We describe the draft genome of the microcrustacean Daphnia pulex, which is only 200 megabases and contains at least 30,907 genes. The high gene count is a consequence of an elevated rate of gene duplication resulting in tandem gene clusters. More than a third of Daphnia's genes have no detectable homologs in any other available proteome, and the most amplified gene families are specific to the Daphnia lineage. The coexpansion of gene families interacting within metabolic pathways suggests that the maintenance of duplicated genes is not random, and the analysis of gene expression under different environmental conditions reveals that numerous paralogs acquire divergent expression patterns soon after duplication. Daphnia-specific genes, including many additional loci within sequenced regions that are otherwise devoid of annotations, are the most responsive genes to ecological challenges. 相似文献
Entomopathogenic fungi represent excellent candidates for biological insecticides. Among the many entomopathogenic fungi, Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Clavicipitaceae) is one of the most promising species. Here, we report the results of infection studies performed using four B. bassiana native isolates (Bb37, Bb38, Bb40, and Bb45) compared with the commercial product Mycotrol® (strain GHA) on adult Mexican bean beetle Epilachna varivestis Mulsant (Coleoptera: Coccinellidae), one of the most important pests of bean production in Mexico. First, single concentration (1 × 108 conidia mL?1) assays were carried out using all isolates applied using an immersion method. Examinations at 10 days after inoculation indicated that isolates Bb37, Bb38, and Bb40 significantly reduced adult survival, causing 60–75% mortality compared to the commercial strain GHA (33%) and control (29%). Second, using two selected isolates (Bb37 and Bb40), the mean lethal concentration values (LC50) were estimated for third instar larvae and adult E. varivestis. The LC50 values for Bb37 and Bb40 isolates decreased 5.26-fold and 3.19-fold, respectively, in third instars compared with adults. However, such difference for Bb40 isolate was not significant. Finally, an experiment, to compare the median survival time (MST) values between third instar and adult E. varivestis, was conducted using Bb37 and Bb40 at 1 × 109 conidia mL?1. MST values were significantly reduced against larvae (87 and 100 h) compared with adults (130 and 134 h) by Bb37 and Bb40, respectively. We conclude that native isolates of B. bassiana represent an important alternative for the control of E. varivestis. However, to demonstrate its effectiveness under field conditions, detailed studies are needed. 相似文献
Chickens from a randomly bred genetic line were segregated into high and low growth rates and high and low water-holding capacities (WHCs). The objective of this study was to identify protein markers associated with slow and fast growth rates and low and high WHCs from water-soluble protein (WSP) and crude myofibrillar protein (CMP) extracts of chicken breast muscle. Proteins were fractionated using two-dimensional electrophoresis, and a total of 22 protein spots were selected, excised, and analyzed by in-gel tryptic digestion and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Proteins expressed in extracts from slow and fast growth rates and low and high WHCs included metabolic enzymes, such as creatine kinase, pyruvate kinase, triosephosphate isomerase, and ubiqitin; housekeeping proteins, such as heat shock protein; contractile proteins, such as myosin heavy chain; actin; and also MHC isoforms and actin isoforms. The mass spectra of 20 protein spots significantly matched (protein score >83; P < 0.05) an online database. In CMP, there were unique proteins that were present only in the fast-growth population: gi|118099530 , gi|20664362 , gi|71895043 , gi|114794125 , gi|297343122 , and gi|71895043 . This information identified protein markers associated with growth rate and water holding capacity. Some of those protein markers could be added to the chicken database. 相似文献
Background, Aim and Scope
Grazing animals have a dominant effect on the movement and utilization of nutrients through the soil and plant system, and
thus on the fertility of pasture soils. Grazing can accelerate and alter the timing of nutrient transfers, and increase the
amount of nutrients cycled from plant to soil. Long periods, position of shade, and water resources for grazing cattle can
influence the spatial distribution of soil biochemical properties including soil organic carbon (C), total extractable inorganic
nitrogen (TEIN), and Melich 1 extractable total phosphorus (TP).
The objective of this study is to test whether cattle congregation sites typical on most Florida ranches, such as mineral
feeders, water troughs, and shade areas are more nutrient-rich and may contribute more nutrients to surface and groundwater
supply than in other pasture locations under Florida conditions.
