Variation between Two Switchgrass Cultivars for Components of Vegetative and Seed Biomass

Biomass production potential in switchgrass (Panicum virgatum L.) populations is inversely related to latitude of origin. However, phenological adaptation limits the latitudinal range from which to select populations for breeding for biomass in the northern Great Plains. Objectives of this study were to compare patterns of biomass partitioning, determine importance of tiller density and size, and identify morphological traits as potential selection criteria for two cultivars, Summer (origin 40° 42′ N, 95° 52′ W) and Sunburst (origin 42° 42′ N, 96° 41′ W), of comparable phenology. Summer (12.6 Mg ha−1) produced 20% more vegetative biomass than Sunburst and had higher percent reproductive tillers (62% vs. 40%) and more phytomers tiller−1 (7.9 vs. 6.4). Sunburst had more tillers m−2 (677 vs. 530). Cultivars did not differ for seed biomass (311 kg ha−1), but seeds of Sunburst (1.8 mg seed−1) were 90% heavier than seeds of Summer. Vegetative biomass decreased acropetally among phytomers. Reproductive tillers per m2 and seed mass per panicle were accurate predictors of vegetative and seed biomass, respectively. Frequency of reproductive tillers, number of phytomers per tiller, and rate of phytomer development morphologically differentiated Summer and Sunburst and were potential selection criteria for improving biomass yield within a maturity class of switchgrass adapted to the northern Great Plains.