Molecular Pathogens 2025, Vol.16 http://microbescipublisher.com/index.php/mp © 2025 MicroSci Publisher, an online publishing platform of Sophia Publishing Group. All Rights Reserved. Sophia Publishing Group (SPG), founded in British Columbia of Canada, is a multilingual publisher.
Molecular Pathogens 2025, Vol.16 http://microbescipublisher.com/index.php/mp © 2025 MicroSci Publisher, an online publishing platform of Sophia Publishing Group. All Rights Reserved. Sophia Publishing Group (SPG), founded in British Columbia of Canada, is a multilingual publisher. Publisher MicroSci Publisher Edited by Editorial Team of Molecular Pathogens Email: edit@mp.microbescipublisher.com Website: http://microbescipublisher.com/index.php/mp Address: 11388 Stevenston Hwy, PO Box 96016, Richmond, V7A 5J5, British Columbia Canada Molecular Pathogens (ISSN 1925-1998) is an open access, peer reviewed journal published online by MicroSciPublisher. The journal is committed to publishing and disseminating all the latest and outstanding research articles, letters and reviews in all areas of molecular pathogens. The range of topics including isolation and identification of emerging pathogens viruses, pathogen-host interactions, genetics and evolution, genomics and gene regulation, proteomics and signal transduction, glycomics and signal recognition, virulence factors and vaccine design and other topical advisory subjects. All the articles published in Molecular Pathogens are Open Access, and are distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. MicroSci Publisher uses CrossCheck service to identify academic plagiarism through the world’s leading plagiarism prevention tool, iParadigms, and to protect the original authors’ copyrights. MicroSci Publisher is an international Open Access publisher specializing in microbiology, bacteriology, mycology, molecular and cellular biology and virology registered at the publishing platform that is operated by Sophia Publishing Group (SPG), founded in British Columbia of Canada.
Molecular Pathogens (online), 2025, Vol. 16, No. 3 ISSN 1925-1998 http://microbescipublisher.com/index.php/mp © 2025 MicroSci Publisher, an online publishing platform of Sophia Publishing Group. All Rights Reserved. Sophia Publishing Group (SPG), founded in British Columbia of Canada, is a multilingual publisher. Latest Content Study on the Occurrence Pattern and Field Management of Sweet Potato Root Rot Xing Zhao, Kaiwen Liang Molecular Pathogens, 2025, Vol. 16, No. 3, 87-99 Effect of Sorghum Crop Rotation Patterns on Reducing Pest and Disease Pressure Yeping Han, Weichang Wu Molecular Pathogens, 2025, Vol. 16, No. 3, 100-110 Disease Prevention Effect of Crop Rotation between Solanaceous Crops and Non-host Plants Ziyi Dong, Chuchu Liu Molecular Pathogens, 2025, Vol. 16, No. 3, 111-120 Investigation of the Co-occurrence Patterns of Major Diseases in Rapeseed Fields Xiuhua Liu, Qikun Huang Molecular Pathogens, 2025, Vol. 16, No. 3, 121-133 Integrated Green Control Strategies for Peak Incidence Periods of Sugarcane Pests and Diseases Chunyang Zhan , Shusheng Liu Molecular Pathogens, 2025, Vol. 16, No. 3, 134-146
Molecular Pathogens, 2025, Vol.16, No.3, 87-99 http://microbescipublisher.com/index.php/mp 87 Research Insight Open Access Study on the Occurrence Pattern and Field Management of Sweet Potato Root Rot Xing Zhao 1, Kaiwen Liang 2 1 Tropical Microbial Resources Research Center, Hainan Institute of Tropical Agricultural Resources, Sanya, 572025, Hainan, China 2 Agri-Products Application Center, Hainan Institute of Tropical Agricultural Resouces, Sanya, 572025, Hainan, China Corresponding email: kaiwen.liang@hitar.org Molecular Pathogens, 2025, Vol.16, No.3 doi: 10.5376/mp.2025.16.0011 Received: 20 Mar., 2025 Accepted: 26 Apr., 2025 Published: 12 May, 2025 Copyright © 2025 Zhao and Liang, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Zhao X., and Liang K.W., 2025, Study on the occurrence pattern and field management of sweet potato root rot, Molecular Pathogens, 16(3): 87-99 (doi: 10.5376/mp.2025.16.0011) Abstract Sweet potato (Ipomoea batatas) is an important food and economic crop, but root rot disease-widespread during cultivation and storage-poses a serious threat to its yield and quality. The disease is mainly caused by soil-borne fungal infections, with Fusarium species, particularly Fusarium oxysporum and F. solani, being the most common pathogens. These fungi cause root decay in both field and storage conditions, often resulting in 10%~20% yield loss. This review summarizes the pathogen types and biological characteristics, disease development patterns and influencing factors, symptom identification and diagnostic techniques, as well as current integrated field control strategies and case studies. Based on a review of recent domestic and international studies, we found that the occurrence of sweet potato root rot is closely related to environmental conditions, varietal resistance, and soil physicochemical properties. Continuous monoculture reduces beneficial microbes and leads to pathogen buildup, increasing disease pressure. To effectively manage this complex disease, integrated green control strategies-including the use of resistant seed roots, improved cultivation practices, crop rotation and fallow periods, biocontrol agents, and soil improvement-are essential. This review provides a scientific basis for field management of