Scientific inquiry is increasing our knowledge of plant and animal genomics. The ability to specify heterogeneous production processes, to sort agricultural inputs by genotype, or to guide breeding programs to satisfy specific markets based on genetic expression may increase producer and consumer benefits. This research develops a decision analysis framework to assess the expected value of genetic information under risk aversion. Expected utilities are evaluated both with and without genetic trait information. Potential gains in the value of information can be quantified as research unravels the linkages between genetics and crop and animal performance and quality. An application to cattle feeding indicates potential gains to developing markets for specific animal genetic characteristics based on the amino acid sequence of the leptin gene. 相似文献
This paper explores the role of drainage as aninstrument for agricultural and rural development andthe related drainage development forces and processes.Five specific roles of drainage are distinguished:foodproduction, agricultural intensification anddiversification, sustainable irrigated land use, ruraldevelopment and environmental protection. Specialattention is given to the drainage development needsof the developing countries. It is argued that whileat early stages of agricultural development, drainagedevelopment is generally driven by ongoingagricultural development, at later stages ofdevelopment these roles often reverse withagricultural development risking to become stagnatedwhen drainage is not improved. These relationshipsshould be taken into account in the design of drainagedevelopment programs and projects. It is emphasizedthat improved drainage can contribute to establishinga more diversified, competitive and sustainable typeof agriculture, enhance sanitary and public healthconditions and generally contribute to ruraldevelopment, rural well being and poverty alleviation.Drainage development in the developing countries ishowever often severely constrained by the lack of supporting public policies, institutional frameworksand professional cadres. Overcoming these constraintsshould be given high priority on the national andinternational drainage development agendas. 相似文献
Serologic diagnosis of ovine contagious agalactia (Mycoplasma agalactiae) with the enzyme-linked immunosorbent assay (ELISA) developed by Agence Fran?aise de Sécurité Sanitaire des Aliments (AFSSA) may produce a few false-positive (FP) and false-negative (FN) results. When the prevalence of disease is low, these erroneous results may generate problems for eradication schemes. To prevent this, 2 commercial ELISAs were compared with the AFSSA ELISA. Flocks of known status were selected and classified into 4 categories: true positive (TP), FP, true negative (TN), and FN; 20 sheep per flock were submitted for blood sampling. A flock was considered positive when at least 1 out of 20 sera was positive or 2 sera were doubtful. In the flock, the diagnostic sensitivity of the 3 kits was very good (100%), and the diagnostic specificity showed an improvement from 46% (AFSSA test) to 88% and 92% (commercial tests). Considering individual animals, very few positive ewes were detected within TN or FP flocks; the proportion of positive ewes varied greatly from one kit to another (48% to 82%) within TP flocks. The kinetics of antibody response in sheep experimentally infected with various field strains of M. agalactiae were quite similar with all 3 ELISAs. The agreement between the 3 tests, assessed using the kappa value, varied from moderate to good (respective values of 0.56, 0.61, and 0.86). The 2 commercial ELISAs showed better performances, probably because of a superior analytical sensitivity, and are a good alternative for the serodiagnosis of contagious agalactia in sheep. 相似文献
The interest of a new approach in taking up the problems of host-parasite relationships with environment is proposed in terms of population biology. Two different integrating levels are considered: a microenvironment that corresponds particularly to the host and a macroenvironment corresponding to the whole host-parasite system. Some examples are given that provide significant reasons in perceiving the biology of Monogenea under these aspects. To conclude we emphasize the importance of developing this new way for the study of hybrids models in relation to parental host systems. 相似文献
Forest plantations are extensively established in eastern Australia for production of timber products and more recently, potentially for sequestration of carbon. Intensive management of these plantations involves clearing of existing vegetation, often using fire, ripping and/or mounding of the soil and weed control, followed by planting, use of fertilizers, and subsequent tending. The plantations are managed on a 10–30-year rotation and often have high growth rates and accumulation of carbon. However, after establishment, there are reduced inputs of carbon into the soil from prior vegetation or rapidly growing weeds, together with accelerated decomposition of soil organic matter as a result of disturbance, and this leads to a net loss of soil organic carbon. In some systems this loss of soil organic carbon is not balanced by carbon biomass sequestration until 5–10 years after establishment and on some sites, a reduction in soil organic carbon may remain until the end of the rotation. The patterns of accumulation and loss of carbon vary according to location, soil type and plantation management system. The effects of intensive forest establishment on soil organic carbon were evaluated in a number of studies in eastern Australia using time sequence and chronosequence studies and comparisons of plantation soils with those from adjacent undisturbed sites. There was a general pattern of reduced carbon in surface soil immediately after plantation establishment and with time this extended deeper into the soil profile. The actual quantities varied greatly depending on the soil type. The decline was primarily a result of losses of labile carbon and was greater when the previous land use had essentially been native vegetation or highly improved pastures as opposed to regrowth woodland, or native pasture, or degraded land. In the absence of further disturbance, soil organic carbon can accumulate to pre-establishment levels but many short rotation plantations are terminated prior to this being attained. The potential upper level of accumulation of soil carbon can be increased by alteration of the soil nutritional status using fertilizer application. 相似文献
Nutritional surveys in New South Wales Pinus radiata plantations have shown differences in both foliage and soil boron status, particularly as a result of variations in soil parent materials. Plantations on acid igneous parent materials are particularly susceptible to the development of B deficiency, which appears to be further exacerbated bu soil/landscape relationships, water stress and certain management practices.
Boron deficiency in P. radiata on acid igneous soils at Sunny Corner State Forest, N.S.W., was particularly noticeable on lower slopes which usually have relatively high available moisture. These lower-slope soils had severely leached surface horizons, less extractable B, and fewer B-sorption characteristics than the upper sections of the soil catena. These soil properties also adversely affect the capacity of these soils to retain either Na-borate or Ca-borate fertilizers (borax and colemanite, respectively). For equal amounts of B, up to 95% of the borax applied to in-situ soil columns rapidly moved beyond the top 0.3 m of the soil profiles within 21 months, while less than 16% of the colemanite had moved beyond the columns. Leached surface soils of the lower-slope site retained lesser amounts of either B-fertilizer.
Colemanite offers the most cost-effective means of maintaining adequate levels of soil-B in these soil types due to its lower solubility. Management of B deficiency in P. radiata involves appropriate site selection, forest management practices and fertilizers usage. 相似文献
685,000 ha of Pinus radiata(D. Don) plantations in Australia werecategorized using a matrix of mean annualrainfall, rainfall regime and Parent Rock Codefrom a Technical Soil Classification. Datawere obtained from a number of differentorganizations which in total managed nearly allthe Australian P. radiata plantations. The selected characteristics were those whichcould be obtained at an acceptable level ofconfidence from all sources. Such acharacterization of plantation sites provided asystem for utilization of technical informationand extrapolation of research results and alsoa basis for the development of Site SpecificManagement systems. Analysis of theinformation indicated the high degree ofvariability of environments in whichplantations have been established withinAustralia and also the distinctive nature ofindividual regions. Such differences betweenareas make extension of silvicultural andrelated information difficult from one area toanother without appropriate validation. Abroad comparison with 1.26 million hectares ofP. radiata plantations in New Zealandindicated only a small overlap of areas of sitetypes between Australia and New Zealand. Assumptions derived in one location on thesites, characteristics, models and/or genotypeswould require significant testing beforeconfident application could be undertaken toanother area. The value of a Site SpecificManagement system for research planning andapplication of research and operational resultswas demonstrated from analysis of a series ofexperimental trials assessing application offertilizer after thinning and from evaluationof soil carbon in P. radiataplantations. 相似文献