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Olga Fedorowicz, Grzegorz Bartoszewski, Maria Kamińska, Pravda Stoeva and Katarzyna Niemirowicz-Szczytt

This study was undertaken to remedy significant yield losses in commercial tomato (Lycopersicon esculentum Mill.) and tobacco (Nicotiana tabacum L.) production caused by tomato spotted wilt virus (TSWV). One of the possible sources of resistance can be incorporation into the host plant of a viral nucleoprotein (N) gene by Agrobacterium-mediated transformation. Twelve primary transformants of tomato and 141 of tobacco were analyzed for the expression of the N gene and for resistance to the TSWV infection. The tests have demonstrated that transgenic plants were protected against virus infection irrespective of whether or not they contained detectable levels of the translational product.

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M.A. Canady, M.R. Stevens and J.W. Scott

Nineteen interspecific hybrid breeding lines were tested for resistance to a TSWV isolate using enzyme-linked immunosorbent assay (ELISA) to check for presence of the virus after inoculation. These lines were all BC1F6 lines derived from L. esculentum crosses with seven L. chilense accessions. All of these lines had been selected for high tolerance/resistance to tomato mottle virus (ToMoV), a geminivirus [Scott et al., Bemisia 1995: Taxonomy, Biology, Damage Control and Management 30: 357–367 (1996)]. The initial TSWV screening indicated that eight of the 19 original lines had “possible” TSWV resistance. Seed from these selected eight lines were then planted and inoculated with TSWV ≈3 weeks after emergence. Three weeks later, ELISA results indicated that all plants from all lines were infected with TSWV. However, none of the plants from Y118 (derived from the LA 1938 cross) showed visual TSWV symptoms. The Y118-derived plants were allowed to grow for several months, and at no time developed significant visual symptoms of the virus. The consistent lack of TSWV symptoms prompted a second ELISA test on the Y118 plants, and the results indicated the plants were completely free of TSWV. Further tests were then initiated with F2 (L. esculentum × Y118) seed, and results indicate a single dominant gene is responsible for TSWV resistance. Data from this segregating population, including a molecular marker study which screened 800 randomly amplified polymorphic DNA (RAPD) primers, will be presented. Approximately two to five RAPD primers are possibly linked to TSWV resistance.

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M.R. Stevens, P.D. Griffiths, J.W. Scott, D.K. Heiny and D.D Rhoads

Sw-5 is a locus introgressed from Lycopersicon peruvianum to some L. esculentum lines conferring dominant resistance to TSWV. Restriction fragment length polymorphism (RFLP) analyses positions Sw-5 to the long arm of chromosome 9 in the sub-telomeric region between CT71 and CT220. RFLP analyses suggest the introgressed region begins distal to CT71, includes CT220, and may extend to the telomere. Randomly amplified polymorphic DNA (RAPD) analyses with >700 random 10-mer primers identified a single 2.2-kbp band with one primer (primer #72 GAGCACGGGA) that is tightly linked to Sw-5. However, we have also produced an equivalent 2.2-kbp band in analysis of other TSWV-susceptible tomato breeding lines. Thus, this band likely derives from L. esculentum DNA very near to Sw-5 and the introgressed region. Additional analyses have recently detected a potential co-dominant RAPD polymorphism linked to Sw-5.

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Mikel R. Stevens, John W. Scott, John J. Cho, Bradley D. Geary and Frederic D. Memmott

Tomato spotted wilt virus (TSWV), a tospovirus, is a thrips-vectored disease infecting more than 1000 species of both monocots and dicots, including many species of agriculture importance. TSWV is the limiting factor for tomato (Lycopersicum esculentum Mill.) production in several areas of the world. For a number of years, the Sw-5 gene (derived from L. peruvianum Mill.) has provided acceptable control of this disease. Recently, Sw-5 derived resistance has been overcome by virulent pathogen isolate(s) in tomato production areas such as Spain and Italy. In earlier studies, we identified a potential new source of resistance to TSWV derived from L. chilense Dun. accession LA 1938. In a set of recent field studies, it was demonstrated that this putative new source of resistance was highly resistant to TSWV in Hawaii, Florida/Georgia, and South Africa. Furthermore, greenhouse screening trials have clearly demonstrated that the L. chilense source of TSWV resistance is resistant to isolates that overcome tomatoes homozygous for Sw-5. In these same greenhouse and field studies, there is uniform evidence that this resistance is dominant. Subsequent greenhouse studies suggest that this resistance is controlled by a single gene. Studies have been initiated to verify the inheritance of the gene(s) and to develop linked molecular markers. Furthermore, studies are under way in Australia to test this resistance on non-TSWV tospoviruses. If the data demonstrate that this is a single dominant gene we suggest this gene be designated Sw-7.

