Streptomyces scabies and S. turgidiscabies as pathogens causing potato common scab, and potential methods for their control

Tieteellinen tiivistelmä Common scab is one of the most important soil-borne diseases of potato (Solanum tuberosum L.) in many potato production areas. It is caused by a number of Streptomyces species, in Finland the causal agents are Streptomyces scabies (Thaxter) Lambert & Loria and S. turgidiscabies Takeuchi. The scab-causing Streptomyces spp. are well-adapted, successful plant pathogens that survive in soil also as saprophytes. Control of these pathogens has proved to be difficult. Most of the methods used to manage potato common scab are aimed at controlling S. scabies, the most common of the scab-causing pathogens. The studies in this thesis investigated S. scabies and S. turgidiscabies as causal organisms of common scab and explored new approaches for control of common scab that would be effective against both species. S. scabies and S. turgidiscabies are known to co-occur in the same fields and in the same tuber lesions in Finland. The present study showed that both these pathogens cause similar symptoms on potato tubers, and the types of symptoms varied depending on cultivar rather than the pathogen species. Pathogenic strains of S. turgidiscabies were antagonistic to S. scabies in vitro indicating that these two species may be competing for the same ecological niche. In addition, strains of S. turgidiscabies were highly virulent in potato and they tolerated lower pH than those of S. scabies. Taken together these results suggest that S. turgidiscabies has become a major problem in potato production in Finland. The bacterial phytotoxins, thaxtomins, are produced by the scab-causing Streptomyces spp. and are essential for the induction of scab symptoms. In this study, thaxtomins were produced in vitro and four thaxtomin compounds isolated and characterized. All four thaxtomins induced similar symptoms of reduced root and shoot growth, root swelling or necrosis on micro-propagated potato seedlings. The main phytotoxin, thaxtomin A, was used as a selective agent in a bioassay in vitro to screen F1 potato progeny from a single cross. Tolerance to thaxtomin A in vitro and scab resistance in the field were correlated indicating that the in vitro bioassay could be used in the early stages of a resistance breeding program to discard scab-susceptible genotypes and elevate the overall levels of common scab resistance in potato breeding populations. The potential for biological control of S. scabies and S. turgidiscabies using a non-pathogenic Streptomyces strain (346) isolated from a scab lesion and S. griseoviridis strain (K61) from a commercially available biocontrol product was studied. Both strains showed antagonistic activity against S. scabies and S. turgidiscabies in vitro and suppressed the development of common scab disease caused by S. turgidiscabies in the glasshouse. Furthermore, strain 346 reduced the incidence of S. turgidiscabies in scab lesions on potato tubers in the field. These results demonstrated for the first time the potential for biological control of S. turgidiscabies in the glasshouse and under field conditions and may be applied to enhance control of common scab in the future.

Content of zinc, iron and their absorption inhibitors in Nicaraguan common beans (Phaseolus vulgaris L.).

Protein-energy malnutrition and mineral deficiencies are two of the three forms of nutritional deficiencies that affect most developing countries due to inadequate access to food and diets based on a sole crop. Common bean (Phaseolus vulgaris L.) is the staple crop of Nicaragua and it has the potential to improve the nutritional status of the poorest group of the nation. Its high content of both protein and nonhaem iron provides many nutrients, but inhibitors also may prevent absorption of iron and zinc by the human consumer. A proper production chain must be followed to ensure the best grain quality for the consumer. To achieve food security, both production and high nutritional content must be maintained. Four nationally important accessions of common bean, with different harvesting dates, were selected to be submitted to two treatments: to evaluate the impact of storage conditions on the end quality of the grain. The duration of the study was six months with sampling every six weeks, and the two treatments were controlled one stored at 40°C and 75 RH %, and the other was stored in in-situ conditions. Proximate and mineral composition was evaluated as well as tannin, phytate and bioavailability. Significant differences among different accessions were found, being the most significant in protein, Fe and Zn content, tannins and phytate. Protein values ranged from 21-23%. Iron content was 61-81 mg/kg but only 3-4% was bioavailable. Zinc content was 21-25 mg/kg and 10-12% was bioavailable. The concentration of phytate ranged from 8.6-9.6 mg/g while tannin values ranged within 37.7-43.8 mg/g. Storage at high temperatures was demonstrated to have an impact on certain nutritional compounds and proved detrimental to final grain quality. Soluble sugar content and tannin content decreased after six months in both storage conditions, IDF decreased in the in-situ and SDF in the stress. The iron content and bioavailability in INTA Biofortificado were not as outstanding as expected, so experiments should be conducted to compare its iron uptake and delivery with other cultivars.

