Thesis (M.Sc. (Horticulture)) -- University of Limpopo, 2017 / Refer to document / National Research Foundation of South Africa, and Agricultural Research Council-Universities Collaboration Centreꞌ for scholarship and research

京都大学 / 0048 / 新制・課程博士 / 博士(地球環境学) / 甲第22022号 / 地環博第186号 / 新制||地||96(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)准教授 岡田 直紀, 教授 舟川 晋也, 准教授 真常 仁志 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DGAM

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第18605号 / 人博第701号 / 新制||人||167(附属図書館) / 26||人博||701(吉田南総合図書館) / 31505 / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 加藤 眞, 教授 市岡 孝朗, 教授 瀬戸口 浩彰, 教授 宮本 嘉久, 教授 新宮 一成 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20635号 / 農博第2242号 / 新制||農||1052(附属図書館) / 学位論文||H29||N5079(農学部図書室) / 京都大学大学院農学研究科食品生物科学専攻 / (主査)教授 入江 一浩, 教授 平井 伸博, 教授 田中 千尋 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Soils and plant microbial communities are intricately linked to ecosystem functioning as they play important roles in nutrients dynamics as decomposers and feedback to plant communities as mutualists and pathogens. Numerous soil physicochemical factors as well as the land use management are shaping the composition and dynamics of microbial community. In addition, global warming and climate change are the most prominent of all environmental factors that influence all kinds of the living organisms including microbes associated to the plant soil systems. A better understanding of the environmental drivers shaping these microbial communities especially under future climate will help to understand and predict the expected changes of ecosystems functions and accordingly of the services they provide. In addition, such knowledge will help to detect potential ways on how soil microorganisms can be harnessed to help mitigating the negative consequences of climate change.The Global Change Experimental Facility (GCEF) is settled in the field research station of the Helmholtz Centre for Environmental Research (UFZ) in Bad Lauchstädt, Saxony-Anhalt, Germany (51_22’60 N, 11_50’60 E, 118 m a.s.l.). This facility has been designed to investigate the consequences of a predicted future climate scenario expected in 50-70 years in Central Germany on ecosystem processes under different land-use regimes applied on large field plots in comparison to similar sets of plots under the ambient climate. We performed our study using this research facility, with the aim to analyze the impact of future climate conditions, soil physicochemical factors, and/or land use type and intensity on microbial communities in different habitats (rhizosphere soil, plant endosphere, and plant residues) in grassland and cropland ecosystems. To assess the microbial communities, we used the highly sensitive and powerful highthroughput next generation sequencing, Illumina Miseq.This thesis constitutes the first assessment of microbial communities in the GCEF experimental facility. The samples were collected in 2015 for manuscript 4, while for manuscripts 1, 2, 3, 5, 6, the samples were collected in 2018-2019. Manuscript 1: (Sansupa, Wahdan, Hossen et al., 2021; Applied Science 2021, 11, 688) “Can we use functional annotation of prokaryotic taxa (FAPROTAX) to assign the ecological functions of investigated the potential use of FAPROTAX for bacterial functional annotation in non-aquatic ecosystems, specifically in soil. For this study, we used microbial datasets of soil systems including rhizosphere soil of Trifolium pratense from the extensively used meadow plots in the GCEF. We hypothesized that FAPROTAX can be used in terrestrial ecosystems. Our survey revealed that FAPROTAX tool can be used for screening or grouping of 16S derived bacterial data from terrestrial ecosystems and its performance could be enhanced through improving the taxonomic and functional reference databases. Manuscript 2: (Wahdan et al., 2021; Frontiers in Microbiology 12:629169) “Targeting the active rhizosphere microbiome of Trifolium pratense in grassland evidences a stronger-than-expected belowground biodiversity-ecosystem functioning link”. In this study, we used the bromodeoxyuridine (BrdU) immunocapture technique combined with pair-end Illumina sequencing to differentiate between total and active microbiomes (including both bacteria and fungi) in the rhizosphere of T. pratense. In the same rhizosphere soil samples, we also measured the activities of three microbial extracellular hydrolytic enzymes, (ß-glucosidase, N-acetylglucosaminidase, and acid phosphatase), which play central roles in the C, N, and P acquisition. We investigated the proportion of active and total rhizosphere microbiomes, and their responses to the manipulated future climate in the GCEF. In addition, we identified the possible links between total and active microbiomes and the soil ecosystem function (extracellular enzyme production). Our results revealed that the active microbes of the rhizosphere represented 42.8 and 32.1% of the total bacterial and fungal operational taxonomic units (OTUs), respectively. Active and total microbial fractions were taxonomically and functionally diverse and displayed different