Population dynamic and management of <Emphasis Type="Italic">Pinus oocarpa</Emphasis> and <Emphasis Type="Italic">Tabebuia rosea</Emphasis> within silvopastoral systems in Central America

Silvopastoral systems—the management of trees within pastures from natural regeneration or planting—are a strategy to promote sustainable livestock systems and ecosystems services. Timber is one of the products from these systems with potential to increase family revenues. The management of natural regeneration and population dynamics of trees is a feasible way to harvest timber and maintain environmental services. In this research, we modeled the population dynamics of Pinus oocarpa and Tabebuia rosea, two important timber species of silvopastoral systems in Central America. The results showed that farmers manage a significant density of different tree species from natural regeneration. However, only the species with well-known uses or desired services are allowed to remain. The natural regeneration is more impressive in silvopastoral systems with natural grass than those with exotic grass. Farming practices, for instance use of fire for weed control, are the main reasons for low rates of natural regeneration in pastures with exotic grass. The models of population dynamics for both species showed that the sustainable timber harvest plans are a viable activity in pasturelands under natural-regeneration management plans. Innovative farmers are willing to adopt silvicultural practices and management of population dynamics to increase timber revenues and sustainability if forestry regulations for sustainable use of trees in farms are simplified.     

The nabicol: A horticultural crop in northwestern Spain

Nabicol (B. napus L. var. pabularia) is a traditional crop in the Northwest of Iberian Peninsula (South of Galicia and North of Portugal) where it is grown during the winter season on small farms and gardens using traditional varieties. A collection of 36 populations of nabicol from Galicia (northwestern Spain) was evaluated during 2002 and 2003 in two locations and two growing seasons (spring/summer and autumn/spring) for 28 agronomic and morphological traits. The objectives of this study were to: (i) evaluate a collection of nabicol landraces from northwestern Spain, (ii) determine the suitability of this germplasm as a summer crop and (iii) study the genetic diversity among local populations. Significant differences were observed among populations for most traits. Genotype × environment interaction was significant for most of them. Spring/summer growing season could be recommended for growing nabicol but resistance to Lepidoptera pests attacking Brassica crops should be improved. Most populations had an agronomic value similar to the commercial variety. The most promising variety for horticultural use was MBG-BRS0063, which showed the highest yield. Morphological and agronomic data were subjected to cluster analysis and four groups were defined with a group clustering most populations. The low genetic diversity could be explained because populations were collected in close geographical areas and the selection made by farmers was always for a horticultural use. These results give information about the diversity and breeding value of the nabicol Spanish germplasm, which could be useful in breeding programs.     

Response to the interaction of thinning and pruning of pine species in Mediterranean mountains

Pruning allows knot-free timber to be obtained, thereby increasing the value of the highest-value wood products. However, the effect of pruning on growth is under discussion, and knowledge about the tree response to the simultaneous development of thinning and pruning is scarce. The objective of this study was to analyze the effect of the interaction of thinning and pruning on tree and stand level and the annual radial growth of two pine species native to Mediterranean mountains. We used long-term data of three trials installed in pine stands where several combinations of pruning and thinning were developed. Five inventories were carried out for each trial, and the mean dasometric features of the different treatments were compared using linear mixed models including a competition index. In addition, we collected cores from ten trees per plot in order to evaluate the annual response of trees to the thinning and pruning. We analyzed the annual radial growth using a semiparametric approach through a smooth penalized spline including rainfall and temperature covariates. Pruning did not show any effect on growth. However, larger diameter and increased annual radial growth were found in thinned plots, both with and without pruning, as compared to unthinned plots. Also, we found significant effects of climate on annual radial growth. We recommend the application of thinning and pruning in stands of Mediterranean mountains in order to get knot-free timber since growth reduction was not found in thinned stands.     

Efficacy of a BVDV subunit vaccine produced in alfalfa transgenic plants

Bovine viral diarrhea virus (BVDV) is considered an important cause of economic loss within bovine herds worldwide. In Argentina, only the use of inactivated vaccines is allowed, however, the efficacy of inactivated BVDV vaccines is variable due to its low immunogenicity. The use of recombinant subunit vaccines has been proposed as an alternative to overcome this difficulty. Different studies on protection against BVDV infection have focused the E2 protein, supporting its putative use in subunit vaccines. Utilization of transgenic plants expressing recombinant antigens for the formulation of experimental vaccines represents an innovative and cost effective alternative to the classical fermentation systems.The aim of this work was to develop transgenic alfalfa plants (Medicago sativa, L.) expressing a truncated version of the structural protein E2 from BVDV fused to a molecule named APCH, that target to antigen presenting cells (APCH-tE2). The concentration of recombinant APCH-tE2 in alfalfa leaves was 1 μg/g at fresh weight and its expression remained stable after vegetative propagation. A methodology based an aqueous two phases system was standardized for concentration and partial purification of APCH-tE2 from alfalfa. Guinea pigs parentally immunized with leaf extracts developed high titers of neutralizing antibodies. In bovine, the APCH-tE2 subunit vaccine was able to induce BVDV-specific neutralizing antibodies. After challenge, bovines inoculated with 3 μg of APCH-tE2 produced in alfalfa transgenic plants showed complete virological protection.     

