Canopy Architecture and Morphology of Switchgrass Populations Differing in Forage Yield

Phenotypic selection has been used to improve forage yield and in vitro dry matter disappearance (IVDMD), but the effects on canopy architecture and morphology are not understood. Our objectives were to determine if canopy architecture and morphology can explain genotype × environment (G ✕ E) yield differences in switchgrass (Panicum virgatum L.) and to evaluate canopy architecture and morphology as selection criteria for increasing yield. This study was conducted in 1993 near Mead, NE, and near Ames, IA. The experimental design was a randomized complete block experiment with a split-plot arrangement of four replicates at each location. Whole plots were tiller population and subplots were sward maturity. Tiller populations were harvested on 9 June, 19 July, and 27 August at Ames and on 10 June, 27 July, and 26 August at Mead and were classified morphologically. Tillers were separated into primary yield components and dried at 55°C to determine total forage yield and dry matter contribution of morphological components. Genotype × environment interactions occurred for total forage yield and tiller density. Previous phenotypic selection for increased forage yield and IVDMD apparently altered morphological changes within the canopy of selected switchgrass populations. The most apparent changes were development of additional collared leaves and internodes in some populations across locations. Although canopy architecture may not be a useful selection criterion because of variability associated with individual canopy traits, indirect measurements showed that leaf area index (LAI) has some potential as a selection criterion for increasing total forage yield. However, selection for individual canopy traits may be most effective for modifying sward growth habits. The research reported in this article is a portion from the dissertation submitted by the senior author in partial fulfillment of the requirements for the Ph.D. degree from the Univ. of Nebraska. Research funded in part by the U.S. Dep. of Energy Biomass Fuels Program, Oak Ridge Natl. Lab. Contract no. DE-A105-900R21954. Joint contribution from the Nebraska Agric. Exp. Stn. and Iowa Agric. and Home Econ. Exp. Stn. Published as Journal Series no. 11442, Nebraska Agric. Exp. Stn.