sweet potato root rot and proposes future research directions in resistance breeding, soil health, and interdisciplinary collaboration to support the sustainable development of sweet potato production. Keywords Sweet potato; Root rot; Fusarium; Disease development; Biological control; Green management 1 Introduction Sweet potato (Ipomoea batatas) is an important food and cash crop with a wide range of cultivation areas around the world. It plays an irreplaceable role in ensuring food security and providing industrial raw materials. According to the Food and Agriculture Organization of the United Nations, the global sweet potato production in 2021 was about 88.9 million tons, of which China's production accounted for about 55%-58% of the world's total, maintaining the first place in the world (Zhang et al., 2021). Sweet potato is highly adaptable, high-yielding and nutritious. It is rich in carbohydrates, dietary fiber and multiple vitamins and minerals. It is known as a "health crop" and a relief food for developing countries (Ray and Ravi, 2021). However, sweet potato production still faces many limiting factors, among which pests and diseases are one of the key obstacles to the stable and high yield of sweet potato. Sweet potato root rot is a common fungal disease in the main sweet potato producing areas around the world. It is a rot disease caused by pathogens in the soil infecting sweet potato tubers or plant roots. The disease can occur during the sweet potato growing season and storage period, among which tuber rot during storage is particularly common and serious (Paul et al., 2021; Kim et al., 2022). Root rot often lurks in wounds after harvest, and gradually expands to form lesions during storage, causing dry rot, hollows, or even complete rot of the tubers, resulting in serious storage losses (Scruggs and Quesada-Ocampo, 2016; Yang et al., 2021). Studies have shown that root rot develops fastest under high temperature and high humidity conditions (Lee et al., 2023). For example, in a storage environment of 23 °C~29 °C and relative humidity >90%, the decay process of sweet potato root rot is significantly accelerated (Paul et al., 2021). The prevalence of this disease will directly reduce the supply of commercial potatoes and reduce the quality of sweet potatoes.
Molecular Pathogens, 2025, Vol.16, No.3, 87-99 http://microbescipublisher.com/index.php/mp 88 In recent years, a lot of research has been conducted at home and abroad on the occurrence and prevention of sweet potato root rot, and some progress has been made. On the one hand, plant pathologists have identified the main pathogenic bacteria that cause sweet potato root rot, and elucidated their morphological and molecular characteristics, providing a basis for disease diagnosis and disease-resistant variety breeding (Paul et al., 2020; Kim et al., 2023). On the other hand, field experiments and laboratory studies have explored the influence of environmental conditions, cultivation methods, soil microecology and other factors on the occurrence of root rot (Imperiali et al., 2017; Gao et al., 2019). In terms of prevention and control, traditional chemical treatments are limited by cost and residue issues. In recent years, more attention has been paid to controlling the spread of root rot through comprehensive measures such as healthy seedlings, crop rotation and fallow, biological antagonists and soil improvement (De Mello et al., 2021). Despite this, the current understanding of sweet potato root rot is still incomplete. For example, the role of complex infection of different pathogens, the long-term impact of continuous planting on rhizosphere microbial communities, and the field applicability of new prevention and control technologies still need to be further studied. To this end, this article intends to summarize the pathogen types and biological characteristics, disease patterns and influencing factors, symptom manifestations and diagnostic techniques of sweet potato root rot, as well as comprehensive prevention and control strategies and typical case experiences based on a review of relevant literature in the past five years, analyze the difficulties faced by current prevention and control, and look forward to the future research direction of integrating green prevention and control technology and multidisciplinary collaboration. It is hoped that this review can provide valuable reference for the scientific prevention and control of sweet potato root rot and disease-resistant breeding. 2 Disease Pathogens and Classification Characteristics 2.1 Identification of main pathogenic fungi Sweet potato root rot is usually caused by a variety of soil-borne fungi, among which Fusarium species are the most common and important (De Mello et al., 2021; Paul et al., 2021). Studies have shown that the pathogens of sweet potato root rot in different regions are mainly combined infections of Fusarium oxysporum f. sp. batatas and Fusarium solani: in a survey in North America, F. solani accounted for about 43% of the strains isolated and F. oxysporum accounted for 39% (Scruggs and Quesada-Ocampo, 2016), and similar proportions were found in Asian cases (Kim et al., 2022). F. oxysporum can cause dry rot and wilting of sweet potato tubers and seedlings, and is the culprit of sweet potato wilt and surface dry rot during storage (Paul et al., 2020); F. solani often invades through root