Natural Sciences
Emergence of a Viral Disease Epidemic of Sweet potato in Eastern Africa is Imminent – Plant virologists warn
When COVID-19 emerged in 2019, it first remained temporarily localized as an epidemic in Huan China until it broke Chinese national and Asian continental borders attaining a global pandemic status. With COVID-19 and other epidemics and/or pandemics of humans and livestock, it is easier to explain the obvious impact on humans and/or livestock.
What about virus epidemics and pandemics that affect plants?
Virus epidemics and pandemics that affect plants cause significant disruptions in food production. In fact, the emergence and re-emergence of extremely dangerous plant viruses is the major pain to the 21st century agriculture and sustainable food production.
Viral diseases of plants lead to complex outcomes of food shortages, economic meltdown and loss of lives especially when the affected crop plants are central to the economics and livelihoods of the people. Think of what would happen if an epidemic caused significant effect or eliminated crops like maize, banana, cassava or sweetpotato from sub-Saharan Africa.
Most viruses affecting livestock and humans are spread and transmitted by means of physical contact between hosts. Furthermore, human and livestock hosts are mobile. On the other hand, plants do not move and must thus depend on other agents (vectors) for the spread of viruses between hosts. Consequently, over 98% of plant viruses are transmitted by vectors. These vectors may include arthropods (especially insects), nematodes, fungi, and parasitic plants. In plants, a virus disease epidemic becomes optimized by the ability of vectors facilitating fast spread of the virus in an agro-ecosystem.
New study predicts emergence of disease epidemic in sweetpotato
A new study led by Prof. Arthur Tugume at the Department of Plant Sciences, Microbiology and Biotechnology in the College of Natural Sciences at Makerere University predicts potential of emergence of a new disease epidemic in sweetpotato.
The study recognizes that by default, viruses are not constrained to perpetually occupy a single ecological niche. This is because viruses have inherent genetic and evolutionary abilities that enable their acquisition of better fitness to always expand their host and geographical ranges.
While viruses enjoy such fitness advantages in nature, the current study points out unique examples where some viruses in eastern Africa behave awkwardly. These viruses first hid under the guise of being less important and seemingly of no impact in cropping systems, and all of a sudden hell broke loose and the entire farming system was caught unaware.
The study titled; “Endemism and reemergence potential of the ipomovirus Sweetpotato mild mottle virus (family Potyviridae) in Eastern Africa: half a century of mystery” shows that a virus, named Sweetpotato mild mottle virus (SPMMV) was first detected in eastern Africa in the 1970’s. SPMMV is currently the third most prevalent virus of sweepotato in the region and is most destructive in mixed infections with other viruses. Very strangely, SPMMV is geographically restricted to eastern Africa (confirmed only in Uganda, Kenya and Tanzania). This sharply contradicts other known sweetpotato viruses that occur globally wherever sweetpotato is grown.
According to Dr. Deusdedith Mbanzibwa a co-author and Head of Disease Control Unit at Tanzanian Agricultural Research Institute, “it is a half-century-old mystery how SPMMV remains localized in East Africa while other viruses on sweetpotato show a global incidence.” Dr. Mbanzibwa adds, “it is important we generate basic information on this virus as soon as possible such that immediately an epidemic explodes we can counter-it based on the information we have as opposed to being caught unaware of the destructive effects of an epidemic.”
Why should we be concerned about outbreak of an epidemic on sweetpotato?
Plant disease epidemics cause a breakdown in food production and availability in communities that depend on the affected plants as food staples. If sweetpotato production breaks down, it directly translates into limited food supplies in local communities that depend on it for food.
According to Dr. Titus Alicai, a senior virologist and co-author based at the National Crops Resources Research Institute (NaCRRI), Namulonge Uganda, “between the 1980’s-1990’s, a devastating viral pandemic (cassava mosaic disease, CMD) destroyed cassava cropping systems in eastern Africa. As a result, dozens of lives were lost because many communities solely depended on cassava for food and income”. Although these viruses had been detected in the region as early as 1800’s, it was not until the 1980s that destructive effects of the disease became apparent.
