Showing papers by "Universidade Federal de Viçosa published in 2008"

Geminivirus strain demarcation and nomenclature

Abstract: Geminivirus taxonomy and nomenclature is growing in complexity with the number of genomic sequences deposited in sequence databases Taxonomic and nomenclatural updates are published at regular intervals (Fauquet et al in Arch Virol 145:1743–1761, 2000, Arch Virol 148:405–421, 2003) A system to standardize virus names, and corresponding guidelines, has been proposed (Fauquet et al in Arch Virol 145:1743–1761, 2000) This system is now followed by a large number of geminivirologists in the world, making geminivirus nomenclature more transparent and useful In 2003, due to difficulties inherent in species identification, the ICTV Geminiviridae Study Group proposed new species demarcation criteria, the most important of which being an 89% nucleotide (nt) identity threshold between full-length DNA-A component nucleotide sequences for begomovirus species This threshold has been utilised since with general satisfaction More recently, an article has been published to clarify the terminology used to describe virus entities below the species level [5] The present publication is proposing demarcation criteria and guidelines to classify and name geminiviruses below the species level Using the Clustal V algorithm (DNAStar MegAlign software), the distribution of pairwise sequence comparisons, for pairs of sequences below the species taxonomic level, identified two peaks: one at 85–94% nt identity that is proposed to correspond to “strain” comparisons and one at 92–100% identity that corresponds to “variant” comparisons Guidelines for descriptors for each of these levels are proposed to standardize nomenclature under the species level In this publication we review the status of geminivirus species and strain demarcation as well as providing updated isolate descriptors for a total of 672 begomovirus isolates As a consequence, we have revised the status of some virus isolates to classify them as “strains”, whereas several others previously classified as “strains” have been upgraded to “species” In all other respects, the classification system has remained robust, and we therefore propose to continue using it An updated list of all geminivirus isolates and a phylogenetic tree with one representative isolate per species are provided

Influência do tempo de incubação e do tamanho de partículas sobre os teores de compostos indigestíveis em alimentos e fezes bovinas obtidos por procedimentos in situ

Abstract: The aim of this work was to evaluate the effects of in situ incubation time and particles size on the estimates of indigestible fractions of dry matter (iDM), neutral detergent fiber (iNDF), and acid detergent fiber (iADF) in cattle feeds and feces. Samples of corn grain, wheat bran, corn silage, elephant grass, sugarcane, signal grass hay, corn straw, and feces obtained from cattle fed high and low concentrate diets were used. The samples were ground through 1 mm, 2 mm, and 3 mm screen sieve and put in 4 × 5 cm non-woven textile bags (20 mg DM/cm² of surface). The samples were divided in three groups, being each group incubated in the rumen of a crossbred heifer. The incubation procedure was conducted three times with the change of groups among animals. The following incubation times were used: 0, 12, 24, 48, 72, 96, 120, 144, 168, 192, 216, 240, and 312 hours. The contents of iDM, iNDF, and iADF were evaluated sequentially in each bag. The degradation profiles were interpreted by a non-linear logistic model. The particles size did not influence the estimates of iNDF and iADF. However, the particles size altered the rumen degradation dynamic rates of DM for corn silage and corn grain; of NDF for sugarcane, corn silage, and corn straw; and ADF for sugarcane. For those samples, the particle size has been positively associated with the incubation time necessary to estimate the indigestible fraction. Incubation times of 240 hours for DM and NDF, and 264 hours for ADF were suggested for obtaining more accurate estimates of indigestible fractions. The use of 2 mm particle size can increase the precision of estimates.

Prospects and risks of the use of castor oil as a fuel

Abstract: Castor oil is more than just a raw material in great demand by the pharmaceutical and chemical industries. In several southern countries its use as a fuel is also being discussed in connection with social and ecological aspects. A few properties, in particular the extremely high viscosity and high water content, complicate the use of straight castor oil as a fuel for internal combustion engines. A better perspective may be possible by transesterification and the addition of this biodiesel to fossil diesel fuel. This, however, calls for considerably lower castor oil prices than are at present being paid on the world market.

