First report of Tomato torrado virus on weed hosts in Spain

Alfaro Fernández, AO.; Córdoba-Sellés, C.; Cebrián, M.; Herrera-Vásquez, J.; Sanchez Navarro, JA.; Juárez, M.; Espino, A.... (2088). First report of Tomato torrado virus on weed hosts in Spain. Plant Disease. 92(5):831-831. https://doi.org/10.1094/pdis-92-5-0831b83183192

Seed transmission of Melon necrotic spot virus and efficacy of seed-disinfection treatments.

[EN] Rates of seed transmission of Melon necrotic spot virus (MNSV) were estimated in seedlings grown from commercial melon (Cucumis melo) cv. Galia F1 seeds. Seedlings at the cotyledon stage and adult plants were assayed for MNSV by DAS-ELISA and RT-PCR. None of the seedling groups tested positive for MNSV by ELISA. The proportion of seedlings infected with MNSV was at least 7 and 8% in seed lots 05 and 06, respectively, as estimated from RT-PCR analysis of grouped seedlings. Fourteen and eight grouped samples (10 seedlings per group), of a total of 200 and 100 seedlings, respectively, grown from infected seeds were MNSV-positive in seed lots 05 and 06, respectively, corresponding to seed-to-seedling transmission rates of 11·3 and 14·8%, respectively. Several seed-disinfection treatments were evaluated for their ability to prevent seed transmission of MNSV. The results suggest that a treatment of 144 h at 70°C can be used to eradicate MNSV in melon seeds without hindering germination.José Angel Herrera-Vásquez was supported by a predoctoral fellowship from Agencia Española de Cooperación Internacional para el Desarrollo (AECID, period 2004-2007), and Instituto para la Formación y Aprovechamiento de Recursos Humanos-Secretaría Nacional de Ciencia y Tecnología (IFARHU-SENACYT, Panamá, period 2007-2010).Herrera-Vásquez, JA.; Córdoba-Sellés, MC.; Cebrián, MC.; Alfaro Fernández, AO.; Jordá, C. (2009). Seed transmission of Melon necrotic spot virus and efficacy of seed-disinfection treatments. Plant Pathology. 58:436-442. https://doi.org/10.1111/j.1365-3059.2008.01985.x4364425

Molecular variability of Spanish and Hungarian isolates of Tomato torrado virus

[EN] The population structure and genetic variation of Tomato torrado virus (ToTV) were estimated from 19 Spanish isolates collected from 2001 to 2009 in different tomato-production areas by analyses of the partial nucleotide sequences of five regions of the virus genome: the protease cofactor (Pro-Co) and the RNA-dependent RNA polymerase (RdRp) in RNA1, and the movement protein (MP) and two subunits of the coat protein (CP; viz. Vp35 and Vp23) in RNA2. Three Hungarian isolates of the virus were also included in the analyses. All the ToTV isolates clustered together in the phylogenetic analysis of the nucleotide sequences of the different regions. However, some genetic diversity was observed in the case of the two CP subunits among the Gran Canaria isolates and the remaining ToTV-isolates analysed, which grouped together. A high similarity was observed among all the isolates and the two published ToTV isolates: the ToTV type isolate (PRI-ToTV0301) and the Polish isolate Wal03. The most variable encoding regions studied were those on RNA2. In general, no correlation was found between genetic diversity and collection date. Studying the genetic distances between pairs of sequences, the ratio between nonsynonymous (amino-acid-replacing) and synonymous (silent mutational) substitutions was low, indicating a strong negative selective pressure in the studied regions. Nine negatively selected sites (distributed in Pro-Co, MP, Vp23 and Vp35) and just one positively selected one (in Pro-Co) were found for all the genome regions studied.This work was supported by grants AGL2005-06682-C03-01 from the Spanish Ministry of Education and Science (MEC). We thank the Instituto Agroforestal Mediterraneo (UPV, Valencia) for fellowship support to AAF. We also thank Dr M. Juarez (Universidad Miguel Hernandez, Orihuela) and Dr A. Lacasa (IMI-DA, Murcia) for their advice and assistance in the field surveys. We wish to also thank Bese Gabor (Csongrad Megyei MgSzH) and A. Forray (Floraton Kft.) for providing the Hungarian isolates of ToTV included in this assay.Alfaro Fernández, AO.; Cebrián, M.; Herrera-Vasquez, JA.; Córdoba-Sellés, MC.; Sanchez Navarro, JA.; Jordá, C. (2010). Molecular variability of Spanish and Hungarian isolates of Tomato torrado virus. Plant Pathology. 59(4):785-793. https://doi.org/10.1111/j.1365-3059.2010.02280.x78579359

