Molecular Microbiology Research, 2025, Vol.15, No.1, 28-36 http://microbescipublisher.com/index.php/mmr 32 some varieties that are more resistant to diseases, and then cross them, and try to pass on the "good genes". Breeders generally judge whether they are resistant to diseases based on the external manifestations of the plants, that is, the "phenotype". Some varieties are born with stronger performance, such as "Zhenghong 22". It can quickly initiate certain metabolic paths when facing stem nematodes, so it is considered a good disease-resistant material (Huang, 2024). There is also a sweet potato variety called "Jinshan 57", which has a strong response to blight, which also shows that it has good defense capabilities. These examples illustrate that traditional methods, although time-consuming, are effective in finding disease-resistant varieties (Lin et al., 2017). Figure 1 Phenotypic changes in the two cultivars after infection with stem nematode. (A) Phenotype of control samples of resistant variety Zhenghong 22. (B) Phenotype at 10 dpi of Zhenghong 22. (C) Phenotype at 30 dpi of Zhenghong 22. (D) Phenotype of control samples of sensitive variety Longshu 9. (E) Phenotype at 10 dpi of Longshu 9. (F) Phenotype at 30 dpi of Longshu 9 (Adopted from Qiao et al., 2023) 6.2 Application of marker-assisted selection (MAS) in disease resistance breeding Marker-assisted selection (MAS) is a relatively new breeding technology. It does not rely on "seeing", but uses molecular markers to determine whether the plant has a disease-resistant gene. This method is much faster than traditional breeding. As long as you find a gene or fragment related to resistance, you can directly select a plant with this characteristic, which greatly saves breeding time. For example, scientists discovered some key genes and defense pathways related to Fusarium oxysporum through transcriptome analysis. These contents can be used as the goal of MAS to help improve the disease resistance of sweet potatoes (Fofana et al., 2020). Now there are still people who put together data from the transcriptome and metabolomic group to analyze. It was found that some genes related to the jasmonic acid pathway may also play an important role in disease resistance, and these can also be used for subsequent breeding (Zhang et al., 2020). 6.3 Transgenic technology and introduction of foreign resistance genes The idea of genetically modified technology is more direct: add some "disease resistance genes" that sweet potatoes originally did not have to help it better deal with various diseases and pests. For example, the researchers asked sweet potato to express an additional gene called IbBBX24. This gene can regulate the jasmonic acid pathway, and as a result, sweet potatoes have increased resistance to Fusarium wilt (Bezrutczyk et al., 2018). This shows that it is a promising goal. There is also a gene called IbMIPS1 that is also very interesting. It not only increases the resistance of sweet potatoes to stem nematodes, but also enhances its adaptability to some abiotic stresses such as drought or salt damage (Zhai et al., 2016). These examples show that although the technical threshold of genetically modified methods is high, they can indeed help us quickly obtain stronger disease-resistant varieties.
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