Dr. Alicai adds that, “when cassava got destroyed by CMD, sweetpotato became an immediate alternative to millions of hungry people, but now sweetpotato is also burdened with diseases arising from viruses.” Despite heavy investments in disease control in cassava, the CMD pandemic is not completely controlled.
Why is eastern Africa important with respect to emergence of plant viruses?
According to this study, SPMMV is not the first unique virus to emerge or reemerge in eastern Africa. An earlier study by Prof. Tugume and colleagues published in 2010 in Molecular Ecology showed that East Africa is a hotspot for the evolutionary diversification of yet another virus in sweetpotato, named Sweetpotato feathery mottle virus (SPFMV).
Many studies show this region as the home of epidemics in rice caused by Rice yellow mottle virus (RYMV). Highly lethal strains of Cassava mosaic geminiviruses (CMGs) causing CMD initiated this epidemic from eastern Africa. Unique strains of Sweetpotato chlorotic stunt virus (SPCSV) are incident in eastern Africa. SPCSV is unique because it almost indiscriminately enhances the viral concentrations of other co-infecting viruses in sweetpotato. The list of damaging plant viruses or their strains that have emerged from eastern African region is long and cannot not be exhausted here.
Biologists studying diversity of plants and animals have also coded eastern Africa as a home of the “hottest hotspot of biodiversity” of endemic land plants and animals located in Eastern Arc Mountains of Kenya and Tanzania. The features of eastern African ecosystem that incite virus epidemics in plants are not fully known. However, it is suspected that the microclimatic changes as modulated by the Indian Ocean dipole could be one of the drivers of virus emergence and reemergence in the region.
Emergence of SPMMV in sweetpotato closely resemble that of viruses in cassava
The current study specifically compared SPMMV with two viruses infecting cassava: cassava brown streak virus, and Ugandan cassava brown streak virus, collectively called cassava brown streak ipomoviruses (CBSIs).
CBSIs first appeared in the 1930’s in coastal east Africa but went completely silent for about 70 years and then suddenly re-emerged in late 1990’s-mid 2000’s to what is today the single largest threat to cassava production in Africa. CBSIs cause a disease called “cassava brown streak disease” (CBSD). Between 1930’s-1990’s, the CBSIs were able to “amass ability” to cause untold suffering of cassava cropping from 2000’s to-date.
Similarly, since the 1970’s when SPMMV was first reported in the region, the virus has been “amassing an ability” to cause more disease in sweetpotato. This is implied directly by evidence of positive selection found in its genes. Positive selection refers to “survival for the fittest” in Charles Darwin’s terms to mean that, individual virus particles in the SPMMV population are becoming more and more highly efficient in causing disease. Today, half a century later, one can argue that it is about time that the SPMMV will incite a new disease.
Note that both SPMMV and CBSIs belong to the same taxonomic grouping of plant viruses in a genus called “Ipomovirus”, and family called “Potyviridae” which is the largest family of plant viruses with RNA genomes. Hence, similarities in the disease spread between SPMMV and CBSIs are not unexpected.
Expert guide to sweetpotato virology research for preparations against the epidemic
“If we can generate advance basic scientific information concerning how the SPMMV infects sweetpotato plants, how it is transmitted by vectors between plants, and circumstances fostering field spread of the virus, we will be better prepared to handle an epidemic that may arise from the virus,” Prof. Tugume states.
He adds: “we should be able to undertake these studies quickly because SPMMV is naturally incident on sweetpotatoes in Uganda, Kenya and Tanzania in levels causing less damage on its own at the moment, although this damage escalates when the virus occurs in multiple infections.”
