Molecular Microbiology Research, 2025, Vol.15, No.1, 28-36 http://microbescipublisher.com/index.php/mmr 29 Among them, F. solani causes root rot, while C. fimbriata causes black rot. These bacteria usually enter from the roots, causing decay, weakening the plant and reducing yield. Studies have found that a probiotic called Bacillus amyloliquefaciens YTB1407 can enhance the disease resistance of sweet potatoes. It activates a defense pathway that relies on salicylic acid (SA) while allowing disease-resistant genes like PR-1 and NPR1 to start working. This bacteria can also reduce hydrogen peroxide levels in plants, thereby alleviating early infections (Wang et al., 2020). In addition, there is a plant compound called Scopoletin, which can also inhibit the growth of Fusarium oxysporum and help plants resist this fungus (Wang et al., 2024). 2.2 Bacterial pathogens (e.g., Ralstonia solanacearum, bacterial wilt) Ralstonia solanacearum is a bacteria that causes bacterial blight from sweet potatoes. This disease will spread rapidly, causing the entire plant to die in severe cases. This bacteria will enter the vascular tissue of the plant, destroying the transportation system, causing the plant to lose water and wilt. Sweet potatoes themselves try to defend, such as activate genes related to cell wall thickening and chitin reactions, and mobilize phenylapropane metabolism and glutathione metabolism pathways to help defend. These pathways can help plants synthesize antibacterial substances and inhibit bacterial growth (Jose et al., 2023). 2.3 Viral pathogens (e.g., Sweet potato virus disease, SPVD) Sweet potato virus disease (SPVD) is caused by a combination of multiple viral infections, mainly including SPFMV (sweet potato feathery mottle virus) and SPCSV (sweet potato chlorotic stunt virus). These viruses work together to make sweet potatoes produce severely. These viruses affect the plant’s defense system and “manipulate” the plant’s cellular activities to help themselves replicate and spread (Lin et al., 2017). Although there is not much knowledge about how sweet potatoes resist this type of virus, plants usually defend through the "RNA silencing" path and the creation of antiviral proteins. 2.4 Pathogen infection processes and pathways in sweet potato The process of pathogen infection with sweet potatoes is usually complicated. Fungi such as Fusarium oxysporum and Ceratocystis fimbriata destroy the tissues of plants, breaking down cell walls, and causing cell necrosis. To defend against sweet potatoes, they will activate two signaling pathways, "jasmonic acid" (JA) and "salicylic acid" (SA) to regulate the expression of disease-resistant genes (Lin et al., 2017; Zhang et al., 2020). Bacterial pathogens like Ralstonia solanacearum will enter the plant's conduction system, causing the entire plant to wilt. Sweet potatoes at this time strengthen the cell wall and create some antibacterial substances to fight bacteria (Wu et al., 2024). Viruses are more cunning. They will control the function of plant cells, help them reproduce, and find ways to turn off the immune response of plants. Overall, sweet potatoes will protect themselves in many ways, including natural defenses and defensive responses that are activated only after being infected. 3 Molecular and Genetic Basis of Sweet Potato Disease Resistance 3.1 Plant pathogen recognition systems (PTI and ETI) Sweet potato has its own "defense system" to identify and resist various pathogens. There are two main ways of this system, one is called PTI (PAMP triggered immunity) and the other is called ETI (effector triggered immunity). PTI is a plant that recognizes some "general signals" (called PAMPs) on the surface of pathogens to initiate a defense response. These signals are recognized by a receptor called PRR, which then triggers a widespread immune response. ETI is more like a "precision strike". It relies on R proteins in plants to identify specific “effectors” secreted by pathogens. Most R proteins belong to the NBS-LRR type, with nucleotide binding regions and repeated leucine regions in the structure. Once these two systems are activated, they will then activate some signal chains in the cell, such as the MAPK signaling pathway. These signal chains are particularly important in combating early stages of disease (Qiao et al., 2023). 3.2 Core genes involved in disease resistance (e.g., R Genes, NBS-LRR gene family) The R gene and NBS-LRR gene are key to sweet potatoes’ resistance to disease. They encode proteins that recognize the effectors of the pathogen and then activate the defense mechanism. Some studies have found that some receptor proteins containing leucine repeat structures are useful for sweet potatoes against stem nematode
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