Nematodes: model organisms for indicating soil health and studying ecological community structure in soybean fields

Open Access
- Author:
- Kidd, Mariah
- Graduate Program:
- Plant Pathology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 13, 2024
- Committee Members:
- Paul David Esker, Thesis Advisor/Co-Advisor
Alyssa Anne Collins, Committee Member
Maria Del Mar Jimenez Gasco, Program Head/Chair
Cristina Rosa, Committee Member
Daniela Carrijo, Committee Member - Keywords:
- Nematodes
Microbial Interactions
Agriculture
Fusarium
Nematology
Soil Health - Abstract:
- Plant parasitic nematode (PPN) populations have increased across Pennsylvania, but contributing factors remain unknown. There is a need for increased knowledge about the soil microbiome, including micro-inhabitants and their relationships with soil health and other microorganisms, particularly those surrounding PPNs. ILeVO has been an establish nematicide and fungicide seed treatment for the last decade, but its impact on non-target soil microbes is unknown. My project explores ILeVO’s impact on microbial community composition and the associations between PPN with soil health parameters, Fusarium pathogens, and field history attributes. My first hypothesis is that ILeVO will not impact the bacterial community but will affect the fungal community as the seed treatment’s active ingredient, fluopyram, inhibits mitochondrial respiration. I further hypothesize that fields with a history of tillage, Fusarium diseases, and inconsistent crop rotations will have higher and more diverse PPN populations. The specific of my thesis project are to (i) determine if ILeVO impacts microbial community composition and, if so, to what degree, (ii) access if PPN abundance and species diversity can provide a more comprehensive outlook on biological soil health than traditional tests, (iii) explore relationships between PPN and Fusarium species, and (iv) investigate correlations between PPN abundance and diversity with field history facets. From field trials conducted in 2022 and 2023, we observed that location was the most influential factor driving microbial composition, accounting for up to 44% of variation in bacterial and fungal communities. In 2022, ILeVO had no significant impact on microbial composition, but it explained 1.2% of variation in microbial communities among 2023 samples. Additionally, we have collected 765 samples across 50 counties for PPNs in Pennsylvania since 2018. For many samples, growers submitted a field history form covering growth practices, common weeds, and past and current diseases. Using Pearson’s correlation coefficient, we observed a weak positive correlation between crop rotation and pin nematodes (r=0.017, n=227), a weak negative correlation between tillage and dagger and pin nematodes (r=0.0138 and r=0.0266 respectively, n=152), a strong positive correlation between dagger nematodes and Fusarium oxysporum (r=0.0947, n=5 ), and a weak positive correlation between dagger nematodes and Fusarium graminearum (r= 0.8885, n=5 ). These results provide information that will help growers form better management recommendations and inspire the creation of future studies surrounding soil microbial interactions.