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131.
Jonathan Mkumbira Linley Chiwona-Karltun Ulf Lagercrantz Nzola Meso Mahungu John Saka Albert Mhone Mpoko Bokanga Leon Brimer Urban Gullberg Hans Rosling 《Euphytica》2003,132(1):7-22
Cassava roots, a major food in Africa, contain cyanogenic glucosides that may cause toxic effects. Malawian women farmers
considered fields of seemingly similar cassava plants to be mixes of both ‘cool’ and ‘bitter’ cultivars. They regard roots
from ‘cool’ cultivars as non-toxic. Roots of ‘bitter’ were considered to require extensive traditional processing done by
women to be safe for consumption. But curiously, these women farmers preferred ‘bitter’ cultivars since toxicity confers protection
against theft, which was a serious threat to the food security of their families. We studied how well these farmers comprehend
the effects of genetic variations in cassava when dealing with cyanogenesis in this complex system. Using molecular markers
we show that most plants farmers identified as belonging to a particular named cultivar had a genotype typical of that cultivar.
Farmers' ethno-classification into ‘cool’ and ‘bitter’ cultivars corresponded to a genetic sub-division of the typical genotypes
of the most common cultivars, with four-fold higher cyanogenic glucoside levels in the bitter cultivars. Examining morphology,
farmers distinguished genotypes better than did the investigators when using a standard botanical key. Undoubtedly, these
women farmers grasp sufficiently the genetic diversity of cassava with regard to cyanogenesis to simultaneously benefit from
it and avoid its dangers. Consequently, acyanogenic cassava – the breeding of which is an announced good of some cassava genetic
improvement programmes – is not a priority to these farmers. Advances in molecular genetics can help improve food supply in
Africa by rapid micropropagation, marker assisted breeding and introduction of transgenic varieties, but can also help to
elucidate tropical small-scale farmers' needs and skills.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
132.
Assessment of EST- and genomic microsatellite markers for variety discrimination and genetic diversity studies in wheat 总被引:22,自引:0,他引:22
Fiona Leigh Vince Lea John Law Petra Wolters Wayne Powell Paolo Donini 《Euphytica》2003,133(3):359-366
It is likely that in the near future sequence information from sequencing programmes and EST libraries will generate an abundance
of genic microsatellite markers. This study is focused on the assessment of their likely impact and performance vis-à-vis
their genomic counterparts. Microsatellites from two sources were used to assess the genetic diversity in 56 old and new varieties
of bread wheat on the UK Recommended List. A set of 12 microsatellite markers generated from genomic libraries and 20 expressed
sequence tag (EST)-derived microsatellites were used in the study, and the performance of both marker sets assessed. The EST-derived
or genic microsatellites delivered fingerprints of superior quality, amplifying clear products with few stutter bands. Diversity
levels as revealed bygenic microsatellites are similar to the few published results. The PIC values for the genic markers
were generally lower than those calculated for the genomic microsatellites, though advantages of both marker classes for variety
identification applications are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
133.
John L. Nieber 《Geoderma》1996,70(2-4):207-229
The mechanism for the growth and persistence of gravity-driven fingered flow of water in initially dry porous media is described. A Galerkin finite element solution of the two-dimensional Richards equation with the associated parameter equations for capillary hysteresis in the water retention function is presented. A scheme for upstream weighting of internodal unsaturated hydraulic conductivities is applied to limit smearing of steep wetting fronts. The growth and persistence of a single finger in an initially dry porous media is simulated using this numerical solution scheme. To adequately simulate fingered flow, it was found that the upstream weighting factor had to be negative, meaning that the internodal unsaturated hydraulic conductivities were weighted more by the downstream node. It is shown that the growth and persistence of a finger is sensitive to the character of the porous media water retention functions. For porous media where the water-entry capillary pressure on the main wetting function is less than the air-entry capillary pressure on the main drainage function, a small perturbation will grow into a finger, and during sequential drainage and wetting the finger will persist. In contrast, for porous media where the water-entry capillary pressure on the main wetting function is greater than the air-entry capillary pressure on the main drainage function, the same small perturbation will dissipate by capillary diffusion. The finger widths derived from the numerical simulation are similar to those predicted by analytical theory. 相似文献
134.
Laboratory studies were conducted to test the ability of brook charr (Salvelinus fontinalis) alevins, the earliest free-swimming life stage of the species, to detect and avoid toxic levels of H+ and inorganic Al. Alevins were tested in steep gradient choice tanks using a range of H+ (pH 4.0 to 5.5) and Al (0 to 500 μg L?1) concentrations in low Ca (2.0 mg L?1) water. The young brook charr actively avoided acidic water with a pH < 5.0. Aluminum additions of 500 μg L?l increased the avoidance response. The observed behavioral response of alevins to low pH and elevated levels of Al, may be of significant adaptive advantage in systems undergoing acidification. 相似文献
135.
