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J.L. Anaya-López, I. Torres-Pacheco, M. González-Chavira, J.A. Garzon-Tiznado, J.L. Pons-Hernandez, R.G. Guevara-González, C.I. Muñoz-Sánchez, L. Guevara-Olvera, R.F. Rivera-Bustamante and S. Hernández-Verdugo

Screening for resistance to mixed infections with pepper huasteco virus (PHV) and pepper golden mosaic virus (PepGMV) was carried out on plants representing wild pepper accessions collected in different states of México. One accession collected in Yucatán (BG-3821) corresponded to Capsicum chinense Jacq., and three collected from Michoacán (BG-3818), Tamaulipas (BG-3820), and Sinaloa (BG-3819) were identified as C. annuum L. Forty-eight plants were initially inoculated with a 1:1 mix of PHV and PepGMV DNAs by a biolistic method. Those plants that did not show typical symptoms after the biolistic method, were inoculated by grafting. Half of the plants (24) were highly susceptible, while the other half expressed different degrees of resistance. Of the resistant individuals, eight plants were asymptomatic and viral DNA of both viruses was detected in low levels. Two individuals showed delayed symptoms 34 days after symptom expression in the control plants. This delay was correlated with an increase in PHV DNA levels when plants became symptomatic. The remaining 14 plants showed symptom remission in newly developed leaves at 31 days postinoculation, and this asymptomatic effect was correlated diminished PHV DNA within the plants. Our results suggest that the resistance shown by some individuals to geminivirus mixed infections (PHV and PepGMV) is likely due to constrains in viral movement.

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Yolanda Godínez-Hernández, José Luis Anaya-López, Raúl Díaz-Plaza, Mario González-Chavira, Irineo Torres-Pacheco, Rafael F. Rivera-Bustamante and Ramón G. Guevara-González

Seven pepper (Capsicum chinense Jacq.) populations from the Yucatán Peninsula, México, that were selected from a field screening for viral diseases were tested for pepper huasteco geminivirus (PHV) resistance. Two populations (UX-SMH-1 and UX-SMH-24) displayed <50% of infection with PHV. Four plants did not show viral symptoms 3 months postinoculation using biolistic and grafting methods. When leaf tissue from these individuals was analyzed for PHV using quantitative PCR, it supported PHV replication, thus, the ineffective PHV infection in these symptomless individuals may be a result of restricted viral movement.

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James D. McCreight, Hsing-Yeh Liu and Thomas A. Turini

still had PCR-detectable virus (data not shown). Recovery from symptoms of geminivirus infection was previously reported in Cucurbita spp. in response to infection by SLCV ( McCreight and Kishaba, 1991 ). The eight PIs all proved to be potential

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Yuanfu Ji, Jay W. Scott, David J. Schuster and Douglas P. Maxwell

.D. 1998 Inheritance and linkage of geminivirus resistance genes derived from Lycopersicon chilense (Dunal) in tomato ( Lycopersicon esculentum Mill) Ph.D. Diss University of Florida Gainesville Griffiths, P.D. Scott, J

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M. Friedmann, M. Lapidot, S. Cohen and M. Pilowsky

Tomato yellow leaf curl virus (TYLCV), transmitted by the tobacco whitefy (Bemisia tabaci Genn.), can be devastating to tomato (Lycopersicon esculentum L.) crops in tropical and subtropical regions. The development of resistant cultivars is the best option for control of TYLCV. However, all the available resistant commercial cultivars tested at the Volcani Center, when inoculated with TYLCV, developed different levels of disease symptoms. In this study, we report the development of a breeding line, TY172, which is a symptomless carrier of TYLCV. Line TY172, whether infected in the greenhouse with viruliferous whiteflies, or when grown in the field under natural infection, showed no symptoms of the disease. Viral DNA was detected in infected TY172 plants, albeit at much lower levels than a susceptible infected control. In addition, grafting experiments using infected susceptible scions grafted onto TY172 stocks, showed that even when exposed continuously to very high levels of virus, line TY172 did not develop disease symptoms, nor did it accumulate high levels of the virus. When TY172 was crossed with susceptible lines, the hybrids exhibited milder symptoms and lower viral content than the susceptible parent, yet higher than that of TY172, suggesting a partial dominance for the TY172 resistance. Upon inoculation of F2 populations, the amount of symptomless individuals appeared in a ratio of≈7:64. This suggests that at least three genes may account for the resistance.

