Maatalous- metsätieteellinen tiedekunta


Nyligen publicerat

  • Cairns, Johannes (Helsingin yliopisto, 2018)
    Antibiotics often occur in different environments at concentrations insufficient to inhibit the growth of susceptible bacteria. Subinhibitory concentrations can, nevertheless, select for chromosomal antibiotic resistance mutations and mobile genetic elements carrying antibiotic resistance genes, such as conjugative plasmids. However, it has been unclear whether this occurs in typical natural habitats where bacteria live in multispecies communities and interact with viral and protozoan consumers. In such settings, similar selection can also occur on other bacterial traits, potentially interfering with antibiotic resistance evolution. In this thesis, the combined effect of low antibiotic concentrations and ecological interactions on antibiotic resistance evolution was investigated. The thesis consists of four studies. In the first and second study, antibiotic and bacteriophage resistance evolution was examined at the phenotypic or whole-genome level when a bacterial population was exposed to one versus both factors. In the third study, the effect of antibiotics and protozoan predation on the spread and maintenance of a conjugative antibiotic resistance plasmid in a bacterial population was determined. The fourth study examined the effect of a low antibiotic concentration, protozoan predation, and spatial layout of habitat on community composition and horizontal transfer of a conjugative plasmid in a multispecies bacterial community. Antibiotic resistance evolution was shown to be promoted by low antibiotic concentrations independent of the presence of ecological interactions. The presence of protozoan predation also promoted the spread and maintenance of a resistance plasmid even in the absence of antibiotics. This demonstrates that ecological factors other than antibiotics can also play a role in the horizontal transfer of antibiotic resistance genes. Moreover, a low antibiotic concentration altered bacterial community composition, diversity, and the strains that received a resistance plasmid, although predation and spatial layout of habitat were equally strong or stronger drivers. Since the community effects of low antibiotic concentrations can be weaker or similar in strength to the effects of other ecological drivers, knowledge of antibiotic alone may be insufficient for predicting changes in the structure or diversity of a community.
  • Samad, Samia (Helsingin yliopisto, 2018)
    Unlike annual plants, perennials have repeated cycling between the vegetative and generative stages. Studying the balance between these two phases would enable breeders to produce higher quality crops. The woodland strawberry is used as a model to study developmental patterns in perennials because it has a wide geographical distribution, a small sequenced genome, and a number of available natural mutants, which provide excellent resources for physiological, molecular and genetic studies. This thesis investigated the genetic and environmental coordination of shoot apical meristem (SAM) and axillary meristem (AXM) fates in woodland strawberry. In woodland strawberry, SAM forms an inflorescence after flower induction, whereas AXMs can differentiate either into runners or branch crowns that are able to form additional inflorescences. Genetic mapping and the experiments using transgenic lines and natural accessions with contrasting environmental responses showed that a number of genes regulated the balance between vegetative and generative development in woodland strawberry. In general, cool temperature or short days (SD) induced flowering and promoted AXM differentiation to branch crowns, while warm temperature and long days (LD) promoted runner formation. High levels of FvTERMINAL FLOWER1 (FvTFL1) expression in FvTFL1 overexpression lines and NOR1 accession inhibited flowering at temperatures of 10-22°C in both SD and LD, but the environmental control of AXM fate was not affected in these plants indicating that environment influenced AXM differentiation irrespective of flowering. In the seasonal flowering genotype, FvSUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (FvSOC1) was observed to quantitatively increase runner formation. The photoperiodic control of flowering and AXM fate was studied in more detail using FvCONSTANS (FvCO) and FvFLOWERING LOCUS T1 (FvFT1) transgenic lines. These studies showed that FvCO controls the expression of FvFT1, and they both have a major role in the control of the balance between the vegetative and generative development in SD and LD. Genetic mapping studies under differing environments identified five QTLs that, together, explained about half of the observed flowering time variance in the mapping population, and two additional QTLs were identified for the number of branch crowns explaining about 20% of variance. The flowering time QTL on LG6 colocalized with FvTFL1, and one of the QTL regions on LG4 that controlled both flowering time and AXM fate was close to the PFRU, a previously identified locus in the commercial strawberry. Among the previously unknown loci, two flowering time QTLs on LG7 colocalized with putative flowering time genes FvEARLY FLOWERING 6 (FvELF6) and FvCENTRORADIALIS1 (FvCEN1), a homolog of FvTFL1. Furthermore, a gene encoding TCP transcription factor and a homolog of DORMANCY ASSOCIATED MADS BOX (DAM) were identified as candidate genes in QTL regions controlling AXM fate on LG4 and LG5, respectively. This study shed new light into the genetic and environmental control of AXM and SAM fates providing new means to control the balance between vegetative and generative reproduction under different environmental conditions.
