Steroidal saponin concentrations in switchgrass cultivars liberty and independence in North America

Authors: Clemensen, Andrea; Lee, Stephen; Mitchell, Robert - Rob; Schmer, Marty; Masterson, Steven - Steve

Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2022
Publication Date: 12/5/2022
Citation: Clemensen, A.K., Lee, S.T., Mitchell, R., Schmer, M.R., Masterson, S.D. 2022. Steroidal saponin concentrations in switchgrass cultivars liberty and independence in North America. Crop, Forage & Turfgrass Management. https://doi.org/10.1002/cft2.20204.
DOI: https://doi.org/10.1002/cft2.20204

Interpretive Summary: Switchgrass (Panicum virgatum L.) is a warm-season grass native to the tallgrass prairie in North America. Switchgrass offers several benefits to agricultural systems, such as increasing soil organic carbon. Switchgrass can be used as forage for cattle or harvested for biofuel. Switchgrass should not be grazed by horses, as the steroidal saponins present can be toxic to them. These steroidal saponins are plant secondary metabolites that are likely the reason switchgrass can withstand various environmental hardships such as insect infestation and disease. Saponins may influence soil nutrient dynamics by decreasing N loss, and may also influence soil water dynamics by increasing soil water holding capacity. Switchgrass cultivars "Liberty" and "Independence" are two important bioenergy cultivars for the Great Plains. However, the steroidal saponins in these two cultivars has not been investigated. Therefore, we determined the relative steroidal saponin concentration in leaf and stem tissues of both cultivars. Both cultivars had three types of steroidal saponins: protodioscin, dichotomin, and saponin B. The three types of steroidal saponins were greater in the leaf than stem tissues in both cultivars. There were also significant differences in the steroidal saponin concentrations between the two cultivars. This research is useful to producers in providing initial information that may be useful in selecting varieties to grow. It is also useful to researchers in helping to understand switchgrass effects on soil nutrient cycling, forage use, and resistance to pests.

Technical Abstract: Switchgrass (Panicum virgatum L.) is a warm-season grass native to the tallgrass prairie in North America with various ecosystem benefits. Depending on management, switchgrass can increase soil organic carbon, enhancing C sequestration potential in soil. Various biotic factors such as insect infestation and disease are associated with switchgrass, but switchgrass appears to be resistant to many of these biotic stresses. These resilient qualities of switchgrass may be due to the steroidal saponins produced by the grass. Steroidal saponins are triterpenes that have antibacterial and antifungal characteristics. In addition, terpenes from plants may increase soil microbial biomass, decrease soil net N mineralization, and are also used as surfactants, which may increase water holding capacity in soil. Switchgrass cultivars “Liberty” and “Independence” are two prominent bioenergy switchgrass cultivars for the Great Plains and Midwest. However, steroidal saponin concentration in these two cultivars has not been investigated. Therefore, our objective was to evaluate the relative steroidal saponin concentration in leaf and stem tissues from both Liberty and Independence switchgrass. The steroidal saponins protodioscin, dichotomin, and saponin B, were detected in all leaf and stem tissues of both Liberty and Independence cultivars, and were all greater (p < 0.05) in the leaf than stem tissues of both Liberty and Independence. Further research is needed to determine steroidal saponin concentration in root tissues and elucidate the soil surfactant potential of switchgrass saponins.