responses to variations of soil physicochemical factors. We also showed that the richness of overall and specific functional groups of active microbes in rhizosphere soil significantly correlated with the measured enzyme activities, while total microbial richness did not. Manuscript 3: (Wahdan et al., 2021; Microbiology Open 10:e1217) “Deciphering Trifolium pratense L. (red clover) holobiont reveals a resistant microbial community assembly to future climate changes predicted for the next 50–70 years”. We investigated the microbial communities of bacteria and fungi associated with four plant parts of T. pratense (the rhizosphere and the endopheres of the roots, whole shoot system (leaves and stems), and of the flower) and evaluated their potential ecological and metabolic functions in response to future climate conditions. This study was performed on the GCEF extensively managed grassland plots. Our analyses indicated that plant tissue/compartments differentiation enables the formation of a unique ecological niches that harbor specific microbial communities. Except for the fungal communities of the aboveground compartments, T. pratense microbiome diversity and community composition showed a resistance against the future climate changes. We also analyzed the predicted bacterial metabolic functional genes of red clover. Thereby, we detected microbial genes involved in plant growth processes, such as biofertilisation (nitrogen fixation, phosphorus solubilisation, and siderophore biosynthesis) and biostimulation (phytohormone and auxin production), which were not influenced by the future climate. Manuscript 4: (Wahdan et al., 2021; Environmental Microbiology) “Organic agricultural practice enhances arbuscular mycorrhizal symbiosis in correspondence to soil warming and altered precipitation patterns”. This study was performed on the conventional and organic farming plots under both ambient and future climate conditions. We evaluated the effect of climate (ambient vs. future), agricultural practice (conventional vs. organic farming) and their interaction on Arbuscular Mycorrhizal Fungi (AMF) community composition and richness inside wheat roots. In addition, we evaluated the relationship between molecular richness of indigenous root AMF and wheat yield parameters. Future climate altered the total AMF community composition and a sub-community of Glomeraceae. Further, application of different agricultural practices altered both total AMF and Glomeraceae community, whereby organic farming appeared to enhance total AMF and Diversisporaceae richness. Under the future climate scenario, organic farming enhanced total AMF and Gigasporaceae richness in comparison with conventional farming. Our results revealed a positive correlation between AMF richness and wheat nutrient contents not only in organic farming system but also under conventionally managed fields. Manuscript 5: (Wahdan et al., 2020; Microorganisms 8, 908) “Future climate significantly alters fungal plant pathogen dynamics during the early phase of wheat litter decomposition”. This study was performed on the conventional farming plots. We investigated the structure and ecological functions of fungal communities colonizing wheat during the early phase of decomposition (0, 30, and 60 days) under current and future climate conditions. We found that plant pathogenic fungi dominated (~87% of the total sequences) within the wheat residue mycobiome. Destructive wheat fungal pathogens such as Fusarium graminearum, Fusarium tricinctum, and Zymoseptoria tritci were detected under ambient and future climates. Additionally, the future climate brought new pathogens to the system. Manuscript 6: (Wahdan et al., 2021; Microbial Ecology 10.1007/s00248-021-01840-6) “Life in the wheat litter: effects of future climate on microbiome and function during the early phase of decomposition”. This study was performed on the conventional farming plots. We assessed the effects of climate change on microbial richness, community compositions, interactions and their functions (production of extracellular enzymes) in decomposing residues of wheat. In addition, we investigated the effects of climate change on litter residues physicochemical factors as well as on mass loss during the early phase of decomposition. Future climate significantly accelerated litter mass loss as compared with ambient one. Our results indicated that future climate significantly increased fungal richness and altered fungal communities over time, while bacterial communities were more resistant in wheat residues. Fungi corresponded to different physicochemical elements of litter under ambient (C, Ca2+ and pH) and future (C/N, N, P, K+, Ca2+ and pH) climate conditions. Also, a highly correlative interactions between richness of bacteria and fungi were detected under future climate. Activities of microbial β-glucosidase and N-acetylglucosaminidase in wheat straw were significantly higher under future climate. Such high enzymatic activities were coupled with a significant positive correlation between microbial (both bacteria and fungi) richness and community compositions with these two enzymatic activities only under future climate.:CONTENTS BIBLIOGRAPHIC DESCRIPTION……………………………………………….......III ZUSAMMENFASSUNG………………………………………………………...........V SUMMARY……………………………………………………………………………..X GENERAL INTRODUCTION…………………………………………………………………...............1 I-1 Ecosystem functions carried out by soil and plant microbiomes…………………..2 I-2 Biodiversity and functional diversity and maintenance of ecosystem functions……………..3 I-3 Total vs. active microbial diversity for assessing ecosystem functions……………4 I-4 Factors influencing soil and plant microbiota…………………………………..