  • Vepsäläinen, Henna (Helsingin yliopisto, 2018)
    Since food behaviors are learned during childhood and may also track into adulthood, promoting healthy food habits among children and families is of special importance. Health promotion has traditionally been focused on individuals, but during the recent decades, the attention has shifted more and more towards environments. The food environment – a concept that encompasses physical, social, cultural, economic and political environmental factors associated with food behavior – is especially important for children, who cannot be considered to be fully responsible for their food choices. Arguably, home, preschool and school are the most prominent food environments for children. It has been shown that parental food consumption and home food availability – the two most commonly used measures for food environment - are consistently associated with dietary behavior among children. However, most of the studies investigating parent-child dietary resemblance have focused on the consumption of single food groups, such as consumption of fruit and vegetables. Similarly, home food availability has mostly been measured unidimensionally: as the availability of a single food group or as healthy/unhealthy food availability. Additionally, the outcomes used in the studies have mostly been food groups or theory-based dietary indices. However, the use of data-driven dietary patterns may give a more realistic picture of the actual diets of the participants. Thus, this study aimed at investigating social and physical environmental factors associated with whole-diet among children. This thesis used data from two cross-sectional studies. Papers I and II were based on data from the DAGIS study, which was conducted in 66 Finnish preschools and investigated health behaviors and associated factors. The participants were 864 children from the groups of 3–6-year-olds. Food consumption among the children and both parents was measured using a food frequency questionnaire (FFQ) filled in by the parents. The parents also reported home food availability and sociodemographic factors of the family. Paper III used data from the ISCOLE study, which examined obesity-related lifestyle and environmental factors among 9–11-year-olds in 12 study sites worldwide. Altogether 6560 children (54% girls) were included in the current analyses. The children reported their own food consumption, whereas the parents of the participating children reported home food availability. Detailed school audits were performed in all participating schools (n=256) to measure school food availability. In paper I, parent-child dietary resemblance and associated sociodemographic factors were studied. A novel statistical method was used in order to compare food consumption of the parent and that of the child on a whole-diet level. Based on the consumption frequency, the food items were ranked separately in the child’s and the parents’ FFQs. A dietary resemblance measure was calculated for each parent-child pair: a similar ranking in both the child’s and the parent’s FFQ yielded a resemblance measure of +1, whereas no resemblance in ranking resulted in the resemblance measure of 0. Father-child resemblance was on average 0.50 (95% CI, confidence interval 0.48–0.52), whereas mother-child resemblance was 0.57 (95% CI 0.55–0.58). However, having mother as a respondent (providing food consumption information on behalf of the child) was inversely associated with father-child resemblance, and a tendency for similar reporter-bias was also seen in the mother-child resemblance. Additionally, the number of weekly family meals was positively associated with mother-child dietary resemblance. Parental educational level was not associated with parent-child dietary resemblance. In papers II and III, the availability of unhealthy foods in the home was positively associated with dietary patterns generally regarded as unhealthy. Although having healthy foods in the home was inversely associated with unhealthy dietary patterns, the abundance of unhealthy foods seemed to at least partly overrule this inverse relation. Respectively, the availability of healthy foods in the home was positively and that of unhealthy foods inversely associated with dietary patterns generally regarded as healthy. The results were similar both among preschoolers and school-aged children. School food availability was not associated with dietary patterns. In conclusion, parent-child dietary resemblance was moderate regardless of the socio-economic background of the family. In addition, an important observation was made: the diet of the child resembled more the diet of the parent providing food consumption data on behalf of the child. Since the possible reporter-bias can affect the interpretation of the results, it would be advisable for researchers to report who filled in food consumption information for the child and take this into account in further analyses. Furthermore, in order to capture the social food environment more comprehensively, fathers – not only mothers - should be involved as parents in family-based studies. Additionally, since the availability of unhealthy foods in the home was associated with unhealthy eating regardless of the availability of healthy foods, the results suggest that it is particularly important to limit the availability of unhealthy foods in the home. The results of this study can be used in planning and carrying out health promotion programs aiming at improving the diets of the families.
