PhD Defence: Nikolaj Lunding Kindtler, University of Copenhagen

Thesis title: Microbiome and fertilizer interactions in old and modern barley cultivars

Supervisor: Flemming Ekelund

Assessment committee:
Associated professor Rasmus Kjøller (Chair), Department of Biology, University of Copenhagen

Professor Elena Simona Radutoiu, Department of Molecular Biology and Genetics, Aarhus University

Investigador Distinguido Enrique Miguel Lara Pandis, Real Jardín Botánico, Department of Mycology, Spain

 We need to grow crops sustainably in the future to decrease the negative impacts of food production on the environment and climate. Therefore, crops will rely on the soil microbiome to acquire nutrients. Modern cultivars rely on mineral fertilizers and pesticides and need not interact with the soil microbiome, which makes them ill adapted for growth in sustainable agriculture. Older cultivars may have retained traits from their wild ancestors, may thus be more suited for growth under sustainable conditions. Barley (Hordeum vulgare L.), has multiple modern and older cultivars available, making it an excellent model crop for studying how domestication and modern breeding have affected plant-microbiome interactions.

Here, I investigated the interactions between nutrient source (organic or mineral), barley cultivar, and the soil microbiome. My studies aimed to achieve two main objectives, 1) to investigate whether breeding has reduced the ability of barley to thrive in low-input systems. 2) to determine if this is related to a decreased interaction with the microbiome. I found that older barley cultivars produced more biomass and took up more nutrients from soil at nutrient-limited conditions. However, this was not linked to differences in the rhizo-microbiome. Furthermore, I found that high microbial diversity of the rhizo-microbiome was more important for old barley compared to modern. I also participated in developing a method for extracting rhizosphere taxonomic information based on total RNA sequencing from small initial sample. I conclude that the most important factors in shaping the rhizo-microbiome in barley are the fertilization regime, the native microbiome in the soil, and the cultivar. The degree of domestication alone does not seem to be a good indicator of whether a particular cultivar will thrive under sustainable conditions, and evaluations must be made on an individual basis from cultivar to cultivar.