Browsing by Subject "Plantago lanceolata"

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  • Hockerstedt, Layla; Susi, Hanna; Laine, Anna-Liisa (2021)
    1. Maternal effects of pathogen infection on progeny development and disease resistance may be adaptive and have important consequences for population dynamics. However, these effects are often context-dependent and examples of adaptive transgenerational responses from perennials are scarce, although they may be a particularly important mechanism generating variation in the offspring of long-lived species. 2. Here, we studied the effect of maternal infection of Plantago lanceolata by Podosphaera plantaginis, a fungal parasite, on the growth, flower production and resistance of the progeny of six maternal genotypes in nutrient-rich and nutrient-poor environments. For this purpose, we combined a common garden study with automated phenotyping measurements of early life stages, and an inoculation experiment. 3. Our results show that the effects of infection on the mother plants transcend to impact their progeny. Although maternal infection decreased total leaf and flower production of the progeny by the end of the growing season, it accelerated early growth and enhanced resistance to the pathogen P. plantaginis. 4. We also discovered that the effects of maternal infection affected progeny development and resistance through a three way-interaction between maternal genotype, maternal infection status and nutrient availability. 5. Synthesis. Our results emphasize the importance of maternal effects mediated through genotypic and environmental factors in long-living perennials and suggest that maternal infection can create a layer of phenotypic diversity in resistance. These results may have important implications for both epidemiological and evolutionary dynamics of host-parasite interactions in the wild.
  • Nurminen, Maarit (Helsingin yliopisto, 2019)
    Tutkimus on perinteisesti keskittynyt taloudellisesti merkittävien, jalostettujen tuotantokasvien tauteihin. Luonnonkasvien tauteja on tutkittu huomattavasti vähemmän, vaikka niillä on suuri merkitys kasviyhteisön monimuotoisuuden säätelijöinä. Etenkin virusten vaikutuksista on hyvin vähän tietoa, koska tartuntoja on hankala havaita. Virukset ovat ehdottomia solunsisäisiä loisia ja tarvitsevat vektoreita levittäytyäkseen kasvien välillä. Virusten esiintymisten ja vaikutusten on havaittu vaihtelevan runsaasti ajallisesti sekä lajien ja populaatioiden välillä. Tässä työssä selvitettiin Plantago lanceolatan latenttiviruksen (PlLV) ja Plantagon latentin caulimoviruksen (caulimovirus), esiintymistä kolmessa eri puolilla Ahvenanmaata sijaitsevassa heinäratamon (Plantago lanceolata) populaatiossa. Kustakin populaatiosta valittiin 20 satunnaista kasvia tutkimukseen. Lehdistä kerättiin näytteitä kerran viikossa kolmen viikon ajan touko-kesäkuussa 2017. Kasvien kukkien ja lehtien lukumäärä sekä pisimmän lehden pituus kirjattiin ylös. Lisäksi mahdolliset viroottiset oireet ja herbivorien aikaansaamat syömäjäljet kirjattiin ylös. Virusten havaitsemista varten kehitettiin qPCR-menetelmä aiempien virussekventointien pohjalta. Alukkeet suunniteltiin mahdollisimman konservoituneille alueille virusten perimässä. qPCR-menetelmän kynnysarvon asettamisen apuna oli lisäksi 218 kasvihuonekasvinäytettä, jotka oli testattu valmiiksi jo olemassa olevalla PCR-menetelmän alukkeilla. Luonnonkasvinäytteet tutkittiin sekä qPCR- että PCR-menetelmillä, joiden tulokset yhdistettiin. Sekä PlLV:ä että caulimovirusta esiintyi kaikilla populaatioilla, mutta esiintymisessä ei ollut merkitseviä populaatioiden välisiä eroja. PlLV-havainnot vähenivät merkitsevästi tutkimusaikana, mutta caulimoviruksen esiintyminen ei vaihdellut. Caulimovirushavainnot korreloivat positiivisesti lehtien lukumäärän sekä erään syömäjälkiluokan kanssa. Muut kasvin ominaisuudet tai herbivorien jättämät syömäjäljet eivät selittäneet virustartuntoja. Viroottiseksi tulkittuja oireita oli sekä virustartuntaisilla että terveiksi todetuilla kasveilla. Vanhat PCR-menetelmät tunnistavat jossain määrin qPCR-menetelmiä paremmin virustartunnat, mutta menetelmät tunnistavat osittain eri tartunnat. Tulokset vahvistavat aiempia havaintoja siitä, että virusten esiintyminen luonnonkasveilla on vaihtelevaa, eivätkä ne aina välttämättä aiheuta näkyviä oireita, mikä tekee niiden vaikutusten arvioinnista haastavaa. Virukset ovat täysin vektoreista riippuvaisia, ja tulos antaa mahdollisia viitteitä caulimoviruksen vektorilajista. Suurikokoiset kasvit vaikuttavat olevan alttiimpia caulimovirustartunnalle. qPCR-menetelmä täydentää PCR-menetelmää, mutta vaatii lisäoptimointia tehokkuuden parantamiseksi. Jatkotutkimukset suuremmalla otannalla ja pidempiaikaisella seurannalla valottaisivat, millaisia vaikutuksia virustartunnoilla on kasveihin missäkin olosuhteissa.
