3. Doktoritööd

Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/2490

Sirvi

Nüüd näidatakse 1 - 20 145

Algae Pseudokircheriella subcapitata in environmental hazard evaluation of chemicals and synthetic nanoparticles
(Eesti Maaülikool, 2011) Aruoja, Villem
Vetikad on peamised fotosünteesivad organismid veekogudes, tootes umbes poole Maa primaarproduktsioonist. Seeõttu on oluline keskkonnasaastuse mõju vetikate kasvule. Vetikad on ka head keskkonnatoksikoloogia mudelorganismid, kuna nad on tundlikud paljudele kemikaalidele ja neid on lihtne laboratoorsetes tingimustes kasvatada. Käesolevas doktoritöös täiustati OECD 201 suuniseid järgivat vetikate P. subcapitata kasvu pärssimise testi. Täiustamisel peeti silmas, et meetod sobiks lisaks vees hästi lahustuvate kemikaalide toksilisuse analüüsiks ka vees halvasti lahustuvate ainete ja osakesi sisaldavate keskkonnaproovide uurimiseks, sh ka suuremahuliseks testimiseks. Täiustatud testmetoodikat rakendati kolmes uuringus: (i) Raskemetallidega (Zn, Cd, Pb) saastunud metallisulatustehaste ümbruse muldade uuring näitas, et vaatamata kõrgetele Zn kontsentratsioonidele mulla vee-ekstraktides, mis pidanuksid olema vetikale mürgised, oli P. subcapitata kasv neis võrreldav kontrolliga. Mullasuspensioonid, mis sisaldasid tunduvalt enam raskemetalle kui vastavad vee-ekstraktid isegi stimuleerisid vetikate kasvu võrreldes vetikate kasvuga kontroll-lahuses. Samas, kui analüüsiti puhtast ja metallidega saastatud mullast valmistatud segusid, ilmnes mullaosakestele seotud metallide doosist sõltuv kahjulik mõju vetikatele. Seega tuleks mullaproovide toksilisuse hindamisel vetikatele võrdluseks kasutada samade füüsikalis-keemiliste omadustega puhast mulda. (ii) ZnO, TiO2 ja CuO nanoosakeste mõjude hindamine vetikate P. subcapitata kasvule näitas, et ZnO ja CuO nanoosakesed olid vetikatele ’väga toksilised’, kuna pärssisid vetikate kasvu juba väga madalates kontsentratsioonides: vastavad 72-tunni EC50 väärtused olid 0,052 mg/l ja 0,89 mg/l. TiO2 nanoosaksesed inhibeerisid vetikate kasvu tunduvalt kõrgemates kontsentratsioonides (EC50=9,9 mg/l), olles vetikatele umbes 6 korda toksilisemad kui vastavad mikroosakesed, pärssides vetikate kasvu tänu nende seondumisele vetikarakkudele. Nominaalsete kontsentratsioonide põhjal olid CuO nanoosakesed 16 korda toksilisemad kui vastavad mikroosakesed, samas kui ZnO puhul olid ühtviisi väga mürgised nii nano- kui mikroosakesed. Lahustunud Zn ja Cu analüüs vetikate kasvukeskkonnast näitas, et ZnO ja CuO osakeste vetikate kasvu pärssiv toime oli seotud osakestest leostunud metalli-ioonidega. Kirjeldatud töö oli esimene CuO nanoosakeste toksilisuse uuring vetikatele. (iii) Konstrueeriti struktuur-aktiivsussõltuvuste (QSAR) analüüsi võimaldav kemikaalipaneel, mis koosnes 58st eri positsioonides erinevalt asendatud aniliinist ja fenoolist. Analüüsides nende toksilisust vetikatele P. subcapitata saadi väikese katseveaga andmestik, mis sisaldas 48 seni avaldamata EC50 väärtust. Ehkki analüüsitud molekulid olid struktuurselt sarnased, erines nende toksilisus vetikatele kahe suurusjärgu võrra, jäädes vahemikku 1,43 mg/l (3,4,5-trikloroaniliin) kuni 197 mg/l (fenool). Uuritud ainete toksilisus sõltus asendajate tüübist (kloro-, metüül-, etüül-), arvust (mono-, di-, tri-) ja asendist (orto-, meta-, para-). Reeglina kaasnes suurema asendajate arvuga ka suurem toksilisus. Kloro-asendatud molekulid olid üldiselt toksilisemad kui alküülrühmadega asendatud analoogid. Andmetest selgusid ka asendajate positsioonist tulenevad efektid, nii näiteks suurendas asendaja para-asendis peaagu kõigi ainete toksilisust, samas kui orto-asendusega analoogid olid kõige vähem toksilised. Näidati ka, et hüdrofoobsuse ja toksilisuse seos on aniliinide ja fenoolide puhul erinev. Antud töös täiustatud vetikate kasvu inhibitsoonil põhinev ainete toksilisuse hindamise meetod osutus sobivaks ka vees lahustumatuid osakesi sisaldavate proovide hindamiseks ning võimaldas väikese töökuluga analüüsida suurt hulka proove. See omakorda võimaldab struktuur-aktiivsus sõltuvuste täiustamist, kuna vetika kasvu inhibitsiooni andmeseeriad on seni olnud küllaltki piiratud. Mainitud meetodid on vajalikud kemikaalide keskkonnaohtuse hindamiseks ning möödapääsmatud kemikaale reguleeriva määruse REACH rakendamiseks.
Alternative biocontrol strategies in the potato phytophthora infestans pathosystem for integrated management of late blight
(Estonian University of Life Sciences, 2022) Najdabbasi, Neda; Mänd, Marika; Haesaert, Geert; Audenaert, Kris; Institute of Agricultural and Environmental Sciences; Larena, Inmaculada (opponent)
Potato late blight caused by a fungus-like microorganism, Phytophthora infestans, has historically been one of the most tragic and devastating potato diseases, that can infect all aboveground and underground organs of potato. In the absence of control measures, the pathogen can cause extensive production losses during the cropping season. P. infestans can destroy the entire crop within 7-10 days under favorable conditions (periods of high moisture and moderate temperature), when disease incidence is high and plants are unprotected. P. infestans is known as re-emerging pathogen leading to the very serious damage to potato cultivation by increasing its aggressiveness towards the host, reducing fungicide efficacy, facilitating its survival in soil or plant debris. Concerning late blight management, despite increasing the frequency of chemical applications along with using resistant cultivars and healthy seed tubers, control of primary inoculum sources remains a major challenge in potato farming. Besides, there is a necessity to develop alternative methods that are less dependent on synthetic fungicides. Although breeding of resistant varieties is the top priority in agricultural systems, development of biological control practices has strongly been proposed as a promising alternative and sustainable strategy to manage late blight, with the aim of minimizing dependency on synthetic fungicides. To this aim, the present dissertation addressed a multilevel investigation of alternative biocontrol strategies in the potato-P. infestans pathosystem for integrated management of late blight (I, II, II). In this respect, different bioassays were performed during the course of PhD study with the main focuse on application of bioprotection strategies. (I) Biocidal activity of plant-derived compounds against Phytophthora infestans: an alternative approach to late blight management. In the first part of the study, biocidal activity of different essential oils (EOs) including juniper (Juniperus communis); clove (Syzygium aromaticum); thyme (Thymus vulgaris); cinnamon (Cinnamomum cassia); turmeric (Curcuma longa); tea tree (Melaleuca alternifoliai); pepper (Piper nigrum); rosemary (Rosmarinus officinalis); and a reference plant extract, Timbor® from Thymus vulgaris against the most aggressive genotype of P. infestans (EU-13-A2) were determined at different application rates. The main objectives of this study were: i) to evaluate effects of different concentrations of EOs and reference products on sporangial germination of P. infestans using optical density method (ii); to analyze effects of different concentrations of plant compounds on the pathogen mycelial growth; (iii) to examine the efficacy of different plant-derived compounds towards disease development in vivo; and (iv) to confirm the efficacy of the most efficient EOs for controlling late blight in greenhouse. Among nine tested compounds, thyme and tea tree EOs showed the strongest inhibitory effect on sporangial germination compared to the fungicide control Ranman-top®. Clove and thyme EOs as well as Timbor® significantly inhibited P. infestans mycelial growth even at the lowest concentration. Our outcomes supported the hypothesis that “Different concentrations of plant-derived compounds are effective to suppress sporangial germination and mycelial growth of P. infestans genotype (EU-13-A2)”. Additionally, some compounds were effective to control late blight on potato leaves in vivo and also under greenhouse conditions, where pepper, rosemary, thyme EOs and Timbor® showed reduction in disease development for over a month, supporting two other hypotheses as “Different concentrations of plant-derived compounds are effective to control late blight on potato leaves in vivo” and “Some selected concentrations of plant-derived compounds are effective to control late blight on potato plants in greenhouse”. The present study provided evidence for the potential use of commercial essential oils and/or plant extracts as botanical fungicides that can be an alternative to synthetic fungicides for controlling late blight disease, as they have low toxicity and residues, and of course are eco-friendly. (II) Green leaf volatile confers management of late blight: a green vaccination in potato There is increasing attention on the agronomic potential of volatile organic compounds (VOCs), as a natural and eco-friendly solution to protect plants from pathogens and environmental stresses. Green leaf valotiles (GLVs), as one of the major VOCs, prime mechanisms of plant’s defense for a stronger, faster, and earlier response upon further stress incidence, resulting in induced resistance to the upcoming stresses. Despite the unique capability of GLVs