wounds, causing sweet potato root dry rot, and the lesions often show obvious concentric ring patterns (Scruggs and Quesada-Ocampo, 2016). In addition to Fusarium, sweet potato tubers are also susceptible to other fungal infections in the field and during storage, causing similar rot symptoms. For example, sweet potato black rot is caused by Ceratocystis fimbriata, which can form black rot spots on the surface of the tubers (Jiang et al., 2019; Wang et al., 2020); Java black rot caused by Monilochaetes infuscans occurs frequently in tropical regions, with symptoms of dark brown necrosis of the potato skin (De Mello et al., 2021). In recent years, studies have also found some cases of infection of sweet potato tubers by unconventional pathogens: Yang et al. (2021) reported that a fungus commonly used as a Biocontrol fungus, Trichoderma asperellum, caused green mold rot of tubers in sweet potato storage in Guangdong, China, which is a new fungal pathogenic variant. This discovery suggests that the pathogenic bacteria of sweet potato root rot may be more complex and diverse than traditionally recognized, and continuous monitoring and identification work is needed. 2.2 Morphological and molecular biological characteristics of pathogens The pathogens of sweet potato root rot have certain morphological characteristics that facilitate routine laboratory isolation and identification. For example, Fusarium oxysporum forms sparse white fuzzy hyphae on the culture medium, produces a large number of small non-septate spores (elliptical to oval), and sickle-shaped multi-septate macroconidia, with the terminal cells often extending tail-like processes. F. solani colonies are mostly cinnamon
Molecular Pathogens, 2025, Vol.16, No.3, 87-99 http://microbescipublisher.com/index.php/mp 89 to light brown velvety, and the conidia are slightly thicker and shorter, usually with 3~5 septa, and less curved than F. oxysporum (Scruggs and Quesada-Ocampo, 2016). The study by Paul et al. (2021) showed the typical lesions of sweet potatoes during storage and the culture characteristics of their corresponding pathogens, such as dry rot symptoms caused by F. oxysporum, black rot caused by salicylic acid precursor infection, and mold layer morphology caused by other fungal infections (Figure 1) (Paul et al., 2020; De Mello et al., 2021). It can be seen that the color and structure of the colonies on the culture medium are unique, providing a morphological intuitive reference for experimental identification. Figure 1 Symptoms of sweet potato postharvest diseases collected from local markets in Korea (Adopted from Paul et al., 2021) Image caption: (A) Fusarium surface rot, (B) charcoal rot, (C) Aspergillus mold, (D) surface rot, (E) end rot, and (F) Penicillium mold. The surface sterilized storage root tissues of Fusarium rot, charcoal rot, and other diseases were placed on potato dextrose agar media containing antibiotics. Examples of fungal colonies grown from the tissues of Fusarium rot (G, H) and charcoal rot (I) are shown (Adopted from Paul et al., 2021) However, due to the subtle morphological differences between different Fusarium species and the fact that sweet potato tubers are often infected by a variety of pathogens, it is difficult to accurately distinguish the composition and dominant species of each pathogen based on morphological characteristics alone. For this reason, modern molecular biological methods have been widely used in the identification and classification of sweet potato root rot pathogens. Paul et al. sequenced and analyzed the ribosomal ITS sequence and elongation factor EF-1α gene of ten strains isolated from sweet potato root rot samples in South Korea, and found that these strains were clustered in a molecular phylogeny and were highly homologous to the standard strain identified as F. oxysporum, thus confirming that these isolates all belonged to Fusarium oxysporum. In addition, serological detection methods have also been applied, such as ELISA detection using polyclonal antibodies against specific Fusarium strains, which can quickly indicate the presence of pathogens (Komada et al., 2021). With the development of genomic and proteomic technologies, progress has also been made in the intraspecific classification and virulence gene analysis of root rot pathogens. For example, genome comparison
Molecular Pathogens, 2025, Vol.16, No.3, 87-99 http://microbescipublisher.com/index.php/mp 90 can distinguish the differences between different specialized types of Fusarium oxysporum (such as the physiological subtypes of sweet potato and tobacco) (Bilgili et al., 2023). 