Efeito do Soil-borne wheat mosaic virus sobre o metabolismo de cinco genótipos de trigo com diferentes níveis de resistência à doença

Com o objetivo de conhecer as alterações metabólicas promovidas pelo Soil-borne wheat mosaic virus (SBWMV), um dos vírus economicamente mais importantes da cultura do trigo (Triticum aestivum), foram analisados os níveis de proteínas solúveis e determinadas as atividades da peroxidase e da protease em quatro cultivares (BRS Guabiju, BRS 194, BRS 179, BR 23) e uma linhagem (PF 980524) de trigo com diferentes níveis de resistência ao vírus. Os dados obtidos foram submetidos à análise de variância, comparando-se as médias, pelo Teste de Duncan a 5%. Os níveis de proteínas solúveis foram mais elevados nas plantas sem sintomas, enquanto que as atividades da peroxidase e da protease foram maiores em plantas com sintoma de mosaico do que em plantas assintomáticas. Além disso, pode-se constatar que quanto maior a suscetibilidade do genótipo, maior o nível de atividade da protease. Estes resultados são promissores para estudos de inibição da protease para controle de viroses.

Pathogenicity, molecular characterization, and cercosporin content of Brazilian isolates of Cercospora kikuchii

Cercospora kikuchii, involved with the defoliation of soybean (Glycine max) plants, is normally associated with Septoria glycines in late season. Seventy-two isolates from different regions in Brazil, obtained mainly from purple stained seeds, showed phenotypic variation. Cercosporin content and rate of colony growth was higly variable among isolates. A strong correlation between cercosporin content and virulence was identified. Genetic variation among and within populations was evaluated based on 86 RAPD loci. The RAPD analysis clustered all isolates into seven groups. No relationship was observed between RAPD groups and geographic origin or cercosporin content. The sequence of the internal spacer regions (ITS1-5.8S-ITS2) from 13 isolates chosen according to the previous RAPD and clustering analysis showed high similarity (97%-100%) to the GenBank sequences of C. kikuchii (AY266160, AY266161, AY152577 and AF291708). It is clear from this work that Brazilian isolates of C. kikuchii from different geographic regions, are variable in relation to virulence, RAPD profiles and cercosporin content. Cercosporin content could be a good parameter for choosing an adequate isolate for screening resistant or tolerant cultivars. Considering that this pathogen is easily seed-borne, findings are expected to show the same haplotypes in different regions. Migration could be favoured by infected seeds as demonstrated by RAPD analysis.

Immersion enthalpy variation of surface-modified mineral activated carbon in lead (II) aqueous solution adsorption: the relation between immersion enthalpy and adsorption capacity

An activated carbon was obtained by chemical activation with phosphoric acid, CM, from a mineral carbon. Afterwards, the carbon was modified with 2 and 5 molL-1, CMox2 and CMox5 nitric acid solutions to increase the surface acid group contents. Immersion enthalpy at pH 4 values and Pb2+ adsorption isotherms were determined by immersing activated carbons in aqueous solution. The surface area values of the adsorbents and total pore volume were approximately 560 m².g-1 and 0.36 cm³g-1, respectively. As regards chemical characteristics, activated carbons had higher acid sites content, 0.92-2.42 meq g-1, than basic sites, 0.63-0.12 meq g-1. pH values were between 7.4 and 4.5 at the point of zero charge, pH PZC. The adsorbed quantity of Pb2+ and the immersion enthalpy in solution of different pH values for CM activated carbon showed that the values are the highest for pH 4, 15.7 mgg-1 and 27.6 Jg-1 respectively. Pb2+ adsorption isotherms and immersion enthalpy were determined for modified activated carbons and the highest values were obtained for the activated carbon that showed the highest content of total acid sites on the surface.

Harmonical oscillator and electro-mechanical analogy: an interdiscinary experiment to high precision mass variation measurements

In general, the traditional Physics courses needs examples of the aplications of the Physics concepts in other areas such as Chemistry and Biology. This lacks tend to demotivate Chemistry and Biology students regarding to deal with Physical concepts developed in classroom. In this work, the analogy among mechanic and electric oscillators is investigated to be applied in Chemistry and Biology areas, showing to be valuable due to its aplication in techniques that aims to measure mass variation with high precision. This measure could be made in a direct or indirect way. These techniques are known as electrogravimetric techniques and they are important in biosensor aplications. Thus, this paper explores the electromechanic analogy in an interdisciplinary way involving areas like Physics, Chemistry and Biology. Based on this analogy, it is proposed an experiment that can be applied in different ways, i.e. by an basic approach or more deeper, depending on the students specific formation, in other words, Physics, Chemistry or Biology.

