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The mycobiome of deep soil profiles in no-till dryland wheat

Timothy Paulitz: USDA ARS

<div>Soil edaphic factors affect the composition of fungal communities, but there is a paucity of information on how communities vary with soil depth and landscape characteristics in no-till cropping systems. The Palouse region of eastern Washington is dominated by dryland wheat systems and is characterized by a highly variable landscape with steep, rolling hills. We used high-throughput sequencing of fungal ITS1 amplicons to characterize fungal communities across soil depth profiles (0-100 cm from the soil surface) among distinct landscape positions (north-facing, south-facing, bottom- and top-slopes) across a no-till wheat field. Fungal communities were highly stratified with soil depth, where deeper depths harbored distinct fungal taxa and more variable, less diverse communities. Fungal communities from deep soils tended to harbor a greater portion of taxa inferred to be pathotrophic or symbiotrophic in addition to saprotrophic lifestyles. Co-occurrence networks of fungal taxa became smaller, more clustered, and had higher ratios of positive:negative associations as soil depth increased. In contrast, differences between communities from north-facing and south-facing slopes were relatively small. Together, these results suggest that upper soil layers harbor highly diverse saprotrophic communities that compete for abundant resources, whereas only a small number of taxa inhabit deeper soil layers, which rely more on pathotrophic or symbiotrophic strategies.</div>