3 Disease Occurrence and Influencing Factors 3.1 Seasonal patterns and environmental conditions Sweet potato root rot is closely linked to environmental conditions. The disease tends to appear more often in warm and humid weather, especially during the summer and autumn growing seasons. High temperatures help the fungi that cause the disease grow and infect the plants. Studies have found that F. solani can live and cause disease in a wide temperature range from 8.5 °C to 34 °C, with the best growth and infection rates around 25 °C~30 °C (Arie, 2019). During hot weather, soil temperature rises, and sweet potato roots become more likely to be infected. Wet soil makes things worse. If it rains for many days, the soil stays too wet and lacks air. This weakens the roots, making it easier for fungi to attack and cause the roots to rot. In drier and better-aerated soil, the disease occurs less often. The weather at harvest time also matters. If sweet potatoes are harvested in cold and wet conditions, their skins may get damaged and not heal well (Lee et al., 2019). This increases the chance of rot during storage. Researchers have shown that wounds made during harvesting are common starting points for infection, especially if the sweet potatoes are not cured properly before storage. Proper storage can help slow down the disease. Keeping sweet potatoes at 13 °C~16 °C and about 85% humidity for curing helps wounds to heal and stops fungi from entering. On the other hand, if stored at 25 °C~30 °C and above 90% humidity, rot can spread fast, with symptoms appearing in 6~8 weeks. 3.2 Variety resistance and cultivation practices Different sweet potato varieties show varying levels of resistance to root rot. Field observations and experiments have shown that some varieties are more resistant than others. For example, a study in Korea tested 21 varieties. One called "Pungwanmi" showed strong resistance to F. oxysporum, while another called "Annobeni" was highly susceptible. Currently, resistance to root rot is considered a complex trait. It is controlled by many genes, not just one. This makes breeding resistant varieties more difficult. Breeders often need to combine different genes and use field screening to find resistant types. Balancing disease resistance with good yield and quality is also important. Some local varieties have high yields but poor resistance, while some wild or landrace varieties resist disease well but don't produce as much (Sugri et al., 2020). So, breeding programs need to find a good middle ground. In recent years, new techniques like genome-wide association studies (GWAS) have helped scientists find specific genes linked to resistance. For example, a Korean study using 96 sweet potato lines found two important genetic markers related to resistance against F. solani. These discoveries can help in developing new resistant varieties using molecular tools. Besides variety resistance, farming practices also affect disease levels. One key step is starting with healthy seed roots or vine cuttings. Both F. oxysporum and F. solani can spread through infected planting material. Before planting, diseased roots or vines should be removed carefully. Studies have found that F. solani can produce many thick-walled spores on infected roots. These spores can stick to vines and spread the disease in the field. That’s why it is best to use cuttings taken at least 2 cm~3 cm above the soil and avoid pulling up vines with soil attached. Crop rotation is another useful method. When sweet potatoes are planted in the same field year after year, disease often gets worse. But rotating with crops like corn or wheat can reduce the risk. Other practices like proper spacing and using raised beds help control the disease by improving air flow and soil drainage (Yan et al., 2022). Research suggests that raised beds can lower the chance of infection by making soil conditions less favorable for the fungi. Fertilization also matters. Using enough potassium helps sweet potato roots stay strong and resist disease. But using too much nitrogen can cause the plants to grow weak vines and become more likely to get infected.
Molecular Pathogens, 2025, Vol.16, No.3, 87-99 http://microbescipublisher.com/index.php/mp 91 3.3 Mechanism of action of soil physical and chemical properties 3.3.1 Regulation of soil pH on pathogen growth and activity Soil pH significantly affects the growth rate and pathogenicity of sweet potato root rot pathogens. Generally speaking, Fusarium fungi grow most vigorously under neutral or slightly acidic conditions (pH 6~7), while their activity decreases in acidic or alkaline environments. Cruz et al. (2019) found in a study on soybean root rot that 14 strains of F. oxysporum grew fastest at pH 6.0~6.3 and 27 °C, while their growth was restricted at pH 4.0 and 8.0 (Figure 2). However, it is worth noting that even at the same pH, the growth rates of different strains are still different. This ecological adaptation differentiation suggests that under continuous cropping or long-term planting conditions, some strains may form dominant groups due to their stronger environmental adaptability, aggravating the severity of the disease. Acidic environment may reduce pathogenicity by inhibiting the activity of pathogen enzymes and limiting spore germination, while neutral environment promotes the action of pathogen cell wall degrading enzymes, making it easier to invade sweet potato tissues. 