Molecular Pathogens, 2025, Vol.16, No.3, 87-99 http://microbescipublisher.com/index.php/mp 94 During fallow seasons, soil disinfection can help. For example, covering the field with plastic in hot summer months or flooding the field with hot water can kill fungi left in the soil. Another key point is keeping the field and storage clean. Roots should be handled carefully at harvest to avoid cuts, as wounds are the main entry for Fusarium. Use sharp tools and avoid rough handling. If roots are damaged, curing is helpful: keep the roots at 30 °C with 85%~90% humidity for 7~10 days so wounds can heal. Good curing helps reduce root rot during storage (Lee et al., 2019). In storage, the temperature should stay between 13 °C~16 °C with good air flow. Rotting roots should be removed regularly to stop disease from spreading. For fields or storage with disease, all sick plant parts should be removed, and the area should be disinfected. After harvest, till the soil deeply so leftover disease parts are exposed to sun and air. In storage, sulfur fumigation or lime water can be used to kill leftover fungi. Lastly, balanced fertilization is important. Potassium and phosphorus help roots grow strong and resist disease, but too much nitrogen can cause weak growth and make plants easy to infect. 5.3 Biological control and soil improvement 5.3.1 Use of beneficial microbes Using good microbes to fight root rot is a popular eco-friendly method. Some helpful microbes can stop Fusarium by competing for food, making antifungal compounds, or helping the plant’s own defense. On sweet potato, some fungi, bacteria, and actinomycetes (like Streptomyces) have shown good results. For example, Paul et al. (2021) found a Trichoderma strain from rotting sweet potatoes that could stop F. oxysporum and F. solani in lab tests. When used on wounded roots, this microbe reduced root rot during storage. Another good microbe is Bacillus, which lives inside plants. Wang et al. (2020) reported a Bacillus amyloliquefaciens strain that made useful chemicals and cut root rot rates by about 50% in greenhouse tests. Similarly, Pantoea dispersa also helped reduce sweet potato rot in tests by Jiang et al. (2019). Actinomycetes, which produce natural antibiotics, are also useful. Some of these microbes can be made into liquid forms and poured around the roots during growth. Sometimes, combining fungi and bacteria works even better, because they use different ways to stop disease. But these microbes don’t always work the same in the field due to weather or soil conditions. In the future, better strains and better ways to apply them are needed to make this method more stable and effective. 5.3.2 Effects of soil conditioners Improving the soil can also help stop root rot. There are several ways: physical, chemical, and organic. First is physical disinfection. Heating wet soil using clear plastic in hot summer can raise the temperature above 50 °C, killing many fungi like Fusarium. This method is good for fields with repeated disease problems. Second is chemical disinfection. For example, Yang et al. (2023) studied a natural oil from perilla plant called perillaldehyde. When used as a fumigant, it stopped F. solani spores from growing. This chemical damages the fungus cells and helps prevent rot during storage. Because it’s plant-based, it’s safer and can be used for food crops. Third is organic improvement. Jaiswal’s study showed that bamboo biochar added to tomato soil increased good fungi like Streptomyces, which helped reduce disease. Similar effects were found in sweet potato soil-biochar reduced root rot and helped recover yields. Some mineral soil treatments like lime nitrogen or superphosphate can also help by changing soil microbes and chemistry. The best results come from combining treatments depending on the soil. For example, in acidic, poor soils, adding both lime and compost can raise pH and improve organic matter. In heavy clay soils, adding sand or rice husk charcoal can help with air and water flow. These actions support healthy roots and are an important part of the whole disease control plan. 6 Case Studies of Sweet Potato Root Rot Disease 6.1 Regional disease patterns and causes Sweet potato root rot happens in most major sweet potato growing areas around the world. However, how serious it is and what causes it can vary by region. This is mainly because of different climates, farming methods, and the
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