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Molecular and phenotypic analyses of pathogenicity, aggressiveness, mycotoxin production, and colonization in the wheat-Gibberella zeae pathosystem
(2004) Cumagun, Christian Joseph R.; Miedaner, Thomas
Fusarium head blight (FHB), caused by Gibberella zeae (Schwein.) Petch (anamorph: Fusarium graminearum Schwabe), is one of the principal diseases responsible for extensive damage in wheat fields and contamination of grain with the mycotoxins deoxynivalenol (DON) and nivalenol (NIV), rendering the harvest unsafe for human and animal consumption. Control of FHB is difficult because of the complex nature of host-pathogen-environment interaction and the nonavailability of highly effective fungicides. Agronomic practices and resistance breeding, therefore, offer the best strategies for disease management. Mapping by molecular markers provides an accurate approach for genetic analyses of simple and complex traits particularly pathogenicity, aggressiveness, and mycotoxin production. Pathogenicity, as defined here, is the ability to cause disease whereas aggressiveness is the quantity of disease induced by a pathogenic isolate on a susceptible host in which isolates do not interact differentially with host cultivars. The project aims to (1) map pathogenicity and aggressiveness of G. zeae based on a published genetic map (2) estimate genetic diversity of four parent isolates by PCR-based markers (3) examine the inheritance of pathogenicity, aggressiveness, mycotoxin type (DON/NIV), and DON production on a phenotypic basis, (4) analyse genetic covariation among aggressiveness, DON, and fungal colonization, (5) and compare aggressiveness of 42 isolates in greenhouse and field environments. Two crosses of G. zeae using nit (nitrate nonutilizing) marker technique were performed: (1) pathogenic DON-producing Z-3639 (Kansas, USA) x nonpathogenic NIV-producing R-5470 (Japan) belonging to lineage 7 and 6, respectively, and (2) DON-producing FG24 (Hungary) x FG3211 (Germany), both aggressive lineage 7 isolates. For the first cross, 99 progeny segregated in a consistent 61:38 for pathogenicity: nonpathogenicity in a two-year greenhouse experiment. Among the 61 pathogenic progeny, disease severity, measured as percentage infected spikelets, varied significantly (P = 0.01). Heritability for aggressiveness was high. Pathogenicity locus was mapped on linkage group IV near loci PIG1 (red pigment production), TOX1 (trichothecene toxin amount), and PER1 (perithecial production) explaining 60%, 43%, and 51% of the phenotypic variation, respectively. Two large aggressiveness QTLs were mapped on linkage group I linked to the locus TRI5 (trichodiene synthase in the trichothecene gene cluster) and an amplified fragment length polymorphism (AFLP) marker (EAAMTG0655K), explaining 51% and 29% of the observed phenotypic variation, respectively. These unlinked loci suggest that genetic basis between pathogenicity and aggressiveness were different. TRI5 is located in the same gene cluster as a previously identified gene known as TRI13, which determines whether DON or NIV will be produced. DON-producing progeny were, on average, twice as aggressive as were those producing NIV. Loci were only detected in the two linkage groups mentioned from the nine linkage groups present in the map. For the second cross FG24 x FG3211 with 153 progeny, head blight rating and relative plot yield were used as aggressiveness traits. DON production was measured by a commercial kit enzyme immunoassay. These three traits were quantitatively inherited among 153 progeny across three environments. Repeatabilities within each environment were medium to high but heritabilities across environments were medium only due to high progeny-environment interaction. DON was a less environmentally stable trait than aggressiveness. Transgressive segregants were detected frequently. This implies that even a cross within a lineage could lead to an increase in aggressiveness. Mapping of this cross was not initiated because the parents were not polymorphic enough to construct a genetic map. Instead, the parents were analysed for polymorphism in comparison to the parents of the first cross