Bioenergy sorghum’s deep roots: A key to sustainable biomass production on annual cropland

Abstract

Bioenergy sorghum has high biomass yield potential, drought resilience, good nitrogen use efficiency, and a root system that contributes to the accumulation of soil organic carbon. In this study, field grown bioenergy sorghum root systems were analyzed during the growing season to characterize their depth, biomass, morphology, anatomy, and gene expression profiles. Bioenergy sorghum roots grew continuously during a 155-day growing season producing ~175 nodal roots, accumulating ~7 Mg of dry biomass per hectare, and reaching >2 m deep in the soil profile. Nodal roots within 20 cm of the stem were 1-5 mm in diameter, whereas roots deeper in soil profiles were enriched in lateral roots with small diameters (~30-500 µm) enabling growth through soil macropores. In older field-grown plants, roots with intact endodermal, vascular and inner root tissues were surrounded by degraded or aerenchymafilled epidermal and cortical cell layers. Transcriptome analysis of nodal, surface, and deep roots identified >2,500 differentially expressed genes involved in root growth, transport, adaptation, defense, and AMF-root interaction. Deep roots (180-240 cm) differentially expressed genes that regulate lateral root growth. Surface roots (0-20 cm) located mid-row differentially expressed genes involved in nitrate transport, whereas ammonium transport genes were expressed in surface and deep roots and genes involved in phosphate transport were expressed in nodal, surface, and deep roots. Overall, bioenergy sorghum's long growing season enables root systems to grow deeper and accumulate more biomass than annual grain crops such as maize, attributes that could help restore annual cropland soil organic carbon levels and improve soil productivity. Deep roots active in nutrient transport are positioned to take-up fertilizer leached deep into soil profiles mitigating potential nutrient run-off. Bioenergy sorghum's large and deep root system is a key to sustainable production of biofuels, biopower, and bioproducts on annual cropland.

Transcriptional regulation of the raffinose family oligosaccharides pathway in Sorghum bicolor reveals potential roles in leaf sucrose transport and stem sucrose accumulation

“…The growth and collection of the BTx623 expression atlas plant tissues are described in McCormick et al, 2018. The growth and collection of the plant tissue from BTx623 leaves are described in Murphy et al, 2011. Additionally, a description of the growth and collection of Della plant tissue are described in McKinley et al, 2016. Tissue from the bioenergy sorghum hybrid TX08001 was obtained from plants grown under well-watered, 14-h day greenhouse conditions (29.4°C day/23.9°C night) in 20 cm by 76 cm PVC rhizotrons (Lamb et al, 2022) filled with sandy loam soil and supplemented with 30 g of Osmocote 14-14-14. Plants were thinned to one plant per rhizotron at 10 days after emergence (DAE).…”

“…Bioenergy sorghum hybrids are more tolerant of drought and heat stress than grain crops because the crop remains in the vegetative phase for most or all of a long growing season thereby avoiding reproductive phase sensitivity to abiotic stress associated with grain crops (Mullet, 2017). In addition, bioenergy sorghum exhibits and is being selected for traits that could further improve adaptation to water-limited environments including but not limited to vertical leaf angles (Truong et al, 2015) and a deep root system (Lamb et al, 2022).…”

Bioenergy sorghum stem growth regulation: intercalary meristem localization, development, and gene regulatory network analysis

“…To take full advantage of this opportunity, bioenergy crops need to be high yielding, resilient, sustainable, and optimized for biofuel production and carbon capture/sequestration. For example, drought tolerant bioenergy sorghum hybrids have high biomass yield, good nitrogen use efficiency, and a large and deep rooting system that enhances resilience, acquisition of nutrients and water, and carbon sequestration in soil (Lamb et al., 2021; Mullet et al., 2014; Olson et al., 2012; Rooney et al., 2007; Shahandeh et al., 2016).…”