  • Lassila, Joose (Helsingin yliopisto, 2020)
    The aim of this study was to examine the leaf endophytic bacteria in Plantago lanceolata. The first aim was to get a comprehensive picture of the bacterial diversity, by screening for the different bacterial genera inside the leaves. Furthermore, I aimed to examine the effect of soil and maternal genotype on the endophytic community within P. lanceolata leaves and search for clues of vertical inheritance of endophytes from parent to offspring via seeds. I studied the endophytic bacteria by extracting DNA from the plant leaves and by trying to amplify any bacterial DNA present to get a view of the bacterial diversity in the leaves. My aim was to compare the bacterial community of the mother plants to that of their offspring and also to compare the bacterial communities of plants grown in different soil conditions. Furthermore, I tried to study how the soil conditions affect the growth of P. lanceolata seedlings. I collected seeds and leaf samples of P. lanceolata from Åland, Southwestern Finland, from a population that is part of the ongoing long-term metapopulation research started in Åland in the early 90’s. I marked 21 plant individuals (hereafter referred to as the “mother plants”) in the field in June, when collecting the first leaf samples. In August I collected all seeds from the same plant individuals and a second set of leaf samples. I also collected soil samples from the same location. With the seeds collected from the wild population I executed a growth experiment in Viikki, Helsinki. I grew one set of seeds in twice autoclaved sand (hereafter referred to as the “sterile soil”) and another set in twice autoclaved sand mixed with soil collected from the Åland population (hereafter referred to as the “environmental soil”). I surface sterilized all seeds and then sowed each in their own growth pot and placed them in a growth chamber. During the experiment I took measurements of the leaves. At end of the growth experiment, I took samples of the leaves and surface sterilized them to exclude any epiphytic microorganisms from the analysis. I also surface sterilized the leaf samples taken from the mother plants. I then extracted DNA from the leaf samples and run PCR to amplify certain regions of the bacterial 16S rDNA gene, that is widely used in bacterial taxonomy. The obtained DNA reads where then clustered into Operational Taxonomic Units (OTUs) and assigned taxonomy using SILVA reference database. Mitochondria and chloroplasts of eukaryotic organisms also harbour 16S rDNA regions, so the challenge of studies looking at endophytic bacteria is to exclude the 16S regions of mitochondria and chloroplasts. This proved to be a problem in my study also. More than 86% of all DNA reads obtained turned out to be from P. lanceolata mitochondria and more than 12% from P. lanceolata chloroplasts. Only a bit more than 1% of the reads were eubacterial. This effectively hindered reliable analysis of the endophyte community. I nevertheless analysed the observed eubacterial diversity although the results must be taken as only preliminary and with utmost caution. The eubacterial reads clustered into 218 OTUs, representing 71 different bacterial genera. Six most common genera constituted over 83% of eubacterial reads. Most of these bacteria, most notably Shewanella, Ralstonia and Halomonas, could be identified as being clearly contaminants and not real endophytes. For the 65 less common bacterial genera I performed community analysis using Bray-Curtis Dissimilarity index and Analysis of Similarities (ANOSIM). The results showed that there was a significant difference between the different soil treatments (P = 0.014, R = 0.3787) and also between the two growth chambers (P = 0.011, R = 0.5493). I found no effect of maternal genotype on the bacterial community. Therefore, I observed no sign of vertical inheritance of endophytes. The growth experiment results showed that germination percentage was significantly lower in the environmental soil than in the sterile soil for all genotypes (F = 10.78, P = 0.0012). However, seedling in the environmental soil grew bigger than the seedlings in the sterile soil (F = 10.91, P < 0.0001). For future studies on similar topics, validating molecular methods before large scale sequencing could yield more reliable results. Size fractionating the DNA products of the first PCR round could exclude most mitochondrial sequences and hence allow better analysis of endophytes. This would enable studying interesting questions on coevolution and ecology of host-endophyte interactions. Although I did find some differences in the bacterial communities of different treatments, these results must be considered with caution and as only preliminary.
