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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Dairy Forage Research » Research » Publications at this Location » Publication #229141

Title: Lignin and Fiber digestibility in Caffeic Acid 3-O-Methyltransferase and Caffeoyl CoA 3-O-Methyltransferase Downregulated Alfalfa

item Riday, Heathcliffe
item Mertens, David
item Jung, Hans Joachim

Submitted to: Trifolium Conference Abstract & Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/16/2008
Publication Date: 6/1/2008
Citation: Riday, H., Whalen, D., Bouton, J., Mertens, D.R., Jung, H.G., Chen, F., Temple, S., McCaslin, M., Dixon, R. 2008. Lignin and Fiber digestibility in Caffeic Acid 3-O-Methyltransferase and Caffeoyl CoA 3-O-Methyltransferase Downregulated Alfalfa [abstract]. Proceedings Joint Meeting of the 41st North American Alfalfa Improvement Conference & 20th Trifolium Conference, June 1-4, 2008, Dallas, TX. Abstract #18.

Interpretive Summary:

Technical Abstract: Alfalfa (Medicago sativa L.) is one of the most important forages in the United States. Increasing alfalfa fiber digestibility would improve forage management and ration formulation flexibility. Currently, growers and breeders rely on near infrared spectroscopy (NIRS) to predict forage quality traits for alfalfa. With the introduction of lignin downregulated alfalfa plants, the question arises if standard alfalfa NIRS equations are accurate at predicting forage quality traits for novel low-lignin alfalfa samples. This study reports in vitro neutral detergent fiber digestibility (NDFD) and lignin analysis (ADL, Klason, total thioacidolysis yield, S-lignin, G-lignin, and H-lignin) of caffeic acid 3-O-methyltransferase (COMT) and caffeoyl CoA 3-O-methyltransferase (CCOMT) downregulated alfalfa. Lower stem samples of 40 COMT, 40 CCOMT, and 20 null type alfalfa plants collected over three locations from a total of 10 harvest by location combinations (2900 field samples) were analyzed in this study. Samples were selected based on predicted ADL from NIRS equations for whole plant alfalfa developed for alfalfa breeders. Although NIRS analysis indicated lower lignin and higher digestibility for COMT and CCOMT, laboratory analysis revealed that the NIRS breeder’s equation had large positive bias in predicting ADL for CCOMT and large negative bias in predicting NDFD for COMT transgenics. This study also reveals that relative values among downregulated alfalfa differed for thioacidolysis measured lignin compared to ADL and Klason lignin. Total thioacidolysis yield was the best predictor of NDFD. In particular S-lignin levels were highly correlated with NDFD among all types of alfalfa samples in this study. New NIRS equations were developed successfully for all laboratory constituents evaluated in this study. NIRS equations used by forage testing laboratories will need updating to accurately predict lignin and digestibility in lignin downregulated alfalfa.