Estimating Hydrogen Cyanide Potential, Biomass yield and UAS-based Regrowth Assessment in Perennial Sorghum and Zea derived lines.

Abstract

There is need to sustainably meet the growing food demand of a predicted population of 9 billion by 2050. Perennial grain crops present an opportunity for increased genetic and ecosystem diversity, yields and other ecological benefits. In 2019 and 2020 an interspecific sorghum population was estimated for hydrogen cyanide potential (HCN-P), biomass yield, composition and regrowth. Trait predictions were assessed using vegetation indices (VIs) and canopy height measurements (CHM) from unoccupied ariel systems (UAS). Additionally, novel perennial maize germplasm was characterized for overwintering. Perennial sorghum is likely safe for grazing at maturity under optimal conditions. Caution is required in earlier growth stages as it may have a higher HCN-P. The pedigrees had significantly different HCN-P across the years. Annual sorghum had significantly lower HCN-P than perennial sorghum. Hydrogen cyanide (HCN) assessment techniques evaluated showed that when a quantitative measure is required, colorimetry is useful, otherwise visual assessment is faster and less complicated method when screening large numbers of samples. The sorghum pedigrees were significant for both mean fresh and dry matter yields. Perennial sorghum produced significantly higher mean fresh and dry matter yields than annual sorghum. Composition analysis revealed no significant variation between perennial and annual sorghum for most of the biomass components. Plant stand counts (PSC), fresh and dry matter yields were best predicted by VIs while CHM best predicted RDS. Green chromatic coordinate index (GCC) best predicted all traits consistently. Machine learning models minimized error in prediction using VIs and CHM than linear regression. Ridge regression had the lowest error rate and was consistent across all traits. Regrowth and root composition of perennial maize was evaluated. The first year seeded trial had significantly higher PSC, rhizome derived shoots and underground rhizome buds from the regrowth. Most of regrowth was observed to originate from the crown rather than rhizomes which was surprising as the rhizome had significantly higher starch and water-soluble carbohydrates, shown in sorghum to be important. These results showed composition may not be the primary or sole factor contributing to overwintering in maize but could explain some variation.