The co-authors highlight serious research gaps for critical research investment in sweetpotato virology. Vector transmission is such an important aspect of virus disease epidemics of plants. Therefore, this study has proposed three possible explanations to account for the virus-vector and virus-host relationships of SPMMV. These are called hypothesis #1, #2, and #3, built in a fashion that allows experimentation to prove them right or wrong:
- Hypothesis #1: “SPMMV is opportunistically aphid-transmitted with potyvirus SPFMV as a helper virus.” This hypothesis postulates that SPMMV is transmitted by “chance” by a group of insects called aphids but this happens when SPMMV co-infects sweetpotatoes with another virus, SPFMV that is transmitted efficiently by aphids.
- Hypothesis #2: “Vector-mediated transmission of SPMMV is modulated by synergism with SPCSV.” Under this hypothesis, the concentrations of SPMMV in plant tissues increases when it co-infects with another virus, SPCSV, and this increases chances of SPMMV being picked by insects for transmission to other plants.
- Hypothesis #3: “SPMMV tropism and histo-localization changes upon co-infection with SPCSV.” How much viral concentration is found in different plant tissues can change depending on which tissues that are preferred by the virus. Certain plant viruses prefer to stay and multiply from certain tissues than others.
Dr. Alicai said, “If we can determine vector transmission dynamics including the actual vector(s) transmitting SPMMV, which plant tissues the virus prefers for its multiplication, and generate many complete sequences of SPMMV genomes, we will be better prepared for epidemics arising from the emergence of SPMMV”.
Sweetpotato is a vegetatively propagated plant in which the top-most 15-40cm part of the plant is used for initiating the new crop, a practice that is the main route of accelerated of virus spread in the cropping system. Also, insects especially aphids and whiteflies are the major vectors transmitting viruses in sweetpotato. The research gaps highlighted with respect to SPMMV require urgent attention for advance preparation in case an epidemic breaks loose on the sweetpotato cropping system.
This study has been published by the American Phytopathological Society (APS) in an open access journal, “Phytobiomes Journal”, and is freely accessible on https://apsjournals.apsnet.org/doi/10.1094/PBIOMES-05-22-0031-RVW
For more details, please contact;
Prof. Arthur Tugume
Lead Scientist
Department of Plant Sciences, Microbiology and Biotechnology
College of Natural Sciences (CoNAS)
Makerere University
Email: arthur.tugume@mak.ac.ug
Tel: +256772514841
Dr. Deusdedith Mbanzibwa
Tanzania Agricultural Research Institute (TARI),
Biosciences Centre, Dodoma, Tanzania
Email: d.mbanzibwa@yahoo.co.uk
Email: Tel: +255755881758
Dr. Titus Alicai
Root Crops Research Program
National Crops Resources Research Institute (NaCRRI)
National Agricultural Research Organization (NARO)
Email: talicai@hotmail.com
Tel: +256772970585
Hasifa Kabejja
Principal Communication Officer
College of Natural Sciences
Makerere University
Email: pr.cns@mak.ac.ug
Tel: +256774904211
A team of researchers from Makerere University has presented findings of a study on the persistent poor performance in Biology in national examinations to senior officials at the Ministry of Education and Sports.
The findings were shared during a dissemination meeting attended by the Ministry’s top management, led by Permanent Secretary Kedrace Turyagenda.
The study, commissioned by the Ministry in 2023, was conducted by researchers from the College of Natural Sciences (CoNAS) and the College of Education and External Studies (CEES). It was spearheaded by Prof. Fredrick Muyodi as Principal Investigator, alongside Assoc. Prof. Josephine Esaete (Co-Principal Investigator) and Prof. Arthur Tugume among others.
Titled “Examining the Factors Accounting for Poor Academic Performance in Biology in Uganda’s National Examinations,” the study covered all regions of the country, engaging more than 5,200 respondents across 100 districts through surveys, interviews, and observations.
Key findings
The research identified limited field-based learning and poor digital access as the most critical and consistent challenges affecting both Ordinary and Advanced Level students across all regions.
