Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2007
Publication Date: 3/19/2008
Citation: Casler, M.D., Jung, H.G., Coblentz, W.K. 2008. Selection for Lignin and Etherified Ferulates in Three Perennial Grasses. Crop Science. 48:424-433. Interpretive Summary: We are studying two different mechanisms by which plants resist digestion by ruminant livestock. The two mechanisms are (1) lignification, the "cementing" of plant sugars into a matrix that we call the cell wall, and (2) crosslinking between lignin and cell-wall carbohydrates, the chemical bonds between the "cement" and structural members of the cell wall. The two mechanisms act independently of each other, both reducing the digestibility of forages. We have shown that these principles apply across several grass species and can probably be taken as fairly broad or universal principles for forage grasses. Lignin appears to be the better choice for grass breeders to develop new grass varieties, because it seems to have fewer negative side effects, such as reduced forage yield.
Technical Abstract: Decreased lignin concentration or decreased ferulate cross-linking between arabinoxylans and lignin are two mechanisms to increase cell-wall digestibility in plants. The objectives of this study were (i) to determine if the genetic correlation between lignin and etherified ferulates can be altered by intensive selection, (ii) to determine the effects of lignin and ferulates on digestibility of neutral detergent fiber (NDF), and (iii) to determine the consistency and clonal repeatability of these traits across multiple harvest dates and years. Thirty clones each of smooth bromegrass (Bromus inermis Leyss), orchardgrass (Dactylis glomerata L.), and reed canarygrass (Phalaris arundinacea L.) were evaluated in a replicated field study at four growth stages in 2004 and 2005 for NDF, lignin, esterified and etherified ferulates, and 24-h and 96-h in vitro NDF digestibility (IVNDFD). Clonal means were generally repeatable across years and harvest dates. Divergent selection created clonal groups with differential lignin and etherified ferulates, but the positive correlation between these two traits was reduced only in smooth bromegrass. Both lignin and etherified ferulates were negatively correlated with 96-h IVNDFD and these relationships were maintained as all three grasses matured. Concentration of NDF was highly correlated with etherified ferulates, making it difficult to partition the impact of components of lignification on IVNDFD.