Molecular Microbiology Research, 2025, Vol.15, No.1, 28-36 http://microbescipublisher.com/index.php/mmr 31 the damage caused by pathogens. These molecules do not work alone, they will work with other signaling pathways to enhance the overall defense of sweet potatoes. 4.4 Synergistic and antagonistic interactions between different pathways These signal pathways used by sweet potato will affect each other, sometimes in collaboration, and sometimes in “fighting”. Among them, the relationship between salicylic acid (SA) and jasmonic acid (JA) pathways is the most obvious. Sometimes they cooperate to enhance the plant’s defensive response; but in some cases, they may also inhibit each other, depending mainly on which pathogen and the environmental conditions at that time (Sung et al., 2023). In addition, in the JA pathway, the interaction between the two proteins IbBBX24 and IbJAZ10 also illustrates how transcription factors are involved in regulating these signaling pathways. This regulation can help plants better allocate “resources” and thus fight pathogens more effectively. Understanding the synergistic and antagonistic relationship between these signaling pathways will be very helpful in improving sweet potato disease resistance in the future. 5 Secondary Metabolites in Sweet Potato Disease Resistance and Their Mechanisms 5.1 Antimicrobial activity of phenolic compounds Sweet potatoes have some natural compounds called phenolic substances, such as caffeic acid and chlorogenic acid. They have been found in the leaves of sweet potatoes and have inhibitory effects on many bacteria (Sultana et al., 2024). These phenolic substances can destroy bacteria's cell walls and interfere with their metabolic activities. This makes it more difficult for pathogens to grow in plants and the chance of infection will decrease. In addition, these substances can make the cell walls of plants thicker and stronger, just like adding "armor", so bacteria will not easily invade. 5.2 Antiviral properties of flavonoids Flavonoids are another natural substance commonly found in sweet potatoes. They are also very powerful, especially in dealing with viruses. Flavonoids like quercetin have been shown to reduce the replication and transmission of viruses in plants (Abdelkhalek et al., 2020). These compounds can also activate a mechanism called "systematic acquired resistance" (SAR), which can increase the overall immunity of plants and strengthen the defense of viruses. In addition, flavonoids also regulate some genes related to phenylagen metabolism. This regulatory effect can also help plants better respond to viral infections (Yogendra and Kushalappa, 2016). 5.3 Lignin accumulation and pathogen barrier formation Lignin is a very important substance in preventing diseases in sweet potatoes. It can "reinforce" the cell wall when pathogens first invade, blocking them like a "wall". Initially, when the bacteria first contacted sweet potato cells, sweet potato activates the styrene pathway. This path allows sweet potatoes to synthesize precursors of lignin, such as phenylalanine and cinnamic acid. Then, these precursors will aggregate in the cell wall and become a hard lignin layer, preventing the bacteria from spreading. This lignin barrier can temporarily limit the spread of bacteria. But if the pathogen is strong, or the sweet potato itself is not resistant enough, it may eventually be broken. At this time, sweet potato cells may choose to "self-sacrifice" - initiate programmed death and prevent further spread of bacteria (Figure 1) (Qiao et al., 2023). Lignin not only plays a role as a "retaining wall", but also releases some antibacterial substances. These compounds can directly inhibit the growth of bacteria and stimulate surrounding cells to strengthen defense. In general, the formation of lignin is a very important part of sweet potato’s own defense system. Plants can determine the amount of lignin by controlling styrene metabolism, thereby responding to bacteria at different stages. However, this defense method is not omnipotent. If the infection takes too long or the pathogen is too strong, the lignin barrier may also fail. Therefore, when planting sweet potatoes, you can choose varieties with high lignin content, or use external methods to activate the lignin synthesis pathway, which can help improve overall disease resistance. 6 Sweet Potato Breeding Strategies and Gene Editing Technologies for Disease Resistance 6.1 Traditional breeding methods and selection of resistant varieties The traditional sweet potato breeding method mainly relies on selection and matching. In other words, first find
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