Field Testing of Sorghum Lines with Stacked Coproduct and Low-Lignin Traits

Abstract

The accumulation of value-added coproducts and the reduction of lignin levels are two essential traits for lignocellulosic biomass intended for bioenergy applications. Sorghum is a premier bioenergy crop candidate, distinguished by its substantial biomass productivity, minimal nutrient needs, and resilience to heat and drought. Brown midrib (BMR) mutants, genetic variants characterized by naturally low lignin content, are particularly promising due to their lower recalcitrance and higher polysaccharide content. While various genetic engineering strategies have been used to enhance the amount of high-value coproducts in sorghum, these traits have not been combined with low-lignin characteristics. We generated new sorghum lines by crossing engineered varieties that accumulate the coproducts protocatechuate (DHBA) or 4-hydroxybenzoate (4-HBA) with a low-lignin BMR line. These lines were field-tested at two different locations to determine biomass composition and yields. Findings indicated that DHBA production remained stable when stacked with the BMR trait, which also preserved low lignin levels without negatively impacting biomass yield. Conversely, the combination of 4-HBA accumulation and the BMR trait led to yield losses relative to the unmodified BMR and reduced 4-HBA titers under certain growth conditions. While this research demonstrates that stacking low lignin with coproduct accumulation in sorghum is feasible, further investigation into the specific cultivation conditions of the modified crops remains necessary to optimize biomass yields and coproduct titers.