……6 I-4.1 Elements of climate changes……………………………………………................7 I-4.2 Climate changes influence microbes in an interacting, complex manner………8 I-4.3 Environmental factors controlling the response of microorganisms to climate changes………………………………………………………………………………….....10 I-5 Interplay between climate and land use intensity in agroecosystems……………11 I-6 Study site, and overall objectives………………………………………………....…12 I-7 Methods used for the taxonomic and functional characterization of the microbiomes……...15 I-8 Presentation of aims and hypotheses of the publications/manuscripts in different chapters.................................................................................................................16 I-9References.........................................................................................................20 CHAPTER 1 Can we use functional annotation of prokaryotic taxa (FAPROTAX) to assign the ecological functions of soil bacteria? .....................................................................29 Publication…………………………………………………………………………...........31 Supplementary materials…………………………………………………………….......42 CHAPTER 2 Targeting the active rhizosphere microbiome of Trifolium pratense in grassland evidences a stronger-than-expected belowground biodiversity-ecosystem functioning link………………..........................................................................…49 Publication………………………………………………………………………………51 Supplementary materials……………………………………………………………..67 CHAPTER 3 Deciphering Trifolium pratense L. holobiont reveals a microbiome resilient to future climate changes……………………………………………….…………………………..89 Publication………………………………………………………………………………….91 Supplementary materials……………………………………………………………….111 CHAPTER 4 Organic agricultural practice enhances arbuscular mycorrhizal symbiosis in correspondence to soil warming and altered precipitation patterns………………125 Publication……………………………………………………………………………….127 Supplementary materials………………………………………………………….......140 CHAPTER 5 Future climate significantly alters fungal plant pathogen dynamics during the early phase of wheat litter decomposition…...................………………….……………..156 Publication………………………………………………...…………….….…………...158 Supplementary materials………………………………………………….…....……..175 CHAPTER 6 Life in the wheat litter: effects of future climate on microbiome and function during the early phase of decomposition…………………………………….....……....…….181 Publication…………………………………..…………………………………….....…...183 Supplementary materials………………………………………………………………..199 GENERAL DISCUSSION…………………………………………………………….......210 D-I Approaches and main findings of the result chapters………………………..…211 D-2 Conclusion and implications of the study findings…………………………...…215 D-3 Technical limitation of the study……………………………………………......…217 D-4 Future prospects of the study field ...……………………………………………217 D-5 References…………………………………………………………………………..219 DATA AVAILABILITY……………………………………………………………………...223 ACKNOWLEDGEMENTS……………………………………………………………......224 CURRICULUM VITAE……………………………………………………………….....…225 LIST OF PUBLICATIONS………………………………………………………….........226 CONFERENCE PROCEEDINGS…………………………………………………….....227 STATUTORY DECLARATION………………………………………………................228 VERIFICATION OF AUTHOR PARTS……………………………………………........229

Arbuscular mycorrhizal fungi (AMF) are a category of fungi that occupy virtually all of the Earth's soils. Their role as plant symbionts for nearly all land plants is well documented, where these fungi forms partnerships with plants through the root system. These relationships vary from mutualistic to parasitic and allow the exchange of nutrients between the partners via fungal hyphae that penetrate the cell walls of roots. However, many details of the nature of this symbiosis are not well understood, and the interaction between plants and AMF has been the subject of increased interest recently given the potential benefit to farming systems and natural ecosystems. This study evaluated the variability of mycorrhizal growth response (MGR) to inoculation by the common AMF species Rhizophagus intraradices in a diverse set of wild sunflower species (Helianthus), focusing on how changes in plant traits due to fungal colonization may determine the relative cost or benefit of AMF partnership for wild plants. Results indicate that the overall impacts of AMF colonization on plant growth rate are small, though MGR is correlated with AMF-driven shifts in leaf chlorophyll content. These findings suggest that relative changes in plant growth rate that result from AMF partnership are mediated by plant functional trait.