using 31 AFLP primer combinations and 56 random amplified polymorphic DNA (RAPD) primers. Polymorphism between Z-3639 and R-5470 was about three to four times higher than between FG24 and FG3211. Cluster analysis revealed that R-5470 was genetically separated from the other three parents, thus confirming the lineage assignments. Among preselected 50 progeny from the same field experiments that showed normal distribution for aggressiveness - head blight rating, fungal colonization, and DON production were correlated (r = 0.7, P = 0.01). Fungal colonization measured as Fusarium exoantigen (ExAg) content using enzyme-linked immunosorbent assay (ELISA) varied also quantitatively, but heritability was lower due to high progeny-environment interaction and error. Strong correlations among all traits indicate control by similar genes or gene complexes. No significant variation was observed for DON/ExAg ratio. Aggressiveness traits and DON production were more environmentally stable compared to Fusarium ExAg content. Our findings imply that aggressiveness may have other components apart from mycotoxin production. Genotypic variation for aggressiveness among the 42 progeny in one greenhouse and three field environments was significant and their correlation was moderate (r = 0.7, P = 0.01). High heritability in both environments again indicates that aggressiveness was a relatively stable trait, although methods of inoculation differed, i.e., injection for greenhouse and spraying for field experiments. Greenhouse aggressiveness could predict aggressiveness in the field, and thereby should reduce costs for resistance and phytopathological studies. In conclusion, we consider G. zeae as medium-risk pathogen with the potential to evolve to a higher level of aggressiveness due to sexual recombination. Erosion of quantitative resistance in FHB cannot be ignored, especially if host resistances with oligogenic inheritance, e.g. Sumai 3 from China, are used on a large acreage. Consequently, the rather simple inheritance of pathogenicity and aggressiveness in G. zeae could lead to a gradual increase of aggressiveness. These results should enhance efforts of plant breeders to use several, genetic distinct sources of resistance in order to avoid possible FHB outbreaks in the future.
Wirkung rassenspezifischer Braunrostresistenzen in genetisch diversifizierten Roggenpopulationen
(2004) Wilde, Katinka; Miedaner, Thomas
Leaf rust (Puccinia recondita f.sp. secalis) is the most frequently occuring leaf disease in German winter rye (Secale cereale L.). To test the usefulness and potentially prolong the durability of race-specific resistance genes, we increased host complexity and diversity by producing synthetic (Syn) populations segregating for one to four resistance sources as a model system for hybrid varieties. Thirty synthetics were grown together with three highly susceptible synthetics as checks, two Russian full-sib families (FSF), a leaf-rust-resistant-hybrid variety, a set of 17 differential genotypes and ten parental lines at six locations in three years (17 environments) in Germany under natural infection. The parental lines were only sown in 11 environments. Disease severity of about 120 plants for each synthetic, FSF, hybrid and about 25 plants for each differential genotype and parental line was estimated as percentage of infected leaf area on the leaf below the flag leaf at the mid and the end of the natural epidemic. Susceptible synthetics showed that disease severity was similarly high in all environments. Only two out of 30 synthetics and both FSF were resistant across 17 environments. Low resistance of the synthetic was caused by the low resistance of the parental lines. Nonetheless, some of the synthetics were more resistant than the tested commercial hybrid variety. Even though the resistance was not used in practical breeding programs to date we detected virulence for each resistance gene tested. In conclusion, the German leaf rust population seems to be highly diverse and none of the self-fertile resistance sources used provided full protection. New race-specific resistances or highly effective quantitative resistances are therefore needed and should be combined.
