The soil ecosystem consists of the largest reservoir of biodiversity on Earth. Microbial communities are unseen drivers in soil ecosystems and they play an important role in determining a wide... Show moreThe soil ecosystem consists of the largest reservoir of biodiversity on Earth. Microbial communities are unseen drivers in soil ecosystems and they play an important role in determining a wide variety of soil processes in terrestrial ecosystems. Soil microbial communities can influence plant performance and can drive plant species composition on a particular soil. Soil microbes are associated with an extensive range of ecosystem processes, in turn, affect plant growth. While these processes can benefit plant growth, the soil microbial community also harbors microbes that compete with plants for nutrients or are pathogenic and impair plant growth. This leads to the question if plants can manipulate the composition of the soil microbial community to their advantage.In agriculture, the physical structure of the soil is often altered to improve crop production and this modifies biological components and microbial properties of the soil. Moreover, green crop management technologies, such as regulation of soil microbial biodiversity, application of beneficial microbial agents and induction of plant hormonal resistance, are regarded as promising approaches against pests and microbial pathogens. Although many experiments have shown that activation of hormonal signaling pathways can boost a plant’s immunity against pathogenic microbial attacks, whether and how these hormonal signaling pathways affect the soil microbial community and consequently plant growth is still poorly understood. Therefore, to better understand the roles of soil microbial communities at both taxonomic and functional level, studies from a plant defensive perspective are timely and needed, and this is the main focus of this thesis. Show less
Plants and soils from natural ecosystems harbor great diversity of soil microorganisms, which could potentially contribute to the sustainability of horticulture. The knowledge about using wild... Show morePlants and soils from natural ecosystems harbor great diversity of soil microorganisms, which could potentially contribute to the sustainability of horticulture. The knowledge about using wild plant species and soil from natural ecosystem to improve the crop health will advance the application of ecological knowledge in horticulture. In this thesis, I evaluate the possibilities of using wild plant species and grassland soil to enhance the growth and reduce the disease susceptibility of chrysanthemum through plant-soil feedback principles. Grass-conditioned inocula contributed more to chrysanthemum growth than forb- or legume-conditioned inocula, this also lead to better chrysanthemum performance under Pythium treatment. Moreover, by mixing two plant-conditioned inocula, they interacted synergistically in terms of plant health but antagonistically in terms of plant growth. The influence of plant-conditioned inocula on chrysanthemum were still significant after two successive growth cycles, but their effects tended to converge because of the overriding effect of chrysanthemum growth. Inoculating greenhouse soil conditioned by wild plant species or grassland soil to greenhouse soil did not significantly improve the negative effects of greenhouse soil on chrysanthemum growth. Olpidium brassicae was identified as a main fungal pathogen of chrysanthemum when growing in greenhouse soil. Show less
