The Use of GE Traits in Alfalfa Improvement.

Although modern plant breeding programs use genetic principles practiced for decades by breeders/geneticists, genomics and genetic engineering have provided new tools for breeders to better utilize native genetic variation or to introduce novel genes/traits.  This presentation presents an outline on the application of GE traits in commercial alfalfa breeding.

Genetic engineering enables breeders to introduce novel traits through insertion of novel genes (e.g. glyphosate tolerance) or by modifying expression of native genes (e.g., reduced lignin alfalfa).  GE traits are commonly grouped into two categories: Agronomic traits that improve productivity or efficiency of crop production, and Quality traits that improve the economic value of the crop product produced.

Agronomic traits

Transgenes enabling herbicide tolerance have been introduced into several crop species to increase flexibility and effectiveness of weed control.  Roundup Ready^® alfalfa was introduced in 2005, the first GE trait commercialized in a perennial forage crop.  Hay growers using Roundup Ready alfalfa report higher yield, improved crop safety, greater flexibility in timing of herbicide application, and better weed control/improved forage quality.  In 2013 Roundup Ready alfalfa comprised approximately 35% of U.S. alfalfa seed sales.

While conventional breeding has increased cold tolerance in alfalfa, little improvement has been made in salt or drought tolerance.  There is considerable interest in both GE and genomics approaches for improving abiotic stress tolerance in alfalfa.

Quality Traits

Gene suppression technology has been used to modify alfalfa’s lignin biosynthetic pathway thereby altering lignin content and composition, and leading to an increase in fiber digestibility (i.e., NDFD).  Genetic up-regulation of various transcription factors involved in regulating the native condensed tannin biosynthetic pathway is being used to produce condensed tannins in novel tissues (leaves and stems), resulting in increased Rumen Undegradable Protein (RUP) and improved efficiency of protein utilization in alfalfa. 

Summary

U.S. alfalfa hay production acres have been in gradual decline for the last decade.  The successful application of biotech tools in alfalfa improvement is critical to keeping the crop competitive.

^®Roundup Ready is a registered trademark of Monsanto Technology LLC.