Quantitativ-genetische Untersuchungen zur Vererbung der Resistenz gegen Ährenfusarium bei Triticale (x Triticosecale Wittmack)
(2004) Heinrich, Nicole; Miedaner, Thomas
Fusarium head blight (FHB), caused by Fusarium culmorum (W.G. Smith) Sacc. and F. graminearum Schwabe, is recognized as one of the most destructive diseases of small-grain cereals. Fusarium infection can cause substantial yield losses. Infected grain may also be contaminated by mycotoxins that are harmful to humans and livestock. Agronomical measures and fungicides are only partly effective in controlling FHB. The development of disease-resistant cultivars together with appropriate crop management practices are effective strategies to control FHB. In this study, seven triticale cultivars and three breeding strains, representing a range of FHB resistances, their 45 diallel F1 crosses, progenies of 15 F2s from a six-parent diallel and their 30 backcrosses (BC, 15 to each parent), and five F2:3 bulks were investigated. Parents and their progenies were grown in several environments (years, locations) and tested for FHB resistance after artificial inoculation with Fusarium culmorum. Within the scope of this study, three experiments were conducted to estimate various quantitative-genetic parameters of several traits. In Experiment 1, the influence of FHB on yield-related traits of the ten parents was assessed. Compared to a non-inoculated variant, Fusarium reduced 1000-grain weight by 10.0%, spike weight by 9.3%, the number of kernels per spike by 4.3%, and test weight by 7.4%. Inoculation also increased deoxynivalenol (DON, 26.4 mg kg-1) and exoantigen (1.34 OD). content of the kernels. Genotypic variation and genotype-environment interaction were significant for all traits. The correlation between symptom ratings (spikes, kernels) and yield traits and between spike weight and kernels per spike were negative and high. The aim of Experiment 2 was to estimate combining ability, hybrid performance and heterosis for FHB ratings, DON and exoantigen content. Heterosis of FHB for spike and kernel rating was small. Across environments, the DON content in F1 crosses, however, was 15.5% higher than their mid-parent value. A high and significant (P = 0.01) correlation of r = 0.8 was found for both spike and kernel FHB symptom ratings between mid-parent and F1 performance. Except for exoantigen content, the general combining ability (GCA) was the main source of variation, suggesting additive gene effects for FHB resistance. Significant specific combining ability variance implies non-additive types of allelic interaction also. Therefore, in some crosses dominant effects can play an important role. The relationship between the GCA effect of a parent and its per se performance was close. In Experiment 3, genetic variation and effects for FHB resistance were estimated in segregating generations. The resistance level of the parents and their F2 progenies were similar. In contrast, the resistance of the BC progenies to the resistant parent was considerably higher than that of the backcrosses to the susceptible parent. Significant differences between the means of the 15 crosses and a high genetic variation within crosses were observed. Transgression could not be detected. F2:3 bulks and their parents had a comparable resistance level. For F2 and BC progenies, the additive effect was more important than the dominant effect. In contrast, the F1 crosses had a higher dominant effect, but with a large error. The study revealed considerable genetic variation in all generations for FHB resistance that can be exploited in a breeding programme. The mainly additive genetic effect makes it possible to select crossing parents on the basis of their per se performance. Due to the importance of genotype-environment interaction, resistance tests in various environments are strongly recommended. Screening for FHB resistance can best be accomplished by assessing symptom ratings of spikes and/or the spike weight relative to a non-inoculated variant. The high cross-environment interaction variance in the F2 generation points to the problem of selecting in unreplicated segregating material. Selection should be postponed to the F3 or later generations. The large genetic variation of FHB resistance and the preponderance of additive gene effects are encouraging to further increase resistance in triticale by recurrent selection.
Bericht der Landesanstalt für Bienenkunde der Universität Hohenheim für das Jahr 2004
(2005) Landesanstalt für Bienenkunde; Rosenkranz, Peter
Bericht der Landesanstalt für Bienenkunde der Universität Hohenheim für das Jahr 2005
(2006) Landesanstalt für Bienenkunde; Rosenkranz, Peter
Genetische Variation für Resistenz gegen Mutterkorn (Claviceps purpurea [Fr.] Tul.) bei selbstinkompatiblen und selbstfertilen Roggenpopulationen
(2006) Mirdita, Vilson; Miedaner, Thomas
Ergot (Claviceps purpurea [Fr.] Tul.) is one of the most important diseases in rye. Infection during flowering results in the production of black, overwintering organs (sclerotia) instead of kernels, which contain harmful alcaloids. Three experiments were conducted to estimate quantitative-genetic parameters of the resistance of rye to ergot under the conditions of organic farming. The general aim was the estimation of genetic variation among and within self-incompatible rye populations and among CMS lines and their male-sterile testcrosses. In 2002 and 2004, genetic variation in resistance to ergot was tested among 65 rye populations at each of two locations (Experiment 1). Thirteen populations were registered rye varieties and the remaining 52 were genetic resources. To assess genetic variation within populations, 50 full-sib families (FSF) from each of five rye populations were developed and tested at four locations (Experiment 2). To test genetic differences in the susceptibility of ovaries towards fungal penetration in the absence