Evaluating Microbial Shifts in Corn and Soybean Across Planting Dates Through Culture and Metabarcoding Techniques

Extreme weather events and shifting planting schedules impact microbial communities associated with corn and soybean seedlings, influencing crop health and disease risk. This study investigates how planting date and environmental factors shape fungal and oomycete communities during early seedling development at three Ohio research stations from 2023 to 2024. Planting dates ranged from March 25 to June 24, with soil temperatures at 5 cm depth varying from 3.6–28.2°C in 2023 and 0.9–34.4°C in 2024. Using a randomized complete block design, we assessed microbial community shifts through a dual approach, combining metabarcoding (ITS2 and Rps10 primers targeting fungi and oomycetes) with traditional culturing techniques. From surface-sterilized seedlings and rhizosphere soil samples, we recovered 370 fungal and 240 oomycete isolates, offering insights into the composition of the culturable microbial communities across diverse environments. Our data indicate that early planting dates are associated with reduced oomycete species evenness, with a few dominant species thriving under cooler temperatures, potentially increasing early-season disease risk. We have consolidated comprehensive soil and weather data, and initial metabarcoding analyses are offering a deeper look into microbial community composition and dynamics. By integrating high-throughput sequencing with culture-based methods, this study provides a clearer understanding of how environmental conditions drive microbial shifts, influencing crop establishment, pathogen pressure, and agronomic strategies.