  • Abaker, Wafa (Helsingin yliopisto, 2018)
    Drylands cover some 40% of the global land area and are extensively degraded, especially in Africa, as indicated by reduced soil organic matter (SOM) contents. The loss of SOM and associated ecosystem services (e.g. prevention of erosion, carbon sequestration, soil fertility and water retention), threaten the livelihood of local communities. Management practices that increase SOM contents, such as increasing tree cover, can be expected to increase soil fertility, infiltration and water retention. Plantations of Acacia senegal (L.) Willd. (now Senegalia senegal (L.) Britton.) of varying age (7 to 24 years) at two sites in Sudan were used to determine: (1) biomass carbon (C) and soil organic carbon (SOC) stocks and changes in the contribution of C3 (trees + herbs) plants to SOC; (2) SOC related changes in soil hydraulic properties, soil moisture (SM), and water balance of the plantations; and (3) soil nitrogen (N), phosphorus (P, total and available) and potassium (K, total and extractable) concentrations and N2 fixation. Adjacent grassland areas were used for comparison (control). Tree biomass C stocks were calculated using an allometric equation and C contents; ground vegetation C stocks by harvesting and C contents; and SOC stocks (0-50 cm) by determining C contents and bulk density. The contribution of C3 plants to SOC was estimated using a 𝛿13C mixing model, and soil and foliar δ15N values used to assess the importance of N2 fixation. Profiles of SM contents were measured using Time Domain Reflectometry (TDR). Daily water balances of the plantations and grasslands were computed using a simple water balance model and the SM measurements used for calibration purposes. Soil hydraulic parameter values were derived using pedotransfer functions based on measured soil texture and SOC contents. Soil contents of nutrients (N, total and available P, and total and extractable K) were determined from samples. Total biomass C stocks increased with plantation age. While most of this increase was due to the trees, the C stock of the ground vegetation also increased with plantation age and was greater in the oldest plantations than in the grasslands. This finding supports the hypothesis that trees facilitate the productivity of ground vegetation in semi-arid environments. Plantation SOC stocks (0-50 cm) also increased with plantation age and were greater than in the grasslands. The age-related increase in SOC stocks was derived not only from the acacia trees but also from the increase in ground vegetation biomass. Measured SM contents were higher in the grasslands than in the plantations, but increased with plantation age, reflecting the similar trend in SOC and related plant available water capacities. The modelling resulted in lower runoff from the plantations, increased infiltration, evapotranspiration, reduced drainage and lower SM, as shown by measurements. Greater SM contents in the grasslands were attributed to lower evapotranspiration and resulted in greater drainage fluxes compared to the plantations. The study highlighted the need for more empirical studies on the effect of tree density on water balance in semi-arid Africa. The concentrations of all studied nutrients were relatively low, but were correlated to SOC concentrations, highest in the topsoil (0–10 cm) and increased with plantation age – all indicating the importance of SOM to soil fertility. High acacia foliage δ15N values indicated that N2 fixation was not an important contributor to the soil N, although A. senegal is known to fix N2 in other sites, and therefore did not account for the accretion of soil N. Neither could reported N deposition loads account for the accretion of soil N. A possible explanation for the increasing soil N may be inputs of excreted N brought into the area by grazing and browsing animals. The research showed that A. senegal in the landscape not only increased C sequestration (increased biomass and soil C stocks), which would help in reducing global warming and mitigation of climate change, but also that the increases in SOM (SOC) contents associated with the trees increased SM and soil nutrient contents, thereby restoring the fertility of degraded land for the benefit of the local communities. Given the multiple benefits and ecosystem services gained by increasing SOC stocks, efforts to increase or at least maintain the cover of A. senegal in the Sahel should therefore be encouraged. This knowledge should be transferred to local communities in order to minimize further disturbance and encourage sustainable management of the landscape.
  • Wang, Yujie (Helsingin yliopisto, 2018)
    β-Glucan (β-(1→3),(1→4)-D-glucan) is the major non-starch polysaccharide in oats and barley, and it is well-known due to its physiological and technological benefits, which are related to the ability to increase the luminal or solution viscosity. However, cereal β-glucan is susceptible to degradation during processing and storage, which may deteriorate the product stability and/or β-glucan functionality. Oxidative degradation of β-glucan has been shown in aqueous systems. In multi-phased food systems containing lipids, the oxidative stability of β-glucan has not yet been studied. In these systems, lipid oxidation is a major source of radicals which can cause co-oxidation of other components. The aim of the study was to understand the oxidative stability of cereal β-glucan during lipid oxidation, and the simultaneous role of β-glucan in retarding lipid oxidation. Furthermore, the study investigated the contribution of the residual phytate in β-glucan to the oxidative stability of β-glucan. Results showed that lipid oxidation induced significant degradation of β-glucan in an oil-in-water emulsion model, as evidenced by a decrease in viscosity and decrease in molecular weight of β-glucan. The increase in the degree of oil oxidation, the concentration of transition metal or the storage temperature caused a greater extent of β-glucan degradation. Simultaneously, a retardation of lipid oxidation was observed in the emulsions containing β-glucan. The mechanism was further investigated by using purified oat and barley β-glucans with different molecular weights. Initially, it seemed that retardation of lipid oxidation was determined by the β-glucan source and the molecular weight. However, the retardation was found to correlate with the content of residual phytate in the β-glucan samples. When the phytate was removed, the retardation of lipid oxidation by β-glucan disappeared regardless of the β-glucan source and molecular weight. Therefore, the residual phytate in the β-glucan samples, instead of β-glucan structural features, played a major role in the retardation of lipid oxidation. The study further proved that the residual phytate protected the β-glucan from oxidative degradation. Under oxidative conditions, oat β-glucan containing a high amount of phytate was more stable than barley β-glucan containing less phytate. The oat β-glucan became as vulnerable as barley β-glucan to the oxidative degradation when the residual phytate was removed. The addition of phytic acid also retarded the degradation of β-glucan, which was affected by the ratio of phytic acid to iron (Fe) and the presence of competitors such as ascorbic acid. The studies indicate that oxidized lipids and co-passengers of β-glucan can influence the oxidative stability of β-glucan, and consequently influence its technological and physiological functionality.
