Plant-associated microbes (collectively the microbiome) are important contributors to plant health. They are known to play roles in increasing yield via improving stress tolerance, promoting growth, and suppressing the activity of plant pathogens. We investigated the wheat seed-head microbiome (phytomicrobiome) as a potential source of resistance to Fusarium head blight (FHB), or scab. FHB is a devastating disease in wheat, and other cereal grains, that causes losses in both quantity, through reduced yield, and quality of grain, through the production of toxins such as Deoxynivalenol. Efforts to combat FHB have focused primarily on breeding cultivars with resistance and applying fungicides. However, new resources for combatting FHB may lie in microbiome-plant interactions. To explore host-microbiome-pathogen interactions, we used field trials to characterize the seed head bacterial community (16S rRNA gene amplicons) across planting locations, host resistance genotypes, varieties, and plant development stages. We identified bacterial amplicon sequence variants (ASVs) present in each sample and then examined ASV community composition based on our variables. Characterizing bacterial relative abundance across samples, we identified 9,063 ASVs. These ASVs clustered according to plant developmental stages or maturity plant, location, and host genotype, but not by variety or maturity group. First, comparing plants at the pre-flowering versus mature grain-head stage, we found that both bacterial community richness and evenness changed significantly. In addition to these developmental changes, we found that bacterial community structure changes across locations, even between locations. Finally, we found that, in the presence of the pathogen, ASVs cluster by host resistance genotype, and that there are important taxonomic groups that are differentially abundant in the presence of the pathogen. Overall, we found that the wheat grain-head microbiome is shaped by environment-host-pathogen interactions, and that these interactions lead to differential abundance of particular community members that may be important in the management of FHB. / Master of Science in Life Sciences / Plant associated microbes are important contributors to plant health. They are known to play roles in increasing yield via improved stress tolerance, promoting growth, and suppressing plant disease. We investigated the wheat grain-head microbial communities as a source of disease resistance. The disease is called Fusarium Head Blight (FHB) and is caused by Fusarium graminaerum. FHB is a devastating disease in wheat and other cereals, causing losses, through reduced yield and quality through the production of toxins that prohibit use of the grain. To combat FHB, research has focused on developing plants that have resistance and the application of chemical fungicides. However, new resources for combating FHB may lie in the interactions between plants and microbes. This research is focused on identifying microbes that naturally interact with the plant, and how the pathogen, Fusarium, interacts with these beneficial microbes. In field trials, we characterized the microbial community by DNA sequencing technologies across locations, wheat with varying levels of genetic resistance, and wheat developmental stages. First, between the wheat kernel samples of pre-flowering and maturity, we found significant differences in microbial community. Consistent with other studies we found that the largest changes in microbial community composition across different growing locations. Finally, we found an interaction between the grain head microbiome and host resistance state when plants were exposed to the pathogen. Overall, we find that the wheat grain head microbiome is shaped by growing location and through interactions with the plant host and pathogen.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/98399 |
| Date | 14 May 2020 |
| Creators | Gonzales Diaz, Andie Alexander Sr. |
| Contributors | Plant Pathology, Physiology and Weed Science, Haak, David C., Vinatzer, Boris A., Belden, Lisa K. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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