to inhibit a wide range of fungal pathogens, their functions as defensive compounds to control potato late blight, caused by the Oomycete pathogen P. infestans, has not been well studied. Therefore, the second part of the study addressed the potential role of the GLV Z-3-hexenyl acetate (Z-3-HAC) in decreasing the severity of late blight and underlying gene-based evidence leading to this effect. Hence, the objectives of this study were: (i) to investigate the protective potential of potato plants pre-exposed to the Z-3-HAC against five genotypes of P. infestans (EU-1-A1, EU-6-A1, EU-13-A2, EU-36-A2 and EU-37-A2) in vivo; and (ii) to examine the possible defense responses of potato plants pre-exposed to the Z-3-HAC against subsequent infection using molecular assays. To these aims, very susceptible potato plants (cv. Bintje) were firstly exposed to the Z-3-HAC using a push–pull cuvette system, before they were inoculated with the pathogen at different time points. We observed strong inhibitory effect on P. infestans genotypes in planta, resulting in a lower sporulation intensity, and disease severity (up to 70 %) compared to untreated plants, supporting the hypothesis that “pre-exposure of potato plants to the GLV Z-3-HAC has protective impact against subsequent infection with genotypes of P. infestans”. To verify the second hypothesis on “pre-exposure of potato plants to the GLV Z-3-HAC induces expression of defense-related genes’ against Phytophthora infection”, we used gene-specific primers involved in reactive oxygen species (ROS) and SA and JA synthesizes. It was shown that the transcript levels of several defense-related genes, especially those that are engaged in ROS production pathways were significantly expressed in potato plants. The present research provided insight into the role of Z-3-HAC in the increased protection of potato plants against late blight through plant immunity and offered new opportunities for the sustainable control of potato diseases. However, widespread use of GLVs in management practices remains a challenge, largely associated with high-cost procedures. (III) Combination of potassium phosphite and reduced doses of fungicides encourages protection against Phytophthora infestans In order to reduce the fungicide doses and spray programs, an integrated approach combining alternative methods of disease control with fungicides can be an encouraging way to meet long term consumer demands. Therefore, the last part of the study demonstrated a protective effect of the potassium phosphite (KPhi) compound against late blight when applied on different potato cultivars with different levels of resistance, resulted in the highest DSI reduction on the cultivar Bintje amongst all cultivars. In the second part of study, the control of P. infestans infection by KPhi compound combined with recommended and reduced doses of five different active ingredients (AIs) of fungicides including cyazofamid, mancozeb, mandipropamid, azoxystrobin, benthiavalicarb-isopropyl was evaluated on potato plants. The results from in vivo, greenhouse, and field experiments strongly revealed that synergy between phosphite and fungicide active ingredients could play an important protective role against Phytophthora infection, even for susceptible cultivars. Accordingly, three hypotheses successfully supported our study: “Detached leaflet bioassay allows rapid in vivo screening of KPhi efficacy, alone and in combination with different doses of active ingredients, against P. infestans on potato leaves”, “KPhi in combination with recommended and reduced doses of different active ingredients reveals the potential protective effect toward potato pathogen P. infestans in greenhouse”, and “Combination of KPhi with the most widely used fungicide shows the potential benefit of integrated control strategy against foliar blight development under multivariable field conditions”. This study suggested that optimizing formulations with the addition of KPhi would result in a reduction of active compounds of fungicides in potato farming. Additionally, the impact of KPhi on late blight development could make KPhi a potential component for incorporation into an integrated management system.
Analysis of molecular genetic and life-history traits in Eurasian perch (Perca fluviatilis L.)
(Eesti Maaülikool, 2016) Pukk, Lilian; Vasemägi, Anti; Gross, Riho; Paaver, Tiit; Volckaert, Filip (opponent)
Fishes provide food and livelihood for hundreds of millions of people around the world and currently fish consumption is higher than ever before. As a consequence, the threats of over-exploitation, illegal fishing and fish trade are very high. Because biologically insensible management actions or lack of necessary regulations may lead to population collapse, better understanding of genetic population structure and fisheries-induced changes in life-history traits is essential for conservation of local fish populations. Thus, the main goals of this thesis were to generate novel genomic resources, characterize population genetic structure, and study the consequences of overfishing of Eurasian perch populations and its potential causes to various life-history traits in Estonia. The over-exploitation of Eurasian perch population had strong influence on size- and age-distribution, juvenile growth rate and age of sexual maturation in males. Development of novel low-cost genome complexity reduction protocol enabled to identify large number of single nucleotide polymorphisms and microsatellite markers. Based on observed genetic structuring between two commercially most important perch fishery locations in Estonia (Väinameri Sea region and Lake Peipus), new microsatellite markers successfully revealed the genetic origin of perch, which can be used to fight against illegal fishing and fish trade. The population genetic framework described within this thesis represents a small but important milestone towards developing biologically sound conservation and management strategies for Eurasian perch.
Analysis of productivity indicators of field-grown potato meristem plants multiplied by different methods
(Eesti Maaülikool, 2011) Särekanno, Marje
Kartuliviirused on taimekahjustajad, mida ei ole võimelik tõrjuda kemikaalidega. Viirusresistentsete sortide kasvatamine või seemnekasvatuse algmaterjali tervendamine viirushaigustest on võtted, mis võimaldavad vähendada saagikadu ja -kvaliteeti. Tänapäevased taimebiotehnoloogia meetodid võimaldavad saada terveid ja suure saagivõimega kartulitaimi ka tugevalt viirushaigustesse nakatunud sortidest. Sama oluline kui seemnekasvatuse algmaterjali tervendamine, on ka selle kiire ja massiline paljundamine, et efektiivselt ära kasutada tervendatud seemne saagivõimet ja lühendada seemnekasvatusperioodi. Eestis tervendatakse, paljundatakse ja uuritakse taimede saagikuse suurendamise võimalusi Eesti Maaviljeluse Instituudi taimebiotehnoloogia osakonnas EVIKA. Seni ei olnud uuritud kartuli meristeemtaimede produktiivsuse näitajate dünaamikat, erinevate meetoditega paljundamisel ja seemnemugulate avamaal kasvatamisel. Käesolev uurimistöö viidi läbi aastatel 2005 – 2007 EVIKA kasvuhoones ja katsepõllul Sakus. Korraldatud katsete eesmärk oli: (1) Võrrelda tipu- ja varrepistikutest regenereerunud ning pealt korra lõigatud ja uuesti kasvanud taimede produktiivsuse näitajaid nagu lehepinna indeks, mugulate arv, ühe mugula keskmine ja kogu taime mugulate toormass, mugulate fraktsioonilisus, kogu taime ja selle mugulate kuivainemass in vitro paljundatud taimede samade näitajatega; (2) analüüsida erinevalt paljundatud kartuli meristeemtaimede produktiivsuse näitajate sõltuvust paljundusmeetodist, katseaastast ja sordist. Katses kasutati nelja taimede paljundusmeetodit (katseklaasis (in vitro) mikropistikud; kilerullis (turbasubstraadil) tipu-, varrepistkud; pealt korra lõigatud taimed). Kasvatati kahte Jõgeva Sordiaretuse Instituudis aretatud kartulisorti: ‘Ants’ (keskhiline) ja ‘Vigri’ (hilisepoolne). Kasvudünaamikat määrati, olenevalt aastast, 12-14 korda vegetatsiooniperioodi jooksul. Katseandmed töödeldi STATISTICA 9.0 programmis ühefaktorilise dispersioonanalüüsi (One-way ANOVA), faktoriaal- (Three way factorial ANOVA) ja korduvmõõtmiste (Reapeted measures ANOVA) meetodil. Kokkuvõtvalt võib antud katsete põhjal väita, et erinevalt paljundatud kartuli meristeemtaimede kõik uuritud produktiivsuse näitajad sõltusid avamaal kasvatamisel oluliselt kasutatud paljundusmeetodist ja katseaastast. Sordi oluline mõju ilmnes lehepinna indeksi, mugulate arvu ja mugula keskmise massi arvestuses. Ilmnes, et katseklaasis in vitro mikropistikutega paljundatud taimedel oli väiksem LPI, arvuliselt moodustus küll rohkem mugulaid taime kohta, aga mugulad olid väiksema keskmise massiga. Tipu- ja varrepistikutega paljundatud ning pealt korra lõigatud taimedest kasvanud mugulad saavutavad seemneks sobiliku suuruse kaks kuni kolm nädalat varem kui in vitro paljundusmeetodi korral. Optimaalne koristusaeg sõltus aasta ilmastikust ja taimede arengust. Käesolev uurimisöö kinnitas, et nii EVIKA-s väljatöötatud (tipu- ja varrepistikud, pealt korra lõigatud ja nendest uuesti kasvanud taimed) ja maailmas enam kasutamist leidnud töömahukam ja kulukam in vitro paljundusmeetod sobivad tervendatud kartuli seemnekasvatuse algmaterjali kiireks ja massiliseks paljundamiseks.