Integration or disintegration? Human resource implications of a common corporate language decision in a crossborder merger

The primary purpose of introducing a common corporate language in crossborder mergers is to integrate two previously separate organizations and facilitate communication. However, the present case study of a cross-border merger between two Nordic banks shows that the common corporate language decision may have disintegrating effects, particularly at organizational levels below top management. We identify such effects on performance appraisal, language training and management development, career paths, promotion and key personnel. Our findings show that top management needs to work through the consequences of the language decision upon those who are expected to make such a decision work.

Essays on the Determinants of International Portfolio Investments

Investors significantly overweight domestic assets in their portfolios. This behavior which is commonly called “home bias” contradicts the prescriptions of portfolio theory. This thesis explores potential reasons for the “home bias” by examining the characteristics of the investing and the target countries and features of the interaction between them. A common theme of the four essays is a focus on the importance of information about foreign markets in explaining the share of these markets in investors’ portfolios. The results indicate that the size of the equity ownership in another country strongly relates to the distance to the financial capital of that country, and to trade in goods with and direct investments (FDI) to that country. The first essay empirically investigates the relationship between trade in real goods and portfolio investments. Overall, the evidence indicates a substantial role for trade in reducing the information cost relating to portfolio investments. The second essay examines the implications of the launch of the European Monetary Union (EMU) on international portfolio investments. The evidence on the allocation of Finnish international portfolio investments is more consistent with an information-based than a diversification motive explanation. The third essay employs new data for a large number of countries and further explores the role of trade on international portfolio investments. The results indicate that trade provides important information especially on firms in countries in which the corporate governance structure and the information environment of firms generate less reliable information. The fourth essay examines the relationship between direct investments (FDI) and portfolio investments. In contrast to the predications of portfolio theory, it provides evidence that FDI is a complement rather than a substitute for portfolio investments.

Common past, divided memories: historical memory of the Polish minority members in Lithuania

The Master’s thesis examines historical memory of the Polish minority members in Lithuania with regard to how their interpretation of the common Polish-Lithuanian history reiterates or differs from the official Polish and Lithuanian narratives conveyed by the school textbooks. History teaching in high schools carries a crucial state-supported role of “identity building policies” – it maintains a national narrative of memory, which might be exclusive to minorities and their peculiar understanding of history. Lithuanians Poles, in this regard, represent a national minority, which is exposed to two conflicting national narratives of the common past – Polish and Lithuanian. As members of the Polish nation, their understanding of the common Polish-Lithuanian history is conditioned by the Polish historical narrative, acquired as part of the collective memory of the family and/or different minority organizations. On the other hand, they encounter Lithuanian historical narrative of the Polish-Lithuanian past throughout the secondary school history education, where the curriculum, even if taught in Polish, largely represents the Lithuanian point of view. The concept of collective memory is utilized to refer to collective representations of national memory (i.e. publicly articulated narratives and images of collective past in history textbooks) as well as to socially framed individual memories (i.e. historical memory of minority members, where individual remembering is framed by the social context of their identity). The thesis compares the official national historical narratives in Lithuania and Poland, as conveyed by the Polish and Lithuanian history textbooks. The consequent analysis of qualitative interviews with the Polish minority members in Lithuania offers insights into historical memory of Lithuanian Poles and its relation to the official Polish and Lithuanian national narratives of the common past. Qualitative content analysis is applied in both parts of the analysis. The narratives which emerge from the interview data could be broadly grouped into two segments. First, a more pronounced view on the past combines the following elements: i) emphasis on the value of multicultural and diverse past of Lithuania, ii) contestation of “Lithuanocentricity” of the Lithuanian narrative and iii) rejection of the term “occupation”, based on the cultural presuppositions – the dominant position of Polish culture and language in the Vilnius region, symbolic belonging and “Lithuanianness” of the local Poles. While the opposition to the term of “occupation” is in accord with the official Polish narrative conveyed by the textbooks, the former two elements do not neatly adhere to either Polish or Lithuanian textbook narratives. They should rather be considered as an expression of claims for inclusion of plural pasts into Lithuanian collective memory and hence as claims for symbolic enfranchisement into the Lithuanian “imagined community”. The second strand of views, on the other hand, does not exclude assertions about the historically dominant position of Polish culture in Lithuania, but at the same time places more emphasis on the political and historical continuity of the Lithuanian state and highlights a long-standing symbolic connectedness of Vilnius and Lithuania, thus, striking a middle way between the Polish and Lithuanian interpretations of the past.

