Roots are vital for crop development, facilitating water and nutrient uptake, adapting to soil conditions, and supporting above-ground plant growth. Sorghum, a climate-resilient and versatile cereal crop, plays a significant role in global food security and bioenergy production, making its study especially relevant. Analyzing root architecture (RA) traditionally involves destructive and time-consuming methods that preclude longitudinal observations of individual plants. Here we used minirhizotrons (MR), wireless, non-destructive devices developed to capture root imagery. With MR, we aim to identify sorghum varieties that are conducive to prolonged underground carbon storage through larger and deeper roots. Insights into sorghum’s RA could also better elucidate the link between RA and above-ground productivity. We conducted two experiments using the MR cameras. The 2023 summer field experiment at the Danforth Field Research Site (FRS) assessed the impact of tilling and cover crop practices on RA in two sorghum varieties, employing 96 MR tubes across 48 plots. An indoor trial on 35 sorghum lines used 73 MR tubes, with RootSnap software facilitating image analysis. Preliminary findings indicate that MR predicts root biomass with high accuracy, both overall and at each depth, and can determine root color with 90% accuracy. Finally, through the development of a neural network, we aim to utilize image analysis to predict root biomass at various depths, providing a labor-saving alternative to soil coring. We also address challenges, including the limited dataset size and image noise, through enhanced feature engineering and provide a comprehensive comparison of multiple machine-learning techniques.

Root exudation refers to the processes by which plants release compounds called root exudates into the soil. These exudates are primarily carbon-containing compounds that interact with microbial communities in the rhizosphere. Microbial consumption of exudates reduces the concentration of the exudated compounds in the soil, causing the plant to exude more of those compounds. Currently, there is limited understanding of the interaction between plant-root exudation mechanisms and the surrounding microbial communities. Among the Sorghum Association Panel (SAP), an established and genetically characterized sorghum diversity panel, we observed a spectrum of root colors (tan, yellow, red, purple-brown, black) identical to the range of observed sorghum seed colors. Previous studies examining differentially expressed metabolites between colorful seeds showed that flavonoids and anthocyanins were higher in dark seeds than white seeds. Root color is genotype-dependent and consistent over time. We hypothesized that the observed color diversity of sorghum roots was due to differential metabolite profiles in the root exudates across genotypes. We designed an experiment to collect exudates from 15 genotypes (n=60). After three weeks of growth, sorghum roots were washed and submerged in ultrapure water for 24 hours. The hydroponic solution was filtered and incubated with methanol. The whole root system was also ground after exudation. The root exudate solutions and the ground-up roots underwent either HILIC and RPLC analysis to separate and detect polar and hydrophobic metabolites. Through metabolite profiling of root exudates, we aim to identify sorghum genotypes that more efficiently allocate carbon below ground via their root systems.