conditions in the summer. In another experiment, spray inoculation was used to compare effects of light intensity and the leaf inoculated on susceptibility of L.. hirsutum PI 127826, L. pimpinellifoliom LA 1580 and `VF Pink' to TSWV isolate 85-9. All three genotypes were susceptible under full sun and 60% shade cloth in the greenhouse. Inoculation of youngest leaves produced the highest virus titer. Background optical density for noninoculated plants differed between lower and upper leaves in the ELISA assay.

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Jong Wook Kim, Thomas L. German, and Samuel S. M. Sun

Nucleocapsid protein (N) gene was isolated from tomato spotted wilt virus (TSWV) Hawaiian L isolate, and introduced into Nicotiana tabacum cv. Xanthi nc in order to test for “CP-mediated protection”. Agrobacterium tumefaciens-mediated transformation was performed. The integrity and the expression of N gene were verified by Southern blot and Northern blot analysis, and the N protein in the transgenic tobacco plants were determined by ELISA and Western blot analysis. Several first generation of transgenic tobacco were tested for virus resistance. Comparably smaller numbers of the local lesions were developed with several day of delay in the in-frame transformants.

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P.A. Stack, L.B. Stack, and F.A. Drummond

A mail survey of greenhouse growers was conducted in 1994 and 1995 to determine the presence and importance of western flower thrips (WFT), Frankliniella occidentalis Pergande, in Maine greenhouses in growing years 1993 and 1994. Respondents were licensed growers with at least 1000 ft2 (93 m2) of greenhouse growing area. The survey objectives were to develop a grower demographic profile; determine the incidence of WFT and two WFT-vectored plant viruses, tomato spotted wilt (TSWV) and impatiens necrotic spot (INSV); and identify current WFT management strategies. The survey shows that Maine greenhouse growers are seasonal, experienced and retail oriented. Their growing area averages less than 10,000 ft2 (929 m2) and they produce a diverse crop mix and choose to import production stock as much as propagate it themselves. Both WFT and TSWV/INSV have increased in severity in Maine greenhouses over the past 10 years. Larger, year-round greenhouses are more likely to experience infestations of WFT and higher virus incidence. An integrated pest management (IPM) strategy is employed by the majority of growers surveyed. Insecticide application is the primary tactic used to control WFT. Fewer than 4% of the growers use natural enemies to control thrips. However, 63% responded that future research in pest management should focus on biological control.

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J.R. Fisher and S.T. Nameth

Ajuga reptans L. is an herbaceous ornamental mint grown in borders or as a groundcover, and is commonly propagated vegetatively and by seed. Three hundred and fifty-six A. reptans samples were obtained from growers in Washington, Michigan, Iowa, and Ohio, and screened for alfalfa mosaic virus (AMV), tobacco streak ilarvirus (TSV), cucumber mosaic cucumovirus (CMV), tomato aspermy cucumovirus (TAV), tomato spotted wilt tospovirus (TSWV), impatiens necrotic spot tospovirus (INSV), tobacco mosaic tobamovirus (TMV), potato virus × potexvirus (PVX), and 80 potyviruses, using direct antibody sandwich (DAS) and indirect enzyme-linked immunosorbent assay (ELISA). Viral-associated double-stranded ribonucleic acid (dsRNA) analysis was used to detect an apparent satellite (sat) RNA, and northern hybridization using a digoxigenin (DIG) labeled (S) CARNA-5 cDNA probe was used to confirm the identity of the apparent satRNA. No incidences of TAV, TMV, TSWV, INSV, PVX, or potyviruses were detected. CMV was detected in 11%, AMV in 22.2%, TSV in 3.7%, and mixed infections of CMV and AMV in 1.1% of the samples. SatRNA was detected in 36 A. reptans `Royalty', two `Rainbow', and two `Burgundy Glow' samples by dsRNA analysis, and confirmed by hybridization in 29 `Royalty' and one `Burgundy Glow' samples. Sixteen A. reptans `Royalty' seedlings grown from seed harvested from CMV-infected plants were tested by ELISA for CMV, AMV, and TSV. All were positive for CMV, and two were positive for a mixed infection of CMV and AMV. SatRNA was detected in all 16 seedlings by RT-PCR.

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John W. Scott, Stephen M. Olson, and Jerry A. Bartz

‘Tribeca’ is a fresh market hybrid tomato ( Solanum lycopersicum L.) that has resistance to Tomato spotted wilt virus (TSWV) and heat-tolerant fruit setting (HT). ‘Tribeca’ has performed well on the peninsula of Florida where its ability to set

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Randy G. Gardner and Dilip R. Panthee

H.N. Hans] races 1 and 2, tomato spotted wilt virus (TSWV), and late blight [ Phytophthora infestans (Montagne, Bary]; moderate resistance to early blight [ Alternaria solani (Ellis and G. Martin) L.R. Jones and Grout]; and tolerance to bacterial

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Randy G. Gardner and Dilip R. Panthee

NC 58S, NC 123S, NC 127S, and NC 132S are fresh-market tomato ( Solanum lycopersicum L.) breeding lines that have the single dominant gene Sw-5 for resistance to tomato spotted wilt virus (TSWV) along with other important disease resistance genes

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Beatriz M. Díaz, Ricardo Biurrún, Aránzazu Moreno, Miguel Nebreda, and Alberto Fereres

Ultraviolet (UV)-absorbing plastic films are being used as a photoselective barrier to control insect vectors and associated virus diseases in different horticultural crops. A 2-year experiment was carried out in northeastern Spain (Navarra) to evaluate the impact of a UV-blocking film (AD-IR AV) on the population density of insect pests and the spread of insect-transmitted virus diseases associated with head lettuce [Lactuca sativa (L.)]. Results showed that the UV-absorbing plastic film did not loose its ability to filter UV radiation after three lettuce crop cycles (14 months). The UV-absorbing plastic film was effective in reducing the abundance and in delaying the colonization of lettuce by aphids [Macrosiphum euphorbiae (Thomas) and Acyrthosiphum lactucae (Passerini)]. A significant increase in the percentage of marketable plants was achieved under UV-absorbing films due to a reduction in the number of plants infested by aphids and by insect-transmitted virus diseases (mainly potyviruses). Also the UV-absorbing plastic films were effective in reducing the population density of Frankliniella occidentalis (Pergande) and the spread of tomato spotted wilt virus (TSWV) as well as the population density of the lepidopteran pest, Autographa gamma (L.), a common pest of lettuce in Spain. However, no effective control of the greenhouse whitefly Trialeurodes vaporariorum (Westwood) was achieved. The results showed that UV-absorbing plastic films are a very promising tool to protect greenhouse lettuce from the main pests and insect-transmitted virus diseases occurring in northeastern Spain.