Using neural networks and cellular automata for modelling intra-urban land-use dynamics

Abstract: Empirical models designed to simulate and predict urban land-use change in real situations are generally based on the utilization of statistical techniques to compute the land-use change probabilities. In contrast to these methods, artificial neural networks arise as an alternative to assess such probabilities by means of non-parametric approaches. This work introduces a simulation experiment on intra-urban land-use change in which a supervised back-propagation neural network has been employed in the parameterization of several biophysical and infrastructure variables considered in the simulation model. The spatial land-use transition probabilities estimated thereof feed a cellular automaton (CA) simulation model, based on stochastic transition rules. The model has been tested in a medium-sized town in the Midwest of Sao Paulo State, Piracicaba. A series of simulation outputs for the case study town in the period 1985-1999 were generated, and statistical validation tests were then conducted for the best results, based on fuzzy similarity measures.

Recommendations for the classification and nomenclature of the DNA-β satellites of begomoviruses

Abstract: The symptom-modulating, single-stranded DNA satellites (known as DNA-β) associated with begomoviruses (family Geminiviridae) have proven to be widespread and important components of a large number of plant diseases across the Old World. Since they were first identified in 2000, over 260 full-length sequences (∼1,360 nucleotides) have been deposited with databases, and this number increases daily. This has highlighted the need for a standardised, concise and unambiguous nomenclature for these components, as well as a meaningful and robust classification system. Pairwise comparisons of all available full-length DNA-β sequences indicate that the minimum numbers of pairs occur at a sequence identity of 78%, which we propose as the species demarcation threshold for a distinct DNA-β. This threshold value divides the presently known DNA-β sequences into 51 distinct satellite species. In addition, we propose a naming convention for the satellites that is based upon the system already in use for geminiviruses. This maintains, whenever possible, the association with the helper begomovirus, the disease symptoms and the host plant and provides a logical and consistent system for referring to already recognised and newly identified satellites.

Land use, habitat integrity, and aquatic insect assemblages in Central Amazonian streams

Abstract: The distribution and composition of aquatic insect communities in streams at a local scale are considered to be primarily determined by environmental factors and interactive relationships within the system. Here, we evaluated the effects of forest fragmentation and forest cover changes on habitat characteristics of streamlets (igarapes) in Amazonian forests and on the aquatic insect communities found there. We also developed a habitat integrity index (HII) based on Petersen’s protocol (1992) to evaluate physical integrity of these streamlets and to determine its efficiency to interpret the environmental impacts on this system. We studied 20 small streams at the Biological Dynamics of Forest Fragments Project (BDFFP INPA/SI) study areas, Central Amazonia, 80 km north of Manaus, Amazonas State, Brazil. The vegetation cover was estimated by using LANDSAT images and classified in the following categories: exposed soil, pastures, secondary forests (capoeiras), and primary forests. Stream habitat features were evaluated by using a HII based on visual assessment of local characteristics. Aquatic insects were sampled in four major stream substrates: litter deposited in pools or backwaters, litter retained in riffles, sand, and marginal banks. Stream habitat characteristics were significantly correlated to land use and riparian forest condition. Overall aquatic insect richness and Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness were significantly lower in pasture streams, and their taxonomic composition differed significantly from streams in forested areas. However, these metrics were not significantly correlated to the stream HII. Taxonomic composition of bank insect assemblages changed significantly between streams with low and high values of HII. There was no significant relationship between the proportion of primary forest cover and the faunal metrics. Only drastic changes in the vegetal cover seem to induce significant changes in the aquatic insect community. Matrix habitat heterogeneity, distance to forest fragments, the presence of areas of secondary forest, and the intrinsic capacity to disperse in many of the insect groups may have contributed to attenuate the effects of habitat disturbance on aquatic insect assemblages in streamlets.