No description available.

3.2. Abstract Soil contamination by heavy metals represents rather serious environmental problem for both human health and an environment itself. One of the perspective technologies dealing with this threat that only recently has been intensely developed is phytoremediation by means of short rotation coppice plantations. As plants used in this technology (mostly poplars and willows) host two major groups of mycorrhizal fungi substantially influencing plant physiology it is important to study plant-mycobiontheavy metals interactions rather than just plant-heavy metals interactions. The present thesis aimed to contribute to the growing knowledge of the field by search for suitable mycobionts of poplar or willow tolerant to heavy metals, by evaluating an activity of the key antioxidative enzyme in selected mycobionts and by looking at physiological responses of plant hosts to their mycobionts in a soil polluted by heavy metals. The first experiment in vitro focused on screening of morphometric criteria of fungi growing on solid growth media amended with mixture of heavy metals. Based on the results, several tolerant ectomycorrhizal strains were chosen for the next inoculation of fast growing trees serving phytoextraction and phytostabilisation strategies. The second, re-synthetic experiment was conducted in...

ABSTRACT Assessing the impact of herbivory on plant growth and reproduction is important to predict the success of biocontrol of invasive plants. Leaf area production is most important, as photosynthesis provides the foundation for all plant growth and fitness. High levels of defoliation generally reduce the productivity of plants. However, leaf area production fluctuates during the season and compensational growth may occur, which both complicate accurate estimations of defoliation impacts. Under field conditions the interaction with neighbouring species and the availability of soil nutrients need to be assessed in order to gauge long term effects of weed invasions on natural environments. In this thesis I have investigated seasonal leaf area dynamics in Buddleia davidii following repeated artificial defoliation, to quantify compensational leaf production and to understand the regulatory mechanisms involved. The impact of defoliation on photosynthesis, seed production, germination and nitrogen translocation patterns were analysed. Finally, possible facilitation between B. davidii and a native nitrogen fixer, Coriaria arborea, and the impact of B. davidii on soil nutrient availability were investigated. In defoliated B. davidii, increased node production (34%), leaf size (35%) and leaf longevity (12%) resulted in 52% greater total emergent leaf area in the short term. However, with time and diminishing tissue resources the compensation declined. No upregulation of photosynthesis was observed in pre-existing leaves. Compensational leaf area production occurred at the expense of reproduction but the germination capacity of individual seeds was unaffected. In B. davidii, nitrogen reserves are stored in old leaves. Thus, the defoliation-induced decline in tissue reserves led to changes in the remobilisation pattern and increased the importance of soil uptake but biomass production especially that of roots had declined significantly (39%). Slight facilitation effects from the neighbouring nitrogen fixer and VA-mycorrhizae were observed on B. davidii in the field, while its impact on soil chemistry during spring was negligible. Defoliation of B. davidii resulted in priority allocation of resources to compensational leaf growth and a concomitant reduction in flower and seed production. The compensational leaf production greatly increased the demand for nitrogen, while continued leaf removal decreased the pool of stored nitrogen. This led to changes in nitrogen remobilisation and an increased importance of root uptake. However, the significant decline in root growth will likely impair adequate nutrient uptake from the soil, which is especially important where B. davidii invades nutrient poor habitats and will increase the success of biocontrol of the species. While mycorrhizae increase nutrient accessibility for B. davidii, it is likely that the additional stress of defoliation will negate the small facilitative effects from nitrogen-fixing species like C. arborea. This research provides new insights into the mechanisms regulating leaf area dynamics at the shoot level and systemic physiological responses to defoliation in plants, such as nitrogen translocation. The compensation in leaf area production was considerable but only transitory and thus, the opportunity to alleviate effects of leaf loss though adjustment of light capture limited. However, to ascertain that photosynthesis at whole plant level does not increase after defoliation, more detailed measurements especially on new grown leaves are necessary. In general, defoliation had greatly reduced plant growth and performance so that an optimistic outlook for controlling this species can be given. Conclusions about the wider impacts of B. davidii on soil chemistry and community function will require further research.