3.3.2 Organic matter regulation and changes in soil microbial community structure The content of soil organic matter affects the structure and function of microbial communities and is an important ecological factor in regulating sweet potato root rot. High organic matter soils often have higher microbial diversity, especially the increase in the proportion of antagonistic microorganisms (such as Streptomyces, Trichoderma, etc.), which helps to form "disease-suppressive soils", thereby inhibiting the colonization of pathogenic fungi such as Fusarium. In poor soils lacking organic matter, the microbial community structure is single, and harmful bacteria are prone to form dominant populations. Imperiali et al. (2017) 0found in a study of agricultural soils in Switzerland that the higher the level of organic carbon in the soil, the more active the expression of antibacterial metabolic genes in the extracted Pseudomonas, and the incidence of crop root rot was significantly reduced. Similarly, in the soil of sweet potato continuous cropping, the study found that the proportion of pathogenic fungi in healthy soil was low, while the richness of actinomycetes and antagonistic fungi was high, which was conducive to the stability of microecological balance. Even under the same pH conditions, there were obvious growth differences between Fusarium strains, suggesting that microbial diversity under organic matter regulation can not only compete for nutrient resources and produce antimicrobial metabolites, but also limit the expansion of pathogenic communities with strong ecological adaptability by changing the buffering properties of the soil environment (Cruz et al., 2019). 3.3.3 Pathogen accumulation and community succession mechanism driven by continuous cropping obstacles Continuous planting of sweet potatoes for many years is prone to cause continuous cropping obstacles. The core problem is the imbalance of soil ecology, which is manifested as the accumulation of pathogens and the reduction of beneficial bacteria, which in turn aggravates the occurrence of soil-borne diseases such as root rot. Gao et al. (2019) used high-throughput sequencing technology to compare the fungal community structure of soil in one-year and three-year continuous cropping sweet potato fields, and found that the relative abundance of Fusarium in continuous cropping soil was more than double that of new crops. At the same time, although the diversity of the microbial community increased on the surface, the proportion of harmful bacteria increased significantly. During the formation of continuous cropping obstacles, root secretions accumulate in the soil, especially toxic metabolites such as phenolic acids, which may inhibit the growth of beneficial microorganisms, promote the reproduction of pathogens, and aggravate the deterioration of soil microecology. In addition, the different Fusarium strains revealed in Figure 1 still show different growth abilities under similar pH environments, indicating that pathogen groups with stronger adaptability and higher infectivity may be gradually selected under continuous cropping conditions, leading to the "involution" of diseases. Effective strategies to deal with continuous cropping obstacles include rotating with gramineous crops (such as corn and wheat) for 2~3 years to break the life cycle of pathogens and reduce the initial infection source; deep
Molecular Pathogens, 2025, Vol.16, No.3, 87-99 http://microbescipublisher.com/index.php/mp 92 plowing and sun drying, water-dry rotation, and planting biological fumigation crops such as mustard can further remove residual pathogens in the soil. In addition, the application of actinomycete microbial agents or organic matter conditioners can help re-establish antagonistic microecological barriers and reduce the risk of root rot. Figure 2 Radial growth of 14 Fusarium oxysporum isolates with respect to temperature and pH of the growth medium. A, B, C, and D, Isolates growing in citrate/phosphate buffer set at pH 4, 5, 6, and 7, respectively. Data represent the mean values of two experiments with four replicate Petri dishes for each treatment combination. (Adopted from Cruz et al., 2019) 4 Symptoms and Diagnosis Methods 4.1 Differences between aboveground and underground symptoms Sweet potato root rot shows different signs in the parts above and below the ground. These signs are related but look different. Above ground, infected plants usually grow poorly and look weak. The leaves start to wilt, especially the older ones. They turn yellow from the tip or edge, then the whole plant looks droopy. This is most clear at noon during hot days. At night or when it’s wet, the plant may recover a little. This “wilt-recover” cycle happens because the fungus damages the roots, making it hard for water to move up the plant. When water is needed most, the plant can’t keep up and wilts. As the disease gets worse, the plant stops growing, new leaves become small, and vines may show brown spots or sores. In the end, the whole plant may die (Wei et al., 2019). Underground symptoms are easier to see. When digging up sick plants, you may find that the roots are discolored or rotting. If the disease is caused by F. oxysporum, the root may show light brown, water-soaked spots that grow into sunken patches. Cutting open the root shows the damage stays in the outer tissues and rarely reaches the woody center. Often, a dark ring can be seen just under the skin, showing where the root is damaged (Cruz et al., 2019). If F. solani causes the infection, the damage goes deeper. The root surface may have round, ring-like spots that start light brown in the center and get darker toward the edges. This kind of rot often begins at the ends of the root and spreads inward, which is why it’s called “end rot.” Cutting the root shows damage reaching deep inside, sometimes forming hollow or cracked dry areas. The inside turns orange to dark brown and becomes soft and crumbly. White fungal threads may grow in these empty spaces. Over time, most of the root tissue breaks down, leaving behind only the shriveled skin and hard remains-this is called “mummification.”
