Electronic Thesis and Dissertation Repository

Thesis Format



Master of Science




Thorn, R. Greg


The root mycobiome plays a direct role in plant productivity, and the study of its community composition allows for identification of organisms that influence plant health. To better understand the role of fungal community composition in crop productivity, the root-associated mycobiomes of historically high and low yield sites of corn and wheat planted in rotation were characterized and analyzed along with soil physicochemical variables and crop yield. In each field studied, root and rhizosphere mycobiomes reflected significant differences in fungal species composition. Several soil variables were found to be predictors of differences in composition of sample types including soil texture and pH. The genera Fusicolla, Epicoccum, and Tetracladium were positively correlated with yield, and Neonectria, Pythium, Corynespora, and Mrakia were negatively correlated. Identifying differences in the root-associated mycobiome of crops and changes in the soil environment could aid in the development of community management tools that maximize crop productivity.

Summary for Lay Audience

Corn and wheat are global staple crops that are used to meet worldwide nutritional and food security needs. To meet the demands of an increasing global population, global agricultural production will need to be increased without exacerbating current environmental problems such as greenhouse gas emissions and loss of biodiversity. Traditional crop and soil management systems may need to be substituted or supplemented with innovative methods of increasing productivity and reducing loss to disease. Compared to intensive farming methods, crop rotation, the sequential planting of crops over time on the same field, is a much more sustainable farming method that increases crop productivity. In Southwestern Ontario, corn, soybean, and wheat are often planted in succession in the same field. The rhizosphere consists of the soil that is in direct contact with the roots of a plant and is rich with microbes, including plant-beneficial organisms and plant pathogens. Increased diversity and composition of bacteria and fungi in the soil have been linked to increased crop productivity and yield. The soil environment, including the organisms present in the soil, can also affect the availability of soil nutrients through various processes. Crop productivity has been linked to the abundance of several nutrients and heavy metals in the soil. Understanding how root-associated fungal communities may be linked to soil management, plant physiological health, and crop productivity is of great interest.

In this project, I sequenced fungal DNA found in the rhizosphere and roots from historically high and low yield sites of corn and wheat planted in rotation. It is common to see sites within the same field that produce high or low crop yields, year after year. I also looked at soil variables in each field to identify which ones may be linked to yield. While I found differences in fungal composition and soil variables of corn and wheat in these sites, the interactions that occur in the samples are complex. Identifying the organisms and soil factors that are driving differences in productivity could help in the development of soil management tools that maximize crop productivity.