Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Biology

Supervisor

Thorn, Richard G.

Abstract

Crop yield often varies within a field of a single genetically uniform crop plant, with the causes presumed to be a mix of both biotic and abiotic factors. Manipulating crop root mycobiomes could potentially increase yield by reducing pathogen impacts and improving access to soil water and nutrients. This study aimed to identify different fungal inoculation treatments that could increase the growth of corn seedlings sown in low productivity soils to that in high productivity soils and shift the root mycobiome composition. Fungal inoculation treatments did not have significantly different root mycobiome composition than seedlings grown in low yield control soils. However, indicator species varied across primary inoculation treatments and controls. Although corn grown in an autoclaved substrate showed growth promotion with the fungal inoculant Fusarium oxysporum, no fungal inoculant added to low productivity soils resulted in a similar yield to that of seedlings grown in high productivity soils.

Summary for Lay Audience

Methods for maximizing crop yield, without negatively affecting the environment, are required because of growing food demands in a world facing climate change. However, some current methods of maximizing crop yield, such as the application of agricultural chemicals (such as insecticides, fungicides, and fertilizers) can harm the environment through processes such as run-off and leaching. To pursue more sustainable agriculture and retain high yield, researchers are exploring how to manipulate the microbial composition of soil instead of the application of agricultural chemicals. Research surrounding the microbial composition of soil must consider the microbiome of crop roots since the root is the crop’s means of interaction with the soil. The root microbiome consists of all root-associated microorganisms (such as bacteria, fungi, and nematodes). Related to the microbiome is the root mycobiome which specifically refers to root-associated fungi. Manipulating the root myco- and microbiome of crops could increase yield by reducing pathogen pressure and improving access to soil water and nutrients. However, understanding how specific fungal impact the root mycobiome and crop yield has not been fully explored. My objective is to investigate how selected fungal isolates affect plant performance and the root mycobiome when applied to soil in which corn seedlings are grown under growth room conditions. In previous studies, A&L Biologicals observed major differences in crop yield in various sites growing corn. When compared, the sites revealed significant differences in root mycobiome of low- and high-yielding corn. Root-associated fungi from these sites were identified through analysis of genetic variations and were isolated in culture. Comparing the fungal communities in high- versus low-yielding sites may help identify key fungal candidates to improve crop health and productivity. Corn seeds were sown into the soil from low-yielding sites that were inoculated with potentially beneficial fungal isolates, with or without a co-inoculated soilborne fungal pathogen of corn. Although the fungal inoculant Fusarium oxysporum showed growth promotion when grown in sterile conditions, I did not observe this phenomenon in seedlings grown in inoculated field soils due to differences in soil composition or inadequate time for effective soil inoculation. While I was not able to identify fungal inoculation treatments resulting in significantly different root mycobiome composition than seedlings grown in low yield control soils, there were indicator species that varied across treatments which could be explored as future fungal inoculants that drive changes in the root mycobiome.

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