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theses

Annual bluegrass (Poa annua; ABG) putting green turf is a unique man-made environment that requires regular fertility inputs to maintain acceptable turfgrass quality and playability. While these inputs can affect foliar diseases such as anthracnose, caused by Colletotrichum cereale, little is known about their impact on microbial communities in this ecosystem. The objectives of this dissertation were to: 1) determine the frequency and distribution of C. cereale in the United States, 2) examine the resident microbial communities in the soil of ABG putting green turf over time using advanced molecular technologies, and 3) identify how nitrogen (N) and/or potassium (K) fertilization affects the distribution, diversity, and abundance of benign and pathogenic microorganisms in this system. More than 50 phyla, representing hundreds of species of archaea, bacteria, and fungi were identified. Above ground, this diversity was highlighted in the form of two distinct lineages of C. cereale, both able to cause anthracnose disease but exhibiting distinct host and geographic preferences. Below ground, the ABG rhizosphere supported a vast microbial community, despite high sand content and regular fertilization and pesticide applications. Few turfgrass pathogens were identified from the soil. However, tremendous variation was characterized within the nonpathogenic microbial community, with the rhizosphere of ABG hosting organisms capable of antibiotic production, fixing nitrogen, or serving as potential biocontrol agents or mycorrhizal partners. Over all, individual microbial groups were present in low abundance across all samples. Fertilization did not affect microbial diversity, but did alter the abundance of specific microbial groups. Changes associated with fertility treatments were limited to approximately 7% of the total archaea/bacteria and 23% of the total fungal community identified. In general, K and low rates of N increased abundance of archaea, bacteria, and fungi in the study sites. Seasonality also strongly influenced microbial communities, with samples collected in summer months clustering separately from those obtained in the spring. The research described here provides the first insight into the diverse microbial community residing in the soil of ABG putting green turf utilizing next-generation sequence-based analyses, and protocols developed to conduct this work should help facilitate future research examining the turfgrass microbiome.

ETD_7028

Ph.D.

Includes bibliographical references

by Lisa A. Beirn

doi:10.7282/T3ZS2ZKP

ETD doctoral

The author owns the copyright to this work.