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

Authors: Casler, Michael; JUNG, HANS-JOACHIM - US Department Of Agriculture (USDA)

Submitted to: Euphytica International Journal on Plant Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2021
Publication Date: 6/25/2021
Citation: Casler, M.D., Jung, H.G. 2021. Agronomic fitness of three temperate forage grasses divergently selected for lignin concentration or ferulate cross-linking. Euphytica International Journal on Plant Breeding. 217. Article 149. https://doi.org/10.1007/s10681-021-02873-1.
DOI: https://doi.org/10.1007/s10681-021-02873-1

Interpretive Summary: Breeding grasses for increased digestibility is one of the most effective ways to improve their value to livestock producers, effectively increasing profitability. Previous research has shown two distinct approaches to increasing the digestibility of grass cell walls: decreasing lignin and decreasing the chemical bonding between lignin and cellulose. This study demonstrated that simple decreases in lignin can be effective for increasing digestibility of grasses without sacrificing forage productivity or persistence. Conversely, decreasing the chemical bonding of lignin with cellulose led to catastrophic reductions in forage productivity and persistence of three different grasses. These results indicate that grass breeders can continue to focus on lignin as a mechanism for increasing digestibility, but should avoid reducing the chemical linkages that lignin forms with cell wall sugars.

Technical Abstract: 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 three divergent phenotypes: high or low etherified ferulates and high or low 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.