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891.
Lolium species (considered the ideal grasses for European agriculture) are not sufficiently robust to meet many of the environmental
challenges that face extensive agriculture in less favoured areas. Fortunately, adaptations to abiotic and biotic stresses
exist amongst Festuca species related closely to Lolium. The complex of species has an enormous wealth of genetic variability and potentiality for genetic exchange, thus offering
unique opportunities for the production of versatile hybrid varieties with new combinations of useful characters suited to
modern grassland farming. The attributes of Lolium and Festuca can be combined into a single genotype by amphiploidy or alternatively, a limited number of characters can be selectively
introgressed from Festucainto Lolium or vice versa. Androgenesis of the interspecific hybrids can generate genotypes combining characters that may not be recovered by sexual
backcrossing. Genomic in situ hybridization(GISH) can differentially ‘paint’ the chromosomes of Lolium and Festuca and identify Lolium-Festuca recombinant chromosomes. GISH is valuable in the analysis of amphiploids, introgressions and androgenic genotypes and can
be used to physically map introgressed traits. Introgression mapping is a powerful new approach to the mapping of traits and
arises from a fusion of physical and genetic mapping. For example, in a diploidLolium introgression genotype with only one introgressed Festucasegment, the gene(s) for any Festucaderived trait expressed by the plant must be located within the segment. Using GISH and molecular markers, a dense but highly
localised map of the Festuca segment is made in isolation of the Loliumgenome – this may simplify QTL analysis.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
892.
Different improved coffee arabica crosseshaving resistance to coffee berry diseaseand leaf rust, plus a standard cultivar,were grown under a range of environmentalconditions in a series of field trials inKenya. The effects of location and year ofproduction and their interactions with theclones were determined for berry yield.These data were used to estimate andcompare methods of analysis of GEI. An AMMImodel, joint regression model and ANOVAwith repeated measurements were used toinvestigate these interactions. The resultsindicated the relative effects of theclones and the environmental conditions,with Meru being the location where therewas greatest discrimination between theclones, probably because it was bettersuited for coffee. Clones,environments and joint regressions combinedaccounted for 31.20% of the interaction,leaving a residual of 68.80%. Significantresidual mean squares showed therelationship between clones andenvironments not to be strictly linear,thus indicating that regression analysisdid not always provide good estimates ofindividual clonal performance acrossenvironments. High correlations wereobtained between mean yield and regressioncoefficients and between ecovalence andmean square deviations as well as thecoefficient of determination. Resultsshowed that the improved clones surpassedthe standard cultivar both in terms ofyield and stability.Different analyses of the various aspectsof genotype response enabled the 21 clonesto be classified into different similaritygroups based on their performance andphenotypic stability as measured by variousstability parameters and the use of biplotsfrom the AMMI analysis. 相似文献
893.
P. Rajasekaran W. T. B. Thomas A. Wilson P. Lawrence G. Young R. P. Ellis 《Plant Breeding》2004,123(1):17-23
A genetic map was constructed using DNA‐based markers in a barley mapping population derived from the cross ‘Tankard’בLivet’, that was developed to explore the genetic control over grain damage in spring barley cultivars. Quantitative trait loci (QTL) were located for husk skinning, gape between the lemma and palea and splitting of the fused pericarp/testa/aleurone tissues. The QTL accounted for 70% of the genetic variation in Split and 60% of the genetic variation in Gape and Skinning. The QTL were clustered on chromosomes 1H, 4H, 5H, 6H and 7H. QTL analysis indicates the possibility of transgressive segregation for grain splitting and so the breeding of lines with more extreme splitting. This is of concern to the malting industry as, without extensive phenotypic assessment, such lines could be commercialized, as was the case of Landlord, and put malting barley supplies at risk. These findings are discussed in relation to the genetic control over traits including grain length and width. 相似文献
894.
Summary A monogenic dominant male sterility is used for hybrid production in autumn and winter cauliflower. The ratio of male sterile plants in the backcross progenies of autumn cauliflower was 1:1 over five years (1987–1991). However, a significant deficit of male sterile plants was observed in the winter type over the same period.The influence of the temperature on the male sterile phenotype was studied within backcross progenies planted inside polythene tunnels. Six classes of phenotype were defined during the flowering period (from May to November). At low temperature, some male sterile plants developed partial to complete male fertility, whereas at high temperature, male fertile plants became male sterile.Segregation among the progenies of self-pollinated unstable male sterile plants did not deviate from the expected 3:1 ratio. Plants homozygous for the male sterility allele have been revealed by test crosses with a male fertile plant.For use in seed production, stable male sterile plants are vegetatively maintained; however, crossing lines isogenic except at the MS locus would allow male sterile plants to be raised from seed. 相似文献
895.
Motor vehicle and motor vehicle parts production tend to exhibit a strong degree of agglomeration. We estimate a location model utilizing detailed plant‐level data for over 1,700 European locations of the largest motor vehicle parts suppliers, as well as the location of all light vehicle assembly plants operational in 2010. This unique data set allows us to estimate a location model for the region at a significantly higher level of resolution than the previous literature. The results suggest that the main forces of agglomeration in the European auto supplier sector are highway access and the desire to locate near assembly plants as well as near other parts‐producing plants. 相似文献
896.