Antennal contact chemoreception in ground beetles (Coleoptera: Carabidae)
(Eesti Maaülikool, 2011) Komendant, Marit
Käesolevas elektrofüsioloogilises uurimuses selgitati kontaktsete kemoretseptorite (maitseharjaste) osa ökoloogiliselt ja taimekaitseliselt oluliste putukate – jooksiklaste toiduotsingus ja elupaiga valikul. Esmakordselt tehti kindlaks suhkru-, alkaloidi- pH- ja puutetundliku neuroni olemasolu jooksiklaste tundlatel paiknevates maitseharjastes ning selgitati nende talitluse iseärasusi. Kaheteistkümnest 1‒1000 mmol l-1 testitud taimsest suhkrust osutusid aktiivsemateks 1.4-glükosiidsidet omavad disahhariidid sahharoos ja maltoos, mis 1000 mmol l-1 kontsentratsioonil kutsusid metsa-süsijooksiku suhkruneuronis esile 70 imp/s (lävikontsentratsioon alla 1 mmol l-1). Glükoosi stimuleeriv toime oli ligikaudu kaks korda madalam. Taimtoidulistel putukatel on suhkrud tugevateks toitumise stimulantideks. Uuritud jooksiklaste tundlikkus taimsete suhkrutele näib olevat samuti seotud nende osalise granivooriaga. Ükski puidu ensümaatilise lagunemise käigus tekkivast vees lahustuvast suhkrust (tsellobioos, arabinoos, ksüloos, mannoos, ramnoos ja galaktoos) ei osutunud füsioloogiliselt aktiivseks, mistõttu nad nähtavasti ei osale selle liigi otsingulises käitumises, näiteks nende liikide eelistatud talvituskohtade otsingus pruunmädaniku poolt lagundatud puidus. Katsed ei näidanud spetsiifilise, aminohapetele tundliku neuroni olemasolu uuritud jooksiklaste tundlate maitseharjastes. Testitud seitsmest 100 mmol l-1 aminohappest vaid mõned (metioniin, seriin, alaniin, glutamiin) avaldasid nõrka stimuleerivat toimet (alla 3 imp/s) metsa-süsijooksiku maitseharjase kemosensoorsetele neuronitele, mida võib aga iseloomustada kui neuronite reaktsiooni mittespetsiifilist modulatsiooni. Testitud seitsmest taimsest alkaloidist vaid kiniin ja selle sool kiniinhüdrokloriid olid füsioloogiliselt aktiivsed, kusjuures viimane osutus käitumiskatsetes tugevaks söömapärssijaks. Kui kiniin ja selle sool alkaloiditundliku neuroni aktiivsust tugevalt stimuleerisid, siis maitseharjase teisi neuroneid (soola- ja pH-neuron) nad pärssisid tugevalt. Mõned taimsed sekundaarsed ühendid (glükosiididest salitsiin ja sinigriin, alkaloididest kofeiin ja nikotiin), mille mõju alkaloidineuronile oli väike või puudus üldse pärssisid samuti tugevalt soola- ja pH-tundliku neuroni impulss-aktiivsust. Jooksiklaste tundlikkus taimsete alkaloidide ja glükosiidide suhtes aitab neil eristada mürgiseid seemneid mittemürgistest. Metsa- ja ümarselg-süsijooksiku maitseharjaseid innerveerivate neuronite reaktsiooni ärrituslahuse pH-tasemele testiti atsetaat- ja fosfaatpuhvritega ning leelistatud sooladega pH-vahemikus 3‒11. Happelises piirkonnas (pH 3‒6) oli pH-neuroni impulss-aktiivsus madal, alla 5 imp/s, kuid neuroni aktiivsus tõusis kiiresti kui ärrituslahuse pH-taset tõsteti, ulatudes pH 8‒11 juures 25 kuni 30 imp/s. pH 3‒6 vastab nende jooksiklaste poolt eelistatud metsabiotoopide pinnase ja talvituskohtade pH-tasemele.
Assessment of Verticillium dahliae Kleb. And Soil Fungal Communities Associated with Strawberry Fields
(Eesti Maaülikool, 2017) Mirmajlessi, Seyed Mahyar; Mänd, Marika; Loit, Evelin; Starzycki, Michael (reviewer); Kvarnheden, Anders (reviewer); Nigro, Franco (opponent)
Strawberry (Fragaria × ananassa) is a high value crop, and it is grown for its berries in many countries. Strawberry industry in Estonia has been fluctuating due to the limited selection of cultivars suitable for Nordic climate that are also susceptible to several diseases. Due to the complexity of soil systems and the inadequacy of conventional techniques for describing microbial community composition, it is difficult to diagnose and forecast all ongoing diseases. Strawberry fields are often subjected to disease complex involving different soil-borne pathogens. One of the most widespread and destructive diseases of strawberry is Verticillum wilt caused by Verticillium dahliae. So, knowing about the presence and amount of V. dahliae in the soil can be a key factor in determining appropriate management strategies. The general goal of the present dissertation was on assessment of V. dahliae inoculum density and soil fungal communities associated with Estonian strawberry fields in order to a better understanding of population dynamics. Additionally, finding new potential biocontrol agents was also important in terms of their implications for biological control. In this respect, PCR-based methods used for detection and/or quantification of the most widespread strawberry pathogens were systematically reviewed (I) and then general description of different real-time PCR (rtPCR) chemistries applied in plant pathology was illustrated (II). Also, a rtPCR assay combined with a conventional technique was developed for detection and quantification of V. dahliae directly from strawberry plants and soils of different major production areas (Vasula, Rohu, Unipiha, Utsu, Kaie-Mare and Marjamaa) in Estonia (III, IV). Moreover, soil fungal communities in same strawberry production areas (except Kaie-Mare) were investigated using Illumina-based sequencing as the first study, which may improve available management strategies against strawberry soil-borne diseases (V). Lastly, the antagonistic potential of a native Ttichoderma harzianum collected from Estonian fields as well as Gliocladium catenulatum isolated from a bifungicide toward V. dahliae was assessed with the aim of protecting biological resources (VI, VII). As the first study in Estonia, the newly developed rtPCR protocol efficiently enabled detecting and quantifying V. dahliae in strawberry plants and soils in which, 10.48 pg μl−1 of pathogen DNA represented at least one Microsclerotia (MS) per gram of soil, showing a high level of quantification in comparison with other studies. In fact, the presence of V. dahliae in strawberry production areas exhibited considerable variation, being high in samples from Vasula and Marjamaa, moderate in Rohu and Utsu, and low in Unipiha. No V. dahliae was detected from Kaie-Mare district. According to Illumina sequencing of strawberry soils from five commercially production sites, a high number of sequence matched V. dahliae in most samples particularly from soils with diseased plants (Vasula and Marjamaa) and so proved the interpretation of earlier estimates using rtPCR. Arbuscular mycorrhizal fungi were more abundant in areas with healthy plants (Rohu, Utsu and Unipiha), which may highlight their suppressive role against fungal pathogens. Moreover, biocontrol ability of T. harzianum isolates and G. catenulatum over V. dahlia was proven, representing as useful candidates for biocontrol of one of the most economically important pathogen of strawberry. The current dissertation provided important insights into the rtPCR as a valuable quantitative technique for diagnosis of important pathogens such as V. dahliae with high accuracy and rapidity as well as presented a comprehensive study to date on soil fungal communities in Estonian strawberry fields, which may help to achieve better understanding of the biological characteristics of soil in development of diseases. The data described within this dissertation may provide useful information for growers and agricultural organizations for applying suitable disease management strategies against plant pathogenic.