  • Ylimaunu, Juha (Suomalaisen Kirjallisuuden Seura, 2000)
    Suomalaisen Kirjallisuuden Seuran Toimituksia 773
  • Vanhatalo, Anni (2018)
    Plants synthesise thousands of biogenic volatile organic compounds (BVOCs) as part of their secondary metabolism. Scots pine (Pinus sylvestris) particularly produces mono- and sesquiterpenes, which are mainly stored in oleoresin in resin ducts. In this study, the monoterpene emission rate from stems was found to increase as a function of increasing resin pressure, which was positively correlated with the air temperature and foliage transpiration rate. Monoterpene synthase activity describes the maximum monoterpene production potential. The seasonal cycle and needle age were observed to explain the majority of the variation in needle monoterpene synthase activities, monoterpene storage pools and monoterpene emissions from shoots. Variation in the monoterpene concentration between seasons, different needle age classes and different trees was observed to be minor. Monoterpene synthase activity was higher in <1-year-old needles compared to older ones. Within a single tree, the compound-specific composition of monoterpene synthase activities and monoterpene storages was not reflected in the composition of emissions. For example, the share of δ-3-carene was substantially higher in the emissions than in the storage pools and synthase activities. An automated enclosure measurement system including a proton transfer reaction mass spectrometer was utilized to follow the VOC emissions from the woody compartments of trees over several years. This was the first study to quantify such emissions for an extended period. Scots pine stems were observed to emit monoterpenes and methanol into the ambient air. The fluxes displayed a seasonal cycle: methanol emissions were highest in the midst of the growing season, whereas monoterpene emissions peaked not only on the hottest summer days, but also in the spring when the photosynthetic capacity of trees recovered. The emissions of some monoterpenes exhibited distinct diurnal patterns in their enantiomeric compositions. The above-canopy air terpene concentrations reflected the emission rates from trees, the atmospheric reactivities of the compounds, the tree species composition of the measurement site and the abundances of different tree chemotypes.
  • Teikari, Jonna (Helsingin yliopisto, 2018)
    The Baltic Sea is a shallow brackish water ecosystem. It is naturally prone to eutrophication, and massive cyanobacterial blooms are an annual phenomenon in this region. Blooms are toxic to humans and animals, and cause economical losses and harm for recreational users. Almost all cyanobacteria are photoautotrophic organisms, and many bloom-forming Baltic Sea cyanobacteria can additionally fix atmospheric nitrogen. Inorganic phosphorus is usually the first and most important growth-limiting factor. Monitoring the external phosphorus inflow is strictly implemented by the coastal states, but uneven point load still occurs. In addition, a heavy and long-term phosphorus load has resulted in substantial phosphorus reservoirs in the sediments and phosphorus can be circulated back to the waterbody. Cyanobacterial blooms in the Baltic Sea are dominated by Aphanizomenon sp., Dolichospermum sp., and Nodularia spumigena, of which Dolichospermum sp. and N. spumigena can produce toxins. Due to their evolutionary history, Dolichospermum sp. is more abundant in the less saline coastal regions, whereas N. spumigena dominates in the open sea. This work studied the effects of changing environmental conditions on the distribution and niche adaptation strategies of toxic and bloom-forming Baltic Sea cyanobacteria using state-of-the-art sequencing and molecular biology methods. Climate change models have predicted that the salinity of the Baltic Sea will possibly decline in the future, and thus the behavior of Dolichospermum sp. and N. spumigena was studied in unfavorable salinities. Comparative genomic analysis showed that Dolichospermum sp. has high synteny between its freshwater counterparts, and possibly therefore the strain was unable to proliferate in moderate salinities. Salt addition induced massive transcriptional shifts, especially within the photosynthesis and nitrogen-fixing pathways. Moreover, moderate salinity increased the production of microcystins and triggered the oxidative stress response. On the contrary, N. spumigena thrived in higher salinities, and its growth and metabolism were hindered by freshwater. Unique sigma factors and an elevated number of transposases were identified in the genome of N. spumigena, suggesting a high genetic capacity to adapt to changing salinities and brackish water conditions. The growth and metabolism of Dolichospermum sp. and N. spumigena were arrested under limited availability of inorganic phosphorus. Both strains upregulated the genes in the pho regulon, indicating that these genes can be used for determining the phosphorus status of cyanobacterial blooms. All studied strains of N. spumigena from the Baltic Sea carried the phnC-M gene cluster, which is responsible for the transport and utilization of the highly stable phosphonates. Naturally produced phosphonates were an additional phosphorus source for N. spumigena cyanobacteria, and produced a competitive advantage in phosphorus-limited conditions. However, methane, an organic remnant of methylphosphonate was released to the gaseous environment. Blooms of N. spumigena cyanobacteria may thus explain the elevated summertime methane concentration in the Baltic Sea. The results presented in this thesis suggest that cyanobacterial blooms will continue to appear in the future if sufficient amount of phosphorus is present but community composition may shift towards freshwater species as a consequence of climate change.
