Enraizamento de folhas e análise citológica de híbridos diplóides e anfidiplóides de arachis.

O gênero Arachis possui 80 espécies descritas, a maioria brasileira. A definição do número de cromossomos e observações morfológicas têm sido muito importante em estudos sobre o gênero. Pontas de raízes obtidas a partir de plântulas são normalmente utilizadas para obtenção de células em divisão. Um método inédito e alternativo de produção de raízes em pecíolos foi desenvolvido a partir de folhas isoladas de ramos de Arachis tratados com colchicina. O objetivo foi o desenvolvimento de uma metodologia que permitisse a contagem do número de cromossomos para a avaliação do grau de ploidia do ramo tratado e avaliar a capacidade de enraizamento de diversas espécies silvestres de Arachis usando a técnica de folhas destacadas. Cento e trinta acessos e 27 híbridos interespecíficos foram avaliados. Para a obtenção de preparações com alta frequência de metáfases e cromossomos com morfologia nítida, as raízes foram tratadas com uma combinação de 8-hidroxiquinolina a 300ppm e cicloheximida a 6,25ppm durante 2 horas. As raízes foram coradas pelo método de Feulgen para a análise dos cromossomos. Trata-se de uma alternativa para a aplicação de técnicas citológicas nos casos de indisponibilidade de sementes elou ineficácia de estaquia. Três avaliações foram realizadas a 15, 31 e 49 dias após o plantio. Acessos foram Classificados como enraizados, não enraizados e folhas mortas.O enraizamento de folhas em espécies silvestres de Arachis confirma a grande variabilidade genética presente no gênero, indicando também que o número de dias interfere na porcentagem de enraizamento.A secção Arachis apresentou maior precocidade, possuindo as maiores taxas de enraizamento de folhas entre as secções estudadas, concentrando as maiores freqüências entre 15 e 31 dias. As secções que apresentaram maiores taxas de enraizamento tardio ou de não enraizamento foram Erectoides, Extranervosae, Rhizomatosae e Procumbentes. A secção Caulorrhizae, Heteranthae e Trierectoides apresentaram taxas de enraizamento intermediários,concentrando seu enraizamento aos 31 dias. A quantidade e qualidade das raízes obtidas através desta técnica foram apropriadas para o uso na caracterização citológica.bitstream/CENARGEN/28292/1/bp106.pd

Concentration and timing of application reveal strong fungistatic effect of tebuconazole in a Daphnia-microparasitic yeast model

Given the importance of pollutant effects on host-parasite relationships and disease spread, the main goal of this study was to assess the influence of different exposure scenarios for the fungicide tebuconazole (concentration × timing of application) on a Daphnia-microparasitic yeast experimental system. Previous results had demonstrated that tebuconazole is able to suppress Metschnikowia bicuspidata infection at ecologically-relevant concentrations; here, we aimed to obtain an understanding of the mechanism underlying the anti-parasitic (fungicidal or fungistatic) action of tebuconazole. We exposed the Daphnia-yeast system to four nominal tebuconazole concentrations at four timings of application (according to the predicted stage of parasite development), replicated on two Daphnia genotypes, in a fully crossed experiment. An “all-or-nothing” effect was observed, with tebuconazole completely suppressing infection from 13.5 µg l -1 upwards, independent of the timing of tebuconazole application. A follow-up experiment confirmed that the suppression of infection occurred within a narrow range of tebuconazole concentrations (3.65–13.5 µg l -1 ), although a later application of the fungicide had to be compensated for by a slight increase in concentration to elicit the same anti-parasitic effect. The mechanism behind this anti-parasitic effect seems to be the inhibition of M. bicuspidata sporulation, since tebuconazole was effective in preventing ascospore production even when applied at a later time. However, this fungicide also seemed to affect the vegetative growth of the yeast, as demonstrated by the enhanced negative effect of the parasite (increasing mortality in one of the host genotypes) at a later time of application of tebuconazole, when no signs of infection were observed. Fungicide contamination can thus affect the severity and spread of disease in natural populations, as well as the inherent co-evolutionary dynamics in host-parasite systems.ERDF -European Regional Development Fund(IF/01198/2014)info:eu-repo/semantics/publishedVersio

Survival and life history responses of Simocephalus vetulus (Müller, 1776) genotypes exposed to sodium chloride: does environmental context matter?