ABSTRACT Information and Communication Technology (ICT) has become an important tool to promote a variety of public goals and policies. In the past years much attention has been given to the expected social benefits from deploying ICTs in different urban fields (transportation, education, public participation in planning, etc.) and to its potential to mitigate various current or emerging urban problems. The growing importance of ICTs in daily life, business activities, and governance prompts the need to consider ICTs more explicitly in urban policies. Alongside the expectation that the private sector will play a major role in the ICT field, the expected benefits from ICTs also encourage urban authorities to formulate proper public ICT policies. Against this background, various intriguing research questions arise. What are the urban policy‐makers’ expectations about ICTs? And how do they assess the future implications of ICTs for their city? A thorough analysis of these questions will provide a better understanding of the extent to which urban authorities are willing to invest in and to adopt a dedicated ICT policy. This study is focusing on the way urban decision‐makers perceive the opportunities of ICT policy. After a sketch of recent development and policy issues, a conceptual model is developed to map out the driving forces of urban ICT policies in cities in Europe. Next, by highlighting the importance of understanding the decision‐maker's “black box,” three crucial variables are identified within this box. In the remaining part of the paper these three variables will be operationalized by using a large survey comprising more than 200 European cities. By means of statistical multivariate methods (i.e., factor and cluster analysis), the decision‐makers were able to be characterized according to the way they perceive their city (the concept of “imaginable city”), their opinion about ICT, and the way they assess the relevance of ICT policies to their city. Next, a solid explanatory framework will be offered by using a log‐linear logit analysis to test the relationships between these three aspects. 相似文献
897.
The Firm as Social Networks: An Organisational Perspective 总被引:1,自引:0,他引:1
HENRY WAI‐CHUNG YEUNG 《Growth and change》2005,36(3):307-328
ABSTRACT This paper offers an organizational perspective on the firm in new economic geographies. It starts with the premise of the firm as a production function in neoclassical economics and a cost minimisation device in transaction cost economics. By pointing out the inadequacy in these mainstream economic perspectives on the firm, I draw upon recent behavioral and managerial theories to develop a relational conception of the firm as social networks in which actors are embedded in ongoing power relations and discursive processes. In further elaborating this relational perspective on the firm as an organisational device, I show how the firm is governed through social relations among different actors, how it is a site of contested ideologies and political representations among these actors, and how space and geographical scales matter in shaping its social construction. Taken together, this organisational perspective aims to shift our research agenda in urban and regional development from promoting the growth of the firm per se to understanding how the firm serves as a relational institution that connects spatially differentiated actors in different places and regions. 相似文献
898.
Ari‐Veikko Anttiroiko 《Growth and change》2015,46(2):233-252
Globalisation is dramatically changing the context of urban communities and the premises for urban development policy. In the context of global intercity competition, cities' major goal is to increase their competitiveness, in which the positioning and attractiveness of a city have a critical function. Attraction‐oriented development strategies aim at effective absorption of external resources from the global space of flows. At the core of attraction strategy are business promotion activities with appealing incentives, but it is assumed that such a competition is risky and may lead to a race to the bottom. Therefore the emphasis is increasingly on less costly and more synergistic city marketing, which utilises city branding and “city profiling” that aim at attract high value‐adding services or high‐tech firms. This paper proposes a city attraction hypothesis that states that global intercity competition is essentially about a city's ability to attract the highest possible value from global flows of values in order to promote urban development. The result of such a global intercity competition determines cities' functions and positions in the global division of labour and thus in the global urban hierarchy, and ultimately determines their ability to increase prosperity and welfare in urban communities. 相似文献
899.
Summary The regular meiotic behaviour of the cultivated oat Avena sativa (2n=6x=42) is genetically controlled. The factors which control the diploid-like meiotic behaviour also restrict the amount of pairing that occurs between alien chromosomes and their homoeologues in A.sativa, and hence increases the difficulties of introducing desirable variation from wild species into the cultivated oat. A genotype of the diploid species A.longiglumis which interferes with the regular meiotic behaviour of A. sativa can be used to induce pairing between alien chromosomes and their corresponding chromosomes in A. sativa. Using this procedure the dominant gene conferring mildew resistance has been transferred from the tetraploid weed species A. barbata into the cultivated oat. 相似文献
900.
Fungal isolations and fungicide efficacy trials were carried out to determine the possible causes of discoloration in oat groats and potential control measures. Alternaria species and Microdochium nivale were isolated from field samples, and Fusarium poae was found in glasshouse tests. Symptoms could be induced reliably in the field through the use of a mist irrigation system. The cultivar ‘Gerald’ was most resistant followed by ‘Jalna’. Cultivar ‘Image’ was most severely affected by discoloration and ‘Millennium’ was of intermediate susceptibility. None of the 28 fungicide‐timing combinations used in the field trials affected the occurrence of discoloured groats. It was concluded that the best strategy for minimizing risk of discoloured groats would be screening new cultivars or breeding material in mist‐irrigated field trials for genetically based resistance. 相似文献