Materials and Methods:
Baseline soil samples around and beneath three congregations sites in established (>10 yr) grazed beef cattle pastures at
the United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Subtropical Agricultural Research
Station (STARS), Brooksville, FL, were collected in 2003, 2004, and 2005.
Results:
The levels of soil TEIN and TP were significantly (p ≤ 0.001) affected by the interaction of congregation sites and distance
away from the center of the sites. Mineral feeders had the highest concentration of TP followed by shades and water troughs.
The concentrations of soil TP decreased almost linearly with distance (x = meter) away from the center of the mineral feeders
(-5.24x + 55.10; R2 = 0.92; p ≤ 0.001) and the shades (-6.25x + 57.21; R2 = 0.85; p ≤ 0.001). However, the level of TP around
the water troughs (-0.25x + 16.91; R2 = 0.09) does not appear to change significantly with distance, staying close to about
13-18 mg kg-1. The levels of TEIN decreased linearly with distance away from the mineral feeders from the center of the shades.
A linear model can describe the relationship between TEIN and distance away from the center of shades: -11.3x + 78.2; R2 =
0.95; p ≤ 0.001. The shaded sites (34.25 ± 1.7 mg kg-1) had higher levels than the mineral feeders (7.22 ± 0.60 mg kg-1) or
water troughs (10.06 ± 0.8 mg kg-1) sites.
Discussion:
The higher soil TP near and around the mineral feeders can be attributed to the presence of phosphorus in the supplemental
feeds. The average level of soil TP in the mineral feeders of 34.05 ± 0.44 mg kg-1 was not high enough to be of environmental
concern. Losses of soil phosphorus by overland flow are becoming a big concern when the concentrations for soil phosphorus
exceeded 150 mg kg-1 in the upper 20 cm of soils. With TN, the shaded sites (34.25 ± 1.7 mg kg-1) had either higher levels
than the mineral feeders (7.22 ± 0.60 mg kg-1) or water trough (10.06 ± 0.80 mg kg-1) sites. Higher TEIN content at the shade
sites may have been more likely due to frequent urination of animals and lack of vegetation immediately adjacent to shades.
The lack of vegetation within and/or near the shades then had no uptake mechanism for removal of inorganic nitrogen, unlike
the heavy demand for inorganic nitrogen by bahiagrass in other areas of the pasture. An accumulation of TEIN immediately adjacent
to shades could lead to a potential point source that would be susceptible to leaching or gaseous losses to the environment.
Conclusions:
Early results of the study are suggesting that cattle congregation sites in beef cattle operations in Florida are not nutrient-rich,
therefore may not contribute more nutrients to surface and groundwater supply under Florida conditions.
Recommendations and Perspectives:
Since there is no apparent vertical build up or horizontal movement of TEIN and TP in the landscape, we can then surmise that
cattle congregation sites may be considered not a potential source of nutrients at the watershed level, at least on the sand
ridge soils in Florida. Further research is continuing, including sampling at cattle congregation sites at other locations
in north and south Florida, which started in July 2004. 相似文献
When continuous measurement of relevant above- and below-ground environmental factors is made, and the dynamics of crop growth and phenology is followed, it is shown that small-plot agronomic experimentation can provide information vital to the development and testing of simulation models. Such models for crops of maize (Zea mays) and the legume cowpea (Vigna unguiculata), grown as sole crops and in an intercrop system, were used to simulate yield at two separate sites in the main savanna farming zones in Ghana, West Africa. Simulation was carried out for these three cropping systems using 20 years of historical rainfall data for the two sites, investigating the effect on yield of management options which included time of planting, rate of nitrogen fertilizer application, and crop planting density.
The yield results of this series of simulations were then subject to two different types of analysis in order to assist the evaluation of agricultural options for the nation. The first analysis was an economic evaluation based on gross margins, but using the stochastic-dominance technique to rank the profitability of the alternative cropping and management systems.
The second, more general methodology employed was multi-criteria analysis (MCA). This analysis covered economic returns and their variability, the amount and quality of residue returned to the soil, and the aerial cover provided by the crop. Other factors which could affect the sustainability of production in the long term, but which could only be evaluated qualitatively, were also included in the analysis, as allowed in MCA methodology. The MCA was then carried out for three scenarios in which different weightings were given to economic outcomes and to factors which are believed to encourage ecological sustainability. These scenarios allow recognition of different priorities which might be given by traditional subsistence farmers as compared to commercial producers.