Genetic structure of the population of Pepino mosaic virus infecting tomato crops in Spain

The population structure of Pepino mosaic virus (PepMV), which has caused severe epidemics in tomato in Spain since 2000, was analyzed. Isolates were characterized by the nucleotide sequence of the triple gene block and coat protein gene and, for a subset of isolates, a part of the RNA-dependent RNA polymerase gene. The full-length sequence of the genomic RNA of a Solanum muricatum isolate from Peru also was determined. In spite of high symptom diversity, the Spanish population of PepMV mostly comprised highly similar isolates belonging to the strain reported in Europe (European tomato strain), which has been the most prevalent genotype in Spain. The Spanish PepMV population was not structured spatially or temporally. Also, isolates highly similar to those from nontomato hosts from Peru (Peruvian strain) or to isolate US2 from the United States (US2 strain) were detected at lower frequency relative to the European strain. These two strains were detected in peninsular Spain only in 2004, but the Peruvian strain has been detected in the Canary Islands since 2000. These results suggest that PepMV was introduced into Spain more than once. Isolates from the Peruvian and US2 strains always were found in mixed infections with the European tomato strain, and interstrain recombinants were detected. The presence of different strains of the virus, and of recombinant isolates, should be considered for the development of control strategies based on genetic resistance

Ultraestructural aspects of tomato leaves single-infected with Tomato torrado virus (ToTV) and co-infected with other tomato viruses

[EN] Optical and electron microscopy studies were carried out to investigate the cytopathology induced in tomato leaves infected by Tomato torrado virus (ToTV), a new picorna-like virus associated with the 'Torrado' disease. Infected leaves, showing typical Torrado disease symptoms were surveyed in commercial greenhouses in the main tomato production areas of Spain. The effect of the co-infection of ToTV with other viruses which commonly infect tomato crops was also studied. Ultra-thin sections of ToTV-infected tomato leaves did not show a strong cellular alteration. However, crystalline arrays of isometric virus-like particles (VLPs) of 20-30 nm in the inclusion bodies were observed in phloem parenchyma cells of the infected tissues. Tissues co-infected by ToTV and either Tomato chlorosis virus (ToCV) or Pepino mosaic virus (PepMV) presented more severe cellular alterations. The most deleterious consequences for tomato cells were found in triple infections of ToTV, PepMV and Tomato spotted wilt virus (TSWV), where characteristic cell wall overgrowth was distinguishable, together with a large amount of necrotic cells.We would like to thank Dr Jesus Sanchez-Navarro and Dr Vicente Pallas for providing the probes to detect ToTV and PMoV, respectively. We also wish to thank Dr Miguel Juarez for collecting samples. This research was supported by grant AGL2005-06682-C03-01 from the Spanish Ministry of Education and Science (MEC, Spain).Alfaro Fernández, AO.; Medina, V.; Córdoba-Sellés, MC.; Font San Ambrosio, MI.; Jornet, J.; Cebrián, MC.; Jordá, C. (2010). Ultraestructural aspects of tomato leaves single-infected with Tomato torrado virus (ToTV) and co-infected with other tomato viruses. Plant Pathology. 59(2):231-239. https://doi.org/10.1111/j.1365-3059.2009.02215.x23123959