José Roberto Vieira Júnior

Componentes primários e secundários do rendimento de óleo de pinhão-manso

The definition of the most suitable plant selection criteria is especially important for Jatropha curcas L. as subsidies the genetic progress estimates and the ideotype characterization, described in terms of the traits that are thought to enhance genetic yield potential. The objective of this study was to estimate the direct and indirect effects of seven vegetative traits and four seed quality traits on J. curcas oil yield. The traits grain yield and the weight of the nuts showed direct and positive effect on the oil yield. The tree volume showed the major indirect and positive effect on the main variable through grain yield. The development of J. curcas with higher oil yield in the evaluated population has to consider the selection of plants with higher yield and tree volume, maintaining the variability of the grain quality traits.

Acaricidal activity of extracts from different structures of Piper tuberculatum against larvae and adults of Rhipicephalus microplus

Estrategias de controle do carrapato dos bovinos, Rhipicephalus microplus, fundamentam-se na utilizacao de pesticidas. Os principais grupos quimicos utilizados atualmente mostram-se ineficazes devido ao surgimento de populacoes resistentes. A pesquisa de novas moleculas com eficiencia acaricida e uma necessidade para manutencao da produtividade dos rebanhos bovinos estabelecidos em regioes de clima tropical. Avaliamos a atividade de Piper tuberculatum para o controle de femeas ingurgitadas e larvas de R. microplus atraves de bioensaios de imersao de adultos e de pacotes de larvas. As concentracoes avaliadas foram de 50; 25; 12,50; 6,25; 3,12 e 1,56 mg mL-1 de extrato etanolico de folha, talo e fruto de P. tuberculatum. As concentracoes letais para 50% dos individuos (CL50) apos 24 horas de exposicao de larvas de R. microplus foram 3,62; 3,99 e 5,30 mg mL-1 para os extratos etanolicos de fruto, talo e folha, respectivamente. Para femeas ingurgitadas, a maior eficacia resultou da concentracao de 50 mg mL-1 de extrato de fruto (71.57%). O principal efeito dos extratos etanolicos de P. tuberculatum foi sobre a eclodibilidade, com uma reducao de 55.63% para extratos de fruto e folha. P. tuberculatum mostra-se promissora como fonte de moleculas candidatas a uso em pesticidas, em formulacoes destinadas ao controle das infestacoes de R. microplus.

Potencialidade antagonística detectada em alguns procariotas agentes de biocontrole de enfermidades de plantas

Along several years, at the Laboratory of Plant Bacteriology and Biological Control of the Department of Plant Pathology of the Federal University of Vicosa, thousands of prokaryote isolates have been obtained from the rhizosphere, rhizoplane and phylloplane of economically important plants. Every obtained isolate is tested as biocontrol agents. As expected, the majority does not show any biocontrol potentiality and is discarded. Few are selected through time-consuming experimental biocontrol trials in greenhouse and field. Even being selected mainly for their ability to induce resistance in target plants, many of them constitutively express mechanisms of antagonism against pathogens that seem to be part of their performance while biocontrol agents.