Universidade Federal de Viçosa

About: Universidade Federal de Viçosa is a education organization based out in Viçosa, Brazil. It is known for research contribution in the topics: Population & Biology. The organization has 16012 authors who have published 26711 publications receiving 353416 citations.

Estoques de carbono e nitrogênio em frações lábeis e estáveis da matéria orgânica de solos sob eucalipto, pastagem e cerrado no Vale do Jequitinhonha - MG

Abstract: A substituicao da vegetacao nativa na regiao de Cerrado por florestas plantadas de eucalipto pode levar a mudancas nos estoques de C e N das diferentes fracoes da materia orgânica do solo (MOS). Contudo, a intensidade e a direcao da mudanca nos teores de MOS dependem do tipo de solo, clima e manejo da area plantada. O objetivo deste trabalho foi determinar o efeito do plantio de eucalipto nos estoques de C e N em fracoes labeis e estaveis da MOS em regiao de Cerrado no Vale do Jequitinhonha, MG. O estudo foi desenvolvido utilizando-se amostras de solos provenientes de povoamentos de Eucalyptus urophylla e de areas adjacentes com vegetacao natural de Cerrado e cultivo de pastagem. Para o plantio do eucalipto, a vegetacao do Cerrado foi cortada, a lenha removida e os residuos enleirados e queimados. As plantacoes de eucalipto com 20 anos apresentaram teores de carbono orgânico total (COT) similares aos da vegetacao de Cerrado e pastagem. Nas fracoes acido humico e acido fulvico (FAH e FAF), os teores de C foram de 16,6 e 17,5 % maiores para o solo de eucalipto em comparacao com os solos da pastagem, e 17,5 e 36,9 % com os solos do Cerrado, respectivamente. O cultivo do eucalipto nao reduziu o estoque de C e N da biomassa microbiana do solo (BMS) em comparacao com a do Cerrado e pastagem, e proporcionou incremento nas quantidades de C e N na materia orgânica leve (MOL), o que contribuiu para o aumento da MOS. A contribuicao do C derivado do eucalipto para a MOS, apos 20 anos de cultivo, foi de 5 %. Isso indica uma baixa taxa de substituicao do C nativo pelo C derivado do eucalipto, com uma media anual de 0,25 %. Assim, a substituicao da vegetacao nativa do Cerrado por eucalipto nao resultou na diminuicao do estoque de C nas fracoes FAH, FAF, MOL e BMS da MOS.

Insecticide resistance, control failure likelihood and the First Law of Geography.

Abstract: Insecticide resistance is a broadly recognized ecological backlash resulting from insecticide use and is widely reported among arthropod pest species with well-recognized underlying mechanisms and consequences. Nonetheless, insecticide resistance is the subject of evolving conceptual views that introduces a different concept useful if recognized in its own right - the risk or likelihood of control failure. Here we suggest an experimental approach to assess the likelihood of control failure of an insecticide allowing for consistent decision-making regarding management of insecticide resistance. We also challenge the current emphasis on limited spatial sampling of arthropod populations for resistance diagnosis in favor of comprehensive spatial sampling. This necessarily requires larger population sampling - aiming to use spatial analysis in area-wide surveys - to recognize focal points of insecticide resistance and/or control failure that will better direct management efforts. The continuous geographical scale of such surveys will depend on the arthropod pest species, the pattern of insecticide use and many other potential factors. Regardless, distance dependence among sampling sites should still hold, following the maxim that the closer two things are, the more they resemble each other, which is the basis of Tobler's First Law of Geography. © 2016 Society of Chemical Industry.

Trimellitated sugarcane bagasse: A versatile adsorbent for removal of cationic dyes from aqueous solution. Part I: Batch adsorption in a monocomponent system

Abstract: Trimellitated-sugarcane bagasse (STA) was used as an environmentally friendly adsorbent for removal of the basic dyes auramine-O (AO) and safranin-T (ST) from aqueous solutions at pH 4.5 and 7.0. Dye adsorption was evaluated as a function of STA dosage, agitation speed, solution pH, contact time, and initial dye concentration. Pseudo-first- and pseudo-second-order, Elovich, intraparticle diffusion, and Boyd models were used to model adsorption kinetics. Langmuir, Dubinin-Radushkevich, Redlich-Peterson, Sips, Hill-de Boer, and Fowler-Guggenheim models were used to model adsorption isotherms, while a Scatchard plot was used to evaluate the existence of different adsorption sites. Maximum adsorption capacities for removal of AO and ST were 1.005 and 0.638 mmol g−1 at pH 4.5, and 1.734 and 1.230 mmol g−1 at pH 7.0, respectively. Adsorption enthalpy changes obtained by isothermal titration calorimetry (ITC) ranged from −21.07 ± 0.25 to −7.19 ± 0.05 kJ mol−1, indicating that both dyes interacted with STA by physisorption. Dye desorption efficiencies ranged from 41 to 51%, and re-adsorption efficiencies ranged from 66 to 87%, showing that STA can be reused in new adsorption cycles. ITC data combined with isotherm studies allowed clarification of adsorption interactions.

Liposome encapsulation and EDTA formulation of dsRNA targeting essential genes increase oral RNAi‐caused mortality in the Neotropical stink bug Euschistus heros

Abstract: Background The Neotropical stink bug Euschistus heros is a major pest in soybean fields. Development of highly species-specific pesticides based on RNA interference (RNAi) could provide a new sustainable and environmentally friendly control strategy. Results Here, the potential of RNAi as a pest control tool against E. heros was assessed. First, target gene selection using a microinjection approach was performed. Seven of the 15 candidate genes tested exhibited > 95% mortality after hemolymph injection of 27.5 ng dsRNA. Subsequently, dsRNA was administered orally using different formulations: naked dsRNA, liposome-encapsulated-dsRNA and dsRNA formulated with EDTA. Liposome-encapsulated dsRNA targeting vATPase A and muscle actin led to significant mortality after 14 days (45% and 42%, respectively), whereas EDTA-formulated dsRNA did so for only one of the target genes. Ex vivo analysis of the dsRNA stability in collected saliva indicated a strong dsRNA-degrading capacity by E. heros saliva, which could explain the need for dsRNA formulations. Conclusion The results demonstrate that continuous ingestion of dsRNA with EDTA or liposome-encapsulated dsRNA can prevent dsRNA from being degraded enzymatically and suggest great potential for using these formulations in dsRNA delivery to use RNAi as a functional genomics tool or for pest management of stink bugs. © 2018 Society of Chemical Industry.