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Brasília, Brazil

Albuquerque L.C.,University of Brasilia | Martin D.P.,University of Cape Town | Avila A.C.,Embrapa Vegetables | Inoue-Nagata A.K.,University of Brasilia
Virus Genes | Year: 2010

Tomato yellow vein streak virus (ToYVSV) is a tentative begomovirus (Family Geminiviridae) species that seriously affects tomato and potato production in Brazil. Here, we have determined the genomic and biological characteristics of a ToYVSV isolate (Ba3) from a potato plant sampled in Rio Grande do Sul State, Brazil. The DNA-A nucleotide sequence of Ba3 and another previously reported ToYVSV isolate share 89.7% sequence identity. These ToYVSV isolates should be classified as a new species in that they are most closely related to Soybean blistering mosaic virus with which they share only ~80% identity. Cloned constructs containing 1.5 mer copies of the ToYVSV genomic components were found, by biolistic bombardment, to be infectious in at least 11 plant species in 2 families (Solanaceae and Malvaceae). Symptoms on tomato and potato plants were identical to those originally observed on field-infected plants. ToYVSV was also sap-transmissible from Nicotiana benthamiana to N. benthamiana and tomato, but not to potato plants. © 2009 Springer Science+Business Media, LLC. Source


de Oliveira A.S.,University of Brasilia | Melo F.L.,University of Brasilia | Inoue-Nagata A.K.,Embrapa Vegetables | Nagata T.,University of Brasilia | And 2 more authors.
PLoS ONE | Year: 2012

Background: Tospoviruses (Genus Tospovirus, Family Bunyaviridae) are phytopathogens responsible for significant worldwide crop losses. They have a tripartite negative and ambisense RNA genome segments, termed S (Small), M (Medium) and L (Large) RNA. The vector-transmission is mediated by thrips in a circulative-propagative manner. For new tospovirus species acceptance, several analyses are needed, e.g., the determination of the viral protein sequences for enlightenment of their evolutionary history. Methodology/Principal Findings: Biological (host range and symptomatology), serological, and molecular (S and M RNA sequencing and evolutionary studies) experiments were performed to characterize and differentiate a new tospovirus species, Bean necrotic mosaic virus (BeNMV), which naturally infects common beans in Brazil. Based upon the results, BeNMV can be classified as a novel species and, together with Soybean vein necrosis-associated virus (SVNaV), they represent members of a new evolutionary lineage within the genus Tospovirus. Conclusion/Significances: Taken together, these evidences suggest that two divergent lineages of tospoviruses are circulating in the American continent and, based on the main clades diversity (American and Eurasian lineages), new tospovirus species related to the BeNMV-SVNaV clade remain to be discovered. This possible greater diversity of tospoviruses may be reflected in a higher number of crops as natural hosts, increasing the economic impact on agriculture. This idea also is supported since BeNMV and SVNaV were discovered naturally infecting atypical hosts (common bean and soybean, respectively), indicating, in this case, a preference for leguminous species. Further studies, for instance a survey focusing on crops, specifically of leguminous plants, may reveal a greater tospovirus diversity not only in the Americas (where both viruses were reported), but throughout the world. © 2012 de Oliveira et al. Source


Nascimento W.M.,Embrapa Vegetables | Huber D.J.,University of Florida | Cantliffe D.J.,University of Florida
Seed Science and Technology | Year: 2013

Carrot (Daucus carota) seed germination and consequently stand establishment may be reduced at temperatures above 35°C. Priming circumvents thermoinhibition in several species, including carrot. Seeds from a thermosensitive population ('07 EC-403', Nunhems) were produced under Florida (USA) field conditions from March to July using artificial vernalised roots. Secondary umbels were labeled at anthesis. At 20, 30 and 40 days after anthesis (DAA), umbels were harvested, dried and manually processed. Part of the seed batch was primed in an aerated polyethylene glycol (PEG) (30%) solution at 15°C for 0, 3, 6 and 9 days, under light. Seed respiration (CO2 production) and germination at 20 and 35°C were evaluated after priming. At 20°C, there was 88, 95 and 95% germination of non-primed seeds from umbels harvested at 20, 30 and 40 DAA, respectively, while at 35°C, there was only 4, 13 and 28% germination, respectively. Seed germination and CO2 production increased in response to seed maturity and soak duration. For example, seeds from umbels harvested at 40 DAA and primed for nine days germinated 98 and 89% at 20 and 35°C, respectively. These seeds also exhibited higher respiration rates. To improve stand establishment, especially during periods of high temperatures, carrot seeds must be primed for a period of nine days. Source


