Graduation Year


Document Type

Master's Thesis


Master of Science


Biological Science

Program Director

Meredith Protas, PhD

First Reader

Wolfgang Schweigkofler, PhD

Second Reader

Erik Nelson, PhD


The presence of fungal species associated with herbaceous plants was monitored in coastal Marin County, California, USA. The research involved a combination of field sampling surveys and data collection using a stratified random design, pathogen identification through microbiological and molecular analysis, and descriptive analysis and ordination of results. A total of two years of repeated sampling (four times a year) was organized to allow for the detection of seasonal differences in pathogen presence on aerial plant parts. The objective of this study was to identify microbial species present on herbaceous plants using ITS1 sequence analysis. Throughout March of 2018 to March of 2020, a total of 843 samples were collected from five sample transect locations in coastal Marin County. From those 843 samples, thirty-four representative fungal and fungus-like isolates were grown into pure cultures; 16 isolates were identified at the species level, and 10 isolates on genus or family level, mostly belonging to the Ascomycota. At least one of the species identified in this study (Phytophthora ramorum, Oomycota) has not been found to be associated with the host plant it was isolated from (Marah fabacea) thus far. No significant effect of seasonality, geographic location, and soil type on microbial biodiversity and abundance was detected.