Alterações no metabolismo de cinco genótipos de trigo com diferentes níveis de resistência ao Soil-borne wheat mosaic virus

Soil-borne wheat mosaic virus - SBWMV, agente causal da virose que se caracteriza, em termos econômicos, como uma das mais importantes enfermidades da cultura de trigo, pode também infectar uma vasta gama de gramíneas. Com o objetivo de conhecer as alterações metabólicas promovidas pelo mosaico do trigo, foram analisados os teores de açúcares totais e a concentração de prolina e determinou-se a atividade da nitrato redutase. O experimento foi conduzido na área experimental da Embrapa Trigo, usando cinco genótipos de trigo (BRS Guabiju, BRS 194, BRS 179, BR 23 e PF 980524) com diferentes níveis de resistência ao SBWMV. As determinações bioquímicas foram realizadas 45 dias após a emergência de plantas. A atividade da nitrato redutase foi mais elevada em plantas sem sintomas, quando comparada às com sintomas. Os níveis de açúcares e de prolina foram mais elevados em plantas com sintomas do que nas sem sintomas. Os resultados encontrados comprovam as alterações metabólicas promovidas pelo SBWMV nos cinco genótipos de trigo testados.

Obtenção de plantas de feijão-caupi resistentes ao Cowpea severe mosaic virus e ao Cowpea aphid-borne mosaic virus

Dentre os vírus que infectam o feijão-caupi (Vigna unguiculata L. Walp.) destacam-se, respectivamente, pela severidade e ampla ocorrência o Cowpea severe mosaic virus (CPSMV) e o Cowpea aphid-borne mosaic virus (CABMV). Portanto, objetivaram-se, no presente trabalho, obter e avaliar plantas de feijão-caupi com resistência ao CPSMV e ao CABMV, visando ao desenvolvimento de cultivares essencialmente derivadas e novas cultivares. Realizaram-se oito cruzamentos seguidos de retrocruzamentos, utilizando a linhagem TE 97-309G-9 e a cultivar Patativa como genitores resistentes, e as cultivares BR3-Tracuateua, BRS-Urubuquara, BRS-Novaera, BRS-Guariba e Pretinho como genitores suscetíveis. As gerações F2 e F2RC1 foram desafiadas quanto à resistência por meio de inoculação mecânica com isolados do CPSMV e do CABMV. Nas gerações F2RC1, além da resistência foram avaliados os caracteres: número de dias para o início da floração, comprimento das vagens, número de grãos. vagem-1, peso de cem grãos e produção de grãos.planta-1. Todos os indivíduos F2 e F2RC1 foram analisados pelo teste χ² e se ajustaram à frequência esperada de 15 plantas suscetíveis 1 planta resistente a ambos os vírus. As médias das plantas F2RC1 resistentes, de cada retrocruzamento, foram comparadas com a média do seu respectivo genitor recorrente pelo teste 't' e as médias dos retrocruzamentos foram comparadas pelo teste de Scott-Knott. Foi detectada variabilidade genética entre os retrocruzamentos para todos os caracteres. Todos os retrocruzamentos foram considerados promissores para produção de cultivares essencialmente derivadas resistentes ao CPSMV e ao CABMV e as plantas selecionadas possuem características que possibilitam a seleção de linhagens com grãos de bom padrão comercial e altamente produtivas.

VARIATION OF MICROFIBRIL ANGLE OF Pinus radiata D. Don IN RELATION TO TREE SPACING IN CHILEAN PLANTATIONS

ABSTRACTFour stands of 28-year-old radiata pine (Pinus radiata D. Don) grown in the eighth region (Biobio) of Chile were sampled to determine the effect of tree spacing on the microfibril angle. The samples were taken at two different stem levels of the tree, 2.5 m and 7.5 m, with increment strip taken in the Nothern direction. The four experimental stands were characterized by the following spacing 2x2, 2x3, 3x4 and 4x4. The microfibril angle was measured by X-ray diffraction with the SilviScan technology at the FP-Innovation-Paprican Division in Vancouver, Canada. The results showed a significant effect of tree spacing on the microfibril angle in both juvenile wood and mature wood as well as at the two stem levels considered. The minimum (9.42º) was reached in 2x2 stand at 7.5 m in mature wood, while maximum microfibril angle (24.54º) was obtained in 2x3 stand at 2.5 m in juvenile wood. Regarding the effect of tree spacing, 4x4 stand had the lowest microfibril angle,except in mature wood at 7.5 m where 4x4 had the highest microfibril angle (11°) of the four stands.

