Efeito da radiação ultravioleta-B sobre a germinação de conídios de Botrytis cinerea e colonização em discos de morango.

RESUMO: O ultravioleta é um fator de grande impacto na agricultura e está intimamente relacionado à camada de ozônio, a qual vem sendo reduzida paulatinamente, em consequência das atividades antrópicas. A camada de ozônio está sendo degradada, principalmente, por ação dos clorofluorcarbonos (CFC) utilizados pelo homem alterando assim a intensidade de radiação ultravioleta na superfície terrestre em especial no comprimento de onda da radiação ultravioleta B (UV-B). O objetivo do trabalho foi avaliar a resistência de conídios de Botrytis cinerea à radiação UV-B. Foram testados 13 isolados do patógeno, onde uma suspensão contendo 105 conídios mL-1 de cada isolado foi preparada e uma alíquota de 20 ?L foi colocada no centro de uma placa de Petri contendo BDA. Os conídios foram expostos à radiação UV-B 5,6 kJ m-2 a uma irradiância de 823 mW m-2. Também foi avaliada a esporulação de B. cinerea em discos de folha de morangueiro em meio de cultura paraquat-clorofenicolágar (PCA). Os isolados apresentaram germinação relativa entre 15% e 90%, sendo que os isolados com maior resistência à radiação UV-B foram o LQC 162, LQC 150 e LQC 159. No teste da esporulação foi observado maior diferenças entre os isolados quanto a formação de conidióforos do patógeno sendo os isolados LQC 150 e LQC 157 superiores aos outros isolados. Foi selecionado o isolado LQC 150 para ensaios posteriores onde será comparada a tolerância desse isolado com isolados de agentes de controle biológico deste patógeno quanto a tolerância a radiação UV-B

Avaliação agronômica de oito genótipos de Sisal (agave ssp.).

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Sistema de produção de leite a pasto com rebanho mestiço: 25 anos de informações.

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Learning about knowledge: A complex network approach

This article describes an approach to modeling knowledge acquisition in terms of walks along complex networks. Each subset of knowledge is represented as a node, and relations between such knowledge are expressed as edges. Two types of edges are considered, corresponding to free and conditional transitions. The latter case implies that a node can only be reached after visiting previously a set of nodes (the required conditions). The process of knowledge acquisition can then be simulated by considering the number of nodes visited as a single agent moves along the network, starting from its lowest layer. It is shown that hierarchical networks, i.e. networks composed of successive interconnected layers, arise naturally as a consequence of compositions of the prerequisite relationships between the nodes. In order to avoid deadlocks, i.e. unreachable nodes, the subnetwork in each layer is assumed to be a connected component. Several configurations of such hierarchical knowledge networks are simulated and the performance of the moving agent quantified in terms of the percentage of visited nodes after each movement. The Barab\'asi-Albert and random models are considered for the layer and interconnecting subnetworks. Although all subnetworks in each realization have the same number of nodes, several interconnectivities, defined by the average node degree of the interconnection networks, have been considered. Two visiting strategies are investigated: random choice among the existing edges and preferential choice to so far untracked edges. A series of interesting results are obtained, including the identification of a series of plateaux of knowledge stagnation in the case of the preferential movements strategy in presence of conditional edges.Comment: 18 pages, 19 figure

Response surface applied to mixtures of castor bean hull and presscake for organic fertilization of castor bean plants

Castor bean presscake and hull are the two sub-products resulting from the extraction of castor bean oil. Their use as organic fertilizers has aroused interest of producers who wish to aggregate value to these products and use them rationally. The growth of castor bean plants of the BRS Energia cultivar in substrates composed of mixtures of two organic materials (castor bean presscake and hull) associated to soil was evaluated in this paper. The experiment was carried out at the Embrapa Algodão greenhouse, in the city of Campina Grande, in Paraíba, Brazil, from February 2010 to June 2010. Five treatments with four replications were evaluated. The treatments were composed of soil, varying from 80 to 100%, and castor bean hull and presscake varying from 0 to 10%. In order to identify the best mixture to promote growth of the plants, the extreme-vertices experimental design was used in a simplex sub-region, due to the restrictions of some components of the mixture. The classification of the best mixture was made based on the following variables: plant height, leaf area, and total dry weight of the plant. These measurements were evaluated by mixture modeling, performed in the MATLAB® computer system. For all of the analyzed variables, the best mixture was composed of 10% of castor bean presscake, 10% of castor bean hull, and 80% of soil

Yield and quality of seeds of lettuce genotypes produced under organic management.

Lettuce is one of the main vegetable species used in organic production. However, studies and research in the organic area are scarce. This study aimed to evaluate the yield and quality of seeds of lettuce genotypes produced in two consecutive years under an organic management system. Two plantations were installed under open field conditions corresponding to autumn/winter in 2016 and 2017. Ten lettuce genotypes were evaluated in four replications using a biofertilizer made from swine manure in the management and manual harvesting of seeds. Evaluations consisted of seed yield (in kg.ha−1), physical test (1000-seed weight), and germination and vigor test (first germination count, germination rate index, and seedling dry matter). The genotype Cubana and two Grand Rapids had higher yields under the tested conditions. Higher seed weights were recorded in 2017. Both genotypes Grand Rapids reached the minimum germination standard established for commercialization (80%). Vanda and AC 5058 showed a better performance for germination rate index and first germination count, while Cinderela had a better seedling dry matter. These varieties were promising for organic cultivation

Bicudo e lagarta-rosada em algodoeiros no sertão sergipano.

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Comunidade de plantas daninhas em relação à distância de renque de eucalipto em sistema de ilpf em Mato Grosso.

Em Mato Grosso vem crescendo de forma exponencial as áreas com sistemas de integração, sendo os dois principais tipos a integração lavoura-pecuária (ILP) e a integração lavoura-pecuária-floresta (ILPF). Ao todo, a área de produção desses sistemas no estado já ultrapassa 500.000 ha. Praticamente não há estudos e resultados de levantamentos sócio-florísticos de comunidades de plantas daninhas nesses sistemas, embora seu conhecimento seja de grande importância para melhor compreensão do efeito desses sistemas sobre as espécies infestantes. Alguns estudos demonstraram que a temperatura e o sombreamento presente no sistema de ILPF afetam diretamente na germinação de plantas daninhas, tais como Amaranthus sp. Além disso, torna-se importanter selecionar as cultivares das culturas a serem inseridas no sistema (CARVALHO; CHRISTOFFOLETI, 2007). De forma a continuar os estudos desses sistemas, considerados importantes na preservação e conservação do solo, o objetivo deste trabalho foi estudar o efeito da distância do renque de eucalipto sobre a comunidade infestante no sistema de integração lavoura-pecuária-floresta