  • Parratt, Steven R.; Laine, Anna-Liisa (2018)
    1. The relative importance of bottom-up versus top-down control of population dynamics has been the focus of much debate. In infectious disease biology, research is typically focused on the bottom-up process of host resistance, wherein the direction of control flows from the lower to the higher trophic level to impact on pathogen population size and epidemiology. However, the importance of top-down control by a pathogen's natural enemies has been mostly overlooked. 2. Here, we explore the effects of, and interaction between, host genotype (i.e., genetic susceptibility to pathogen infection) and infection by a hyperparasitic fungus, Ampelomyces spp., on the establishment and early epidemic growth and transmission of a powdery mildew plant pathogen (Podosphaera plantaginis). We used a semi-natural field experiment to contrast the impacts of hyperparasite infection, host-plant resistance and spatial structure to reveal the key factors that determine pathogen spread. We then used a laboratory-based inoculation approach to test whether the field experiment results hold across multiple pathogen-host genetic combinations and to explore hyperparasite effects on the pathogen's later life-history stages. 3. We found that hyperparasite infection had a negligible effect on within-host infection development and between-host spread of the pathogen during the onset of epidemics. In contrast, host-plant resistance was the major determinant of whether plants became infected, and host genotype and proximity to an infection source determined infection severity. 4. Our laboratory study showed that, while the interaction between host and pathogen genotypes was the key determinant of infection outcome, hyperparasitism did, on average, reduce the severity of infection. Moreover, hyperparasite infection negatively influenced the production of the pathogen's overwintering structures. 5. Synthesis and applications. Our results suggest that bottom-up host resistance affects pathogen spread, but top-down control of powdery mildew pathogens is likely more effective against later life-history stages. Further, while hyperparasitism in this system can reduce early pathogen growth under stable laboratory conditions, this effect is not detectable in a semi-natural environment. Considering the effects of hyperparasites at multiple points in pathogen's life history will be important when considering hyperparasite-derived biocontrol measures in other natural and agricultural systems.
  • Eck, Jenalle L.; Barrès, Benoit; Soubeyrand, Samuel; Siren, Jukka; Numminen, Elina; Laine, Anna-Liisa (2022)
    The inherently variable nature of epidemics renders predictions of when and where infection is expected to occur challenging. Differences in pathogen strain composition, diversity, fitness, and spatial distribution are generally ignored in epidemiological modeling and are rarely studied in natural populations, yet they may be important drivers of epidemic trajectories. To examine how these factors are linked to epidemics in natural host populations, we collected epidemiological and genetic data from 15 populations of the powdery mildew fungus, Podosphaera plantaginis, on Plantago lanceolata in the angstrom land Islands, Finland. In each population, we tracked spatiotemporal disease progression throughout one epidemic season and coupled our survey of infection with intensive field sampling of the pathogen. We found that strain composition varied greatly among populations in the landscape. Within populations, strain composition was driven by the sequence of strain activity: early-active strains reached higher abundances, leading to consistent strain compositions over time. Co-occurring strains also varied in their contribution to the growth of the local epidemic, and these fitness inequalities were linked to epidemic dynamics: a higher proportion of hosts became infected in populations containing strains that were more similar in fitness. Epidemic trajectories in the populations were also linked to strain diversity and spatial dynamics: higher infection rates occurred in populations containing higher strain diversity, while spatially clustered epidemics experienced lower infection rates. Together, our results suggest that spatial and/or temporal variation in the strain composition, diversity, and fitness of pathogen populations are important factors generating variation in epidemiological trajectories among infected host populations.