Associations between metabolic profile and coagulation ability of bovine milk effect of feeding and lactation stage
(Eesti Maaülikool, 2013) Harzia, Hedi; Kärt, Olav; Soomets, Ursel; Kilk, Kalle
Most of the milk produced in Europe is converted into cheese by enzymatic coagulation. Therefore the coagulation ability of milk is of great economical interest and widely studied trait. Yet, there is no clear genetic or environmental explanation why milk has different coagulation properties. Therefore it was hypothesised that through milks’ molecular composition the technological properties can be estimated and the coagulation ability, as well as the metabolic profile of milk can be associated with lactation stage and feeding. Therefore studies to describe metabolic profiles and its association with coagulation ability were carried out in order to investigate factors affecting coagulation at molecular level. On that notion a robust method to analyse milk with liquid chromatography tandem mass spectrometry was devised and metabolic profiles of 646 milk samples were acquired. Associations with extreme coagulation ability, feeding and lactation stage were investigated. The metabolic profiles of non- and well-coagulating milk were determined to be different and metabolites associated with coagulation (e.g. L-carnitine, oligosaccharides) were identified. Change of glycogenic precursor in dairy cows diet had altered coagulation ability and metabolic profile of milk. Feeding crude glycerol resulted as favourable effect on milk by increasing microbial and milk protein content, thus improving coagulation ability. Metabolic profile during whole lactation stage changed, and few metabolites were associated with curd firmness, but non with RCT. Further investigation of metabolites detected, could provide an economic advantage to the dairy industry, and farming (e.g. improving productivity).
Begomovirus infection in tomato fruit
(Eesti Maaülikool, 2017) Just, Kadri; Luik, Anne; Kvarnheden, Anders; Wege, Christina (opponent)
In an era of globalization and increased food trade, and considering the implementations of climate change on establishment of pathogens into new areas, it is of importance to monitor traded plant material for the presence of plant pathogens. Tomato is economically one of the most important vegetable crop worldwide and it is susceptible to more than 200 plant diseases. Among viruses infecting tomato, Tomato yellow leaf curl virus (TYLCV, genus Begomovirus) is most destructive. It is transmitted by insect vector Bemisia tabaci as well as by infected seeds and can cause up to 100% yield loss. Both B. tabaci and TYLCV are quarantine pests in EU. However, they are widespread in tomato-production areas in southern Europe and B. tabaci occurs in greenhouses in temperate areas. Additionally, they are both disseminated by traded plant material. Thus, there is a risk that both begomoviruses and B. tabaci may spread and establish towards more northern areas. The current thesis was therefore designed to determine if infectious begomoviruses are present in tomato fruit imported to northern Europe. In addition, the aim of this thesis was also to monitor the TYLCV infection process in tomato fruit. Presence of infective TYLCV in imported tomato fruit in Estonia and Sweden as well as quantification and localization of TYLCV in tomato fruit was reported here for the first time. Among imported tomato fruit batches tested in Estonia and Sweden, 20% in total were infected by TYLCV. The amount of TYLCV increased with developmental stage of the fruit and virus localized to phloem tissue of tomato fruit. In addition, virus hybridization signals were also found in the embryo of seeds. This study shows that improvement of border inspection and existing phytosanitary control measures is needed. Tomato growers should pay attention on the possible inadvertent transmission of TYLCV via seed derived from infected fruit.
Bio-waste composting in the framework of a circular economy
(Estonian University of Life Sciences, 2023) Lanno, Marge; Shanskiy, Merrit; Kriipsalu, Mait; Kisand, Anu; Institute of Agricultural and Environmental Sciences; Fuchs, Jacques Gabrie (opponent)
Organic wastes can be stabilized by composting and turned into solid organic fertilizers and soil improvers, while closing the cycle of nutrients. Evaluation of total nutrient concentrations, as well as safety and hygiene parameters of composts, are regulated; however, some beneficial properties of compost are not reported. The aim of this PhD thesis was to determine the value of fish by-catch, an underutilized type of biowaste, through proximity composting, and increase our knowledge about the properties and added value of various composts. The distribution of phosphorus forms and concentration and properties of humic substances were determined from the fish waste composts and compared with other common types of compost. This study confirmed that proximity composting of fish waste is technologically feasible and meets hygiene requirements according to regulations (temperature 1 h > 70 °C). Composts made from different input materials varied in relative proportions and concentrations of phosphorus forms. Fish waste compost contained the highest concentration of immediately bioavailable phosphorus (6.90–7.75 g P/kg DW; 57–66% of total phosphorus). All selected composts contained humic substances, including humic acids (HA) and fulvic acids (FA), but their concentrations, properties, and relative proportions depended on compost input materials. The HA/FA ratio, reflecting humification, was highest in horse manure compost (7.88) and lowest in chicken waste compost (1.42). Composts revealed similar peaks of excitation/emission matrices of fluorescence spectra for FA, but varied in their HA spectra. In conclusion, this PhD thesis highlights the potential value of small biowaste streams, which have not been sufficiently considered to date. Such waste can be a valuable source material for high-quality composts that can be used to improve the physical and chemical properties of soil, as well as to increase crop yields.
