Submitted to: Journal of the French Academy of Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/23/2004
Publication Date: 5/13/2004
Citation: Ralph, J., Guillaume, S., Grabber, J.H., Lapierre, C., Barriere, Y. Genetic and molecular basis of grass cell wall biosynthesis and degradability III. Towards a forage grass ideotype. Journal of the French Academy of Science. 2004. v. 327. p. 467-479. Interpretive Summary: Forage grasses are major feedstuffs for livestock and grass cereal crops like maize, rice, wheat, oats and rye supply most of the dietary energy needs of people and many types of livestock. Fiber makes up 25 to 80% of the dry weight of grasses and it is composed primarily of complex carbohydrates. These carbohydrates are potentially an important source of digestible energy for livestock and they may also be converted into various chemicals for use in automobile fuels, plastics, and other products. Unfortunately, the enzymatic breakdown of complex carbohydrates into sugars is limited by an indigestible component in fiber known as 'lignin'. In the 3rd part of this review, we describe how molecular biology has and will be used to develop grasses with desirable lignin characteristics and improved fiber digestibility. This review will help scientists to develop improved grasses and processing methods so that lignin is less of a barrier to fiber digestion. Ultimately these studies will lower the cost and environmental impact of converting grasses and cereal crop residues into food, fuel, and industrial products.
Technical Abstract: Enhanced digestibility is a major target for improving the feeding value of grasses, and lignification of cell walls is the major factor controlling the digestibility. QTL investigations have been numerous in maize, but only a limited number have been devoted to feeding value of forage maize or other grasses. Thus far, about 15 locations involved in cell wall lignification or digestibility have been identified, many of which co-localize with QTL involved in corn borer susceptibility. Genetic diversity for enhancing cell wall digestibility in maize must be identified in novel germplasm, because this trait was not considered during hybrid development in past decades, and because it was likely counter-selected when breeding for stalk standability. Genetic engineering is a very relevant way both to design specific cell wall characteristics for improved digestibility and to identify genes involved in these traits for further identification of alleles of interest in grass germplasm.