  • Kaakkurivaara, Tomi (Helsingin yliopisto, 2018)
    The aim of this thesis was to investigate the use of portable bearing capacity measurement devices and alternative fly ash structures to improve forest road quality and rehabilitation practices. So far, few tools have proved suitable for practical evaluation of forest road trafficability. Bearing capacity is the main component of trafficability and bearing capacity measurements are rarely conducted on forest roads. Replacing subjective criteria with objective measurement methods is the first step towards avoiding rutting damages as well as improving rehabilitation decisions. Three bearing capacity measuring devices were tested for predicting forest road rutting in the context of bearing capacity improvements with fly ash structures. Modulus of elasticity (E-modulus) was used as the measurement unit. E-modulus was used to quantify road stiffness as measured by two portable measurement devices and one trailer-mounted device. A light falling weight deflectometer (LFWD) and a dynamic cone penetrometer (DCP) were used to challenge the conventional falling weight deflectometer (FWD). Test sections were located on forest roads with both mineral and peat subgrades. The comparison showed logical correlations between the measured E-modulus values, and reliable regression models are presented for the differences between measuring devices. In most cases DCP and LFWD can be utilized on forest roads instead of the expensive FWD. The measurement results for the portable devices and the FWD were compared to rutting, as represented by the increases in rut depth per passing truck (mm/pass) measured by mobile laser scanning (MLS). The devices were used to quantify the relationships between the E-modulus and rutting. Rutting threshold values were then based on these relations. A rough rutting susceptibility table was outlined to aid forestry professionals to estimate the rutting damage risk per timber truck on forest roads during periods of thaw-weakening. Growing bioenergy production and consumption has resulted in an increase in the amount of fly ash produced by the forestry sector. At the same time the cost for ash deposition at land-fills has increased considerably. Utilizing fly ash in forest roads is therefore seen as a potentially cost-efficient alternative for improving bearing capacity. The fly ash part of the study investigated therefore road rehabilitation work from both technical and economical perspectives. Four different rehabilitation methods were tested using wood- and peat-based fly ash. The four rehabilitation methods involved two structures mixed with aggregate and two structures with uniform fly ash. The resulting bearing capacity of the rehabilitated road sections was improved compared to the reference sections, especially for the mixed structures. The improvements were verified by statistical comparisons. The study also defined the various work phases of rehabilitation and estimated construction costs based on phase-specific machine productivities. Cost calculation equations were established for earthwork and the transportation of construction materials. The lowest construction costs were calculated for a 250-mm thick uniform layer of fly ash structure, however, a 500-mm thick uniform layer of fly ash provided the lowest total costs when taking into consideration the alternative cost for landfill deposition.
  • Berka, Anna (Helsingin yliopisto, 2018)
    This dissertation explores the governance, local impacts and costs of community-owned renewable energy (CRE). The objective is to understand if and in what context collective local ownership models represent a feasible and effective means to operationalising a more ‘sustainable development’ in the renewable energy sector and beyond. The articles draw on a range of fields, from energy governance and project economics to impact evaluation. Specific methodologies used are systematic literature review, discourse analysis, historical institutional analysis and risk-extended net present valuation. Unique contributions of this work are a meta-level understanding of the community energy sector in the UK and an understanding of its emergence in context of technological and institutional change. In addition, it provides an explicit assessment of Quality of Evidence problems in this subfield of energy and social science research, placing it firmly in the context of current literature and methods in project economics and impact evaluation. Findings show that ownership patterns in the energy sector are precarious and subject to changing narratives that emerge in response to domestic socio-economic and political dilemma’s, exogenous shocks, and emerging economic schools of thought. CRE projects have the potential to generate a variety of positive local impacts that vary depending on the motivation and management of projects and project revenues. Under certain conditions CRE can empower community organisations to address systemic socio-economic problems in the public domain. Finally, in a competitive market setting and where CRE is implemented by newly-established grassroots organisations, projects face a range of risks that commercial projects do not, and that erode their financial viability. As such, the development and expansion of community renewable energy as a substantial proportion of the energy sector requires policy makers to assign it special status and provide policy support on the basis of its local social, economic and environmental benefits. Policy support for community renewable energy requires a willingness to integrate energy and social policy domains.