Determination of the influence of the variation of reducing and non-reducing sugars on coffee quality with use of artificial neural network

The present study aimed at evaluating the use of Artificial Neural Network to correlate the values resulting from chemical analyses of samples of coffee with the values of their sensory analyses. The coffee samples used were from the Coffea arabica L., cultivars Acaiá do Cerrado, Topázio, Acaiá 474-19 and Bourbon, collected in the southern region of the state of Minas Gerais. The chemical analyses were carried out for reducing and non-reducing sugars. The quality of the beverage was evaluated by sensory analysis. The Artificial Neural Network method used values from chemical analyses as input variables and values from sensory analysis as output values. The multiple linear regression of sensory analysis values, according to the values from chemical analyses, presented a determination coefficient of 0.3106, while the Artificial Neural Network achieved a level of 80.00% of success in the classification of values from the sensory analysis.

Floristic and structural variation of weeds in eucalyptus plantations as influenced by relief and time of year

The objective of this work was to analyze the floristic variation and phytosociological structure of weeds as influenced by relief and time of year in eucalyptus plantations in Santana do Paraíso and Guanhães - MG. The total area sampled for each locality was approximately 10 ± 3 hectares, comprising three types of relief: lowland, slope, and upper area. In each type of relief, 10 plots of 1 m² were sampled, corresponding to 30 plots per locality, where they were randomly allocated in a zigzag. The taxonomic identification was performed in four assessments, corresponding to the months of November and March, comprising two ratings each season, always at the same points, and geo-referenced using the Global Positioning System (GPS). A total of 3,893 individuals, 18 families and 61 species, were identified in Santana do Paraiso and a total of 1,166 individuals, 13 families and 58 species, in Guanhães. In both localities, the most representative families in terms of wealth were: Poaceae, Asteraceae, and Fabaceae. Galinsoga parviflora was the most abundant species. The Vernonia polyantes was identified only in the lowlands, while Arrabida florida was identified in the slope and upper area. On the other hand, Emilia coccinea, Sida rhombifolia, S. paniculatum and Spermacoce latifolia were common to all three environments. Commelina benghalensis was present only in the month of March, while G. parviflora was present only in the month of November. It was concluded that the floristic and phytosociological variation of weeds in eucalyptus plantations is influenced by the type of relief and time of year, which should guide the management practices used in the culture.

Fructan variation in the rhizophores of Vernonia herbacea (Vell.) Rusby, as influenced by temperature

The influence of climatic variations on fructan content in tropical regions is not well known. The present study deals with the effects of temperature on fructan contents in rhizophores of plants of Vernonia herbacea, a native species from the Brazilian cerrado vegetation. Intact plants and fragmented rhizophores were subjected to different temperatures under natural and controlled environmental conditions. Rhizophores of plants in pre-dormant stage (aerial parts showing some yellowish leaves) presented higher fructan content at 5oC than those kept at 25oC, whereas in dormant plants (aerial parts absent) temperature treatments did not affect fructan contents. Fragmented rhizophores obtained from dormant plants presented higher levels of fructo-polysaccharides at the end of the experiment than at the beginning of the treatment, regardless of the temperature they were stored, whereas fragments obtained from vegetative plants showed a decrease in fructan content under the same treatments. It was concluded that variations observed in fructan contents are related to the phenological state of the plants prior to the treatment rather than to extraneous temperatures they are subjected to during this stage.