Biochemical methane potential of Estonian substrates and evaluation of some inhibitors of anaerobic digestion
(Eesti Maaülikool, 2011) Luna del Risco, Mario Alberto
Energia sõltuvus fossiilsetest kütustest on sundinud riike üle maailma leidma uusi alternatiive energia tootmiseks. Võimalike taastuvate ener-giaallikate seas peetakse üheks potentsiaalseks energia saamise alternatii-viks biogaasi tootmist, kuna samaaegselt lahendatakse ökoloogilisi prob-leeme. Anaeroobse kääritamise protsess, milles rühm spetsialiseerunud anaeroobseid baktereid muudab orgaanilist biomassi biogaasiks, on hästi dokumenteeritud. Siiski ei ole andmed tavaliste keemiliste näitajate ja biomassi metaanitootlikkuse potentsiaali kohta alati esitatud standardi-seeritud vormis, mis teeb nende interpretatsiooni raskeks nii teadlaste kui ka biogaasijaamade operaatorite jaoks. Levinumad substraadid biogaasi tootmiseks Eestis võiksid olla looma-sõnnik, energiakultuurid, silod. Hinnanguliselt on Eestis umbes 286 000 ha vabanenud põllumajanduslikku maad, mida võib kasutada ener-giakultuuride kasvatamiseks, ja umbes 128 000 ha poollooduslikku rohumaad. Siiski on Eestis 2011. aastal ainult üks põllumajanduslikul toormel töötav biogaasijaam. Biogaasi toodetakse Eestis reoveepuhastites ja prügilates. Palju uurimusi on läbi viidud eesmärgiga suurendada biogaasi tootmi-se efektiivsust. Need uuringud keskenduvad uute reaktorite konfigurat-sioonile, erinevate substraatide kooskääritamisele ja samuti anaeroobse kääritamise inhibiitorite väljaselgitamisele. Kirjandusest teadaolevad inhibiitorid on ammoniaak, pika ahelaga rasvhapped, raskmetallid ja teised. Viimastel aastatel on erinevates teadusvaldkondades (pinnateadu-sed, orgaaniline keemia, molekulaarbioloogia, pooljuhtide füüsika ja ka põllumajandusteadused) suurenenud huvi nanotehnoloogia vastu, mis võib põhjustada uute toksiliste ainete sattumist keskkonda. Uute kemi-kaalide – nanoosakeste – ökotoksilisus ja mõju anaeroobsetele mikro-organismidele pole veel teada. Käesoleva doktoritöö peamisteks eesmärkideks olid 1) andmebaasi loomine, mis koondaks kirjanduses avaldatud teadustöö-de ja rakenduslike projektide andmeid erinevate substraatide keemili-se koostise ja metaanitootlikkuse potentsiaali kohta (artikkel I); 2) Eesti põllumajandusliku biomassi ja põllumajandustootmise jäätmete metaanitootlikkuse potentsiaali ja metaani tootmise kineetika uuri-mine (artiklid II ja III); 3) metallioksiidide nanoosakeste kahjuliku mõju uurimine biogaasi tootmisel, võrreldes neid tava- ehk mikrosuuruses osakestega (artikkel IV). Metoodika Metaanitootlikkuse potentsiaali andmebaas loodi elektrooniliselt, kasu-tades kolme programmeerimiskeelt: HTML, PHP ja MySQL. See on kättesaadav aadressil http://bioconversion.emu.ee/. Juurdepääs andme-baasile on vaba peale e-registreerimist ja andmebaasi administraatori heakskiitu. Andmed on organiseeritud substraadi tüübi alusel. Iga subst-raadi jaoks on lisatud andmed koos viidetega algallikatele nii substraadi kui olemasolul ka kääritusjäägi keemilise koostise ja metaanitootlikkuse potentsiaali kohta pärast ühikute standardiseerimist (artikkel I). Analüüsiti 61 Eestist pärit substraadi (rohtne biomass ja põllumajan-dustootmise jäätmed) keemilist koostist ja määrati nende metaanisaagis, kasutades biokeemilise metaanitootlikkuse potentsiaali testi (artiklid II ja III). Lisaks viidi läbi anaeroobne inhibeerimistest CuO ja ZnO nano-osakeste ja tavasuuruses osakestega (artikkel IV). Inokulum mõlemate katsete jaoks saadi Tallinna reoveepuhasti anaeroobsest reaktorist. Testid teostati hapnikuvabas keskkonnas temperatuuril 36 °C, metaani teket mõõdeti gaaskromatograafiliselt. Metaani kumulatiivne saagis arvutati, lahutades inkubatsiooni aja jooksul tekkinud metaani summast substraa-dita võrdluskatses tekkinud metaani saagis. Gaasi produktsiooni väljen-dati metaani liitrites, arvutatuna 0 °C ja 1 atm tingimustele katses lisatud substraadi kuivaine või orgaanilise aine kilogrammi kohta (artiklid II ja III). Metaanitootlikkuse potentsiaali (kõrgeim kumulatiivne metaani saagis testi jooksul) ja protsessi kiiruskonstandi väärtuse sõltuvust subst-raadi keemilisest koostisest analüüsiti Pearsoni korrelatsioonanalüüsi abil (artikkel III). Biogaasi ja metaani tootmise inhibeerumine arvuta-ti inhibiitorit sisaldavates katsetes tekkinud biogaasi ja metaani koguste võrdlemisel kontrollkatsetega. REGTOXi programmi Log-Normali mu- delit kasutades arvutati üldlevinud toksilisusparameetrid EC10, EC20 ja EC50 (artikkel IV). Tulemused ja arutelu Loodud metaanitootlikkuse potentsiaali andmebaas sisaldas 2011. a septembriks andmeid 226 erineva substraadi kohta 88 kirjandusallikast. Sama substraadi kohta on sageli andmeid erinevatest publikatsioonidest. Andmebaasis on 535 erinevat kirjet energiakultuuride, 63 sõnniku, 98 kooskääritamise ja 102 jäätmete rühmas (artikkel I). Katsetöös uuritud substraatide keemilise koostise andmed sarnanesid teis-te autorite poolt avaldatud tulemustega. Rohtse biomassi (energiakultuu-rid, silod, hein) metaanisaagised olid vahemikus 286-323 L CH4/kg VS. Vedelsõnniku proovidest oli sea vedelsõnnikul kõrgem metaanisaagis (317 L CH4/kg VS) kui veise vedelsõnnikul (238 L CH4/kg VS). Ana-lüüsitud energikultuuridest oli metaanitootlikkus kõige kõrgem aas-rebasesaba korral (323 L CH4/kg VS). Uuritud toiduainetööstuse ülejää-kidest oli kõrgeim metaanisaagis juustul (658 L CH4/kg VS), samas kui madalaim saagis leiti teraviljaveski jääkidest (328 L CH4/kg VS) (artiklid II ja III). Kõrgeim kineetiline kiiruskonstant määrati piima (0,344 ± 0,03 1/d) ja madalaim (0,061 1/d) energiarohu Szarvasi-1 korral. Põllumajandus-liku rohtse biomassi (rohusilo, maisisilo, silosegu ja hein) korral olid kiiruskonstandid vahemikus 0,086–0,230 1/d. Sea vedelsõnnikust oli metaani tekkimine kiirem kui veise vedelsõnnikust, kiiruskonstandid vastavalt 0,139 ja 0,092 1/d. Tööstuslikest jääkidest oli metaani tekki-mine aeglaseim katsetes piiritustööstuse praagaga. Erinevused protsessi kiirustes on seletatavad substraatide erineva keemilise koostisega (artik-kel III). Analüüsides substraatide metaanisaagise sõltuvust keemilisest koosti-sest, ilmnes metaani saagise positiivne korrelatsioon orgaanilise aine ja valkude sisaldusega substraadi koostises. Ligniinisisaldus substraatides mõjutas metaani produktsiooni negatiivselt. Olulised positiivsed seosed keemilise koostise ja kiiruskonstandi vahel leiti P, Ca, Mg ja K puhul. Mida kõrgem oli aga lignotselluloosse materjali (hemitselluloos, tsellu-loos, ligniin) sisaldus substraatides, seda väiksem oli metaani tekke kiirus (artikkel III). Inhibeerimistestides näitasid CuO ja ZnO nanoosakesed negatiivsemat mõju anaeroobsele käärimisprotsessile kui nende tava- ehk mikrosuuru-ses osakesed. Katsetes ZnO nanoosakestega oli biogaasi ja metaani teke vähem inhibeeritud kui katsetes CuO nanoosakestega. Metaani teket uurides leitud EC50 väärtused tava- ja nanosuuruses CuO-osakestega katsetes olid vastavalt 129 ja 10,7 mg Cu/L, ZnO puhul vastavalt 101 ja 57,3 mg Zn/L. Keemiline analüüs näitas CuO nanoosakeste suuremat lahustuvust, võrreldes mikrosuuruses osakestega (artikkel IV). Tulemus-test selgus, et nanosuuruses CuO inhibeeriv mõju võib osaliselt olla põh-justatud lahustunud Cu2+-ioonidest katsekeskkonnas. Järeldused Loodud andmebaas võimaldab kasutajatel koondatult ja ühtsetele ühi-kutele viidult kätte saada andmeid erinevate kultuuride ja orgaaniliste jäätmete keemilise koostise ja metaanitootlikkuse potentsiaali kohta koos vastavate kirjandusviidetega Open Accessi keskkonnas. Teadlased saaksid andmebaasi kasutada substraatide võrdlemisel, uurides biomassi koostise mõju metaani saagisele, ja statistilise analüüsi eesmärgil. Inseneride jaoks võiks andmebaas olla oluline abivahend biogaasijaamade projekteerimi-sel ja opereerimiseks vajalike andmete koondamisel. Doktoritöö tulemused näitasid Eesti rohtse biomassi, loomade vedel-sõnniku ja põllumajandusjäätmete kõrget metaani tootlikkuse potent-siaali. Saadud metaanisaagised varieerusid vahemikus 238 L CH4/kg VS (veise vedelsõnnik) kuni 658 L CH4/kg VS (juustujäägid). Kiireim substraadi biokonversioon metaaniks toimus katsetes piimaga, kus ku-lus ainult kolm päeva ultimatiivsest metaani saagisest 80% saavutami-seni. Samas kulus energiarohu korral selleks 31 päeva. Kuigi tulemused näitasid põllumajanduslikest substraatidest biogaasi tootmise suurt po-tentsiaali, on kääritamisprotsessi erinevate aspektide ja kommertsiaalse süsteemi toimimise analüüsimiseks vajalik ka pilootseadmetega uurin-gute läbiviimine. Nanoosakeste mõju kohta anaeroobsetes süsteemides on avaldatud üksi-kuid andmeid. Doktoritöös saadud tulemused on olulised, täiendamaks nanoosakeste potentsiaalse mõju iseloomustamist anaeroobses käärita-misprotsessis. Tulemused näitasid, et CuO- ja ZnO-osakeste suurusel oli otsene mõju biogaasi ja metaani saagisele. Nanoosakeste suurem inhi-beeriv toime võib osaliselt olla selgitatud toksiliste metalliioonide (Cu2+, Zn2+) sattumisega vette. Edasised uuringud inhibeerimise mehhanismide osas on olulised, et selgitada teiste võimalike tegurite mõju. Rohtsest biomassist biogaasi tootmine, kasvatades vabanenud maal kõr-ge energiapotentsiaaliga sobivaid kultuure, võimaldaks Eestil täita taas-tuvenergia tootmise vajadust. Loomade vedelsõnnik ja tööstuse jäätmed on sobivateks substraatideks kooskääritamisel, nende kasutamine bio-gaasi tootmiseks on tähtis ka jäätmetekke vältimise ning õhu ja veeko-gude keskkonnakaitse seisukohast. Võtmeküsimuseks on koostöö põllu-majandustootjate ja valitsusringkondade vahel, et soodustada investeeri-mist uute biogaasijaamade rajamisse.