Bennett JO Krishnan AH Wiebold WJ Krishnan HB 《Journal of agricultural and food chemistry》2003,51(23):6882-6886
Soybean (Glycine max [L.] Merr.) protein and oil qualities, with respect to monogastric nutrition, have been linked to the relative abundance of specific protein subunits and fatty acids, respectively. An analysis of field-grown soybean seeds by near-infrared spectroscopy revealed significant differences in their protein and oil contents as a function of nodal position. Seed proteins from the plant apex were high in protein and low in oil content, while those from the basal region exhibited an opposite pattern of accumulation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total seed proteins revealed that the beta-subunit of beta-conglycinin content was 4-fold higher in seeds from the apical nodes than in seeds from basal nodes. The glycinin A3 polypeptide content gradually increased in successively lower nodes from the top of the plant. Its accumulation was drastically reduced when nitrogen was applied at specific growth stages. Exogenous nitrogen did not alter the pattern of beta-subunit accumulation, but accrual of the acidic and basic polypeptides of glycinin was diminished. The remaining seed storage protein components were not influenced by nodal position or nitrogen application. Gas chromatographic analysis of fatty acids indicated that only oleic (18:0) and linoleic (18:2) acids showed variability in accumulation at different nodes. Neither the abundance nor the distribution of the fatty acids was altered by nitrogen application. 相似文献
136.
137.
Historical Trace Metal Accumulation in the Sediments of an Urbanized Region of the Lake Champlain Watershed, Burlington, Vermont 总被引:3,自引:0,他引:3
Ellen L. Mecray John W. King Peter G. Appleby Allen S. Hunt 《Water, air, and soil pollution》2001,125(1):201-230
This study documents the history ofpollution inputs in the Burlington region of LakeChamplain, Vermont using measurements of anthropogenicmetals (Cu, Zn, Cr, Pb, Cd, and Ag) in four age-datedsediment cores. Sediments record a history ofcontamination in a region and can be used to assessthe changing threat to biota over time and to evaluatethe effectiveness of discharge regulations onanthropogenic inputs.Grain size, magnetic susceptibility, radiometricdating and pollen stratigraphy were combined withtrace metal data to provide an assessment of thehistory of contamination over the last 350 yr inthe Burlington region of Lake Champlain. Magneticsusceptibility was initially used to identify land-usehistory for each site because it is a proxy indicatorof soil erosion. Historical trends in metal inputs inthe Burlington region from the seventeenth through thetwentieth centuries are reflected in downcorevariations in metal concentrations and accumulationrates. Metal concentrations increase above backgroundvalues in the early to mid nineteenth century. Themetal input rate to the sediments increases around1920 and maximum concentrations and accumulation ratesare observed in the late 1960s. Decreases inconcentration and accumulation rate between 1970 andthe present are observed for most metals. Theobserved trends are primarily a function of variationsin anthropogenic inputs and not variations in sedimentgrain size. Grain size data were used to removetexture variations from the metal profiles and resultsshow trends in the anthropogenic metal signals remain. Radiometric dating and pollen stratigraphy providewell-constrained dates for the sediments therebyallowing the metal profiles to be interpreted in termsof land-use history. 相似文献
138.
Manufactured soil for landscaping purposes was produced by composting for 6 weeks (1) municipal green waste alone, (2) green
waste amended with 25% v/v poultry manure, or (3) green waste immersed in, and then removed from, a mixture of liquid grease trap waste/septage. Composting
temperatures increased most rapidly and reached highest values (78oC) in the grease trap/septage-amended green waste. In comparison
with green waste alone, addition of poultry manure prolonged the period of elevated temperatures and increased the maximum
temperature attained from 52oC to 61oC. Following composting, each of the materials was split into (1) 100% compost, (2) 80%
compost plus 20% v/v soil, and (3) 70% compost plus 20% soil plus 10% coal fly ash. Addition of poultry manure or grease trap/septage to green
waste prior to composting increased bulk density and reduced total porosity of the composted product. Addition of soil, or
soil and ash, to composts increased bulk density, reduced total porosity, decreased percentage macropores, and increased percentage
mesopores and available water-holding capacity. Bicarbonate-extractable P, exchangeable NH4+ and NO3−, electrical conductivity (EC), soluble C, soluble C as a percentage of organic C, basal respiration, and metabolic quotient
were all markedly greater in the grease trap/septage-amended than poultry manure-amended or green waste alone treatments.
Values for extractable P and EC were considered large enough to be damaging to plant growth and germination index (GI) of
watercress was less than 60% for all grease trap/septage composts. Extractable P and EC were also high, and GI was <100%,
in the green waste alone and poultry manure-amended green waste alone treatments. Addition of soil or soil and ash to these
composts resulted in GI values >100%. 相似文献
139.
140.
Charles C. Coslor Christine Vandervoort John C. Wise 《International Journal of Fruit Science》2019,19(2):151-164
We evaluated the potential for using preplant trunk injections of emamectin benzoate in nonbearing apple trees. Trees were evaluated for pest injury and emamectin residues throughout the planting season and into the following year. Injections into the trunk best delivered emamectin benzoate to the canopy compared with injections into the taproot, and the higher rate reduced insect pests more than the lower rate. In the following year, differences in insect control between trunk and root injections were less pronounced, but the higher rate of emamectin benzoate persisted longer and better reduced pests relative to the other treatments. 相似文献