Developing doubled haploid technology for alfalfa breeding

Alfalfa (Medicago sativa L.) is a perennial, outcrossing legume crop predominantly grown for hay, silage, and livestock grazing. Compared with other major crops, alfalfa has a complex genome and is self-incompatible, making it difficult to mine alfalfa germplasm and obtain pure homozygous inbred lines. The emergence of doubled haploid (DH) technology has dramatically reduced the time needed for plant breeding, allowing homozygous parental material to be obtained within 1-2 generations, making it a key technology for crop breeding. Here, we review progress in haploid breeding in alfalfa and provide some potential strategies to facilitate this process. Based on recent findings, we propose ways to use haploid breeding technology to assist in the creation of pure lines and male-sterile lines of alfalfa, accelerate precision breeding in alfalfa (IMGE/Hi-edit), and fix hybrid vigor by combining DH technology with MiMe (Mitosis instead of Meiosis).