At Advanced Level, the lack of project-based learning was also cited as a significant constraint. Learners reported limited engagement with Biology beyond the classroom, a factor that weakens conceptual understanding and application in examinations.
The study further highlighted the role of community attitudes and perceptions in shaping student performance in the subject.
Recommendations
The researchers recommended increased investment in field-based learning, including field trips and project work, as well as expansion of digital infrastructure to improve access to learning resources.
Other proposed measures include strengthening school laboratory facilities, enhancing teacher capacity through continuous professional development, promoting student engagement through academic clubs and mentorship programmes, and fostering stronger family and community support for science education.
Next steps
The research team is seeking funding to pilot targeted interventions, particularly in regions most affected by the challenges identified, and to develop a monitoring and evaluation framework to guide implementation.
The findings are expected to inform policy and interventions aimed at improving Biology performance and strengthening science education in Uganda.
By Dr. Alice Nabatanzi
At the Department of Plant Sciences, Microbiology, and Biotechnology (PMB) in the College of Natural Sciences, we are moving beyond the classroom to bring science to life. We are proud to showcase our innovative work with the Biotechnology Class of 2026. Our Product Development Centre has transitioned from theoretical research to practical, market-ready innovations. By applying advanced scientific principles, our students are developing tangible solutions that address everyday needs in nutrition, health, and industry.
Below are the latest products developed by our talented innovators:
- Nutrition & Food Technology: Vitamin A-rich bread, banana vinegar, food syrups, and fortified bio-snacks.
- Clinical Hygiene: Perfumes, Deodorants, Antibacterial gels, herbal toothpaste, shaving cream, and herbal mouthwash.
- Natural Wellness: Natural formulas for gut health, pain relief, cough lozenges, and nasal decongestants.
- Advanced Cosmeceuticals: Turmeric SunGuard patches, skin serums, toners, and anti-dandruff shampoo.
- Home & Industrial Solutions: Shoe deodorizing sprays, surface cleaners, and scented hygiene products.
- Agri-Tech: Natural bioindicator kits designed to monitor and improve soil health.
Through these initiatives, PMB continues to lead the way in re-engineering science for the benefit of our community and the world.
Meet the Biotechnology Class of 2026. While everyone else is still stuck in textbooks writing about “how things might work,” we’re in the lab making sure they actually do. We’ve officially moved past the days of just talking about science and stepped into the era of real-world industry. From our Product Development Centre to the global market, we are setting a new standard for Biotechnology at CoNAS. We aren’t just graduating with degrees; we’re graduating with the future in our hands.
What’s Next: We’re Just Getting Started
This is only the beginning. We’re already working on the next wave of products, from eco-friendly bio-packaging and better probiotics to smart-crop tech that will change how we eat, heal, and live. We aren’t just waiting for the future to happen we’re in the lab building it right now.
Dr. Alice Nabatanzi is a Senior Lecturer of Phytomedicine and Nutraceuticals at the College of Natural Sciences (CoNAS), Makerere University
Natural Sciences
Transforming Food Waste into Clean Energy: Makerere University Researchers Equip Mbarara City Residents with Biogas Production Skills
*****Led by Dr. Patience Tugume from the Department of Plant Sciences, Microbiology and Biotechnology at Makerere University, a project titled “Bio-innovation of biogas, biofertilizer, and biopesticide through the utilization of bio-waste” is promoting the transformation of household food waste into biogas and other valuable bio-products. The project team disseminated the research findings to stakeholders in Mbarara City on 15th April 2026.
About the Project
A one-year bio-innovation initiative focused on converting household food waste into biogas, biofertilizer, and biopesticides has yielded promising results in improving access to clean energy and promoting sustainable agricultural practices in peri-urban communities of Mbarara City.
The project, implemented by Makerere University in collaboration with Frevasema Ltd in Mbarara, was supported by UNESCO and the International Development Research Centre (IDRC) – Canada through the Organization for Women in Science for the Developing World (OWSD). Launched in January 2024, it is led by Dr. Patience Tugume from the Department of Plant Sciences, Microbiology and Biotechnology at Makerere University.
