Impacto do aumento da concentração de CO2 do ar sobre a cercosporiose do cafeeiro.

A concentração de gases do efeito estufa está aumentando consideravelmente desde a revolução industrial, especialmente o dióxido de carbono (CO2). As previsões mais otimistas prevêem o aumento na concentração deste gás para 550 ppm até o final do século. Essa alteração pode ser benéfica para algumas plantas, porém há poucos estudos analisando os efeitos sobre os problemas fitossanitários. O Brasil é o maior produtor de café do mundo. Uma doença que reduz a produção dessa cultura é a cercosporiose, causada pelo fungo Cercospora coffeicola Berkeley & Cooke. Não há informações sobre os impactos das mudanças climáticas sobre essa doença. O objetivo deste trabalho foi avaliar o desenvolvimento da cercosporiose em diferentes concentrações de CO2, em experimento conduzido em estufas de topo aberto (opentop chambers - OTC) com concentração de 390 (ar ambiente) e 550 ppm de CO2. Para avaliação da doença, foram feitas inspeções semanais do número de folhas lesionadas e número de lesões por folha lesionada. As folhas com sintomas foram fotografadas para análise da porcentagem de área foliar lesionada utilizando o software Assess 2.0. Também foi calculada a área abaixo da curva de progresso da doença (AACPD). Os resultados mostraram que não houve diferença significativa na incidência e na severidade da doença entre os diferentes tratamentos

Eradication of Ralstonia solanacearum from tomato growth substrate using a solar collector.

Bacterial wilt caused by Ralstonia solanacearum constitutes one of the most difficult diseases to control. The use of disinfested substrates is important for the production of disease-free seedlings and prevents the dissemination of this pathogen. An equipment was developed at Embrapa Environment, in Brazil, aiming to disinfest substrates with solar radiation. The solar collector is efficient to control several fungal plant pathogens, including species of Fusarium, Pythium, Rhizoctonia, Sclerotium, Sclerotinia, Phytophthora, as well as nematodes such as Meloydogyne (1, 2), after the treatment of the substrate during only one sunny day. The purpose of this work was to determine the efficacy of the solar collector for the control of the bacterial wilt caused by R. solanacearum

Estimation of Molecular Pairwise Relatedness in Autopolyploid Crops

A suitable pairwise relatedness estimation is key to genetic studies. Several methods are proposed to compute relatedness in autopolyploids based on molecular data. However, unlike diploids, autopolyploids still need further studies considering scenarios with many linked molecular markers with known dosage. In this study, we provide guidelines for plant geneticists and breeders to access trustworthy pairwise relatedness estimates. To this end, we simulated populations considering different ploidy levels, meiotic pairings patterns, number of loci and alleles, and inbreeding levels. Analysis were performed to access the accuracy of distinct methods and to demonstrate the usefulness of molecular marker in practical situations. Overall, our results suggest that at least 100 effective biallelic molecular markers are required to have good pairwise relatedness estimation if methods based on correlation is used. For this number of loci, current methods based on multiallelic markers show lower performance than biallelic ones. To estimate relatedness in cases of inbreeding or close relationships (as parent-offspring, full-sibs, or half-sibs) is more challenging. Methods to estimate pairwise relatedness based on molecular markers, for different ploidy levels or pedigrees were implemented in the AGHmatrix R package

Textures and Newtonian Gravity

Newtonian theory is used to study the gravitational effects of a texture, in particular the formation of massive structures.Comment: 4 pages, 4 ps figures, REVTEX, accepted for publication in PR

Aspects of Magnetic Field Configurations in Planar Nonlinear Electrodynamics

In the framework of three-dimensional Born-Infeld Electrodynamics, we pursue an investigation of the consequences of the space-time dimensionality on the existence of magnetostatic fields generated by electric charges at rest in an inertial frame, which are present in its four-dimensional version. Our analysis reveals interesting features of the model. In fact, a magnetostatic field associated with an electric charge at rest does not appear in this case. Interestingly, the addition of the topological term (Chern-Simons) to Born-Infeld Electrodynamics yields the appearance of the magnetostatic field. We also contemplate the fields associated to the would-be-magnetic monopole in three dimensions.Comment: 8 page

Remarks on Screening in a Gauge-Invariant Formalism

In this paper we display a direct and physically attractive derivation of the screening contribution to the interaction potential in the Chiral Schwinger model and generalized Maxwell-Chern-Simons gauge theory. It is shown that these results emerge naturally when a correct separation between gauge-invariant and gauge degrees of freedom is made. Explicit expressions for gauge-invariant fields are found.Comment: 13 pages, 1 figure, to appear in PR