Molecular Pathogens, 2025, Vol.16, No.3, 87-99 http://microbescipublisher.com/index.php/mp 93 4.2 Traditional and molecular diagnosis methods There are two main ways to diagnose root rot in sweet potatoes: traditional methods and modern molecular methods. Traditional diagnosis looks at the symptoms and tries to grow the fungus from the sick plants. Trained plant doctors can tell from the wilting leaves and root rot whether the plant has root rot, and guess whether it’s caused by F. oxysporum or F. solani (Lee et al., 2019). To confirm, they take a piece of root from the edge between sick and healthy areas, clean it, and put it on a special growing plate. Komada medium is often used for this-it helps grow Fusarium while stopping other fungi. Under a microscope, they check the shape and color of the spores and compare with known types. While these methods work, they are slow and need clean lab conditions. So, many labs now use molecular tools to speed things up. PCR (Polymerase Chain Reaction) is the most common method. It finds small pieces of fungal DNA in just a few hours. Scientists have made special primers that detect F. oxysporum f. sp. batatas (the type that attacks sweet potatoes). There are also PCR kits that can detect several root rot fungi in one go and even measure how much fungal DNA is present in the soil or plant. This helps to estimate how serious the disease risk is (Wei et al., 2019). Besides PCR, antibody-based tests are also used. These use test strips or ELISA kits that react if Fusarium is present in root juice samples. Though mostly used for major crops, they can help identify sweet potato infections too. For complicated samples, DNA sequencing is now used. This method reads all the DNA in the sample, telling us exactly which fungi are present-even rare or unknown ones. This is helpful when the traditional method misses something. In short, traditional and molecular tools work best together. Growing the fungus in a lab is still the gold standard for identifying what it is. But PCR and sequencing make it easier to test many samples quickly. Together, they make diagnosing sweet potato root rot faster and more accurate. 5 Integrated Control Strategies 5.1 Variety selection and breeding Choosing healthy sweet potato roots and growing resistant varieties are basic and long-term ways to control root rot. First, farmers should use only clean, virus-free planting materials. Any root with dark spots or leaking black liquid should not be used. During seedling production, using sterile soil or disinfected nursery beds can help reduce harmful fungi in the soil. When cutting sweet potato vines for planting, it’s better to cut them 2 cm~3 cm above the soil instead of pulling out the whole root, to avoid spreading soil-borne disease. In places with good conditions, water-floating or greenhouse tray methods can be used to grow seedlings and stop Fusarium from spreading through soil (Bodah, 2017). For farmers who keep seeds from their own fields, it's important to check fields often, remove sick plants quickly, and burn or bury them far from the field. This helps stop the disease from returning the next year. Also, breeding and using resistant varieties is a key step. Although no sweet potato variety is completely immune to root rot, many new lines show better resistance. Researchers in several countries have made progress in developing new types that are both productive and more tolerant to disease. In China, some new varieties show much lower infection rates than old ones. With better genetic tools, like marker-assisted selection, it may become faster to breed varieties resistant to root rot. For example, Kim et al. (2023) found new genes linked to F. solani resistance, which could help future breeding efforts. 5.2 Field management and crop rotation Good farming practices are very important to reduce root rot in the field. First, field conditions should be improved to stop the fungus from infecting plants. Sweet potato should be planted in sunny, well-drained sandy soil. Avoid planting in wet lowland areas, which makes it easy for disease to start. Planting on high ridges and using plastic mulch can help keep the plant base dry and reduce disease. Also, sweet potato should not be planted in the same field year after year. Rotating with crops like rice, corn, or soybean for 2~3 years can help reduce harmful fungi in the soil. In fields with serious disease, rotation is the best way to kill Fusarium and bring back healthy soil microbes.
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
Molecular Pathogens, 2025, Vol.16, No.3, 87-99 http://microbescipublisher.com/index.php/mp 95 resistance of local sweet potato varieties. For example, in China and South Korea, where sweet potatoes are mostly grown in warm areas, root rot mainly happens during storage. After harvesting, the roots often rot while being stored. In hot and wet years, the infection rate can go up a lot after three months of storage. In some cases, more than 15% of stored roots are lost (Pan et al., 2023). The main reasons are: the sweet potato types grown here are high-yielding but not very disease-resistant, and farmers often use traditional storage cellars that do not have good air flow or temperature control, which makes it easier for fungi to grow. In contrast, in the southern U.S. states like North Carolina, root rot is a problem both in the field and during storage. The popular variety 'Covington' grows well but is not resistant to disease. Farmers use overhead irrigation, and in hot, wet summers, this makes the stems and roots more likely to get infected by Fusarium fungi. This can lead to large field losses (Zheng et al., 2021). In tropical areas of South America and Africa, soft rot diseases are more common. These are often caused by Rhizopus fungi, and they spread quickly if the sweet potatoes are damaged during harvest or transport. But in these places, people often eat or process the sweet potatoes soon after harvest, so the time in storage is short. As a result, Fusarium dry rot causes less damage overall. Different regions face different disease risks, so they need different control methods. In temperate areas, the focus is on stopping dry rot in storage. In tropical areas, farmers must deal with both dry and soft rot. For example, China and Korea should improve storage and grow more resistant types. The U.S. needs to improve field management. In Africa, simple and cheap methods like treating seed roots with biological products can help. Sharing these experiences between regions can help improve global sweet potato disease control. 