  • Kemppinen, Asmo (Helsingin yliopisto, 2018)
    Short-chain triacylglycerols (SC-TAGs) comprise at least one esterified fatty acid with two to six carbon atoms. A high molar proportion of SC-TAGs in bovine milk fat (MF) is a unique feature among edible fats and oils and results in characteristic biological, chemical, physical, and technological properties of MF. Further, high content of SC-TAGs induces specific requirements for TAG analysis. The main objective of the present study was to develop chromatographic (gas chromatography, GC; normal-phase high-performance liquid chromatography, np-HPLC) and mass spectrometric (MS) (electron ionization MS, EI–MS; electrospray ionization MS, ESI–MS/ESI–MS/MS) methods to separate, identify, and quantify regio- and acyl chain isomers of SC-TAG species in model TAG mixtures and in butterfat (BF). An improved method was developed to fractionate BF TAGs into saturated, monoene, and polyene TAGs on a solid-phase extraction column in silver ion mode prior to GC and GC–EI–MS. This method enabled quantification of otherwise coeluting regio- and acyl chain isomers of SC-TAG species with the same number of acyl carbons but different degree of unsaturation. The elution order of the acyl chain isomers of isobaric TAG species and the regioisomers of SC-TAGs on a polarizable phenyl(65%)methylsilicone GC-column was empirically established using retention indices calculated for a high number (112) of synthesized TAG species and isomers. Separation power of the column proved to be high enough to resolve the regioisomers of mono-SC-TAGs. Correspondingly, np-HPLC was shown to resolve the regioisomers of mono- and dibutyryl TAGs to the baseline, monocaproyl TAGs close to the baseline, and dicaproyl TAGs partially. Even few regioisomer pairs of long-chain TAGs containing fatty acyl 20:0 were resolved as well. The present study established that in ESI–MS/MS, the cleavage of SC-acyls (4:0, 6:0) from the sn-1(3) positions of mono-SC-TAGs was at least 2.3 times higher than that from the sn-2 position, hence enabling clear-cut differentiation between regioisomers. Due to intricate TAG composition of BF specific molar correction factors (MCFs) were used in quantification of TAGs by GC, GC–EI–MS, and np-HPLC–ESI–MS. In both MS methods, extensive variation in MCFs was observed due to different molecular size, degree of unsaturation, and regio- and acyl chain isomerism of TAGs, but substantial number (>100) of empirically determined MCFs enabled extrapolation of MCFs for more uncommon TAGs. Both MS methods provided new information that emphasized the need to use specific MCFs for the sn-1(3) and sn-2 TAG isomers. All quantification methods yielded relatively unsurprising and similar general distribution of TAG classes and selection of the most common TAG species in BF. However, 64 minor TAGs of 336 even-numbered TAG species that were determined by np-HPLC–ESI–MS were confirmed for the first time to exist in BF. A high number of them were SC-TAGs including monoacetyl TAGs, rare sn-2 isomers of mono-SC-TAGs, and di- and tri-SC-TAGs. The present study suggested that the developed methods were reliable choices to determine both the most common TAGs and more rare TAGs in BF. All methods enabled quantification of the regioisomers of SC-TAGs in BF. The methods can be adapted to detect adulteration of MF, to elucidate biological or technological function of MF, and to develop effective procedures of MF modification. They can be applied to investigation of structured TAGs with short-chain fatty acyls.
