The Use of Metabolic Engineering to Improve Forage Quality in Alfalfa.

Alfalfa earned the title “Queen of the Forages” based on its exceptional forage quality - providing high quality protein and fiber for dairy and beef diets.  New biotech tools for modifying plant biochemical pathways present exciting opportunities for significantly improving fiber digestibility and protein use efficiency in alfalfa.

In collaboration with the Noble Foundation and the U.S. Dairy Forage Research Center, FGI has down-regulated key enzymes in the lignin biosynthetic pathway and evaluated transgenic plants for lignin content, lignin composition, fiber digestibility and agronomic performance.  A commercial Reduced Lignin alfalfa transgenic event is now in being reviewed for deregulation by USDA/APHIS.  A summary of various field and animal feeding trials will be presented.

Alfalfa produces more protein per acre than any other crop grown in the U.S.  Unfortunately alfalfa protein is rapidly degraded in the rumen and inefficiently utilized by high producing dairy cows.  The production of condensed tannins in alfalfa would offer an opportunity to slow protein degradation in the rumen, increasing rumen undegradable protein (RUP) and improving efficiency of protein use by high producing dairy cows.  This will potentially decrease the need for protein supplementation in dairy diets and reduce N losses to the environment.  Alfalfa produces condensed tannins in seed coats, but not in vegetative tissue.  In a broad collaboration with several parties FGI has used GE methods to introduce various transcription factors regulating components of the condensed tannin biosynthetic pathway.  A summary of these results will be presented.

This work is an important step to improve forage quality of alfalfa, benefitting alfalfa producers, end-users and the environment.  The broad collaborative nature of these projects reflects the opportunity for inter-institutional, inter-disciplinary approaches to solve long term challenges in crop improvement.