Bumble bee parasite strains vary in resistance to phytochemicals

Nectar and pollen contain diverse phytochemicals that can reduce disease in pollinators. However, prior studies showed variable effects of nectar chemicals on infection, which could reflect variable phytochemical resistance among parasite strains. Inter-strain variation in resistance could influence evolutionary interactions between plants, pollinators, and pollinator disease, but testing direct effects of phytochemicals on parasites requires elimination of variation between bees. Using cell cultures of the bumble bee parasite Crithidia bombi, we determined (1) growth-inhibiting effects of nine floral phytochemicals and (2) variation in phytochemical resistance among four parasite strains. C. bombi growth was unaffected by naturally occurring concentrations of the known antitrypanosomal phenolics gallic acid, caffeic acid, and chlorogenic acid. However, C. bombi growth was inhibited by anabasine, eugenol, and thymol. Strains varied >3-fold in phytochemical resistance, suggesting that selection for phytochemical resistance could drive parasite evolution. Inhibitory concentrations of thymol (4.53-22.2 ppm) were similar to concentrations in Thymus vulgaris nectar (mean 5.2 ppm). Exposure of C. bombi to naturally occurring levels of phytochemicals—either within bees or during parasite transmission via flowers—could influence infection in nature. Flowers that produce antiparasitic phytochemical, including thymol, could potentially reduce infection in Bombus populations, thereby counteracting a possible contributor to pollinator decline

Competências críticas na interação das subsidiárias com a comunidade local: um estudo de caso no setor de telecomunicações

Este artigo analisa as competências críticas necessárias para a interação das subsidiárias à comunidade local a qual está inserida. O estudo é realizado no setor de telecomunicações brasileiro, com foco nas subsidiárias dos fornecedores especializados de equipamentos (FEEs). Trata-se de um estudo empírico e de natureza exploratória, que utiliza o método do estudo de caso

Avaliação agronômica e identificação de quimiotipos de erva cidreira no Distrito Federal Agronomic evaluation and identification of Lippia alba chemotypes from Distrito Federal, Brazil

Com o objetivo de avaliar o comportamento agronômico, o potencial de rendimento de óleo essencial e identificar os quimiotipos de 16 acessos de Lippa alba (erva cidreira) da coleção da Universidade de Brasília foi conduzido um experimento de campo em Latossolo Vermelho, sob irrigação por gotejamento na região do Cerrado do Distrito Federal. Foram avaliados a época de florescimento, hábito de crescimento, área foliar, comprimento da haste, massa fresca de folhas e hastes, massa foliar seca, teor e rendimento de óleo essencial e perfil aromático. O óleo essencial foi extraído por hidrodestilação em aparelho de Clevenger modificado e os constituintes identificados e quantificados através de cromatografia em fase gasosa acoplada a espectrometria de massas. O delineamento experimental utilizado foi de blocos ao acaso, com três repetições, contendo três plantas úteis por parcela. Foram identificados os quimiotipos citral-limoneno, citral-mirceno, limoneno-carvona, citral, linalol, mirceno e linalol-limoneno. Os acessos apresentaram teores máximos de linalol de 89,8% (L.16); mirceno de 47,6% (L.37); limoneno de 36,0%, carvona de 46,9% (L.27) e citral de 56,7% (L.17). Os genótipos com maiores áreas foliares e maiores comprimentos de hastes tenderam a apresentar maiores teores de óleo e maior concentração de linalol. A concentração de óleo foi inversamente proporcional à produção de massa foliar seca. Os acessos que apresentaram os maiores rendimentos dos compostos majoritários do óleo essencial foram: L.16 (0,77 g pl-1), como fonte potencial para a produção de linalol; L.17 (0,17 g pl-1), como fonte de mirceno; L. 27 (0,17 g pl-1), como fonte de limoneno e de carvona (0,21 g pl-1) e L.38 (0,24 g pl-1), como fonte de citral.<br>The main objective of this work was to describe the essential oil profile of 16 genotypes of Lippia alba from the germplasm collection of the Universidade de Brasília and to analyze its potential of production. A field assay was carried out in the rural area of Distrito Federal and the following parameters were analyzed: flowering period, growing habit, foliar area, length of the main branch, fresh and dry weight of the biomass (leaves and branches), essential oil content and profile of the constituent volatile oils. Essential oil was extracted using a modified Clevenger apparatus and the constituent volatile oils were analyzed by gas chromatography and GC/MS. The experimental design was randomized blocks with three plants per plot. The following chemotypes were reported: citral-limonene, citral-myrcene, limonene-carvone, citral, linalool, myrcene and linalool-limonene. Higher levels of linalool were found in genotype L.16 (89.8%); myrcene in L.37 (47.6%); limonene in L.27 (36.0%); carvone in L.27 (46.9%) and citral in L.17 (56.7%). The genotypes with the highest leaf area and leaf length of the main branch seem to be correlated with the best yield of essential oil and the higher level of linalool. The yield of essential oil was inversely proportional to the dry weight of biomass. The accessions which presented the highest average yield of the major essential constituent oils were: L.16 (0.77 g pl-1) as a source of raw material for linalool production; L.17 (0.17 g pl-1) as source of myrcene; L. 27 as source of limonene (0.17 g pl-1) and carvone (0.21 g pl-1); and L.38 (0.24 g pl-1) as a citral source