  • Marcenaro, Delfia (Helsingin yliopisto, 2018)
    The common bean (Phaseolus vulgaris L.) is an important legume crop grown widely around the world due to its high nutritional values. In developing countries of Africa and Latin America (e.g. Tanzania and Nicaragua) bean crop is linked to food security and income generation especially in poorest groups made up of small farmers. Disease problems, pests, unimproved seeds, inappropriate agricultural management and environmental conditions are often the main constraints in bean crop production. In Nicaragua and Tanzania, the unavailability of certified seed of local bean varieties causes significant losses in yield and quality. Other limitation present in Nicaragua and Tanzania concerning bean diseases is that seed-borne fungi and viruses has gained little attention. Thus, for better understanding in seed-borne fungi and viruses associated with beans we investigated seed-borne fungi in an important new local bean variety. Sampling from four seed storehouses and six seed lots of cv. INTA Rojo was done in the main bean production areas in Nicaragua. In addition, to detect viruses infecting bean plants, we surveyed seedborne viruses in landraces and new common bean varieties introduced to Nicaragua (Central America) as well as improved varieties grown in Tanzania (eastern Africa). The main results for seedborne fungi included 87 pathogenic isolates from eight genera: Fusarium spp. (F. chlamydosporum, F. equiseti, F. incarnatum), Lasiodiplodia theobromae, Macrophomina phaseolina, Corynespora cassiicola, Colletotrichum capsici, Colletotrichum gloeosporioides, Diaporthe sp. (Phomopsis), Aspergillus flavus, and Penicillium citrinum. Subsequently, results based on germination in seed lots of common bean (‘INTA Rojo’) from four bean production areas in Nicaragua showed that germination was constantly less than 40% and could be as low as 16%, indicating disastrous yield losses for producers. Four different species-specific primer pairs to detect F. equiseti, F. chlamydosporum, F. incarnatum, C. capsici, C. gloesporiodes and C. cassiicola were developed in this study based on sequence alignment of the internal transcribed spacer sequences (ITS1 and ITS2) from different fungi. They were tested in pure cultures of fungi and used successfully in detection of fungal pathogens from infected plants. These specific primers are able to give the basis to be used in seed health inspection (seeds and plants) for further research of the epidemiology, ecology, and control of the pathogenic fungi of common beans in the field. The presence of Phaseolus vulgaris endornavirus 1 (PvEV-1) and PvEV-2 was detected in Nicaraguan and Tanzanian bean varieties. Likewise, Cowpea mild mosaic virus was detected in one region of Tanzania. There is apparently indication that the new Nicaragua bean varieties are carrying virus resistance genes because no seedborne viruses were found in them. In Tanzania improved protection against pathogenic seed-borne viruses is developed by resistance breeding. These findings are the first report showing that several pathogenic seed-borne fungi occur in Nicaraguan beans. Previously, little information has been available on pathogenic fungi such as F. equiseti, F. incarnatum, L. theobromae, C. cassiicola, and Diaporthe spp in Nicaraguan common beans. This study has contributed in taking first steps to improve the pathological and genetic components in the national seed production system in Nicaragua and Tanzania by providing new knowledge concerning seed-borne pathogens associated with common bean.
  • Coloma, Sebastián (Helsingin yliopisto, 2018)
    Biotic and abiotic factors are known to influence the formation of blooms by diazotrophic cyanobacteria, which may dramatically modify the nutrient environment affecting the pelagic food web and the plankton community. Abiotic factors, e.g. nutrient availability and weather conditions, have been widely studied and discussed. However, biotic factors such as the impact of phages remain less studied. This study aims to describe the effects of a Baltic Sea cyanophage on a filamentous cyanobacterium (Nodularia spumigena) and other aspects in plankton communities utilizing an experimental approach. Specifically, the study addresses bacteria-phage interactions, plankton community dynamics, and nitrogen transfer between the plankton components (phytoplankton species and rotifers) in the food web. To perform the experimental study, a Baltic Sea cyanophage infecting Nodularia was isolated, characterized and named 2AV2. The cyanophage 2AV2 belongs to the Siphovirus family with a lytic life cycle between 12–18 hours with a restricted host range of 12 out of 45 tested Nodularia strains. Lysis of the susceptible host caused an approximately 80% reduction in the cyanobacterial population resulting in selection for phage-resistant Nodularia cells. The evolution of phage resistance significantly reduced the release of nitrogen resulting from lysis of susceptible host cells in the presence of phage. In addition, isolates from the phage-resistant population had two morphotypes, short filaments (40%) and long filaments (60%), while the susceptible population only displayed long filaments. Further, differences between these morphotypes were detected in traits such as growth rate and buoyancy. The divergence in phenotypic traits among phage-resistant cyanobacteria is suggested to represent an evolutionary trade-off between phage resistance and fitness in the absence of phage. This is the first study to show a change in morphology (filament length) in Nodularia spumigena after the evolution of phage resistance. In an experimental plankton community, Nodularia, cyanophage 2AV2, Chlorella and rotifer biomasses developed differently between treatments with different initial frequencies of phage phage-resistant Nodularia, determining the ecological succession and nitrogen transfer in the food web. This study supports the hypothesis that cyanophages not only affect cyanobacterial populations but they also have a wider influence on plankton community dynamics and nitrogen transfer in food webs.