Biomass from semi-natural grassland for bioenergy
(Eesti Maaülikool, 2014) Melts, Indrek; Heinsoo, Katrin; Kull, Tiiu
One of the under-utilised potential agricultural sources of bioenergy feedstock is the herbaceous biomass obtained from semi-natural grasslands. For biodiversity maintenance, it is important that semi-natural grasslands are managed continuously using extensive methods (one cut per year and without seeding, fertilisation). However, many countries are facing great difficulties with consuming the biomass from these grasslands due to its low forage value. Therefore finding an alternative use of biomass from semi-natural grasslands has become a challenging option for bioenergy production. The main aim of the thesis is to evaluate the energy potential of herbaceous biomass from three Estonian semi-natural grassland types (alluvial meadow, dry to mesic meadow and wooded meadow) for bioenergy production. The share of different functional groups (grasses, legumes, sedges/rushes and other forbs), characteristics relevant for bioenergy production and factors that influence these parameters were examined. The biomass potential varies between semi-natural grassland types studied. In Estonian conditions the highest biomass yield can be obtained from alluvial meadows and this is the only type where the amount of biomass increases significantly from June to July. In alluvial meadows the largest proportion of biomass was contributed by sedges/rushes, in dry to mesic meadows the dominant functional group was grasses and other forbs group was prevalent in wooded meadows. The chemical composition and calorific value of biomass varies by functional groups. The highest cellulose concentration is in grasses and hemicellulose in sedges/rushes, while the concentration of lignin is the highest in legumes and other forbs. The average lignin and Ca concentration in biomass increases in time, but N concentration in biomass declines during summer. The highest Cl concentration is in grasses and the lowest in legumes, whilst the highest N and Ca concentration are in legumes. The other forbs group has the highest K, Mg and ash concentrations with the lowest calorific value and the sedges/rushes and legumes have lower ash content with higher calorific values. Biomass ensiling does not influence methane yield, but methane potential varies by functional groups. The feedstock-specific methane yield was the highest in grasses and sedges/rushes and the lowest in the other forbs. The highest energy potential can be obtained from alluvial meadows (>100 GJ ha-1) followed by dry to mesic meadows and wooded meadows. Theoretical energy yield through combustion is higher than that of methane production. Even with conservative assumptions about energy input (10 GJ ha-1), the energy yield from semi-natural grasslands, especially from alluvial meadows can be comparable with that of dedicated energy crops in boreal region. Alternative usage of the herbaceous biomass from semi-natural grasslands for bioenergy is a reasonable option for both sustainable management of semi-natural grasslands to achieve nature conservation goals and for embodying resource-efficiency principles.
Biomass production of different green manure crops and their effect on the succeeding crops yield
(Eesti Maaülikool, 2013) Talgre, Liina; Lauringson, Enn; Roostalu, Hugo
As green manure crops and green manure undersows haven’t been comparatively studied in Estonia, the current research is focused on comparing different green manure crops and their cultivation in Estonia – both when pure sown or when undersown with cereals. Hypotheses of present thesis are: (i) when organic matter from green manure reaches the soil, its mineralization rate and its effect on succeeding crops is influenced by the way it was sown (pure or undersown), the amount of biomass, its chemical composition and weather conditions; (ii) the decomposition rate of organic matter and its release of nutrients to the soil varies with plant species; it also differs between roots and above-ground biomass; (iii)it is possible to influence succeeding crop yields by different ploughing times of green manures; the duration of the effect of the ploughed biomass depends on the plant species; (iv) the biomass formation and nutrient binding capacities of catch crops depend on the plant species, the climatic conditions and the length of the growing period. The objectives of the present study were as follows: (i) to determine the amount of the aboveground biomass and root system of various green manure crops, as well as their decomposition rate and amount of nutrients (N, P, K) introduced to soil; (ii) to investigate the duration of the effect of, and the efficiency of, biologically bound nitrogen based on the yield and yield quality of succeeding crops; (iii) to investigate the decomposition rate of organic matter at different C:N ratios; (iv) to determine catch crop biomass amount, nutrient binding capacity and effect on soil plant available nitrogen content and succeeding crop yield, and to identify catch crops most suitable for Estonian conditions. The formation of legume crop biomass varied with legume species, trial year weather and herbage use duration. Of the pure crop legumes studied by us, red clover, hybrid lucerne and white melilot produced the greatest biomass. When under sown, the amounts of biomass, N and C returned to the soil depended on aftermath formation. The amounts of nutrients returned to the soil were mostly influenced by biomass size and its nutrient content. Of the legumes used in the trials, bird’s foot trefoil was not suitable as a green manure crop when under-sown, and even when pure sown its efficiency on succeeding crop yield was the lowest. Westerwold ryegrass use reduced succeeding crop yield. The biomass of bird’s foot trefoil and red clover decomposed faster and their effect materialised in the succeeding crop yield. The effect of the lucernes and white melilot, which decompose more slowly, on succeeding crop yield materialised also in the second and third years. Another major conclusion is that it is important for the N effect of green manures to be utilised by subsequent crops. Red clover, white melilot and hybrid lucerne pure sowing biomass effect was roughly equal to that of the N100 treatment. The effect of bird’s foot trefoil was smaller than that of other leguminous green manure crops, with following cereal yield approximately equal to that after N50. Cereal yield was similar after under-sowings biomass incorporation into soil. After spring ploughing of green manure, the succeeding crop yield increased more than with spring ploughing alone, but this effect was not evident in all trial years. Where legumes were grown as under-sowings the C:N ratio of incorporated organic matter improved, which creates better conditions for organic matter decomposition in soil and reduces microbiological soil nitrogen binding. The effectiveness of catch crops depended on the choice of species, sowing time and main crop harvesting time, as well as on weather conditions during the autumn and winter. The optimal catch crops in Estonian weather conditions were fodder radish and white mustard.
Breeding and migration ecology of Common Crane (Grus grus L.)