The potential of microbial ecological indicators to guide ecosophisticated management of hydrocarbon-contaminated soils

Soil is an unrenewable natural resource under increasing anthropogenic pressure. One of the main threats to soils, compromising their ability to provide us with the goods and ecosystem services we expect, is pollution. Oil hydrocarbons are the most common soil contaminants, and they disturb not just the biota but also the physicochemical properties of soils. Indigenous soil micro-organisms respond rapidly to changes in the soil ecosystem, and are chronically in direct contact with the hydrophobic pollutants on the soil surfaces. Soil microbial variables could thus serve as an intrinsically relevant indicator of soil quality, to be used in the ecological risk assessment of contaminated and remediated soils. Two contrasting studies were designed to investigate soil microbial ecological responses to hydrocarbons, together with parallel changes in soil physicochemical and ecotoxicological properties. The aim was to identify quantitative or qualitative microbiological variables that would be practicable and broadly applicable for the assessment of the quality and restoration of oil-polluted soil. Soil bacteria commonly react on hydrocarbons as a beneficial substrate, which lead to a positive response in the classical microbiological soil quality indicators; negative impacts were accurately reflected only after severe contamination. Hydrocarbon contaminants become less bioavailable due to weathering processes, and their potentially toxic effects decrease faster than the total concentration. Indigenous hydrocarbon degrader bacteria, naturally present in any terrestrial environment, use specific mechanisms to improve access to the hydrocarbon molecules adsorbed on soil surfaces. Thus when contaminants are unavailable even to the specialised degraders, they should pose no hazard to other biota either. Change in the ratio of hydrocarbon degrader numbers to total microbes was detected to predictably indicate pollutant effects and bioavailability. Also bacterial diversity, a qualitative community characteristic, decreased as a response to hydrocarbons. Stabilisation of community evenness, and community structure that reflected clean reference soil, indicated community recovery. If long-term temporal monitoring is difficult and appropriate clean reference soil unavailable, such comparison could possibly be based on DNA-based community analysis, reflecting past+present, and RNA-based community analysis, showing exclusively present conditions. Microbial ecological indicators cannot replace chemical oil analyses, but they are theoretically relevant and operationally practicable additional tools for ecological risk assessment. As such, they can guide ecologically informed and sustainable ecosophisticated management of oil-contaminated lands.

Common Infrastructure for Finite-State Based Methods and Linguistics Descriptions

Finite-state methods have been adopted widely in computational morphology and related linguistic applications. To enable efficient development of finite-state based linguistic descriptions, these methods should be a freely available resource for academic language research and the language technology industry. The following needs can be identified: (i) a registry that maps the existing approaches, implementations and descriptions, (ii) managing the incompatibilities of the existing tools, (iii) increasing synergy and complementary functionality of the tools, (iv) persistent availability of the tools used to manipulate the archived descriptions, (v) an archive for free finite-state based tools and linguistic descriptions. Addressing these challenges contributes to building a common research infrastructure for advanced language technology.