Breeding switchgrass for reduced nitrogen demand

Abstract Background Developing switchgrass ( Panicum virgatum L.) cultivars with reduced nitrogen (N) demand is essential for sustainable biomass production. Conventional breeding under non‐limiting N rates has increased yield but left unresolved the relationship between genetic diversity and nitrogen use efficiency (NUE). Methods This study quantified genetic variation for biomass yield, N concentration, and N removal in two switchgrass populations that were evaluated for 2 years at two locations. A handheld near‐infrared reflectance spectrophotometer (NIRS) was used to quantify biomass N content, and several selection criteria, that is, single‐trait, ratio, and multi‐trait index, were evaluated to model long‐term gains. Results Trait heritabilities were highest for N removal (0.41–0.67) and highly variable among the selection criteria. Biomass yield and N concentration were weakly and negatively correlated, whereas N removal was strongly positively correlated with both traits. Long‐term predictions indicated that single‐trait selection for yield would increase N demand by >100% over 20 cycles. Index‐based selection outperformed single‐trait selection with a favorable gain for biomass yield with reasonable increments to N demand. High predictive accuracies (>90%) were obtained with the handheld NIRS. Conclusions Results demonstrate that multi‐trait selection combined with portable NIRS could be effective in breeding switchgrass for improved NUE while maintaining high gains in biomass yield.