The initiative has been implemented across five divisions of Mbarara City – Kakoba, Kamukuzi, Nyamitanga, Biharwe, and Nyakayojo – with additional field trials conducted in Masha Sub-county, Isingiro District.
Objectives of the project
The central aim of the project was to demonstrate how biodegradable household waste can be transformed into useful products, particularly biogas for cooking, as well as organic biofertilizers and biopesticides for improved crop production.
Key objectives of the project included: establishing a spin-off centre of bioreactors at the business partner institution (Frevasema Ltd) to demonstrate sustainable production of biogas, biopesticides and bio-fertilizers; training and equipping women and youth with hands-on skills in biogas production and usage; evaluation of yields from different bio wastes; and creation of linkages between academia, the private partner and rural communities in up-scaling production of biogas, biopesticides and bio-fertilizer from household/urban biodegradable wastes.
Key Activities and Dissemination of Project Findings
The project team conducted a survey to assess community perceptions and the factors influencing the adoption of biogas as an alternative cooking energy source in peri-urban areas of Mbarara City. In addition, biodigester tanks were constructed at FREVASEMA Ltd to support training and knowledge transfer activities.
Field experiments were undertaken in Masha Sub-county, Isingiro District to evaluate the effectiveness of an integrated biofertilizer–biopesticide. Further experiments to assess biogas yield from different types of food waste were conducted at Makerere University.
The team also developed an integrated biofertilizer–biopesticide by enhancing bioslurry, a by-product of biogas production, with plant extracts known for their pesticidal properties. The effectiveness of this product was tested on the growth performance of green pepper, cabbage, and eggplant.
In line with one of the project objectives, the team also conducted hands-on training in biogas production from food waste for 35 students and 6 staff members of MAMITA Technical and Business Institute.
Dissemination workshop
On 15th April 2026, the project team led by Dr. Tugume held a dissemination workshop to share findings with stakeholders and discuss strategies for scaling up the outcomes.
Findings from the research highlight the strong potential of biogas in contributing to sustainable energy solutions, improving livelihoods, and enhancing environmental conservation through proper food waste management.
Key research findings
- The application of integrated biofertilizer–biopesticide presents a viable alternative to scarce, expensive, and environmentally harmful inorganic fertilizers for enhancing vegetable productivity.
- The study revealed that approximately 90.7% of respondents depend on charcoal and firewood as their primary cooking fuel.
- While 92.1% of respondents were aware that biogas is produced from animal and plant materials, only 7.9% recognized that food waste can also serve as a feedstock, indicating limited awareness of its full potential.
- Banana and potato peels, as well as posho and potatoes leftovers, and green vegetable trimmings, were identified as the most commonly generated food wastes.
- A majority of respondents strongly agreed that biogas is a cleaner and more sustainable energy alternative compared to firewood.
- Key barriers to biogas adoption included inadequate technical knowledge, safety concerns regarding biogas systems, and the high costs of constructing and maintaining biodigesters.
- The extremely low adoption rate of biogas technology (0.3%) indicates significant underutilization despite its potential to mitigate fuel shortages.
- There is a prevailing perception that biogas is suitable for cooking and can effectively replace biomass fuels, given the availability of sufficient feedstock from household food waste, human waste, and animal manure.
- Potato and posho residues were identified as the most suitable primary feedstocks for biogas production due to their high nitrogen content, volatile solids, and total organic carbon (TOC).
- Effective collection and proper segregation of food waste are essential for ensuring a consistent and uncontaminated supply of feedstock for biogas production systems.
- Further research is recommended on integrated biogas systems that combine anaerobic digestion with other renewable energy technologies, such as solar energy or bioelectrochemical systems, to improve overall energy recovery efficiency.