Floristic composition and topographic variation in a tidal floodplain forest in the Amazon Estuary

Slight topographic variations appear to exert dramatic effects on the structure of forests subject to inundation. In a late successional tidal floodplain forest near the Amazon port of Belém, Brazil, we examined these effects by studying floristic composition along a topographic gradient. We predicted that, relative to high sites, low sites would be characterized by high representation of life forms and taxa characteristic of inundated sites. We found striking variations in floristic composition along a slight topographic gradient. In comparison with topographically high sites, low sites were characterized by a high representation of Palm trees (Arecaceae), low diversity of trees and lianas, and high plant density. These variations appear to reflect edaphic limitations imposed by periodic flooding. The high spatial variation in floristic composition found in this ecosystem suggest caution in implementing intensive forms of agriculture.

Distyly and variation in floral traits in natural populations of Psychotria ipecacuanha (Brot.) Stokes (Rubiaceae)

Psychotria ipecacuanha is a perennial, medicinal herb that grows in clusters in the understory of humid, shady areas of the Atlantic Rain Forest of southeastern Brazil. The present study characterized the variation in floral traits among 35 clusters from three natural populations of this plant species. Field observations showed that the clusters are isomorphic, that is, a given cluster will either set long-styled or short-styled flowers. Stigmas and anthers are reciprocally placed in each morph, a dimorphism characteristic of distyly. The populations are isoplethic, that is, a given population exhibits an equilibrium 1:1 ratio of floral morphs. Morphometric analyses revealed that anther length, stigma length, corolla diameter, and pollen grain diameter were consistently greater in short-styled flowers, regardless of the population investigated. Significant differences for floral traits in the short-styled morph were found among populations. Floral traits in the long-styled morph also showed some significant differences among populations, but not for stigma height and corolla length. Controlled pollinations carried out in natural populations showed that fruit production was higher after inter-morph pollination. Nevertheless, observations of pollen tube growth in style, and also fruit production after spontaneous self-pollination and intra-morph pollination, indicated partial intramorph compatibility in this plant species.

Leaf anatomy variation within and between three "restinga" populations of Erythroxylum ovalifolium Peyr: (Erythroxylaceae) in Southeast Brazil

Erythroxylum ovalifolium is a woody shrub widespread in the "restinga", i.e. the open scrub vegetation of the Brazilian coastal sandy plains. We examined leaf anatomy variation of this species both within populations and between populations of three "restingas" in the state of Rio de Janeiro. Sites were ca.100 km far from each other and differed in regard to rainfall and vegetation structure: a dry, open site; a wet, dense site and an intermediate one. Microhabitats within sites were: (i) exposed to full irradiance, outside vegetation islands; (ii) partially exposed to full irradiance, at the border of vegetation islands; (iii) shaded, inside vegetation islands. Leaf anatomy parameters were measured for five leaves collected in each of five plants per microhabitat, in each population; they were thickness of the leaf blade, of the palisade and spongy parenchyma, and of the adaxial and abaxial epidermis. Leaves from the dry, open site had narrower abaxial epidermis and a smaller contribution of spongy parenchyma to total leaf blade thickeness than the other two sites, which we attributed to water stress. Adaxial epidermis and leaf are thicker in more exposed microhabitats (i and ii, above), irrespective of site. We proposed that between-site anatomical variation in traits related to water stress, and within-site anatomical variation in traits related to light-use are indicative of ecological plasticity and might help explain the high abundance of E. ovalifolium in the studied populations and along the State of Rio de Janeiro coast.

Spatial variation in the structure and floristic composition of "restinga" vegetation in southeastern Brazil

We examined large-scale spatial variation of structural parameters and floristic composition in open Clusia scrub, a vegetation type of the Brazilian "restingas" (sandy coastal plain vegetation). This vegetation is organized in islands separated by sandy stretches with sparse herbaceous vegetation. We located 12 sample areas on three consecutive beach ridges, lying parallel to the coastline and at different distances from the ocean, in close proximity to two lagoons (Cabiúnas and Comprida). Each sample area was divided into three strips. We used the line intercept method to sample all woody plants ³ 50 cm tall. We used nested ANOVA to verify structural variation between different sampling scales. TWINSPAN analysis was performed to examine the variation in floristic composition between areas. The overall diversity index was 3.07. Six species are repeatedly dominant throughout the entire sampling area. There was homogeneity in relation to diversity and species richness between beach ridges but not within beach ridges. Floristic composition and structural parameters did not vary in relation to distance from the sea but floristic composition did vary as a function of proximity to Cabiúnas or Comprida lagoon. Differences in plant cover between sample areas may be related to the paleoformation of this sandy coastal plain.