Pantigoso Guevara, Hugo A., authorVivanco, Jorge M., advisorManter, Daniel, committee memberMinas, Ioannis, committee memberFonte, Steven, committee member2019-06-142019-06-142019https://hdl.handle.net/10217/195345Recent studies in plant-microbe interactions have revealed the importance of the rhizosphere microbiome in agriculture. However, little is known about the impact of fertilization on the rhizosphere and its associated microbial communities. This thesis investigates whether phosphorus (P) fertilizer has led to a shift in bacterial community composition and functions in both cultivated and non-cultivated plants. Two independent greenhouse experiments were conducted to evaluate P impacts. The first study explored the effects of low (0 and 50 kg ha-1) and higher P levels (101 and 192 kg ha-1) of triple super phosphate (0-45-0) amendments on soil microbial community composition associated with the rhizosphere of blueberry plants. The abundance of soil bacteria with phosphatase genes was also tested. The second experiment used a gradient of domesticated potato plants (modern cultivars, landrace and wild) to evaluate the effect of P addition on plant biomass and bacterial communities associated with the potato rhizosphere. Further, the study aimed to detect the most abundant microbial taxa, shared and unique, across six genotypes of Solanum genera. Four tuber-bearing and two non-tuber bearing potatoes were used in this study. Tuber-bearing included Solanum tuberosum subsp. tuberosum (a direct progenitor of modern potatoes) and the potato cultivars 'Red Norland', 'Yukon Gold' and 'Russet Burbank'. The non-tuber bearing potatoes included Solanum bulbocastanum and Solanum tuberosum subsp. tuberosum. Plants were grown in soils collected from an agricultural field where cover crops were previously cultivated. Three levels of phosphorus were applied (0, 67, 133 kg ha-1) during the experiment. Rhizosphere soil was collected and analyzed by amplicon sequencing targeting 16S rRNA gene. Our results showed that potato genotype is the main driver of microbial community composition, followed by fertilizer level. Non-tuber bearing potatoes were different from tuber-bearing potatoes and showed a higher degree of dissimilarity in microbial taxa compared to others. Additionally, a shift in bacterial abundance within the community was observed in response to high P levels. Xanthomonadacea and Alteromonadacea were the two families consistently increase or decrease (respectively) in response to incremental P levels. Interestingly, the latter was only present in non-cultivated potato plants, this family could be an important microbial member that has been lost with cultivation.born digitalmasters thesesengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.Text