Teor e acúmulo de nutrientes em folhas e frutos de pinhão-manso

Abstract: Knowledge about the nutritional demand of a crop is essential for fertilizer recommendation. In this study nutrient concentration and accumulation in leaves and fruits of Jatropha curcas L. were measured and nutrient extraction by fruits harvested between the 1st and 4th year of cultivation were estimated. The study was carried out at the Paraiso Farm, iin Vicosa, Minas Gerais State. Four leaf and fruit samples, each one containing 15 leaves or 20 fruits were randomly collected from an area with 6.000 Jatropha curcas L. trees, all planted in April 2006, at a spacing of 4 x 2 m. Expanded leaves between the 6th and 8th leaf below the inflorescence were collected for analysis. Only normal leaves (without signs of nutritional deficiency, insect attack and/or diseases) were used. Fruits were collected at maturity (yellow husk). The sampled leaves and fruits were washed, dried, weighed, and had their nutrient content analyzed. The nutrient concentration in Jatropha curcas L. leaves were ranked in the following order: N > Ca > K > Mg > P > S > Mn > Fe > B > Zn > Cu; and in the fruits the order was: N > K > Ca > P > Mg > S > Mn > Fe > B > Zn > Cu. The N/K ratio was 2.3 in the leaves and 1.4 in fruits, which indicates that K requirements increase when the plant begins fruit production. Although P is only the 4th (in fruits) and the 5th (in leaves) most demanded nutrient by the crop, it should be supplied in higher amounts than those accumulated in leaves and fruits due to soil adsorption. This study suggests that high nutrient amounts are extracted at Jatropha curcas L. harvest, thus the crop requires adequate fertilization to avoid soil exhaustion along the successive cultivation years.

Simulating the surface waters of the Amazon River basin: impacts of new river geomorphic and flow parameterizations

Abstract: This paper describes the impacts of new river geomorphic and flow parameterizations on the simulated surface waters dynamics of the Amazon River basin. Three major improvements to a hydrologic model are presented: (1) the river flow velocity equation is expanded to be dependent on river sinuosity and friction in addition to gradient forces; (2) equations defining the morphological characteristics of the river, such as river height, width and bankfull volume, are derived from 31 622 measurements of river morphology and applied within the model; (3) 1 km resolution topographic data from the Shuttle Radar Topography Mission (SRTM) are used to provide physically based fractional flooding of grid cells from a statistical representation of sub-grid-scale floodplain morphology. The discharge and floodplain inundation of the Amazon River is simulated for the period 1968–1998, validated against observations, and compared with results from a previous version of the model. These modifications result in considerable improvement in the simulations of the hydrological features of the Amazon River system. The major impact is that the average wet-season flooded area on the Amazon mainstem for the period 1983–1988 is now within 5% of satellite-derived estimates of flooded area, whereas the previous model overestimates the flooded area by about 80%. The improvements are a consequence of the new empirical river geomorphologic functions and the SRTM topography. The new formulation of the flow velocity equation results in increased river velocity on the mainstem and major tributaries and a better correlation between the mean monthly simulated and observed discharge. Copyright © 2007 John Wiley & Sons, Ltd.

Allometric models for non-destructive leaf area estimation in coffee (Coffea arabica and Coffea canephora)

Abstract: We aimed to evaluate the currently used allometric models, as well as to propose a reliable and accurate model using non-destructive measurements of leaf length (L) and/or width (W), for estimating the area of leaves of eight field-grown coffee cultivars. For model construction, a total of 1563 leaves were randomly selected from different levels of the tree canopies and encompassed the full spectrum of measurable leaf sizes (0.3-263 cm 2 ) for each genotype. Power models better fit coffee leaf area (LA) than linear models. To validate the model, an independent data set of 388 leaves was used. We demonstrated that the currently used allometric models are biased, underestimating the area of a coffee leaf. We developed a single power model (Y =β 0 x β 1) based on two leaf dimensions [LA = 0.6626 (LW) 1.0116 ; standard errors: β 0 = 0.0064, β 1 = 0.0019; R 2 = 0.996] with high precision and accuracy, random dispersion pattern of residuals and also unbiased, irrespective of cultivar and leaf size and shape. Even when the L (but not width) alone was used as the single leaf dimension, the power model developed still predicted with good accuracy the LA but at the expense of some loss of precision, as particularly found for 8% of the leaves sampled with length-to-width ratios below 2.0 or above 3.0.