Euparyphium albuferensis and Echinostoma friedi (Trematoda: Echinostomatidae): experimental cercarial transmission success in sympatric snail communities

Euparyphium albuferensis and Echinostoma friedi cercarial infectivity to four species of sympatric snails was examined under single- or multiple-choice laboratory conditions to show the level of parasite-snail host compatibility. Radix peregra, Lymnaeafuscus, Physella acuta and Gyraulus chinensis act as second intermediate hosts of both parasite species although different cercarial transmission success (CTS) was observed. In single-host experiments, R. peregra and P. acuta showed a high degree of compatibility with E. albuferensis, while only P. acuta in the case of E. friedi. In two-choice snail communities, a snail with high CTS increased the values of another with low compatibility, in both parasite species. In multiple-choice snail communities, high CTS of some hosts decreased, while low CTS of other hosts increased. The degree of parasite-host compatibility of each snail species could be determined by the presence of other snails in the community.     

On-farm evaluation of a low-input rice production system in Panama

On-farm trials were conducted to evaluate the potential of the System of Rice Intensification (SRI), a low-input crop management system, to increase rice yields and reduce water consumption on subsistence farms in several regions of Panama and to determine how inherent soil fertility might affect SRI yields and the yield response to SRI management in the first season of SRI management. SRI practices increased yield by 47% on average and showed potential to increase yield by over 90%, while reducing water consumption by as much as 86%. SRI yields were correlated with available soil K and the difference between SRI and the conventional system yields was positively correlated with extractable Ca, Mg and Mn. The results of this study indicate that SRI is a promising rice production system for smallholder farmers in rural Panama farming under Panamanian soil conditions.     

Dose-Response on the Chemopreventive Effects of Sarcophine-Diol on UVB-Induced Skin Tumor Development in SKH-1 Hairless Mice

Sarcophine-diol (SD) is a lactone ring-opened analogue of sarcophine. It has shown chemopreventive effects on chemically-induced skin tumor development in female CD-1 mice, as well as in a UVB-induced skin tumor development model in hairless SKH-1 mice at a dose of 30 μg SD applied topically and 180 mJ/cm² UVB. The objective of this study was to determine the dose-response on the chemopreventive effects of SD on SKH-1 hairless mice when exposed to a UVB radiation dose of 30 mJ/cm². This UVB dose better represents chronic human skin exposure to sunlight leading to skin cancer than previous studies applying much higher UVB doses. Carcinogenesis was initiated and promoted by UVB radiation. Female hairless SKH-1 mice were divided into five groups. The control group was topically treated with 200 μL of acetone (vehicle), and the SD treatment groups were topically treated with SD (30 μg, 45 μg, and 60 μg dissolved in 200 μL of acetone) 1 h before UVB radiation (30 mJ/cm²). The last group of animals received 60 μg SD/200 μL acetone without UVB exposure. These treatments were continued for 27 weeks. Tumor multiplicity and tumor volumes were recorded on a weekly basis for 27 weeks. Weight gain and any signs of toxicity were also closely monitored. Histological characteristics and the proliferating cell nuclear antigen (PCNA) were evaluated in the mice skin collected at the end of the experiment. The dose-response study proved a modest increase in chemopreventive effects with the increase in SD dose. SD reduced the number of cells positively stained with PCNA proliferation marker in mice skin. The study also showed that SD application without UVB exposure has no effect on the structure of skin. The results from this study suggest that broader range doses of SD are necessary to improve the chemopreventive effects.     

Free radical scavengers and antioxidants from Lemongrass (Cymbopogon citratus (DC.) Stapf.)

Methanol, MeOH/water extracts, infusion, and decoction of Cymbopogon citratus were assessed for free radical scavenging effects measured by the bleaching of the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical, scavenging of the superoxide anion, and inhibition of the enzyme xanthine oxidase (XO) and lipid peroxidation in human erythrocytes. The extracts presented effect in the DPPH and superoxide anion assay, with values ranging between 40 and 68% and 15-32% at 33 and 50 microg/mL, respectively, inhibited lipid peroxidation in erythrocytes by 19-71% at 500 microg/mL and were inactive toward the XO at 50 microg/mL. Isoorientin, isoscoparin, swertiajaponin, isoorientin 2' '-O-rhamnoside, orientin, chlorogenic acid, and caffeic acid were isolated and identified by spectroscopic methods. Isoorientin and orientin presented similar activities toward the DPPH (IC(50): 9-10 microM) and inhibited lipid peroxidation by 70% at 100 microg/mL. Caffeic and chlorogenic acid were active superoxide anion scavengers with IC(50) values of 68.8 and 54.2 microM, respectively, and a strong effect toward DPPH. Caffeic acid inhibited lipid peroxidation by 85% at 100 microg/mL.     

FTIR approaches for diuron determination in commercial pesticide formulations

Two strategies have been developed for Diuron determination by FTIR spectrometry, an off-line extraction and stopped-flow determination and a fully mechanized procedure, based on the on-line extraction of Diuron and FIA-FTIR measurement of the extracts. The aforementioned procedures have been compared with a reference chromatographic method. The off-line FTIR spectra were obtained at a nominal resolution of 4 cm(-1) from 4000 to 900 cm(-1) by accumulating 25 scans. Diuron was determined using peak height measurements at 1582 cm(-1) corrected using a baseline defined between 1562 and 1614 cm(-1). The waste generation of the off-line procedure was 3.4 mL chloroform for each sample, and the method provided a LOD of 40 microg g(-1), corresponding to 0.8% (w/w) Diuron in the original sample. The fully mechanized FIA method provided a LOD of 35 microg g(-1), which corresponds to 0.7% (w/w) in the solid sample and a maximum sampling frequency of the whole procedure of 30 h(-1), with a waste generation of 9.3 mL per sample, taking into account the volume of CHCl(3) required for sample dissolution and that need as a carrier. All those methods consume less organic solvent than a HPLC method, which involves the use of 39 mL of acetonitrile per sample and a sampling frequency of 12 h(-1).