Molecular Pathogens, 2025, Vol.16, No.1, 27-35 http://microbescipublisher.com/index.php/mp 29 3.2.3 Diversity of resistance proteins and their roles in different sweet potato varieties Different sweet potato varieties have different resistance to viruses. This is mainly because their resistant proteins are not exactly the same. The gene expression of the species Tio Joe is relatively stable, so it can better combat the co-infection of SPCSV and SPPV. On the contrary, the Melinda variety is susceptible to infection because of its gene expression problematic and its defense response is relatively weak (Figure 1) (Kiemo et al., 2024). This shows that in disease-resistant breeding, it is very important to select varieties that are highly resistant in themselves (Musa et al., 2022). Figure 1 Virus symptoms in the sweet potato pakakuy virus (SPPV) and sweet potato chlorotic stunt virus (SPCSV) coinfected plants (Adopted from Kiemo et al., 2024) Image caption: The inoculum source was stunted, with distorted leaves, vein clearing, chlorosis, and rugosity symptoms 9 weeks after planting (a). Melinda exhibited vein clearing and downward leaf curling in the top mature leaf 8 wpi (b). Tio Joe developed mild chlorosis and adaxial swelling in the top mature leaf 12 weeks postinoculation (wpi). The necrotic lesions in Tio Joe were caused by mechanical damage (c) (Adopted from Kiemo et al., 2024) 3.3 Gene networks involved in systemic resistance to viral pathogens Plants’ disease resistance does not depend on one or two genes, but on many genes working together. These genes are like a network, cooperating with each other to form a defense system. In this system, the salicylic acid (SA) signaling pathway is particularly important. It can enable immune responses in various parts of the plant together, and it can also prevent the virus from continuing to spread (Lukan et al., 2020; Zhang et al., 2024a). In addition to the SA pathway, some defense genes will also be activated. For example, PR proteins, such proteins will be produced in large quantities when plants are attacked, which can help plants enhance their overall resistance. Studies have found that they perform very effectively in fighting potato Y virus (Yarullina et al., 2024). Overall, these genes and signal paths work together to not only control the spread of viruses, but also protect the plant's own genetic information from being destroyed by viruses (Kiemo et al., 2024). 4 Mechanisms of Resistance Against Fungal Pathogens 4.1 Production of antimicrobial compounds and phytoalexins To deal with fungi, sweet potatoes can make some antibacterial compounds themselves. One of them is called "scopoletin", which is a natural ingredient that can inhibit the growth of Fusarium oxysporum. Fusarium oxysporumis a very common fungus on sweet potatoes that can cause blight. The synthesis process of scopoletin requires several specific genes, such as IbF6’H2 and IbCOSY. The existence of these genes is very important for the synthesis of this substance and can also help sweet potatoes to better resist diseases (Wang et al., 2024). In addition, there is an endophytic bacteria called YTB1407, which belongs to Bacillus amyloidus. It can secrete some antifungal metabolites, which can work when the fungus is first infected, slowing down the disease and thus enhancing the resistance of sweet potatoes (Wu et al., 2024). 4.2 Signal transduction pathways in fungal resistance When sweet potatoes fight against fungi, they not only rely on the substance itself, but also start a series of signal transmission processes. Salicylic acid (SA) is a critical signaling molecule that can help sweet potatoes increase
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