Outcomes of this broad analysis of development alternatives provided scientific support for the traditional Ghanaian practice of grain/legume intercropping which is also widespread in the tropics. The suite of methodologies illustrated by the case study appears to be suitable for the evaluation of alternative farming systems at the scale of a small nation such as Ghana. 相似文献
We compared trapping of Rhizobiumleguminosarum biovar trifolii isolates under field soil and non-soil environmental conditions. Isolates were obtained from white clover (Trifoliumrepens L.) and red clover (T. pratense L.) grown directly in the field and from plants inoculated with soil from the same site using a plant infection technique. Isolates were identified by genomic polymerase chain reaction (PCR) fingerprinting using primers derived from the enterobacterial repetitive intergenic consensus (ERIC) sequences. The isolates trapped from soil dilutions in the laboratory included a number of major ERIC types that were not found in the field trapped nodules, suggesting that sampling of clover Rhizobium strains from soil dilutions may not be representative of the field nodulating population. 相似文献
The soy isoflavones daidzin, glycitin, and genistin were purified from defatted soy flour using preparative-scale reverse-phase HPLC. The stabilities of the three isoflavones at different heating temperatures were investigated. Daidzin, glycitin, and genistin were lost at a rate of 26, 27, and 27% of their original concentration, respectively, after 3 min at 185 degrees C. At 215 degrees C, decreases of daidzin, glycitin, and genistin were 65, 98, and 74% after 3 min and 91, 99, and 94% after 15 min, respectively. The order of the thermal stabilities, from lowest to highest, was glycitin, genistin, and daidzin. Acetyl daidzin and acetyl genistin, daidzein, glycitein, and genistein were produced during heating at temperatures above 135 degrees C. The rate of binding of an acetyl group to form acetyl daidzin and acetyl genistin from daidzin and genistin was higher than the rate of loss of a glucoside group to form daidzein and genistein. However, acetyl daidzin and acetyl genistin decreased sharply at temperatures above 200 degrees C, while daidzein, glycitein, and genistein were relatively stable over 30 min. The stability of daidzein was higher than that of glycitein or genistein. 相似文献
The purpose of this paper is to summarize the current state of knowledge concerning direct forest damage caused by atmospheric gaseous pollutants. The major gaseous pollutants affecting forest growth are O3, SO2, and HF. Ozone is the most prevalent phytotoxic air pollutant on a regional scale in eastern North America. It has been demonstrated to cause foliar injury and growth effects on trees in both laboratory and field studies. Both SO2 and HF have been found to cause damage to forests primarily in the vicinity of strong point sources. Case histories of forest damage are reported in the paper which describe foliar and radial growth effects, with associated volume losses. Threshold levels of the gaseous pollutants causing effects on forest growth are provided. 相似文献
Trials were carried out on 11 farms to assess the effectiveness of 2.5 per cent w/v cypermethrin pour-on for the control of ticks on sheep. Treatment at the rate of 5 ml/10 kg bodyweight gave 92 per cent control of ticks on ewes for up to nine weeks and 88 per cent control on lambs for up to eight weeks. 相似文献
Babesiosis is a worldwide tick-borne protozoan disease of a variety of wild and domestic animals. For decades, various babesia strains were considered host-specific. However, babesiosis has been diagnosed as the cause of acute illness in 13 human beings in recent years, three of whom died. Studies of babesiosis in domestic animals indicate that for every clinically demonstrable case, there are hundreds of cases of latent infection. In an effort to determine if human babesia infections might be present in Mexico, we selected as our testing ground an endemic rural area along the Gulf Coast where continuous epizootics of equine, bovine, ovine and canine babesiosis were known to occur. Of the 101 individuals examined serologically by the indirect hemagglutination (IHA) test using Babesia canis as antigen, 38 reacted at titers from 1 : 10 to 1 : 80. Blood from these reactors was injected into splenectomized hamsters. Hamsters inoculated with blood from three of the individuals showed babesia in their peripheral blood. The growth of the organism was established by subpassages into additional hamsters. The persons from whom the organisms were isolated were asymptomatic for babesiosis. None of the 29 individuals residing in Mexico City, which represented the urban population in the survey, reacted in the IHA test. This is the first documented finding of the latent form of human babesiosis. 相似文献