Disentangling corn root mycobiome in relation to soil physicochemical factors and plant productivity

Soil bacteria and fungi are integral parts of healthy ecosystem functioning in production agriculture. Whereas the role of bacteria has been studied in some detail, the effects of fungal abundance and diversity on crop productivity is poorly understood. We sampled 10 corn farms at the V10 growth stage across southwestern Ontario, Canada, using aerial infrared imaging to identify zones of healthy (high yield) or stressed (low yield) corn plants. Root samples from low and high yield zones, and soil physical and chemical properties were measured in conjunction with sequencing of the mycobiome communities using Illumina MiSeq amplification of 4 rRNA amplicons, two targeting general fungi, and one each for Ascomycetes and arbuscular mycorrhizal fungi. Sequence analyses identified indicator species associated with high and low productive sites within a farm, but communities varied across locations, demonstrating the impact of soil texture and chemistry in shaping the mycobiome. Across all 4 primer sets, roots from high-yielding sites shared 35 major OTUs including Penicillium, Trichoderma, Chalara fungorum, and Gibellulopsis. Low-yielding sites shared 31 OTUs including Fusarium, Pythium, Setophoma terrestris, and Neonectria. Soil physical and chemical parameters that most represented yield and its links to mycobiome diversity across farms included: % clay, % sand, % phosphorus saturation, cation exchange capacity, aluminum, pH, iron, and chlorine. Further research will clarify our understanding of these relationships and will play a crucial role in improving low production sites, thereby increasing overall farm yields