Molecular Pathogens, 2025, Vol.16, No.6, 276-284 http://microbescipublisher.com/index.php/mp 280 5.3 Roles of metabolites and secondary metabolic regulation in disease resistance Once the metabolic aspects are analyzed, the differences between resistant and sensitive varieties become clearer. Substances like anthocyanins accumulate in particularly large quantities in disease-resistant strains, and they can also maintain the stability of lysophospholipids - which is quite crucial for maintaining cell structure and signal transmission. On the other hand, metabolic pathways such as phenylpropanin and flavonoids, which are involved in strengthening cell walls and antibacterial responses, will also become active (Sun et al., 2021; Wang et al., 2025). But these metabolites are not the result of plants "fighting alone". More and more evidence shows that there is mutual influence between their generation and the rhizosphere microbial community. It may be this "joint operation" that enables plants to be more resilient against pathogenic bacteria (Wang et al., 2024). 6 Case Studies: Field-Based Evidence of Pathogenic Communities and Resistance in Salinized Areas 6.1 Epidemiological survey and pathogen community characteristics in salinized regions of Northeast China In the salinized fields of Northeast China, the prevalence of root rot is not solely determined by the number of pathogenic bacteria. The variable of soil salinity is often the "behind-the-scenes driver" that influences the direction of the situation. With the increase of salinity, some salt-tolerant bacterial communities, such as Firmicutes and Bacteroides, will prevail in the microbial community, while the overall diversity tends to decline instead (Rath et al., 2018; Hou et al., 2021). This change in the structure of the microbiota is very likely to have a chain reaction on the incidence rate of corn root rot, the types of pathogenic bacteria, and even the outbreak timing. It is worth noting that those rare bacterial species with small numbers but "active" behaviors sometimes participate in the transmission of antibiotic resistance genes (ARGs), and this phenomenon may be a variable that cannot be ignored in the dynamic evolution of pathogenic bacteria (Guo et al., 2025). 6.2 Rhizosphere microbial community analysis and disease patterns in saline–alkali coastal soils of Shandong If the problems of the saline-alkali land in Northeast China mainly lie in the imbalance of flora, then the saline-alkali land along the coast of Shandong presents a different ecological picture. The rhizosphere microorganisms here are not only diverse in species, but also have significantly higher enzyme activities than those in inland non-saline land. However, the composition of these communities is greatly influenced by salinity, especially fungi, which are often more "sensitive" to salt than bacteria. Some beneficial microorganisms appear more frequently at higher salinity - for example, those bacteria that can inhibit diseases and promote growth, and their relative abundance shows a positive correlation with salinity (Hou et al., 2021). This might explain why in such fields, the occurrence of corn root rot is not always so severe, as if there is a set of "natural microecological defense lines" at work. 6.3 Comparative analysis of resistant maize varieties and pathogen responses in salinized farmlands of Xinjiang The situation is a bit different in Xinjiang. In some farmlands with severe salinization, some corn varieties have demonstrated relatively prominent resistance, and the "assist" behind this seems to be the microbial community beneath their feet. In the rhizosphere microbiota of disease-resistant varieties, it is often observed that bacteria with strong salt tolerance and diverse functions account for a relatively high proportion. On the one hand, these microorganisms help plants obtain nutrients better; on the other hand, they may also play a role in inhibiting pathogenic bacteria (Hou et al., 2021). The reduction of diseases is very likely related to them. Unlike in Northeast China or Shandong, the relationship between the genotypes of plants themselves and the root microenvironment here is closer, forming a more "troublesome" system against pathogenic bacteria (Rath et al., 2018). These observations remind us that when managing corn diseases in salinized areas, merely looking at pathogenic bacteria may be far from enough. Taking the microbial ecosystem into account might be a more effective approach (Figure 2).
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