6.2 Summary of prevention and control practices and results in high-incidence areas For areas with high incidence of sweet potato root rot, various comprehensive prevention and control measures have been adopted in various places and achieved certain results. Take the case of Shandong Province, the main sweet potato producing area in my country, as an example: the local sweet potato is the dominant variety for fresh consumption. In recent years, root rot has significantly worsened in some long-term continuous cropping plots, which once caused a large number of potatoes to rot during storage. To this end, the local agricultural department has implemented a series of comprehensive control measures, including: adjusting the rotation system, adding one year of fallow or intercropping green manure on the basis of the sweet potato-wheat double-cropping system to interrupt the pathogen cycle; promoting the "well-cellar-style" ventilated storage technology of sweet potatoes, by setting ventilation ducts at the top and bottom of the cellar to achieve air convection cooling and dehumidification, and effectively control storage diseases; distributing and demonstrating the use of biological microbial agents, such as Trichoderma agent mixed with soil in the cellar and biocontrol Bacillus subtilis sprayed on the cellar wall, to reduce the content of pathogens in the storage environment. According to statistics from the local plant protection station, after the pilot demonstration of the above measures, the average incidence of root rot of sweet potatoes in the pilot warehouses during storage has dropped by more than 60%, and the storage loss rate has dropped from the original 20% to less than 8% (INNSPUB, 2025). For example, North Carolina, USA, has achieved good results in the comprehensive application of disease-resistant varieties and chemical control for field root rot. They replaced the original highly susceptible ‘Goldrush’ with the moderately disease-resistant ‘Beauregard’ improved variety, and dipped the seedlings in the agent for preventing and controlling black pox in the seedbed (the main ingredient is azole fungicide) when transplanting the seedlings. As a result, the incidence of root rot and stem blight in the field was significantly reduced, and the yield loss was reduced by about 15%. It can be seen that the successful experience of high-incidence areas lies in the coordinated efforts of multiple measures: such as variety replacement + cleaning seedlings + transformation of storage facilities + combination of biological/chemical control measures. 6.3 Case enlightenment countermeasures and their promotion potential The cases of sweet potato root rot prevention and control in various places provide us with valuable inspiration. First, the concept of integrated prevention and control must be implemented throughout. From the experience of
Molecular Pathogens, 2025, Vol.16, No.3, 87-99 http://microbescipublisher.com/index.php/mp 96 high-incidence areas, no single measure can completely cure root rot. What is truly effective is to integrate disease-resistant varieties, agricultural prevention, biological prevention, chemical prevention and other multi-link means to achieve complementary advantages. This "integrated management" idea is completely consistent with the IPM (Integrated Pest Management) concept of modern plant protection, and is also the development direction of disease management in the future (da Silva and Clark, 2013). Secondly, the regional adaptability and feasibility of plant protection measures are extremely important. Some methods that are effective under experimental conditions are difficult for farmers to adopt in time if the cost is high or the operation is complicated, and the actual promotion value is limited. Although these simple technologies seem to be local methods, they are feasible and sustainable in specific situations and are worth promoting according to local conditions. Thirdly, the disease monitoring and early warning system should be improved. By strengthening disease monitoring in production areas, signs of the prevalence of sweet potato root rot can be discovered in time and countermeasures can be taken early. For example, a root rot disease prediction model based on meteorological and soil data is established. When the epidemic risk is predicted to increase, farmers are reminded to make preparations in advance such as pre-harvest water control and lowering storage temperature and humidity to minimize losses (Zhao et al., 2024). Finally, regional cooperation and technical exchanges are also critical. Diseases have no borders, and each production area should share experiences and jointly respond to challenges. For example, Africa can learn storage management and disease-resistant breeding experience from Asia, and Asia can also refer to the practices of the Americas in precision pesticide application and big data monitoring. In recent years, international agricultural research institutions (such as the CIP International Potato Center) have actively promoted global cooperation in the management of sweet potato pests and diseases, hoping to improve the overall prevention and control level through cross-regional promotion of cases and technologies (Zheng et al., 2021). Looking to the future, as the concept of green plant protection is deeply rooted in the hearts of the people and various new technologies are developed, the regional comprehensive management model of sweet potato root rot will continue to improve and have a broader potential for promotion and application. 