of pollen, (i) 64 currently available CMS lines and (ii) their male-sterile crosses with three testers (=sets) were tested in 2003 and 2004, and in 2004, respectively. Inoculation was performed by spraying an aggressive mixture of isolates of Claviceps purpurea three times during the flowering period. The micro-plots were grown in a chess-board design separated by wheat plots to reduce the neighbouring effects. Traits of resistance were the proportion of infected spikes relative to the total number of spikes per plot, and the percentage by weight of ergot sclerotia in the grain. In Experiment 3, the weight of slcerotia per spike and per pair of spikelet were measured due to the absence of grain. Amount of pollen shedding was rated on the basis of the anther size and extrusion. Highly significant genotypic and genotype-environment interaction variances were found among rye populations in the percentage of ergot sclerotia in the grain. All genotypes were infected by ergot. No differences in mean among the registered rye varieties and genetic resources were detected. Because all populations were highly pollen shedding, the results indicate the existence of genetically determined resistance to ergot within the self-incompatible rye. Correlation between both resistance traits was significant (rp = 0.92). Genetic variation within populations was highly significant for all five populations. Individual progenies with resistance higher than the population mean were observed. The mean resistance of initial populations hardly differed from the mean of their progeny indicating a predominantly additive inheritance. Highly significant genetic variation in resistance to ergot was also detected among the currently available 64 CMS lines. Corresponding testcrosses mostly had a higher weight of sclerotia per spike than the lines. Considerable differences in the level of resistance were observed among testcrosses. Crosses with tester line 1 were substantially more susceptible, whereas those with tester 2 were hardly over the mean of the parental lines. The material showed a quantitative distribution of ergot resistance. Weak to medium-sized correlations (0.33 ? 0.47) between locations were detected among lines. The correlation between locations was even weaker in testcrosses. Weak correlations in ergot weight per spike were observed between CMS lines and their testcrosses in sets 2 and 3. In set 1, the estimated phenotypic correlation was higher (rp = 0.65). Estimates of error-corrected correlations were always higher than phenotypic correlations. No genetic difference was detected among the CMS lines for the amount of alkaloids in their sclerotia. This study shows that incompatible rye populations as well as self-fertile hybrid populations contain a substantial genetic variation for resistance to ergot that is inherited quantitatively. In both materials, mainly additive genetic variance was found. Because of a significant genotype-environment interaction, multi-environment trials are necessary to select for resistance. The results of this study nevertheless indicate good prospects to improve resistance to ergot in rye breeding in the long term.
Bericht der Landesanstalt für Bienenkunde der Universität Hohenheim für das Jahr 2006
(2007) Landesanstalt für Bienenkunde; Rosenkranz, Peter
Untersuchungen zur Aufbereitung und Umwandlung von Energiepflanzen in Biogas und Bioethanol
(2008) Schumacher, Britt; Jungbluth, Thomas
Due to finite fossil resources, one opportunity for the future is to increase the supply of energy out of renewable energy sources. One of many opportunities is the use of biomass, which offers plenty combinations of different kinds of biomass, paths of utilization and conversion techniques for a flexible adaptation to natural local and regional frameworks as well as the anthropogenic needs. For an efficient utilization of the limited arable land for the supply of bioenergy, there is a need of up-to-date and proof data about specific energy yields and yields per hectare. The aim of this investigation was to determine these data for the biogas and bioethanol sectors. Batch-tests were carried out in laboratory scaled digesters to investigate specific biogas and bioethanol yields. Additionally the testing of different techniques of pre-treatment for energy crops and their effects on the biogas yield and the progression of the formation of methane were focused. The conversion of maize silage and full ripe triticale into biogas and bioethanol was compared by an energy and environmental balance. The steam explosion technique was included. Pre-treatment The steam explosion pre-treatment of biomass increases the speed of formation of methane and partly increases the methane yields. The effects differ depending on the kind of biomass and the stage of ripening. Other techniques of pre-treatment like microwaving and cooking did not show significant or partly negative effects. A variation of parameters in the trial setup might be interesting. Besides the positive effects of the steam explosion technique there are some arguments like the additional costs of investment, the diminished concentration of nutrients respectively the increase of material flow against it. The additional energy consumption, mostly thermal energy, can be supplied from waste heat out of the combined heat and power plant (CHP). The screening and the production of technical enzymes for the efficient pre-degradation of raw materials containing high amounts of lignocellulose should be the subject of research and development in the future. The combination of biological (enzymatic), chemical, thermal and mechanical pre-treatment techniques need to be investigated with the focus on energy efficiency. Methane yields of energy crops and stillage A broad number of biogas tests had been carried out on various maize cultivars. The specific methane yields of the maize cultivars varied over the