(Eesti Maaülikool, 2019) Ojaste, Ivar; Sepp, Kalev; Leito, Aivar; Väli, Ülo; Végvári, Zsolt (opponent)
The objectives of this thesis were to analyse the breeding population trends and distribution of the Common Cranes in Estonia and the availability of potential breeding habitat (I, IV), to describe nesting habitats in Estonia and to explore the relationships between habitat and nesting success and nesting phenology (II), to investigate the relation between the numbers and distribution of autumn staging cranes and agricultural land use (III), to examine the stability of the habitat network used by cranes (IV) and to study the long-distance migration pattern of cranes (V). The population of the Common Crane started to increase in Estonia since 1970s (I). In parallel, the mean density of pairs increased, and distribution widened all over the country (I). First time breeders started to occupy new suitable habitats for nesting (I). The extended distribution of the crane has been favoured by the good availability of potential nesting sites (IV). The Common Crane nesting sites are different wetlands in Estonia have similar water regimes, plant communities and microrelief. The preferred breeding habitats are mires (II). The breeding success is associated with quality of breeding habitat and distance between neighbouring nests. The beginning of egg laying has a significant trend of advancement over time. Human activity had a significantly negative effect on the breeding success of cranes (II). The Common Crane numbers in staging sites are positively correlated with cropping area of cereals and negatively with the extent of potato fields. Changes in the local numbers and distribution of cranes when staging during their migration depend on changes in agricultural land use in staging areas (III). Migration routes used by cranes form a widespread ecological network (IV). Despite the modest contribution of nature conservation to the population increase of cranes (IV), the conservation efforts to protect peatlands play key roles in conservation of the Common Crane in the longer term. The climate change scenario modelling suggests minimal impact on cranes in future (IV). Common Crane’s long-distance autumn migration strategies differed between northern and southern sub-populations by the density and location of stopovers, daily flight distances, and the total migration duration. Cranes used during migration both, time- and energy-minimization strategies (V).
Change in Estonian natural resource use: the case of wild food plants
(Eesti Maaülikool, 2017) Kalle, Raivo; Kull, Tiiu; Puri, Rajindra K; Sõukand, Renata; Paal, Taimi (pre-opponent); Santayana, Manuel Pardo de (opponent)
The use of wild food plants is one example of the importance of biocultural diversity. Wild food plants are, in the context of this work, those plants that grow without the direct intentional help (cultivation or management) of humans, or are cultivated but not for food. The goals of the present study were to identify the wild food plant taxa used in the territory of present-day Estonia, to document changes in their use and to understand the reasons for such changes. Within the period 1777–1960, 146 wild food plant taxa were documented in written and archival sources. To detect any changes, a written questionnaire was distributed during the winter of 2011/2012 all across Estonia; and the responses reported the use of 118 plant species and 18 taxa identified at genus or family level. The results showed that snacking on roots and tubers as well as the use of wild additives in bread have practically disappeared. The use of condiments for bear and near-bear (from 16 taxa historically to only one now), vodka (6/0) and blood and white sausages (5/1) also decreased considerably. An increase in use was noted in the category of fresh salads made during spring (now 21 taxa, earlier 8) and green soups. During fieldwork in Saaremaa (June-August 2014) several factors influencing these changes were detected, including: a) a reduction in suitable habitat; b) changes in paths and routes; c) a decrease in the economic importance of taxa; d) cultivation; e) pollution; f) a decrease in harvest due to insects; g) age-related changes in taste preferences; h) diminished need; and i) changes to traditional rural and coastal life. To capture this feature of changing knowledge systems the term unlearning debt (knowledge loss deficit) was proposed. This term refers to knowledge regarding the practical use of local ecological resources which, while still remembered by older generations, is considered lost because it is no longer practiced or transferred to younger generations.
Changes in the biochemical composition of apple (Malus domestica Borkh.) fruits depending on rootstock and calcium treatment
(Eesti Maaülikool, 2013) Mainla, Leila; Karp, Kadri; Moor, Ulvi
In the Baltic States, the main goal in apple- related research has been to find out the winter hardy rootstocks and cultivars. The focus in yield quality studies has been on apple size, appearance and storability. Different in vitro and in vivo studies have shown the beneficial effect of phytochemicals, such as carotenoids, flavonoids, isoflavonoids and phenolic acids, in fruits and vegetables on human health. Therefore, the focus in yield studies has turned on apple biochemical composition, especially on polyphenol concentration and total antioxidant capacity. However, the appearance, taste and storability of apples are still important. In addition to genotype, the polyphenol concentration in apples is influenced by the geographic location of the plantation, weather condition during the vegetation period, agricultural practices (fertilization, plant protection, canopy pruning), crop load, fruit position within the canopy and fruit maturity. The influence of rootstock on polyphenol composition is less studied. At present, there are literature reports on the contents of selected apple polyphenols in a small number of cultivars. Data about phenolic content in Baltic apple cultivars is almost non-existent. Pre-harvest Ca treatment is widely used in many parts of the world mainly to reduce the incidence of physiological disorders of apples during storage. The influence of preharvest Ca treatment on apple polyphenol composition is less investigated. The aims of the study were to find out: 1) the influence of pre-harvest Ca treatment on apple mineral composition and different physiological disorders; 2) the effect of pre-harvest Ca treatment on different rootstocks on apple taste-related properties, polyphenol concentrations and total antioxidant capacity; 3) the effect of rootstocks on apple mineral composition, taste-related properties and polyphenol concentrations; 4) the influence of genotype on apple polyphenol composition. From experiments it can be concluded: 1) The Ca treatment (CaCl2 and Ca(NO3)2) did not reduce bitter pit, but reduced other physiological disorders: physiological spot and superficial scald. Last mentioned disorder correlated positively with N/Ca and Mg/Ca ratio in fruits and had a negative correlation with fruit Ca content. 2) By combining pre-harvest Ca treatment with certain rootstocks, it is possible to manipulate apple taste related properties. The pre-harvest Ca treatment (CaCl2) decreased TA and increased SSC/TA in apples. 3) Rootstocks affected mineral composition of apples: apples from trees on semi-dwarfing rootstock had higher Ca content and on dwarfing rootstock higher N content was measured. 4) The influence of rootstocks on apple taste-related properties was significant, but varied between the years and cultivars. Consistent effect appeared in ‘Valge klaarõun’: rootstock B.396 had large enough influence on apple taste-related properties to be perceived as a change in apple acidity and probably also flavor. 5) The polyphenol concentration in apple cultivars grown in Estonia is very variable. Different polyphenols have different antioxidant activity; from human health point of view it is primarily important to increase the concentration of polyphenols with higher antioxidant activity. The metabolism of phenolic compounds can be influenced by different agricultural practices, but more attention should be paid to the combined effects (e.g. pre-harvest Ca treatment and rootstock), which might be different from the influence each factor has separately. By influencing apple mineral composition, it is possible to increase the polyphenol concentration and finally, also the total antioxidant capacity (TAC) of apples. Different polyphenols were differently affected by the fruit mineral composition. Largest contributors to TAC, such as quercetin, quercitrin and quercetin galactoside, had a positive correlation with Ca and a negative correlation with N concentration in apples. In the current study, rootstock and regulation of N and Ca concentrations in apples caused almost a double increase of TAC in fruits.
Coastal meadows : maintenance, restoration and recovery
(Eesti Maaülikool, 2021) Kose, Marika; Kauer, Karin; Tali, Kadri; Joyce, Chris (opponent)
This thesis is a synthesis of 20 years of research into the restoration and recovery of Estonian coastal meadows. The restoration of semi-natural grasslands in Estonia is a new nature conservation activity with only 20 years of history. While the restoration activities and methods used for coastal meadows in Estonia have been elaborated upon and tested many times, the methodology for evaluating success and the biodiversity assessment criteria are not sufficient. One reason may be that coastal meadow habitats and plant communities vary in different parts of Estonia and are very complex, making it difficult to identify good indicators for vegetation assessment. Our observations and conclusions are as follows: Recovery of coastal meadow vegetation from reed and bush encroachment resulting from land abandonment may take decades. In the best cases, vegetation may recover and become similar to well-maintained meadows in 15 years. This is not enough for meadows that are wetter and have been abandoned for longer periods. Edaphic changes have led to paludification and massive reedbeds, and restoration may result in, for example, sedge communities instead of desired coastal meadow plant communities. It is essential to develop a long-term monitoring plan that begins with restoration activities and follows the recovery process, as the effects of short- and long-term restoration as well as different restoration activities may vary or be misleading. Mowing is the best measure for supporting the populations of tall perennial herbs, while grazing is the most recognised measure for restoration and maintenance of seminatural grassland. When implementing grazing as a conservation tool, the suitable grazing pressure should be adjusted to sustain protected plant species. To restore and maintain coastal meadows in Estonia, policies should target the whole range of ecosystem services and biodiversity issues, rather than focusing on single species.
