COS 224-6 - CANCELLED - Roots of Change: understanding the influence of Sorghum bicolor breeding on the root metabolome and microbiome

Abstract: Sorghum bicolor is the fifth most cultivated crop, globally, and modern germplasm development has prioritized using S. bicolor as a second-generation bioenergy feedstock, which requires reduced ecosystem impacts when compared to fossil-fuel-based energy. Therefore, assessing the adverse ecosystem impacts of S. bicolor germplasm is a necessary step for its use as a bioenergy feedstock. The plant microbiome influences plant growth and health but also contributes to agroecosystem sustainability through biogeochemical cycling. Plants manipulate the microbiome associated with the roots, termed the rhizosphere, by altering carbon allocation patterns within the root system, via changes in root system architecture, morphology, and metabolomics, the latter of which drives hotspots of microbial activity within the rhizosphere. Priming of the microbiome by roots varies with species and genotype and can stimulate carbon sequestration or respiration. When compared to African and American landrace sorghum varieties, bioenergy sorghum varieties have drastically altered carbon allocation patterns due to breeding manipulations of their photoperiod sensitivity. Through these manipulations, bioenergy sorghum remains within the vegetative stage, accumulating biomass, and re-directing belowground carbon into vegetative biomass. Therefore, this research seeks to understand the impact of S. bicolor breeding history on the root metabolome and rhizosphere microbiome. This was done by comparing the root metabolome and microbiome of 26 Sorghum bicolor genotypes, including African and American landraces, and bioenergy hybrids. We assessed these plant-associated microbial communities using 16S rRNA amplicon sequencing, and flash-frozen root tissue was analyzed with untargeted LC-MS metabolomics. Breeding history and genotype significantly influence microbiome composition (PERMANOVA, History x Genotype, R² = 0.20, P = 0.001). Differential analyses identified significant differences in the abundance of copiotroph and oligotroph taxa due to breeding. African landrace varieties were differentially abundant in slow-growing Acidobacteria. In contrast, fast-growing Bacteriodetes were enriched within the American and Bioenergy types, suggesting breeding-driven changes in carbon partitioning into the rhizosphere microbiome. Ultimately, this research aims to understand how germplasm development can adversely influence the microbiome via changes in root chemistry, which is an important step for comparing the ecosystem impacts of Bioenergy feedstocks to classical fossil fuel-based energy.