  • Burg, Skylar (Helsingin yliopisto, 2021)
    In this study, a greenhouse experiment was used to assess if temperature sensitivity, specifically, thermoregulatory plasticity, has a functional role in floral reflectance and pigmentation in a population of P. lanceolata grown in three different temperature treatments, reflecting past, present, and future summer temperatures. Spectrophotometry, surface temperature readings, and near-infrared (NIR) region image analysis were used to identify how the spectral absorbance properties and biochemical makeup of P. lanceolata flowers differed between treatments. Reflectance and phenolic absorbance were both found to be influenced by ambient temperature. However, surface temperature of flower spikes was not affected by growing temperature, reflectance, or phenolic absorbance. The results suggest that Plantago lanceolata may utilize thermoregulatory plasticity in reflectance and phenolic absorbance to adjust to rising temperatures. These findings have important implications in species reactions to climate change and denotes that increased selection on thermal function traits may occur under a future climate scenario of continued warming in temperate and boreal biomes.
  • Numminen, Elina; Vaumourin, Elise; Parratt, Steven R.; Poulin, Lucie; Laine, Anna-Liisa (2019)
    BackgroundUnderstanding the mechanisms by which diversity is maintained in pathogen populations is critical for epidemiological predictions. Life-history trade-offs have been proposed as a hypothesis for explaining long-term maintenance of variation in pathogen populations, yet the empirical evidence supporting trade-offs has remained mixed. This is in part due to the challenges of documenting successive pathogen life-history stages in many pathosystems. Moreover, little is understood of the role of natural enemies of pathogens on their life-history evolution.ResultsWe characterize life-history-trait variation and possible trade-offs in fungal pathogen Podosphaera plantaginis infecting the host plant Plantago lanceolata. We measured the timing of both asexual and sexual stages, as well as resistance to a hyperparasite of seven pathogen strains that vary in their prevalence in nature. We find significant variation among the strains in their life-history traits that constitute the infection cycle, but no evidence for trade-offs among pathogen development stages, apart from fast pathogen growth coninciding with fast hyperparasite growth. Also, the seemingly least fit pathogen strain was the most prevalent in the nature.ConclusionsWe conclude that in the nature environmental variation, and interactions with the antagonists of pathogens themselves may maintain variation in pathogen populations.
  • Numminen, Elina; Vaumourin, Elise; Parratt, Steven R; Poulin, Lucie; Laine, Anna-Liisa (BioMed Central, 2019)
    Abstract Background Understanding the mechanisms by which diversity is maintained in pathogen populations is critical for epidemiological predictions. Life-history trade-offs have been proposed as a hypothesis for explaining long-term maintenance of variation in pathogen populations, yet the empirical evidence supporting trade-offs has remained mixed. This is in part due to the challenges of documenting successive pathogen life-history stages in many pathosystems. Moreover, little is understood of the role of natural enemies of pathogens on their life-history evolution. Results We characterize life-history-trait variation and possible trade-offs in fungal pathogen Podosphaera plantaginis infecting the host plant Plantago lanceolata. We measured the timing of both asexual and sexual stages, as well as resistance to a hyperparasite of seven pathogen strains that vary in their prevalence in nature. We find significant variation among the strains in their life-history traits that constitute the infection cycle, but no evidence for trade-offs among pathogen development stages, apart from fast pathogen growth coninciding with fast hyperparasite growth. Also, the seemingly least fit pathogen strain was the most prevalent in the nature. Conclusions We conclude that in the nature environmental variation, and interactions with the antagonists of pathogens themselves may maintain variation in pathogen populations.