- Vegetables treated with the integrated biofertilizer–biopesticide consistently exhibited superior performance across all growth parameters compared to those treated with inorganic fertilizers (including 5% cypermethrin pesticide) and untreated controls.
Stakeholder engagement and appreciation of the initiative
During the dissemination workshop, Dr. Patience Tugume, the Principal Investigator, expressed gratitude to UNESCO and the International Development Research Centre (IDRC)-Canada, through the Organization for Women in Science for the Developing World (OWSD), for funding the project. She appreciated the research team composed of Dr. Asiimwe Savina, Prof. Maud Kamatensi-Mugisha, Prof. Bazirake Byarugaba, Ms. Catherine Kiconco and Mr. Muhumuza Robert for their contribution. She equally appreciated all participants for contributing valuable information to the study.
Stakeholders commended the project for its relevance and community impact.
Prof. Bunny Lejju Julius from Mbarara University of Science and Technology, appreciated the project team for developing an innovation that directly addresses community needs and aligns with the principles of the competency-based curriculum, particularly the translation of academic knowledge into practical application. He advised that sustainability of the initiative could be strengthened through a multiplier approach, where the trained learners cascade the knowledge to other community members. He further recommended the identification of institutional staff who can undergo training at the spin-off centre and subsequently serve as trainers within their respective communities.
The portable biodigester system was recognized as a simple, affordable, and practical technology with the potential to provide a cost-effective alternative to charcoal and electricity. Participants noted that while resistance to change remains a challenge, continuous awareness creation is essential to promote adoption and facilitate behavioral change.
Mbarara District Forest Officer, Ms. Ainembazi Joses, highlighted the importance of the biogas production project in environmental conservation. She noted that the initiative contributes to reducing deforestation by offering an alternative to firewood and charcoal, thereby supporting sustainable natural resource management.
The Local Council Chairperson of Mailo-Biharwe Division, Mr. Didas Katabazi, appreciated the project team for the innovative work and its potential benefits to the community. He pledged to use his office to advocate for increased government support to scale up the project.
The Resident City Commissioner of Mbarara City expressed concern over the rising levels of deforestation in the district and commended the Principal Investigator for spearheading the innovation. He reaffirmed the government’s commitment to supporting science and innovation. He emphasized the importance of integrating environmental protection with agricultural productivity, explaining that food security remains a national priority. He further noted that the project demonstrates the concept of waste valorization, where organic waste is transformed into valuable products such as biofertilizers and biopesticides, thereby enhancing agricultural productivity. He pledged to engage the Office of the President to support wider dissemination of the project outcomes. Additionally, he encouraged the trained students to act as ambassadors of the project by sensitizing communities on the benefits of biogas as an alternative source of cooking energy.
Way forward
- The government should invest in constructing bio digesters for households at subsidized prices or offer them financial assistance to cater for bio digester construction.
- Awareness campaigns about the production and use of biogas and associated benefits should be intensified in communities to dispel the negative perceptions.
- Provision of technical training in operating and maintenance of biogas installations should be conducted.
- Sorting of wastes at household level should be emphasised to separate biodegradable from non biodegradable ones.
- The integrated bio-fertilizer-bio-pesticide is an effective, sustainable strategy to increase vegetable productivity while improving soil health in nutrient-limited soils.
- The project recommends adoption of bio-fertilizers (e.g., bio-slurry) which are affordable and can be made from kitchen and market waste to reduce dependence on expensive chemical fertilizers to improve crop growth while controlling pests safely in addition to being safe for humans and the environment.
Donation of portable biodigester systems
As part of the commitment to translate research into tangible benefits, the project awarded two women and MAMITA Technical and Business Institute with portable biodigester systems for installation and use in their households and institution respectively. These systems will serve as demonstration units within the community showcasing the practicality, affordability, and impact of clean energy solutions at the household level.
Report compiled by Dr Patience Tugume, Principal Investigator & Senior Academic Staff in the Department of Plant Sciences, Microbiology & Biotechnology at Makerere University
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