harvesting date differently. The cultivars with a low ripening number reached higher specific methane yields. The dominant factor for the energy yield per hectare was the dry matter yield, not the specific methane yield. In general it is recommended to use well adapted cultivars with high dry matter yields and a good ensilaging behaviour. The catch crops increased the methane yields per hectare just partly. But for reasons of soil conservation the cultivation is recommended. The nitrogen fertilizer had mostly a positive effect on the dry matter yields and the energy yields per hectare, respectively. Maize gained higher energy yields per hectare than switch grass. The utilization of stillage out of whole maize plants or triticale´s grain from the ethanol production as well as the utilization of by-products like straw in the biogas production could double the energy output per hectare compared to the simple ethanol production. Further options for the optimization of the biogas production under conditions of practice are digester systems well-adapted on the substrate, the use of multi step systems and the development of analytic methods in order to gain effective process control. Correlation between chemical components and measured methane yields The specific methane yields calculated out of the neutral detergents fibre, starch, sugar, raw proteins and its substrate-specific factors were very close to the experimentally determined yields of the maize cultivars for the four harvesting times. But the measured and calculated values showed no correlation. Whether the biogas tests can be replaced, by other methods or techniques of analysis of the components and the determination of additional components for the estimation of the potential of new cultivars, should be subject of further investigations. Bioethanol yields The energy yields on the conversion pathway bioethanol without using the by-products are lower than the yields via conversion into biogas, because the ethanol fermentation is limited on material that can be converted into sugar first. The advantage of the ethanol production is a fluid fuel as result of the process. Combining the ethanol production with a biogas plant, the by-products also can be used energetically and a gaseous energy carrier can be produced. There are high potentials for the bioprocess engineering, for instance in breeding of microorganisms for the degradation of lignocellulosic biomass or of C5-sugar. Furthermore a process optimization of water and energy input is recommended. Energy and environmental balance Biogas as well as bioethanol (combined with biogas) is able to reduce the consumption of non-renewable energy carrier and its emission under the investigated scenarios and the scoop set. A future task will be the development of differentiated and well-adapted concepts on the basis of a decision between (liquid) fuels or stationary supply of thermal and electrical energy out of biomass. The aim is an efficient use of the limited areas of arable land and forests for the supply with bioenergy carriers by a useful combination of biomass, paths of utilization and conversion technique depending on natural local and regional conditions as well as the anthropogenic needs.
Bericht der Landesanstalt für Bienenkunde der Universität Hohenheim für das Jahr 2007
(2008) Landesanstalt für Bienenkunde; Rosenkranz, Peter
Payments for environmental services : incentives through carbon sequestration compensation for cocoa-based agroforestry systems in Central Sulawesi, Indonesia
(2008) Zeller, Manfred; Seeberg-Elverfeldt, Christina; Schwarze, Stefan
Up to 25 percent of all anthropogenic greenhouse gas emissions are caused by deforestation, and Indonesia is the third largest greenhouse gas emitter worldwide due to land use change and deforestation. On the island of Sulawesi in the vicinity of the Lore Lindu National Park (LLNP), many smallholders contribute to conversion processes at the forest margin as a result of their agricultural practices. Specifically the area dedicated to cocoa plantations has increased from zero (1979) to nearly 18,000 hectares (2001). Some of these plots have been established inside the 220,000 hectares of the LLNP. An intensification process is observed with a consequent reduction of the shade tree density. This study assesses which impact carbon sequestration payments for forest management systems have on the prevailing land use systems. Additionally, the level of incentives is determined which motivates farmers to desist from further deforestation and land use intensification activities. Household behaviour and resource allocation is analysed with a comparative static linear programming model. As these models prove to be a reliable tool for policy analysis, the output can indicate the adjustments in resource allocation and land use shifts when introducing compensation payments. The data was collected in a household survey in six villages around the LLNP. Four household categories are identified according to their dominant agroforestry systems. These range from low intensity management with a high degree of shading to highly intensified shade free systems. At the plot level, the payments from carbon sequestration are the highest for the full shade cocoa agroforestry system, but with low carbon prices of ? 5 tCO2e-1 these constitute 5 percent of the cocoa gross margin. Focusing on the household level, however, an increase of up to 18 percent of the total gross margin can be realised. Furthermore, for differentiated carbon prices up to ? 32 tCO2e-1 the majority of the households have an incentive to adopt the more sustainable shade intensive agroforestry system. A win-win situation seems to appear, whereby, when targeting only the shade intensive agroforestry systems with carbon payments, the poorest households economically benefit the most and land use systems with high environmental benefits are promoted.
