Performance of Bnopr3 after different treatments and F1 hybrids. A Seed set of Bnopr3 after spraying with MeJA or water and hybrids after pollination by normal variety. B, CBnopr3 mutant and hybrid plants at seedling stage. D Genotype analysis of Bnopr3 mutant, normal variety, and F1 hybrids by using the B. napus 50 K Illumina Infinium SNP array. Gray and red represent the loci in the two parents, respectively. Blue lines represent heterozygous SNP alleles in hybrid plants. EBnopr3 mutant and hybrid plants at flowering stage. F Yield traits, including plant height, branch number, pod number per plant, pod length, thousand-seed weight, and yield per plant; comparison between two parents and F1 hybrid. *<0.05; **, P < 0.01; examined by Student’s t-test. G Flowering phenotype of two hybrids. F1-1, hybrids of ‘Westar’ and WB; F1-2, hybrids of Bnopr3 and WB. H Disease symptoms of two hybrids after S. sclerotiorum infection for 24 h (top) and 48 h (bottom). IT1 plant from seeds of Bnopr3 after MeJA treatment. J, K Flower morphology in Bnopr3 mutant in T1 generation and wild type. Scale bar = 1 cm. L Schematic diagram of two-line system with phytohormone genic male sterility in rapeseed. Male-sterile plants treated with MeJA can restore fertility and set seeds. Any normal variety can serve as a restorer line to pollinate this genic male-sterile line and generate F1 hybrids.
News — Hybrid seed production hinges on male sterility systems to manage pollination. While traditional three-line systems are effective, they are often complex and labor-intensive. Two-line systems, which utilize thermosensitive or photoperiod-dependent male sterility, offer broader applicability but are prone to instability due to environmental fluctuations. These challenges underscore the urgent need for a more reliable and manageable two-line system for hybrid breeding.
Conducted by researchers at the Oil Crops Research Institute of the Chinese Academy of Agricultural Sciences, this was published on October 27, 2023, in . The team used CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeat) to edit Oxophytodienoic acid reductase 3 (OPR3) genes in Brassica napus, creating male-sterile lines that can regain fertility through jasmonate treatment. This development marks a major leap forward in hybrid seed production, offering a more stable and controllable system for breeders.
The study introduced a novel two-line pollination control system by mutating two OPR3 homologs in Brassica napus using CRISPR/Cas9. The edited plants exhibited complete male sterility, which could be reversed with methyl jasmonate (MeJA) treatment. This method not only ensured stable male sterility but also allowed precise fertility control, addressing the instability issues of conventional two-line systems. Hybrids derived from these sterile lines demonstrated significant heterosis, validating the system's efficiency. The technology is straightforward and adaptable, with broad potential applications across other Brassica species, streamlining hybrid seed production and boosting agricultural efficiency.
Dr. Hongtao Cheng, a principal researcher of the study, remarked, “This breakthrough provides a novel route for stable and efficient hybrid seed production in rapeseed and other Brassica crops. CRISPR technology enables precise control over male sterility and fertility, a critical step towards sustainable agriculture and future crop improvements.”
This CRISPR-based two-line system for rapeseed hybrid production holds significant potential for expanding agricultural applications. The approach can be adapted to other Brassica species, potentially transforming hybrid breeding across diverse crops. By enhancing the stability and efficiency of hybrid seed production and reducing dependence on environmental factors, this technology paves the way for more resilient and sustainable agricultural practices worldwide.
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This work was supported by the Agricultural Science and Technology Innovation Project (CAAS-ZDRW202105), the Sci-Tech Innovation 2030 Agenda (2022ZD04009), the National Key Research and Development Program of China (2022YFD1200804), Key Research Projects of Hubei Province (No. 2021EHB026 and 2022BBA0039), and the Fundamental Research Funds for Central Non-profit Scientific Institution (No. 1610172020001).
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