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Santiago García-Martínez, Adrián Grau, Aranzazu Alonso, Fernando Rubio, Pedro Carbonell and Juan J. Ruiz

spotted wilt virus (TSWV), and Tomato yellow leaf curl virus (TYLCV) ( Picó et al., 2002 ). A breeding program for introgression of resistance to ToMV, TSWV, and TYLCV into several tomato landraces has been carried out over the last 15 years at the

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Santiago García-Martínez, Adrián Grau, Aranzazu Alonso, Fernando Rubio, Pedro Carbonell and Juan J. Ruiz

), Tomato spotted wilt virus (TSWV), and Tomato yellow leaf curl virus (TYLCV) can make the Muchamiel (and other) landraces cultivation nonviable in many areas, especially in open field ( Picó et al., 2002 ). The Miguel Hernández University breeding

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Santiago García-Martínez, Adrián Grau, Aranzazu Alonso, Fernando Rubio, Manuel Valero and Juan J. Ruiz

The incidence of several viral diseases such as those caused by Tomato mosaic virus (ToMV) and Tomato spotted wilt virus (TSWV) makes tomato landrace cultivation practically nonviable in many areas of southeastern Spain, especially in open

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Juan C. Díaz-Pérez, K. Dean Batal, Darbie Granberry, Denne Bertrand, David Giddings and Hanu Pappu

Tomato spotted wilt virus (TSWV) is a serious constraint to tomato production worldwide. Losses are significant because the disease is difficult to control and most of the commercially available tomato cultivars are susceptible to TSWV. This study was intended to provide information that could be used to design more appropriate disease management strategies. The objective was to determine the relationship of tomato plant growth and fruit yield with the time of TSWV symptom appearance. Experiments were carried out during Spring 1999 and 2000, using drip irrigation and plastic film mulched beds with black plastic mulch alone (1999) or different colored mulches (2000). The mulches used were black, black-on-silver, gray-on-black, red, silver-on-black, silver (painted) and white-on-black, and bare soil. The 1999 experiment included a single TSWV-susceptible cultivar (Florida-47), while the 2000-experiment included two TSWV-susceptible (Florida-91 and Sun Chaser) and one TSWV-resistant cultivars (BHN-444). Colored mulches and tomato cultivars affected the time between transplanting and appearance of first symptoms of TSWV. For all tomato cultivars, vegetative top fresh weight (FW), fruit number and total fruit yield increased linearly with the time the plants remained free from TSWV symptoms. Marketable fruit yield also increased as the time from transplanting to the first appearance of symptoms increased. When data for cultivars were pooled, vegetative top FW and total fruit yield were reduced by 2.1% and 2.3%, respectively, for each day prior to harvesting that plants showed TSWV symptoms.

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Santiago García-Martínez, Adrián Grau, Aranzazu Alonso, Pedro Carbonell, Juan F. Salinas, José A. Cabrera and Juan J. Ruiz

years, cherry tomato has shown an increasing market share. Like all tomato landraces, cherry cultivars are susceptible to several viruses, such as Tomato mosaic virus (ToMV), Tomato spotted wilt virus (TSWV), Tomato yellow curl virus (TYLCV

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Santiago García-Martínez, Adrián Grau, Aranzazu Alonso, Pedro Carbonell, Juan Francisco Salinas, José Ángel Cabrera and Juan J. Ruiz

many tomato landraces, ‘Moruno’ cultivars are highly susceptible to several viruses, such as Tomato mosaic virus (ToMV), Tomato spotted wilt virus (TSWV), and Tomato yellow leaf curl virus (TYLCV) ( Cebolla-Cornejo et al., 2007 ), Pepino mosaic