Tätigkeitsbericht 2007 / Landesanstalt für Landwirtschaftliche Chemie
(2008) ; Landesanstalt für Landwirtschaftliche Chemie
Bericht der Landesanstalt für Bienenkunde der Universität Hohenheim für das Jahr 2001
(2009) Landesanstalt für Bienenkunde; Rosenkranz, Peter
Bericht der Landesanstalt für Bienenkunde der Universität Hohenheim für das Jahr 2000
(2009) Landesanstalt für Bienenkunde; Rosenkranz, Peter
Market field structure and dynamics in industrial automation
(2009) Slowak, André P.
There is a research tradition in the economics of standards which addresses standards wars, antitrust concerns or positive externalities from standards. Recent research has also dealt with the process characteristics of standardisation, de facto standard-setting consortia and intellectual property concerns in the technology specification or implementation phase. Nonetheless, there are no studies which analyse capabilities, comparative industry dynamics or incentive structures sufficiently in the context of standard-setting. In my study, I address the characteristics of collaborative research and standard-setting as a new mode of deploying assets beyond motivations well-known from R&D consortia or market alliances. On the basis of a case study of a leading user organisation in the market for industrial automation technology, but also a descriptive network analysis of cross-community affiliations, I demonstrate that there must be a paradoxical relationship between cooperation and competition. More precisely, I explain how there can be a dual relationship between value creation and value capture respecting exploration and exploitation. My case study emphasises the dynamics between knowledge stocks (knowledge alignment, narrowing and deepening) produced by collaborative standard setting and innovation; it also sheds light on an evolutional relationship between the exploration of assets and use cases and each firm's exploitation activities in the market. I derive standard-setting capabilities from an empirical analysis of membership structures, policies and incumbent firm characteristics in selected, but leading, user organisations. The results are as follows: the market for industrial automation technology is characterised by collaboration on standards, high technology influences of other industries and network effects on standards. Further, system integrators play a decisive role in value creation in the customer-specific business case. Standard-setting activities appear to be loosely coupled to the products offered on the market. Core leaders in world standards in industrial automation own a variety of assets and they are affiliated to many standard-setting communities rather than exclusively committed to a few standards. Furthermore, their R&D ratios outperform those of peripheral members and experience in standard-setting processes can be assumed. Standard-setting communities specify common core concepts as the basis for the development of each member's proprietary products, complementary technologies and industrial services. From a knowledge-based perspective, the targeted disclosure of certain knowledge can be used to achieve high innovation returns through systemic products which add proprietary features to open standards. Finally, the interplay between exploitation and exploration respecting the deployment of standard-setting capabilities linked to cooperative, pre-competitive processes leads to an evolution in common technology owned and exploited by the standard-setting community as a particular kind of innovation ecosystem.
Mismatches between actual and preferred work time : empirical evidence of hours constraints in 21 countries
(2009) Otterbach, Steffen
This paper analyzes the discrepancy between actual and desired working hours in a multinational setting. Using the latest data of the International Social Survey Program (ISSP) with a focus on work orientations hours constraints in 21 heterogeneous countries are analyzed. One major finding is that hours constraints are interrelated with macroeconomic variables such as (i) unemployment rates, (ii) GDP per capita as a measure of welfare, (iii) average weekly work hours, and (iv) income inequality. A subsequent multivariate analysis reveals that, on both macro- and microlevels, sociodemographic variables like prosperity and income, high risk of unemployment, and working conditions play an important role in determining working hours constraints. The results further suggest that, with respect to working conditions, such constraints are also affected by gender issues.
Tätigkeitsbericht 2008 / Landesanstalt für Landwirtschaftliche Chemie
(2009) ; Landesanstalt für Landwirtschaftliche Chemie
Bericht der Landesanstalt für Bienenkunde der Universität Hohenheim für das Jahr 2008
(2009) Landesanstalt für Bienenkunde; Rosenkranz, Peter
New economic geography reloaded : localized knowledge spillovers and the geography of innovation
(2009) Christ, Julian P.
