Journal of Energy Bioscience 2024, Vol.15, No.6, 368-377 http://bioscipublisher.com/index.php/jeb 369 processing technologies will be studied to maximize the efficiency of oil extraction and biodiesel conversion, and by integrating environmental and economic performance assessments, we will strive to fully understand the potential for optimizing rapeseed biodiesel production. The research scope ranges from field agricultural practices to industrial processing methods to provide best practices for identifying higher yields and better quality biodiesel, and to promote biodiesel production in a sustainable manner. 2 Genetic Improvements for Higher Oil Content 2.1 Advances in breeding techniques Traditional breeding techniques, such as hybridization and mutation breeding, have long been used to increase the oil content of rapeseed. These methods have led to the development of improved varieties through multiple generations of selection for superior traits. For example, rapeseed lines with high oleic acid and low linolenic acid content were developed using the chemical mutagen ethyl methane sulfonic acid (EMS), but these lines initially showed low agronomic value. These lines were further optimized by marker-assisted selection, combining good oil quality with high agronomic value, showing the great potential of traditional breeding methods when combined with modern genetic tools (Spasibionek et al., 2020). 2.2 Identification of key yield-related genes Recent studies have identified some key genes that significantly affect seed oil content (SOC) and yield-related traits. For example, the seed fatty acid reductase (SFAR) gene has been shown to play a key role in SOC and fatty acid composition. Targeted mutagenesis of these genes using CRISPR-Cas9 significantly increased SOC without adversely affecting seed germination and vigor (Karunarathna et al., 2020). In addition, genome-wide association studies (GWAS) have identified many quantitative trait nucleotides (QTNs) associated with yield-related traits such as silique number, number of seeds per silique, and thousand-grain weight. Combining GWAS with transcriptome analysis has further located candidate genes such as RNA helicase and lipase that affect these traits, providing valuable targets for genetic improvement (Zhang et al., 2023). 2.3 Application of genomic selection and CRISPR-Cas9 The advent of CRISPR-Cas9 technology has greatly revolutionized the field of genetic improvement of rapeseed. This precise genome editing tool can target specific genes for modification, thereby accelerating the breeding process. For example, the BnFAD2 gene was successfully edited using CRISPR-Cas9, significantly increasing the seed oleic acid content (Liu et al., 2022). Similarly, this technology has also been used to knock out multiple homologous genes in the BnLPAT2 and BnLPAT5 gene families, which are involved in oil biosynthesis, thereby increasing oil yield (Zhang et al., 2019). In addition, CRISPR-Cas9 has also been used to develop glyphosate-resistant rapeseed varieties by modifying the EPSPS gene, demonstrating its versatility in simultaneously addressing yield and quality traits (Wang et al., 2021). Despite technical challenges such as off-target effects and gene redundancy in polyploid species such as Brassica napus, continuous improvements in CRISPR technology are continuously improving its efficiency and applicability (Figure 1) (Sandgrind, 2022; Tian et al., 2022; Ali and Zhang, 2023). 3 Agronomic Practices Enhancing Oil Yield 3.1 Soil and nutrient management Effective soil and nutrient management are key to optimizing rapeseed oil production. Studies have shown that the application of biochar can significantly improve soil fertility, including increasing soil pH, available phosphorus, organic carbon, and water retention capacity, thereby increasing rapeseed yield. However, these benefits will gradually weaken over time, so continuous soil management is required (Jin et al., 2019). In addition, the balanced application of fertilizers such as nitrogen, phosphorus, potassium, sulfur, and boron can significantly increase dry matter accumulation and seed oil content, thereby increasing total yield and economic benefits (Tian et al., 2020). In acidic soils, the application of lime and trace elements such as zinc, boron, and molybdenum can also improve soil properties and productivity by improving soil pH, organic carbon content, and nutrient supply (Tanner et al., 2023).
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