Composition and antifungal activity of the essential oil of the Brazilian Chenopodium ambrosioides L.

Abstract: The antifungal activity of essential oil (EO) from the Brazilian epazote (Chenopodium ambrosioides L.) was evaluated by the poison food assay at concentrations of 0.3%, 0.1%, and 0.05% with eight postharvest deteriorating fungi (Aspergillus flavus, Aspergillus glaucus, Aspergillus niger, Aspergillus ochraceous, Colletotrichum gloesporioides, Colletotrichum musae, Fusarium oxysporum, and Fusarium semitectum). EO components were tentatively identified by Kovats retention indices (RIs) using gas chromatography and gas chromatography combined with mass spectrometry (GC-MS). Growth of all fungi was completely inhibited at 0.3% concentration, and by 90% to 100% at 0.1% concentration. The following 13 tentatively identified compounds (relative percent) accounted for 90.4% of the total volatile oil: α-terpinene (0.9), p-cymene (2.0), benzyl alcohol (0.3), p-cresol (0.3), p-mentha-1,3,8-triene (0.2), p-cimen-8-ol (0.6), α-terpineol (0.5), (Z)-ascaridole (61.4), piperitone (0.9), carvacrol (3.9), (E)-ascaridole (18.6), (E)-piperitol acetate (0.5), and (Z)-carvyl acetate (0.3). Autobiographic thin layer chromatography of the EO to separate the principal fungitoxic fraction yielded only one fraction that completely inhibited the growth of all test fungi at a concentration of 0.1%. This fraction was characterized by RIs and GC-MS presenting a composition (%) of p-cymene (25.4), (Z)-ascaridole (44.4), and (E)-ascaridole (30.2). The results suggest ascaridoles were the principal fungitoxic components of the EO.

Regulated nuclear trafficking of rpL10A mediated by NIK1 represents a defense strategy of plant cells against virus.

Abstract: The NSP-interacting kinase (NIK) receptor-mediated defense pathway has been identified recently as a virulence target of the geminivirus nuclear shuttle protein (NSP). However, the NIK1–NSP interaction does not fit into the elicitor–receptor model of resistance, and hence the molecular mechanism that links this antiviral response to receptor activation remains obscure. Here, we identified a ribosomal protein, rpL10A, as a specific partner and substrate of NIK1 that functions as an immediate downstream effector of NIK1-mediated response. Phosphorylation of cytosolic rpL10A by NIK1 redirects the protein to the nucleus where it may act to modulate viral infection. While ectopic expression of normal NIK1 or a hyperactive NIK1 mutant promotes the accumulation of phosphorylated rpL10A within the nuclei, an inactive NIK1 mutant fails to redirect the protein to the nuclei of co-transfected cells. Likewise, a mutant rpL10A defective for NIK1 phosphorylation is not redirected to the nucleus. Furthermore, loss of rpL10A function enhances susceptibility to geminivirus infection, resembling the phenotype of nik1 null alleles. We also provide evidence that geminivirus infection directly interferes with NIK1-mediated nuclear relocalization of rpL10A as a counterdefensive measure. However, the NIK1-mediated defense signaling neither activates RNA silencing nor promotes a hypersensitive response but inhibits plant growth and development. Although the virulence function of the particular geminivirus NSP studied here overcomes this layer of defense in Arabidopsis, the NIK1-mediated signaling response may be involved in restricting the host range of other viruses.

The importance of termites (Isoptera) for the recycling of herbivore dung in tropical ecosystems: a review

Abstract: While the key role of termites in the decomposition of litter in the tropics has been acknowledged for a long time, much less information exists on their importance in the recycling of dung of primary consumers, especially herbivores. A review of published studies shows that a diverse group of termites (at least 126 species) has been reported to feed on a wide range of mammalian dung (18 species). Predominantly, wood-feeding and polyphagous wood-litter feeding species were found to feed also frequently on dung. Moreover, we found that termites can quickly remove large amounts of mammalian dung, especially in the dry season, when on average about 1/3 of the dung deposited in a given habitat is removed by termites within one month (with the highest rates observed in savannas). No distinctive preference for mammalian dung over other organic food sources was observed for fungus-growing termites (Macrotermitinae), whereas the majority of the non-fungus growing taxa studied prefer dung over other food. As termites bring large quantities of dung below the soil surface, disturb and enrich soils with nutrients, dung feeding by termites appears to be a previously underestimated process important in the functioning of tropical ecosystems.