Despite the increasing and newly inspired interests in geographical economics and industry location theory, the majority of existing New Economic Geography models ignores the interdependence between spatial concentration, knowledge diffusion, invention and growth. For this reason, the paper exclusively surveys the emergence and development of New Economic Geography Growth models in the context of the existing geography of innovation literature. The first part of the paper contributes with a classification of first- and second-nature causes of agglomeration and clustering. This part will also discriminate between static and dynamic externalities. Therefore, the chapter particularly compiles the differences between urbanization and localization externalities, and MAR, Jacobian and Porter externalities. A second concern of the paper is to highlight the modeling peculiarities of New Economic Geography Growth models. Besides approaching the main differences and similarities between first- and second-generation NEG models, the paper additionally reviews and discloses complemental contributions to the geography of innovation literature in the course of time. For this purpose, the paper examines in a meta-study 61 empirical contributions, which are related to the knowledge production function, the concept of spatial dependence and knowledge spillovers. The meta-study is complemented by bibliometric research. The paper ultimately concludes that the empirical studies that are related to the concept of (localized) knowledge spillovers and spatial association have caused a fundamental upgrading of the New Economic Geography literature towards non-pecuniary externalities. Consequently, the paper shows that recently developed second-generation NEG models offer alternative backward and forward linkages, which similarly determine centripetal and centrifugal forces, circular causality and finally the geography of innovation.
Why blu-ray vs. HD-DVD is not VHS vs. Betamax : the co-evolution of standard-setting consortia
(2009) Christ, Julian P.; Slowak, André P.
Extensive research has been conducted on the economics of standards in the last three decades. To date, standard-setting studies emphasize a superior role of demand-side-driven technology diffusion; these contributions assume the evolution of a user-driven momentum and network externalities. We find that consumers wait for a dominant standard if they are unable to evaluate technological supremacy. Thus, supply-side-driven activities necessarily need to address an absence of demand-side technology adoption. Our paper focuses on Blu-ray vs. HD-DVD as an illustrative case of consortia standard wars. One central role of consortia is to coordinate strategic behavior between heterogeneous agents, e.g. incumbents, complementors (content providers) and others, but also to form a coalition against other standard candidates. More precisely, we argue that agents signal standard-setting war outcomes through consortia events. We depict the essential role of consortia structures for the recently determined standard war between the High-Definition disc specifications Blu-ray and HD-DVD. Therefore, the paper suggests that unique supply-side dynamics from consortia structures, consortia announcements and exclusive backing decisions of firms determined the standard-setting process in the Blu-ray vs. HD-DVD standard war. This study is based on the following data: movie releases and sales numbers, membership affiliation for structural consortia analysis, and an in-depth event study. A detailed comparison of the technological specifications of both standard specifications supports our argument that there was no technological supremacy of one standard candidate from a consumer-oriented usecase perspective. We furthermore clarify that content providers (complementors) such as movie studios and movie rental services feature a gate-keeping position in the Blu-ray vs. HD-DVD standard war. In the case of Blu-ray, film studios decided the standard war because the availability of movie releases, but not technological supremacy, made the standard attractive to consumers. Finally, we find that there is a co-evolution of the consortia in terms of membership dynamics. Particularly, firm allegiance of heterogeneous agents plays a crucial role.
Unemployment in an interdependent world
(2009) Felbermayr, Gabriel; Larch, Mario; Lechthaler, Wolfgang
We introduce search and matching unemployment into a model of trade with differentiated goods and heterogeneous firms. Countries may differ with respect to size, geographical location, and labor market institutions. Contrary to the literature, our single-sector perspective pays special attention to the role of income effects and shows that bad institutions in one country worsen labor market outcomes not only in that country but also in its trading partners. This spill-over effect is conditioned by trade costs and country size: smaller and/or more centrally located nations suffer less from inefficient policies at home and are more heavily affected from spill-overs abroad than larger and/or peripheral ones. We offer empirical evidence for a panel of 20 rich OECD countries. Carefully controlling for institutional features and for business cycle comovements between countries, we confirm our qualitative theoretical predictions. However, the magnitude of spill-over effects is larger in the data than in the theoretical model. We show that introducing real wage rigidity can remedy this problem.

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