International Journal of Molecular Evolution and Biodiversity, 2025, Vol.15, No.2, 84-98 http://ecoevopublisher.com/index.php/ijmeb 86 In order to cope with the risk of drought, some studies have proposed improving the drought resistance of rapeseed by improving soil structure. For example, the application of biochar not only improves soil water retention, but also increases soil nutrient supply, which helps maintain the normal physiological activities and yield levels of rapeseed in arid environments (Khan et al., 2021). 3 Genetic Basis of Drought Tolerance in Rapeseed 3.1 Identification and function of key genes for drought resistance The drought resistance of rapeseed (Brassica napus) is determined by a complex genetic network. The latest research shows that multiple key genes regulate the plant's response to drought stress through synergistic effects. A genome-wide association analysis revealed 139 SNP loci significantly associated with drought resistance, among which genetic variation on chromosome A10 showed particularly prominent association strength (Shahzad et al., 2021). In-depth analysis found that four genes, including BnaC09.RPS6, play a core regulatory function under water stress conditions. These genes jointly maintain the physiological homeostasis of plants in drought environments by affecting different physiological and metabolic processes. In addition, studies have shown that overexpression of the bZIP transcription factor encoding gene BnaABF2 in Arabidopsis can significantly enhance its drought resistance. This gene maintains cellular osmotic balance and metabolic homeostasis by upregulating the expression of stress-related genes such as RD29B, RAB18 and KIN2 (Zhao et al., 2016). These results emphasize the importance of targeting key genes for functional verification and provide basic information and potential gene resources for molecular breeding of rapeseed drought resistance. 3.2 Drought-resistant regulatory role of DREB, NAC and WRKY transcription factors In the drought resistance regulatory network, transcription factors (TFs) play a pivotal role in signal transduction and gene expression regulation. The DREB (dehydration response element binding protein), NAC and WRKY transcription factor families are considered to be the core elements for regulating drought resistance because of their extensive involvement in drought signal transduction and response. For example, after the DREB1A gene is heterologously expressed in sage, it can upregulate downstream genes related to stress response, photosynthesis regulation and carbohydrate metabolism, thereby improving the drought tolerance of plants (Wei et al., 2016). This mechanism provides a reference for the application of corresponding regulatory factors in rapeseed. NAC family transcription factors play a key role in regulating plant drought response. Studies have shown that the expression profile of papaya CpNAC genes is significantly reprogrammed under water stress conditions, suggesting that they are involved in drought signal transduction (Arroyo-Álvarez et al., 2023). It is also worth noting that members of the WRKY transcription factor family, such as WRKY57, enhance plant drought resistance through a dual regulatory mechanism: on the one hand, they activate the ABA signal transduction pathway, and on the other hand, they increase the activity of antioxidant enzymes such as superoxide dismutase (Yang et al., 2020). This synergistic effect effectively removes excess reactive oxygen species in cells and reduces the damage of oxidative stress to the membrane system (Jiang et al., 2012). 3.3 Study on the localization of quantitative trait loci (QTL) for drought resistance The localization of quantitative trait loci (QTL) provides an effective tool for analyzing the genetic mechanisms behind complex traits, especially showing great potential in revealing genomic regions related to drought resistance. In rapeseed, although the QTL research on drought resistance is still relatively limited, the existing research on waterlogging resistance provides a valuable reference for subsequent expansion. Some physiological indicators respond to both drought and waterlogging stresses, so there may be intersections between the two in some genetic pathways. Important progress has been made in the study of rapeseed waterlogging tolerance. Through systematic analysis, 66 key QTL loci were identified, which regulate important traits such as root development and biomass accumulation (Xiaoyu et al., 2020). The study found that these loci can be clustered into 6 main functional modules, providing new targets for molecular marker-assisted breeding.
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