Agronomic fitness of three temperate forage grasses divergently selected for lignin concentration or ferulate cross-linking

Reductions in either lignin concentration or ferulate cross-linking have been shown to be independent mechanisms for increasing herbage digestibility by increasing the enzymatic degradability of cell-wall polysaccharides. However, both of these traits are frequently associated with reductions in agronomic fitness, including dwarfing, developmental abnormalities, and loss of persistence. The objective of this study was to evaluate the impacts of selection for these two traits on agronomic fitness of three temperate perennial grasses: orchardgrass (Dactylis glomerate L.), reed canarygrass (Phalaris arundinacea L.), and smooth bromegrass (Bromus inermis Leyss.). All possible crosses were made within three groups of eight parents, with parents selected to represent four divergent phenotypes: high or low etherified ferulates and high or low Klason lignin. Progeny were evaluated for forage yield under a three-cut management and for tiller density and ground cover under a frequent-harvest management. Selection for reduced lignin concentration had highly variable and inconsistent impacts on agronomic fitness, varying widely among species. Conversely, selection for reduced ferulate cross-linking resulted in a general decline for all measures of agronomic fitness within each species. The results support the hypothesis put forward from an earlier study and from the literature that reduced ferulate cross-linking results in significant impairments to stem development of these temperate grasses.