7 Outlook and Research Suggestions 7.1 Development trend of technology integration and green control Facing complex soil-borne diseases such as sweet potato root rot, future control will develop in the direction of "technology integration" and "green control". Technology integration requires us to break through the limitations of a single discipline and measures and integrate multiple advanced methods for disease management. For example, by combining remote sensing and big data, we can digitally model and accurately monitor the disease pressure of large areas of sweet potato fields. Once it is found that the soil moisture, temperature and other indicators in a certain area are close to the critical value of the root rot epidemic, farmers can be warned in time through mobile terminals to guide them to take measures such as dehumidification and ventilation. This is a new application of digital agricultural technology in plant protection, which is expected to significantly improve the timeliness and pertinence of control (Zheng et al., 2021). Similarly, modern biotechnology and traditional breeding are also merging, and the cultivation of disease-resistant varieties has entered the molecular design breeding stage. Genomic selection and gene editing (CRISPR-Cas, etc.) will shorten the breeding cycle of sweet potato disease resistance, and new and superior varieties with high resistance to root rot may be bred in the next 5-10 years. In addition, the combination of chemical control and biological control is also one of the trends - some new environmentally friendly agents (such as plant-derived essential oils, inducers) mixed with biocontrol agents can produce synergistic effects, which not only expands the antibacterial spectrum, but also reduces the amount of chemical drugs used. The concept of "green control" will run through all aspects of sweet potato disease management. Green control emphasizes ecological regulation and biological measures, supplemented by safe and efficient necessary chemical means. At the same time, it increases investment in the research and development of biological and physical
Molecular Pathogens, 2025, Vol.16, No.3, 87-99 http://microbescipublisher.com/index.php/mp 97 control technologies to improve their practicality and economy, so that farmers are willing to adopt them (Luo et al., 2024). For example, by screening local dominant antagonistic strains and developing cheap culture media, the cost of biocontrol agents can be reduced; promoting simple operating procedures for physical methods such as solar high-temperature disinfection, making it easier for farmers to master. 7.2 Suggestions for multidisciplinary joint research directions The occurrence mechanism and prevention and control strategies of sweet potato root rot involve knowledge in multiple disciplines such as plant pathology, microbiology, soil science, and molecular biology. Therefore, it is necessary to carry out in-depth research in the following directions through multidisciplinary cross-collaboration in the future: First, the crop-soil-microorganism interaction mechanism. Root rot is a system determined by the interaction between pathogens, hosts and soil environment. We need to integrate the methods of plant immunology and microbial ecology to analyze the immune dynamics of sweet potato roots in the soil microenvironment. Secondly, the mining of new disease-resistant resources and genes. Make full use of the gene pool of sweet potato and related wild species, find hidden disease-resistant genes through genome resequencing, association analysis and other methods, and use gene function research methods to clarify their mechanism of action. Similarly, some antifungal proteins discovered in recent years, such as pathogenesis-related proteins and phytoalexin synthase, are also worth introducing into sweet potatoes through transgenic or gene editing methods to test whether they confer new resistance. Third, in-depth study of pathogenic bacterial community succession and pathogenic mechanism. At present, our understanding of the complex infection pathogens of sweet potato root rot is still insufficient. For example, the differences in pathogenicity and host range of different Fusarium physiological races on sweet potatoes need to be clarified through genotyping and virulence determination of field strains. The conditions and mechanisms of pathogenicity of some secondary pathogens such as Lasiodiplodia and Trichoderma asperellum in specific environments also need to be clarified (Dania and Thomas, 2019). In addition, whether there is an interactive (synergistic or antagonistic) relationship between Fusarium and other saprophytic fungi during mixed infection is also a question worth exploring. In this regard, clues can be obtained through experiments such as co-culture of double bacteria and competitive colonization of labeled strains, and verified by field observations. Fourth, research and development of new technologies for agronomic and engineering prevention and control. For example, the application of Internet of Things technology in sweet potato storage monitoring can automatically control storage temperature and humidity and warn of mildew; another example is the development of efficient potato cleaning and wound protection equipment, which mechanizes post-harvest processing to reduce human damage and infection opportunities. In future research, there should be both theoretical exploration of mechanisms and focus on the implementation of practical technologies. Through the close integration of industry, academia and research, we have reason to believe that we can gradually overcome the stubborn disease of sweet potato root rot that restricts industrial development and promote sweet potato production towards high yield, green and sustainable directions. Acknowledgements We are grateful to Dr. W. Wang for his assistance with the serious reading and helpful discussions during the course of this work. Conflict of Interest Disclosure The authors confirm that the study was conducted without any commercial or financial relationships and could be interpreted as a potential conflict of interest. References Arie T., 2019, Fusarium diseases of cultivated plants: control diagnosis and molecular and genetic studies, Journal of Pesticide Science, 44(4): 275-281. https://doi.org/10.1584/jpestics.J19-03 Bilgili A., Bilgili A.V., Tenekeci M.E., and Karadağ K., 2023, Spectral characterization and classification of two different crown root rot and vascular wilt diseases (Fusarium oxysporum f.sp.radicis lycopersici and Fusarium solani) in tomato plants using different machine learning algorithms, European Journal of Plant Pathology, 165(2): 271-286. https://doi.org/10.1007/s10658-022-02605-8
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