Collaboration in Estonian rural tourism
(Eesti Maaülikool, 2021) Pilving, Tarmo; Viira, Ants-Hannes; Kull, Tiiu; Suškevičs, Monika; Czernek-Marszałek, Katarzyna (opponent)
Collaboration is important for fostering rural tourism and a way to overcome challenges. More knowledge can answer how collaboration changes, what keeps stakeholders in the collaboration, how collaboration can be beneficial, and what influences its sustainability. The purpose of this thesis is to identify what affects the evolution and sustainability of rural tourism collaboration in Estonia. Major institutional changes have offered opportunities but have also hindered tourism collaboration that is fragmented, informal and has no clear governance. There is a myriad of small informal tourism networks with limitations and weak links between them. Collaboration aims can differ between regional tourism networks, and strong connections between the members of one community do not necessarily produce strong ties with other communities. Joint aims are only attainable when bottom-up initiatives and top-down management exist in unison. The first aim of a successful tourism strategy should focus on the collaboration platform with initiation from a governing body that is accepted by all stakeholders. Shared collaborative identity helps to foster collaboration and bind the stakeholders but also push them away from each other. Identity creation is manifested on a collaboration platform where individual and collective identities interact and are influenced by the place, occupational, environmental and cultural identities of the stakeholders. Formalisation can make collaboration more attractive, but it is still framed by place, environment and culture. Collaboration networks can simultaneously follow formal and informal timelines during their life cycle where they can evolve in a cyclical way and the formal one adds more strength to the informal one. Rural tourism collaboration will never disappear completely, as it shifts from one condition to another. Its sustainability can be increased with the right use of the benefits that wider regional collaboration and the surrounding institutional environment offers. It increases trust and lowers the fear that the collaboration will fall into the wrong hands.
Combining unmanned aerial vehicles and a mesocosm experiment to unveil plant communities shifts under global change conditions in coastal meadows
(Estonian University of Life Sciences, 2022) Fernandes Bergamo, Thaisa; Sepp, Kalev; Ward, Raymond D.; Joyce, Christopher B.; Institute of Agricultural and Environmental Sciences; Edwards, Keith (opponent)
Semi-natural grasslands are an essential part of the cultural landscape of Europe. Semi-natural grasslands are commonly characterised by a very high biodiversity, including rare species. Beyond the high biodiversity value, semi-natural grasslands worldwide provide many ecosystem services, including: carbon sequestration and storage, nutrient cycling, regulation of soil quality, habitats for migrating birds, erosion control, and flood regulation. Within the realm of semi-natural grasslands, coastal meadows are particularly important. However, coastal grasslands are threatened by a range of factors such as coastal squeeze, transformation into monoculture ponds, pollution, and climate change. Coastal areas are threatened at a range of spatial scales as a result of sea-level rise, and can include higher flooding frequency in coastal areas, salt water intrusion in aquifers, and potential declines in the extent of coastal wetlands. A warmer climate also implies a modification in precipitation patterns affecting runoff into the sea. In coastal areas, both water levels and salinity have a strong impact on species distribution and therefore on the structure and composition of aquatic and coastal floral and faunal communities. Consequently, plant communities in coastal meadows are expected to undergo changes in their composition and structure. The current thesis explores different methodologies to assess plant community distribution, above-ground biomass, and the effects of management type, duration, and intensity on sward structure using UAV-derived multispectral data and aerial photogrammetry. In addition, the keystone of this thesis is a mesocosm experiment that was used to assess shifts in species richness and abundance in plant community types in Estonian coastal meadows related to future change scenarios of water level and salinity for the Baltic Sea. a. Unmanned Aerial Vehicle (UAV) The use of UAV demonstrated to be able to identify plant community extent and distribution in high biodiversity value coastal meadows in West Estonia. Species diversity and biomass significantly influence the quality of data and this should be accounted for when planning the sample collection to achieve better results. This study has shown that UAVs are useful tools of mapping grasslands at a plant community level. Also, UAV showed to be possible to reveal the structure of the grassland and how it is affected by the management history. For example, the grassland turns more homogeneous under long-term monospecific grazing, b. Mesoscosm Experiment The mesocosm experiment in the present study revealed different temporal changes of wetland communities to altered salinity and water conditions, highlighting the response of plant species to environmental variables. These changes were not significant according to alteration of water level and salinity in the Open Pioneer community, but they were over time. On the other hand, Lower Shore and Upper Shore had significant changes according to time and treatments. These could be explained by dynamic differences in the communities, since Open Pioneer was more variable. c. Conclusions Both methodologies, remote sensing and the mesocosm experiment, are evidently important to evaluate the structure and function of Estonian coastal meadows. The mapping of the extent and structure of coastal plant communities allows an evaluation of the current state of the ecosystem. The mesocosm experiment helps to understand changes in plant community composition under altered conditions of water level and salinity in Estonian coastal meadows and consequently, understand how species richness, abundance, and biomass will respond to those changes. This information is important when considering the protection and potential management of these areas taking into account the species diversity of fauna and flora as well as that of livestock.
Cultivar resistance and population studies of late blight pathogen in potato breeding in Estonia
(Eesti Maaülikool, 2016) Tähtjärv, Terje; Mänd, Marika; Runno-Paurson, Eve; Tsahkna, Aide; Polgár, Zsolt (opponent)
Potato (Solanum spp.) is the third most important food crop in the world after rice and wheat by FAO in 2014 in terms of human consumption. In the cold temperate climate zone, potato is one of the essential vitamins source throughout the year. People’s preferences and consumption habits have changed; thereby fluctuating demands of the food industry are setting up additional requirements for new potato cultivars. Potato late blight caused by pathogen Phytophthora infestans is one of the most destructive disease of potato. Changed environmental factors with globalization of intensive agriculture have caused disease to become more aggressive. When the ratio of Phytophthora infestans A1:A2 mating types is 50:50, the disease is able to reproduce sexually and therefore could cause soil-borne infection of late blight. In investigated fields the both mating types A1 and A2 were determined and the ratio refers to possibility of sexual reproduction. This research summarizes the development of the new medium maturity potato cultivar ‘Teele’. The cultivar has high yield and excellent culinary quality. ‘Teele’ is a B type table potato cultivar. All the properties of the cultivar ‘Teele’ were stable over the tested years. ‘Teele’ is highly resistant to the potato cyst nematode (G. rostochiensis) and moderately resistant to late blight, common scab and black scurf. The most sustainable strategy to protect yield in potato production is cultivation of late blight resistant cultivars. This study clearly showed that local potato cultivars have higher field resistance to late blight than the most widely cultivated European potato cultivars grown in Estonia.
Cultivation of willows (Salix sp.) using residues of the wastewater purification process and biogas production as fertilisers
(Eesti Maaülikool, 2015) Holm, Bert; Heinsoo, Katrin
This thesis suggests that society’s waste products such as municipal wastewater, sewage sludge and biogas digestate could all be used in willow cultivation providing valuable resources to develop the production of bioenergy raw materials and to foster organic waste management. From the results of the current thesis we can conclude the following: • Willow SRC is effective in reducing significantly the N and P content applied with pre-treated municipal wastewater and composted sewage sludge. Hence, these results suggest that the biological potential of willow SRC should be more widely accepted in recycling pre-purified municipal wastewater, sewage sludge and biogas digestate for producing biomass for energy purposes. • Wastewater irrigation and sewage sludge application does not affect the plant survival rate but excessive application of biogas digestate reduces the survival of young willow plants. It is essential to keep the plantations as weed-free as possible, particularly during the establishment phase of commercial SRC plantation to avoid low plant survival and inadequate SRC wood production. • Plants irrigated with pre-treated wastewater have a higher number of shoots per plant. Denser canopy increases the leaf rust severity in the case of S. viminalis genotypes. • The application of pre-treated wastewater, biogas digestate solution and composted sewage sludge increased the average DW of plants and the average wood yield per SRC area significantly. • The treatment and nutrient load affects the biomass allocation of young willows. In order to increase the harvestable wood biomass of SRC willows it is suggested that moderate fertiliser applications are made to young plantations during the years immediately following planting in order to optimise biomass allocation to roots • Clonal effects were significant for all factors studied indicating large genotypic variation of the planting material.

Sirvi

Sirvi 3. Doktoritööd Pealkiri järgi

Tulemused lehekülje kohta

Sorteerimisvalikud