Esterification of Oleic Acid for Biodiesel Production Catalyzed by SnCl2: A Kinetic Investigation

Abstract: Abiney L Cardoso, Soraia Cristina Gonzaga Neves and Marcio J da Silva * Departament of Chemistry, Federal University of Vicosa, Vicosa, Minas Gerais, Brazil, 36570-000 * Author to whom correspondence should be addressed; E-Mail:silvamj2003@ufvbr Received: 5 August 2008; in revised form: 16 September 2008 / Accepted: 17 September 2008 / Published: 24 September 2008 Abstract: The production of biodiesel from low-cost raw materials which generally contain high amounts of free fatty acids (FFAs) is a valuable alternative that would make their production costs more competitive than petroleum-derived fuel Currently, the production of biodiesel from this kind of raw materials comprises a two-stage process, which requires an initial acid-catalyzed esterification of the FFA, followed by a base-catalyzed transesterification of the triglycerides Commonly, the acid H

Development and Evaluation of Active Packaging for Sliced Mozzarella Preservation

Abstract: Antimicrobial films were formed by the incorporation of nisin (NI), natamycin (NA) and a combination of both (NI + NA) into cellulose polymer. Film efficacies were evaluated in vitro against Staphylococcus aureus ATCC 6538, Listeria monocytogenes ATCC 15313, Penicillium sp. and Geotrichum sp. The films were also evaluated on sliced mozzarella cheese against moulds and yeasts, Staphylococcus sp. and psychrotrophic bacteria. Mechanical and microscopic properties of the films and the diffusion of the antimicrobial agents from the film to the cheese were also evaluated. Films containing NI showed an antimicrobial effect in vitro against S. aureus and L. monocytogenes, while films containing NA were effective in vitro against Penicillium sp. and Geotrichum sp. By the ninth day of storage at 12 ± 2°C, the count of yeasts and moulds on cheese covered with films containing NA decreased 2 log10 units compared with the count on cheese with control films. NI film did not show an effect against Staphylococcus sp., but it was effective against psychrotrophic bacteria for 6 days of storage of the cheese. The incorporation of antimicrobial compounds decreased the resistance and elongation of the films and caused changes in their molecular conformation. NI diffusion from the films to the cheese was not detected; however, time-dependent diffusion of NA from the film containing NI + NA was measured. The incorporation of NI and NA together in the films did not show an effect. The film containing NA showed potential for application as active food packaging for sliced mozzarella cheese. Copyright © 2008 John Wiley & Sons, Ltd.

Evaluation of the Chemical Composition of Brazilian Commercial Cymbopogon citratus (D.C.) Stapf Samples

Abstract: The concentration and the chemical composition of the essential oils obtained from different samples of Cymbopogon citratus were evaluated. Among the 12 samples investigated (11 dried leaf samples and fresh plant leaves), seven presented essential oil concentrations within the threshold established by the Brazilian legislation. The moisture content was also determined and the majority of the samples presented humidity contents near 12%. The GC and GC/MS analyses of the essential oils led to identification of 22 compounds, with neral and geranial as the two major components. The total percentage of these two compounds varied within the investigated sample oils from 40.7% to 75.4%. In addition, a considerable variation in the chemical composition of the analyzed samples was observed. The process of grinding the leaves significantly decreased (by up to 68%) the essential oil content, as well as the percentage of myrcene in the oils.

Six novel begomoviruses infecting tomato and associated weeds in Southeastern Brazil.

