关键词: 紫花苜蓿, 分子设计育种, 基因组, 种质资源

Abstract:

Alfalfa (Medicago sativa subsp. sativa L.), as the world's most important leguminous forage, plays an indispensable role in modern livestock farming and ecological systems due to its high yield, superior quality, and excellent adaptability. However, China's alfalfa industry has long faced a "bottleneck" in its seed industry, primarily characterized by the insufficient innovation capacity in germplasm resources and a low supply rate of elite proprietary varieties. The root of this challenge lies not only in the relatively late start and underdeveloped technical framework of alfalfa breeding in China, but also in the complex genetic characters obstacles inherent to alfalfa itself—namely, its autotetraploid nature with high heterozygosity and a self-incompatibility mechanism. Therefore, a systematic review of alfalfa's breeding history, current research status, and a forward-looking perspective on biotechnological breeding is of significant referential value for accelerating genetic improvement in China. The history of alfalfa domestication and spread was extensive. Originating from the Transcaucasus region, it was introduced to China via the "Silk Road" and subsequently spread worldwide. The vast enrichment of its genetic diversity benefited historically from the introduction of germplasm from different geographical origins and inter/intraspecific hybridization, particularly through genetic introgression from the stress-tolerant subspecies, M. sativa subsp. falcata. This laid a solid genetic foundation for breeding varieties adapted to diverse ecological niches. Developed countries, such as the United States, have established a comprehensive system for alfalfa breeding that covered germplasm collection, evaluation, and new variety development, with a history spanning over a century. Nevertheless, even in the United States, yield improvement plateaued after 1990, revealing the potential limitations of conventional breeding strategies. Although China has made considerable progress in alfalfa breeding, successfully developing adapted varieties, such as the "Zhongmu" and "Gannong" series, the overall effort still faced significant challenges. Firstly, the number of registered varieties is relatively less (128 as of 2024, far fewer than the 1 738 in the U.S.), which severely limits the ability to select optimal varieties for China's diverse ecological environments. Secondly, conventional breeding strategies themselves have constrained the effective utilization of heterosis. Historically, breeders often employed a strategy of population mixing and recurrent selection with varieties from different geographical origins. However, this approach aggregated favorable genes to some extent, and it also led to a homogenization of the genetic backgrounds among different breeding populations, thereby diminishing the potential for generating strong heterosis through subsequent hybridization. Consequently, breaking through the limitations of traditional methods by introducing efficient modern biotechnologies has become an inevitable choice for contemporary alfalfa breeding. In recent years, modern biotechnology centered on genomics has presented unprecedented opportunities to overcome the challenges in alfalfa breeding. China has achieved notable success in foundational genomics research, completing tasks ranging from genetic analysis of germplasm resources and genetic mapping to the key molecular markers and the development of elite germplasm. These genomic resources have made it possible to dissect the genetic regulatory networks of complex traits, such as yield, quality, and stress resistance at the molecular level. Looking ahead, alfalfa breeding in China should adopt a strategy that integrates conventional breeding with modern biotechnology, transitioning from source innovation to the "Breeding 4.0" era of precision design. The integration of modern biotechnologies—including genomics, marker-assisted selection, and gene editing—to conduct precise and efficient molecular design breeding is the core pathway to resolving the "bottleneck" in China's alfalfa seed industry and achieving fast development.

Key words: alfalfa, molecular design breeding, genomics, germplasm