Molecular Soil Biology 2025, Vol.16, No.6, 297-305 http://bioscipublisher.com/index.php/msb 299 LBD37 and CKX3 are often located in the same genetic region as root traits. Under drought stress conditions, Li et al. (2023) combined GWAS analysis with differential expression analysis to screen out multiple genetic loci related to 13 root traits and identified candidate genes such as ZmCIPK3. 3.2 Agronomic approaches to enhancing root traits Applying nitrogen fertilizer to the middle layer of soil at a depth of 16 to 24 cm is very beneficial to the root system, significantly increasing the nitrate nitrogen and available phosphorus in this layer of soil. The number of lateral roots in the 16~32 cm soil layer increases, and the root surface area also expands. Root hairs will elongate and the activity of phosphatase in the root system will increase (Liu et al., 2025). If compound fertilizer is applied to a deeper position, approximately 0.25 meters, the root system will grow downward and outwards. Within the depth range of 0-1.0 m, both the root length density and the root surface area increase. Deep root systems absorb more water, mainly concentrated in the 0.4~1.4 m soil layer, and the inorganic nitrogen content in the root SAP also increases. The water use efficiency and nitrogen absorption efficiency increased by 10%~39%, and the crop yield increased by approximately 14% (Wu et al., 2022). In cold arid and semi-arid regions, the dosage of nitrogen fertilizer and soil moisture content should be considered together. When the soil moisture was maintained at 80% of the field capacity and 200 kg N ha-1 nitrogen fertilizer was applied simultaneously, the activity of antioxidant enzymes in the root system was significantly enhanced and the accumulation of reactive oxygen species decreased. The increase in hormone contents such as IAA, GA and zeaxanthin makes the root system state more stable and is also conducive to the absorption of nutrients such as potassium, calcium and magnesium (Chi et al., 2025). 3.3 Environmental influence on root growth and nutrient acquisition Under drought, low nitrogen, and salt stress, maize roots often change in clear ways (Li et al., 2023; Yu et al., 2024). When there is not enough water in the soil or when nitrogen levels are low, different maize types do not respond in the same way. In some plants, roots grow longer. In others, changes in root surface area or root volume are more obvious (Jiang and Whalen, 2025). Salt stress also affects maize roots. In salty soil, roots usually become thicker, and the total root volume often increases. This helps the plant grow better in hard soil or soil with high salt content. When nitrogen is limited, maize often adapts by extending its roots further into the soil. At the same time, root surface area and specific root length increase. This allows the root system to spread over a larger soil area and take up more nutrients (Keerthi et al., 2025). Soil conditions also play a role in root development. Soil pH and organic matter levels can influence root growth. During drought, the substances released by roots and by microbes around the roots may change. These changes can further affect how fast roots grow and how well they absorb nutrients (Hao et al., 2025). 4 Advances in Root Architecture Modification for Maize 4.1 Breeding programs focused on root architecture The field soil-digging root phenotypes of six main cultivated maize varieties in the southwest region under the gradient of 0-300 kg N ha-1 showed that with the increase of nitrogen application, the total root length, root surface area, root opening Angle and maximum root width all increased significantly, and these four RSA indicators were significantly positively correlated with the yield. The root opening Angle and the maximum root width were significantly positively correlated with nitrogen accumulation in plants. The linear-plateau model fitting showed that when the root opening Angle reached approximately 99.5° and the root width reached 15.2 cm, nitrogen accumulation reached the plateau value within 0~300 kg N ha-1 (Guo et al., 2022). In terms of nitrogen-efficient breeding, the phylogenetic root phenotypes and anatomical analyses of 6 hybrids and 9 parents under full nitrogen (180 kg/ha) and low nitrogen (30 kg/ha) conditions revealed that the n-efficient hybrid (EE type) For example, WK702 shows a 6.0%~15.7% narrower root opening Angle, a 11.9%~12.4% larger root projection area, a 16.3%~22.6% deeper maximum root depth, and a 22.6%~37.1% larger cortical ventilation tissue area under low nitrogen conditions (Chen et al., 2025). GWAS analysis of 14,301 field plants identified 81 highly reliable RSA candidate genes, and it was found that 28 known root-related genes were selected during domestication and improvement. Favorable alleles related to "steep root angles" in modern materials continued to accumulate in different breeding eras. Two auxin genes, ZmRSA3.1 and ZmRSA3.2, were functionally verified to regulate root Angle and root depth (Ren et al., 2022).
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