Abstract: The incidence of tomato-infecting begomoviruses has sharply increased in Brazil following the introduction of the B biotype of the whitefly vector in the early 1990s. Five definitive species and six tentative species have been described since then. Here, we report the detection of members of an additional six novel species, three in tomato and three infecting weeds that are commonly associated with tomato fields: Blainvillea rhomboidea, Sida rhombifolia and Sida micrantha. Tomato and weed samples were collected in two major tomato-growing regions of southeastern Brazil in 2005 and 2007. Two of the novel viruses were present in tomato plants collected in Paty do Alferes, Rio de Janeiro state. Three novel viruses were present in weed samples collected in Coimbra, Minas Gerais state. One virus was present in tomato samples collected at both locations. Genome features indicate that all six species are typical New World, bipartite begomoviruses. However, the viruses belonging to two of the novel species did not cluster with the Brazilian viruses in a phylogenetic tree. These species could represent a distinct lineage of New World begomoviruses, found in Brazil for the first time.

Plantas medicinais utilizadas pela população atendida no "Programa de Saúde da Família", Governador Valadares, MG, Brasil

Abstract: This study was conducted to evaluate the use of medicinal plants by the population assisted by the "Programa de Saude da Familia" in Governador Valadares -MG, in order to rescue, preserve and use this knowledge in works carried out with the community. The preestablished questionnaire methodology was used. Those questionnaires were applied by the Family Health Agents. The study was accomplished in 27 residential quarters, as being applied 2454 questionnaires, and 232 plants were mentioned as medicinal ones by the interviewed population. The main indications for using the medicinal plants were: as sedative (10%), against influenza (18%) and infections (9%). Most plants under use are prepared as tea (78%) and are obtained in own cropping (57%). In general, the knowledge on the use and preparation of the medicinal plants proceeded from their relatives (67%). Most mentioned and popularly used species have pharmacological activity already proven in the literature. However, this population needs a correct orientation on their cropping and therapeutic use.

Parasitoid Increases Survival of Its Pupae by Inducing Hosts to Fight Predators

Abstract: Many true parasites and parasitoids modify the behaviour of their host, and these changes are thought to be to the benefit of the parasites. However, field tests of this hypothesis are scarce, and it is often unclear whether the host or the parasite profits from the behavioural changes, or even if parasitism is a cause or consequence of the behaviour. We show that braconid parasitoids (Glyptapanteles sp.) induce their caterpillar host (Thyrinteina leucocerae) to behave as a bodyguard of the parasitoid pupae. After parasitoid larvae exit from the host to pupate, the host stops feeding, remains close to the pupae, knocks off predators with violent head-swings, and dies before reaching adulthood. Unparasitized caterpillars do not show these behaviours. In the field, the presence of bodyguard hosts resulted in a two-fold reduction in mortality of parasitoid pupae. Hence, the behaviour appears to be parasitoid-induced and confers benefits exclusively to the parasitoid.

In field‐grown coffee trees source–sink manipulation alters photosynthetic rates, independently of carbon metabolism, via alterations in stomatal function

Abstract: Perturbations of the source-sink balances were performed in field-grown coffee (Coffea arabica) trees to investigate the possible role of carbohydrates in feedback regulation of photosynthesis. Four treatments were applied at the whole-plant level: (i) complete defruiting and maintenance of the full leaf area, (ii) the half crop load and full leaf area, (iii) the full crop load and full leaf area and (iv) the full crop load and half leaf area. Sampling and measurements were performed twice during the phase of dry matter accumulation of fruits. Gas exchange, chlorophyll a fluorescence, carbon isotope labelling and steady-state metabolite measurements were assessed in source leaves. The average rate of net photosynthetic rate (A) and stomatal conductance (g(s)) were larger (> 50%), and carbon isotope composition ratio was lower, in trees with a full crop load and half leaf area than in defruited trees, with individuals of the other two treatments showing intermediate values. However, differences in A seem unlikely to have been caused either by photochemical impairments or a direct end-product-mediated feedback down-regulation of photosynthesis. It is proposed that the decreased A in defruited coffee trees was independent of carbon metabolism and was rather directly related to a lower CO(2) availability coupled to lower g(s).