Surveying the Sweetpotato Rhizosphere, Endophyte, and Surrounding Soil Microbiomes at Two North Carolina Farms Reveals Underpinnings of Sweetpotato Microbiome Community Assembly

Farmers grow sweetpotatoes worldwide and some sub-Saharan African and Asian diets include sweetpotato as a staple, yet the sweetpotato microbiome is conspicuously less studied relative to crops such as maize, soybean, and wheat. Studying sweetpotato microbiome ecology may reveal paths to engineer the microbiome to improve sweetpotato yield, and/or combat sweetpotato pests and diseases. We sampled sweetpotatoes and surrounding soil from two North Carolina farms. We took samples from sweetpotato fields under two different land management regimes, conventional and organic, and collected two sweetpotato cultivars, 'Beauregard' and 'Covington'. By comparing small subunit rRNA gene amplicon sequence profiles from sweetpotato storage root skin, rhizosphere, and surrounding soil, we found the skin microbiome possessed the least composition heterogeneity among samples, lowest alpha-diversity, and was significantly nested by the rhizosphere in amplicon sequence variant (ASV) membership. Many ASVs were specific to a single field and/or only found in either the skin, rhizosphere, or surrounding soil. Notably, sweetpotato skin enriched for Planctomycetaceae in relative abundance at both farms. This study elucidates underpinnings of sweetpotato microbiome community assembly, quantifies microbiome composition variance within a single farm, and reveals microorganisms associated with sweetpotato skin that belong to common but uncultured soil phylotypes.