Cladocerans are typically viewed as freshwater organisms with importance as regulators of primary production. However, populations of these filter-feeders can be found in brackish ecosystems, facing regular or sporadic inputs of seawater. According to climate change predictions, saline intrusion may affect vulnerable freshwater habitats. Nonetheless, populations adapt to local conditions and this may confound our ability to assess noxious effects of salinity. Bearing this in mind, our goal was to analyze the halotolerance of different genotypes of Simocephalus vetulus differing in their original environmental context (brackish versus freshwater populations). Clonal lineages were established from three extant populations: one from a brackish lagoon and two from freshwater systems. To assess short-time sensitivity of 23 genotypes to NaCl, they were exposed to a range of concentrations from 2 to 5gL−1 in standard 48-h acute assays and to a fixed concentration of 6 g L−1 in 12-h survival time (ST) trials. Life-history responses were analyzed in extreme genotypes, whose fitness was compared along a gradient of growing NaCl concentrations. While EC50 values demonstrated an overlap of the sensitivity of genotypes to NaCl, ST supported the idea of population differentiation. All tolerant genotypes (in terms of ST) to high levels of NaCl, except one, originated from the brackish population. On the contrary, life-history assays of extreme genotypes showed that fitness under saline stress was overall unrelated to environmental context. Furthermore, lifehistory experiments showed that tolerance to salinity is present in freshwater populations, thus demonstrating their potential to adapt to salinity increases.publishe

Pasture production under different irrigation depths

ABSTRACT This study aimed to evaluate the production of two pasture species, Brachiaria brizantha cv. BRS Piatã and Panicum maximum cv. Mombaça, under different irrigation depths. The experiment was carried out from May to December 2014, at the State University of Maringá, in the municipality of Cidade Gaúcha-PR, Brazil. The experiment was set out in a strip-plot design, with four replicates, six irrigation depths in the plot and two pasture species in the subplot. Irrigation depths were represented by a percentage of reference evapotranspiration (ET0), which was estimated by the Penman-Monteith equation. Four pasture cuts were performed during the studied period and there were no differences between the yields of both evaluated pasture species; however, irrigation depths caused a quadratic response on pasture yield. The maximum values of dry matter yield of the pastures under irrigated conditions were 52.1, 41.6, 26.2 and 25.1% higher than under non-irrigated conditions, for the 1st, 2nd, 3rd and 4th cuts, respectively. Irrigation depths that applied water volumes close to ET0 promoted considerable increases in pasture yield

Relearning traditional knowledge for sustainability: honey gathering in the Miombo Woodland of Northern Mozambique

Mozambique's Niassa Reserve contains Africa's best preserved miombo woodlands. Half of the households there gather wild honey from natural hives for consumption and income. However, most collectors used destructive techniques: setting fire to the grasses under the hive tree to create smoke and then felling the tree. Cutting trees to obtain honey was the principal source of tree mortality. Trees grow very slowly, about 0.25 cm diameter at breast hight [dbh] per year, meaning an average hive tree was nearly 200 years old. Furthermore, of the trees > 20 cm dbh of species important for nectar and hives, only about 15% had cavities. Although fire is intrinsic to miombo woodlands, the increased frequency resulting from anthropogenic sources impedes regeneration of some tree species as well as affecting bees, other wildlife and villages. A few people in the reserve had learned from earlier generations how to gather honey in a nondestructive way, using certain plant species to keep bees from stinging and climbing the trees using ropes to take the honeycombs out of the hives. Traditional practices included leaving the larval combs behind so the colony continued to grow. Previously, the older men who had this knowledge had not been willing to share it with younger men. The project arranged for one of the traditional honey hunters to participate in an international conference on honey collection with other indigenous collectors from around the world. This helped him recognise the value of his knowledge. The project team then arranged for him to demonstrate these traditional techniques to groups of honey hunters in nine communities within the reserve. A year later, monitoring revealed that many collectors had adopted these nondestructive techniques. They found them less time consuming, and appreciated that they allowed collectors to return to the same trees repeatedly to obtain honey. Sharing traditional knowledge made honey hunting compatible with the conservation of miombo woodlands