Togni P.H.B.,University of Brasilia | Laumann R.A.,Biological Control | Medeiros M.A.,Embrapa Vegetables | Sujii E.R.,Biological Control
Entomologia Experimentalis et Applicata | Year: 2010

The silverleaf whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), is one of the most important pest insects in tomato crop systems worldwide. It has been previously demonstrated that intercropping tomato [Solanum lycopersicum L. Mill. (Solanaceae)] with coriander [Coriandrum sativum L. (Apiaceae)] reduces the incidence and severity of damage caused by B. tabaci. However, it is not yet known how coriander affects the insect′s behaviour. We evaluated the attractiveness of tomato constitutive volatiles to B. tabaci and what effect coriander constitutive volatiles have on the insect′s behaviour. To this end, we conducted three bioassays in a multiple-choice four-arm olfactometer ('×' type), measuring B. tabaci behaviour when offered tomato and coriander constitutive volatiles presented alone as well as together. We also evaluated the colonisation and establishment of B. tabaci in experimental plots with only single tomato plants and tomatoes intercropped with coriander in a greenhouse. Bemisia tabaci males and females recognised tomato constitutive volatiles as a positive stimulus (kairomonal effect), indicating that semiochemicals from this plant can play an important role in the insect's host plant selection. Coriander constitutive volatiles reduced the attractiveness of tomato volatiles but no repellency to these volatiles was observed. Greater numbers of adults and nymphs of B. tabaci per plant were observed in tomato monoculture plots than in tomato intercropped with coriander. We suggest that coriander constitutive volatiles have an odour masking effect on tomato volatiles, thus interfering in the host plant selection of B. tabaci. © 2010 Agriculture and Agri-Food Canada. Journal compilation © 2010 The Netherlands Entomological Society. Source


Pineli L.L.O.,University of Brasilia | Moretti C.L.,Embrapa Vegetables | Chiarello M.D.,Catholic University of Brasilia
Journal of Food, Agriculture and Environment | Year: 2012

Oxidative stress is a major issue in human health. It is usually associated with an increase in the generation of free radicals and the inability of biological systems to tackle this disequilibrium. Antioxidants from fruits and vegetables are considered an important protection factor against oxidative stress and its deleterious consequences to human health. We evaluated quality and bioactive compounds and antioxidant characteristics of 'Osogrande' and 'Camino Real' strawberries grown in the Brazilian savannah. Strawberries were harvested, selected, graded and stored at 5°C and 15°C for eight days. Berries were evaluated for vitamin C, total phenolic compounds, total anthocyanins, total ellagic acid, antioxidant activity by DPPH and FRAP assays, decay, mass loss, color, soluble solids and total titratable acidity. An increase in total phenolic compounds content ranging from 64% to 79% was observed for both cultivars at both temperatures between the fourth and the sixth days. 'Camino Real' strawberries showed higher contents at 15°C in the sixth day of the experiment. 'Osogrande' strawberries had the highest concentrations of total ellagic acid. Vitamin C content increased in all treatments when berries were stored at 15°C. No significant changes in antioxidant activity assayed by DPPH were observed for 'Osogrande' strawberries stored at 5°C. Antioxidants of strawberries were comparable to those of fruit grown in other locations. After 2 days of storage only 'Camino Real' strawberries at 5°C presented acceptable (>3.0) quality index. For fruits stored at 5°C, decay was dramatically observed between the second and the fourth storage days, when 32% and 40% of 'Osogrande' and 'Camino Real' fruit surfaces were affected, respectively. Firmness of 'Camino Real' strawberries was approximately 2 times higher than 'Osogrande' fruits throughout the experimental period. Titratable acidity in 'Camino Real' strawberries decreased 19.5% and 17.4% after eight days at 5°C and 15°C, respectively. For 'Osogrande' fruits hue angle increased after four days, indicating a decrease in redness. Chroma did not change during storage time for both cultivars. The results of this study showed that antioxidant variables were not good markers of strawberry quality, given that they were positively related to decay variables. Source

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