Hybrid rapeseed relies on heterosis to boost yield and resilience, but conventional systems such as cytoplasmic male sterility (CMS) face significant limitations, including labor-intensive maintenance and environmental sensitivity. Recessive genic male sterility (RGMS) has emerged as a promising alternative, yet it struggles with large-scale sterile seed production. Traditional methods, often relying on extensive backcrossing, are hampered by the absence of efficient visual markers for sorting. These challenges underscore the urgent need for cutting-edge technologies to simplify and scale hybrid seed production.
In a study (DOI: 10.1093/hr/uhae270) published on September 25, 2024, in Horticulture Research, researchers from Huazhong Agricultural University unveiled a game-changing CRISPR/Cas9-based system paired with the RUBY reporter to generate male-sterile rapeseed lines. Their breakthrough approach involved the precise editing of the BnaMS1/BnaMS2 genes, introducing a color-based screening system that enables efficient hybrid seed propagation, all while avoiding the use of transgenic components in the final product.
The research team demonstrated the successful knockout of the BnaMS1 and BnaMS2 genes in elite rapeseed lines using CRISPR/Cas9, producing stable male-sterile plants that retained normal female fertility. They also developed an enhanced epicotyl transformation method that worked efficiently across different genotypes, overcoming a major bottleneck in rapeseed biotechnology.
The true innovation of the study lies in the RUBY reporter system, which produces vivid betaine pigments. This allowed researchers and breeders to quickly distinguish sterile (green) and fertile (red/pink) seedlings with the naked eye just days after germination. This is a dramatic improvement over previous fluorescent or anthocyanin-based markers, which required specialized equipment or specific growing conditions.
The study established a practical two-line system in which crosses between sterile lines and RUBY-linked maintainer lines consistently produced 50% sterile and 50% fertile progeny. This system simplifies hybrid seed production and ensures that the resulting hybrid seeds are free of transgenic components, addressing regulatory concerns and consumer preferences. The RUBY marker's unique dosage effect, where homozygous insertions produce red seedlings and heterozygous ones produce pink, provides an additional tool for precise genotype identification.
Dr. Chuchuan Fan, the corresponding author, stated, "Our system integrates the precision of gene editing with the simplicity of visual screening, eliminating the need for costly fluorescence-based sorting. By decoupling transgenes from hybrid seeds, we offer a sustainable solution for commercial rapeseed breeding and potentially other crops."
This technological breakthrough is poised to revolutionize hybrid seed production by significantly reducing both costs and time. The system's ability to produce non-transgenic hybrid seeds makes it particularly appealing to global markets with stringent GMO regulations. The RUBY reporter's versatility suggests potential applications in other major crops like wheat and maize, which face similar challenges in hybrid breeding.
Looking to the future, researchers aim to optimize the gene editing process further to enhance sterility stability and expand this system to other Brassica species. The successful integration of CRISPR technology with visual marker systems has set a new standard for precision breeding in agriculture, offering a blueprint that could be adapted across various crop species to improve hybrid seed production on a global scale.
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References
DOI
10.1093/hr/uhae270
Original Source URL
https://doi.org/10.1093/hr/uhae270
Funding information
Funding for this research was obtained from various sources, including the Technology Major Project on Key Techniques of Agricultural Biological Breeding (2023ZD0404203), the Key Research Projects of Hubei Province (2022BBA0039), the National Natural Science Foundation of China (32172021, 31371240, 31671279), the Wuhan Science and Technology Major Project on Key Techniques of Biological Breeding and Breeding of New Varieties (grant no. 2022021302024851), and the Open Project of Key Laboratory of Biology and Genetic Improvement of Oil Crops, Ministry of Agriculture and Rural Affairs, PR China (KF2023006).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.