Molecular Pathogens, 2025, Vol.16, No.3, 100-110 http://microbescipublisher.com/index.php/mp 104 3.2.2 Regulatory role of mycorrhizal fungi Arbuscular mycorrhizal fungi (AMF) are important symbionts of plant roots. Their hyphae can extend to micro-regions in the soil far away from the rhizosphere, effectively improving the crop's ability to absorb nutrients such as phosphorus and zinc, and enhancing its adaptability to drought and pathogenic stress (Li et al., 2024). The role of AMF in the rotation system is particularly critical. Studies have shown that compared with monocropping, sorghum rotation significantly increases the diversity and rhizosphere infection rate of AMF, especially in the composite system of sorghum-leguminous-wheat (Sun et al., 2024). AMF can inhibit the colonization and expansion of pathogenic fungi in the rhizosphere by competing for rhizosphere space, changing the secretion of root allelopathic substances, and activating plant resistance genes (Carrión et al., 2019). A field experiment showed that under corn-sorghum-soybean rotation, the AMF inoculation rate increased by an average of 12.3%, while the incidence of Fusarium root rot decreased by nearly 40% (Zhou et al., 2023). More importantly, AMF has an indirect regulatory effect on soil microbial communities. Its mycelial excretions and extracellular enzymes promote the mineralization of organic matter, accelerate the turnover of nutrients, and enhance the competitiveness of coexisting bacteria, thus constructing a rhizosphere ecosystem dominated by beneficial organisms (Li et al., 2024). This also makes sorghum rotation not only conducive to nutrient absorption and crop growth, but also invisibly establishes an ecological defense line of "using bacteria to treat bacteria". 4 The Regulatory Effect of Sorghum Rotation on Typical Diseases 4.1 The mechanism of rotation mitigation of continuous cropping diseases Long-term continuous cropping of sorghum is prone to the accumulation of continuous cropping diseases, such as stem base rot, root rot, anthracnose, etc. These diseases are often caused by soil-borne pathogens, which have strong survival ability and high host specificity, and are one of the main causes of continuous cropping obstacles (Little et al., 2023). Studies have shown that the implementation of a rotation system can effectively break the life cycle of pathogens, reduce the base number of pathogens in the soil, and thus alleviate the occurrence of continuous cropping diseases (Zhou et al., 2023). In a long-term positioning experiment in Kansas, USA, compared with sorghum monoculture, sorghum-leguminous rotation significantly reduced the incidence of stem base rot, and the diseased plant rate of sorghum in the second season decreased by about 35%, and the root system was well developed, and the yield increased by nearly 12% (Schlegel et al., 2017). The mechanism mainly includes two aspects: first, crop rotation interrupts the host supply chain of pathogens, causing the pathogens to gradually decline in a host-free state; second, the root secretions of the previous crop improve the soil microecology, promote the growth of antagonistic microorganisms, and thus inhibit the spread of pathogens (Sun et al., 2024). In addition, the physical and chemical properties of the soil are also optimized under crop rotation conditions. For example, sorghum straw is rich in cellulose and lignin, which can be used as an organic carbon source to regulate the structure of soil microbial communities (Li et al., 2024). Studies have found that after crop rotation, the soil pH tends to be neutral and the nitrate nitrogen content decreases, which is conducive to limiting the reproduction of Fusarium pathogenic fungi (Carrión et al., 2019). These factors work together to build a long-term inhibitory effect on continuous cropping diseases. 4.2 Response of crop rotation to specific pathogens (such as root rot and stem base rot) There are significant differences in the response of different pathogens to crop rotation, which is closely related to their biological characteristics and ecological adaptability. For sorghum, root rot and stem base rot are two representative soil-borne diseases, and their main pathogens are Macrophomina phaseolina and Fusarium spp. (Little et al., 2023). For Fusarium stem base rot, the study found that rotation with legumes is the best. In a sorghum-soybean rotation experiment in Oklahoma, the incidence of sorghum stem base rot in the rotation plots was only 52% of that in the
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