  • Gürbüz, Göker (Helsingin yliopisto, 2018)
    Oxidative reactions in food systems during processing and storage constitute a significant problem that determines the nutritional and sensory qualities of the food product as well as the textural and functional properties. Proteins and lipids, as essential components of foods, are highly prone to oxidative degradation that results in undesired modifications in food systems. Although lipid oxidation as a topic has been given a widespread attention, protein oxidation and its consequences in foods have been studied relatively recently. In particular, co-oxidation of food proteins and lipids, in terms of their interactions within the complex mechanism of oxidative reactions, has been gathering interest only lately. The behavior of proteins from various food sources and technological pre-treatments as well as the outcomes of this behavior under oxidative conditions in the presence of lipids is a much required subject on which to focus both by academia and industry. The purpose of this work was to elucidate the degradation of proteins and lipids within the oxidative system, and to characterize the consecutive modifications of oxidative interactions between food proteins and lipids in model investigations. In order to achieve this, experimental oxidation models were set up that investigate firstly the molecular level interactions between lipid oxidation product malondialdehyde (MDA) and whey protein, β-lactoglobulin (β-Lg) peptides. In this work, LC-MS/MS methods were employed to characterize and identify the interaction products. Later studies focused on the oxidative behavior of plant proteins such as quinoa, amaranth and faba beans, utilized in emulsification of rapeseed oil. Results from the analyses of primary and secondary volatile lipid oxidation products as well as tryptophan fluorescence of proteins were gathered to assess the oxidative process. The results of the first study showed that two distinct compounds were generated through Schiff-base adduct formation between MDA and β-Lg peptides, one of which had strong fluorescent properties. Emulsions studies demonstrated that amaranth proteins produced oxidatively and physically more stable emulsions compared to quinoa proteins. However, due to protein oxidation neither type of emulsions were as stable as the commercial emulsifier Tween®20. Emulsions with proteins of faba beans that had undergone pre-treatments were less oxidized compared to native samples which was due to hindering of the endogenous enzyme activity. Proteins located at the lipid droplet interface were degraded more than those in the water phase. This thesis demonstrates that interdependent relations between proteins and lipids such as adduct formation, free-radical transfer, and reactions between oxidized species have a significant effect on the overall course of oxidation of the food system which affect the final observed modifications. Therefore, customized solutions against oxidation should regard the intricate relations of protein-lipid co oxidation in a food system that contains proteins and lipids as major constituents.
  • Pekkarinen, Antti-Juhani (Helsingin yliopisto, 2018)
    The reindeer (Rangifer tarandus L.) is a key species in Fennoscandia, where nearly 40% of the land area is used as reindeer pasture. Reindeer herding is an important source of income for local people and an intrinsic part of the Sami culture In this thesis, the reindeer herding system is studied using a detailed interdisciplinary dynamic model. An age- and sex-structured reindeer-lichen model is developed using findings from previous research and novel data. The model also takes other winter resources, including supplementary food, into account in addition to ground lichens. This ecological model is combined with economic optimization and a description of the herding system with empirically estimated prices, costs, and governmental subsidies. The model is validated and calibrated to describe the reindeer herding system in the northern part of Finnish Lapland. The results for population dynamics without harvesting show that the reindeer-lichen system described by the model is unstable in the absence of predators. However, high availability of arboreal lichens stabilizes the system. In economically optimal solutions increasing the interest rate increases the steady-state reindeer population level, opposite to classical understanding in resource economics. Natural mortality is close to zero in optimal steady-state solutions and harvesting is concentrated on calves. The number of adult males is kept as low as possible without decreasing the reproduction rate of the population. This leads to much higher shadow values for males compared to females. The results show that in order to study sustainable and economically viable reindeer management, both ecological and economic factors must be taken into account, as they strongly affect the solutions and management recommendations. One of the main findings is that the economically optimal steady-state lichen biomass can be surprisingly low. High interest rate, lack of pasture rotation, low growth rate of ground lichen, high availability of arboreal lichens, and government subsidies all decrease the steady-state lichen biomass. Using intensive supplementary feeding to support larger reindeer herds, which leads to the depletation of lichens, can additionally become optimal in certain cases. When recovering from overgrazed lichen pastures, use of supplementary feeding and the amount of arboreal lichens have an important role in the optimal adaptation process. The wintertime wastages estimated in this study are close to earlier suggestions, but summertime wastage is higher than expected. Seasonal pasture rotation could thus considerably help reduce the summertime trampling of winter pastures. The model validation solutions show that the model is able to describe changes in lichen biomass with good accuracy. Using the validated model and calibrated wastage values we found that reindeer numbers in northernmost Finland in the present situation are in most cases higher than in the management solutions given by the model.