The Progress of Genetic Improvement in Alfalfa (Medicago sativa L.)

Alfalfa (Medicago sativa L.) is a perennial and outcrossing species, widely grown as a forage legume for hay, pasture and silage. The genetic engineering approaches involve the transfer of useful or novel gene(s) into alfalfa to improve desired traits. The recent development of genetic engineering is extensively applied to basic and applied research for alfalfa improvement, including improvement of herbicide resistance, reinforcement of the resistance to biotic and abiotic stresses, production of novel compounds, improved yield for industrial and/or pharmaceutical proteins and renewable energy sources. On the other hand, alfalfa forage needs to possess additional fermentable carbohydrates, proteins with a balanced amino acid profile that are gradually degraded in the rumen of domestic livestock, and zero anti-nutritional factors, which are the major concerns of recent interest in alfalfa. However, an advance of transgenic approach is contentious, requiring vigilant experimental methods and design to contest bio-safety challenges. More importantly, the technology of clustered regularly interspaced short palindromic repeats (CRISPR) is rapidly growing and might be a game player or changer in alfalfa. The present review can enable us to identify the proper direction, get familiar with new research methods and success of genetic engineering technology in alfalfa, to produce maximally improved cultivars.