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Peter M. Hanson, Dario Bernacchi, Sylvia Green, Steven D. Tanksley, Venkataramappa Muniyappa, Attiganal S. Padmaja, Huei-mei Chen, George Kuo, Denise Fang and Jen-tzu Chen

Tomato yellow leaf curl virus (TYLCV), a heterogeneous complex of whitefly-vectored geminiviruses, is a serious production constraint of tomato (Lycopersicon esculentum Mill.) in Asia, the Middle East, and the Americas. In this study we report on mapping of a DNA fragment introgressed into cultivated tomato presumably from the wild species L. hirsutum Humb. and Bonpl. and found to be associated with TYLCV resistance. To locate introgressions of wild tomato alleles in TYLCV-resistant tomato line H24, its DNA was digested with six restriction enzymes and probed with 90 RFLP markers evenly spaced throughout the genome. This polymorphism survey revealed the presence of one wild tomato introgression each on chromosomes 8 and 11. Plants of a F2 cross between H24 and a susceptible tomato line were probed with randomly amplified polymorphic DNA (RFLP) markers linked to the targeted regions and F3 families were developed by self-pollination of F2 plants that carried none, one, or both introgressions in either homozygous or heterozygous states. Plants of F3 families, parents, and control tomato line Ty52 (homozygous for the Ty-1 allele for TYLCV tolerance) were exposed to viruliferous whiteflies (Bemisia tabaci Gennadius) in greenhouses at the Asian Vegetable Research and Development Center, Taiwan, and the University of Agricultural Sciences, Bangalore, India. Results indicated that F3 families homozygous for the introgression on chromosome 11 were resistant to TYLCV at both locations. Additional probing showed that the chromosome 11 introgression spanned markers TG36 to TG393, covering a distance of at least 14.6 centimorgans. This is the first report of TYLCV resistance in tomato mapped to chromosome 11.

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Juan M. Osorno, Carlos G. Muñoz, James S. Beaver, Feiko H. Ferwerda, Mark J. Bassett, Phil N. Miklas, Teresa Olczyk and Bill Bussey

In Central America and the Caribbean, bean golden yellow mosaic virus (BGYMV) can cause significant reductions in seed yield and quality ( Morales, 2000 ). Symptoms incited by this whitefly-transmitted geminivirus include intense leaf chlorosis

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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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James D. McCreight, Hsing-Yeh Liu and Thomas A. Turini

Cucurbit leaf crumple geminivirus (CuLCrV) is transmitted by sweet-potato whitefly (Bemisia tabaci) biotype B (SPWF-B) and occurs on cucurbits in Arizona, California, Texas, and Mexico. This virus is identical to Cucurbit leaf curl virus, and their symptoms are similar to Squash leaf curl virus on squash (Cucurbita sp.) and Melonleaf curl virus on melon (Cucumis melo L.). Melon has been reported to be either susceptible to CuLCrV, or to have the ability to recover from infection. Twenty-three melon cultigens were inoculated with CuLCrV in greenhouse tests using SPWF-B. Eighteen of the cultigens tested were highly susceptible to CuLCrV (≥60% infected plants) and generally exhibited pronounced CuLCrV symptoms: `Amarillo', `Edisto 47', `Esteem', `Fuyu 3', `Impac', `Moscatel Grande', `Negro', `Perlita', PI 234607, PI 236355, PI 414723, `PMR 5', `Seminole', `Sol Dorado', `Sol Real', `Top Mark', `Vedrantais', and WMR 29. Five cultigens were resistant to CuLCrV (<40% infected plants that exhibited restricted, mild symptoms): MR-1, PI 124111, PI 124112, PI 179901, and PI 313970. Symptoms abated with time in both groups although infected plants remained positive for the virus. Ten of the cultigens (`Edisto 47', `Fuyu 3', `Impac', MR-1, PI 124112, PI 313970, PI 414723, `PMR 5', `Top Mark', and WMR 29) were included in field tests in 2003 and 2004 that were naturally infected with CuLCrV. With the exception of PI 414723, the greenhouse and field data were consistent for reaction to CuLCrV.

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P.D. Griffiths and J.W. Scott

Tomato mottle virus (ToMoV) is a silverleaf whitefly (Bemisia argentifolii Bellows and Perring n. sp.) transmitted, bipartite geminivirus that infects tomatoes (Lycopersicon esculentum Mill.). Inbred lines resistant to ToMoV were derived from Lycopersicon chilense Dunal accession LA 1932. Inheritance was studied using a family developed from the crossing of a resistant inbred with a susceptible tomato inbred over two seasons. The F1 had resistance intermediate to the parents and generation means analysis of F1 and F2, backcross and parental populations suggested that the action of at least two additive genes with high heritability (h2 n.s. = 0.87) controlled ToMoV resistance. When data from the two seasons were combined, an acceptable fit to an additive-dominance genetic model was obtained. Single plant comparisons, bulk comparisons, and tailends of F2 populations segregating for ToMoV resistance derived from LA 1932 identified randomly amplified polymorphic DNA (RAPD) markers using eight hundred 10-mer oligonucleotide primers. The F2 populations used for inheritance studies were screened for polymorphic markers, and 12 RAPD markers associated with the ToMoV resistant line were linked to the morphological markers self-pruning (sp) and potato leaf (c) on chromosome 6. RAPD markers that were associated with ToMoV resistance segregated into two linked regions flanking either side of the sp and c loci. The molecular studies suggested that the action of at least two additive regions controlled ToMoV resistance which supported the inheritance analysis.