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Emergence of a Viral Disease Epidemic of Sweet potato in Eastern Africa is Imminent – Plant virologists warn

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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.

Sweetpotato is one of the many crops in a locality with a mixture of crop husbandry and agro-forestry in Kanungu, southwestern Uganda, creating a heterogeneous community of crop stands of a diversity of alternative hosts of viruses and vectors. Research Project Makerere University, Kampala, Uganda.
Sweetpotato is one of the many crops in a locality with a mixture of crop husbandry and agro-forestry in Kanungu, southwestern Uganda, creating a heterogeneous community of crop stands of a diversity of alternative hosts of viruses and vectors.

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.

Symptoms of sweetpotato virus disease on a plant that emerged as a sprout from an abandoned storage tuber from a previous garden of sweetpotato in Mbale District, Eastern Uganda. Research Project Makerere University, Kampala, Uganda.
Symptoms of sweetpotato virus disease on a plant that emerged as a sprout from an abandoned storage tuber from a previous garden of sweetpotato in Mbale District, Eastern Uganda.

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.

Sweetpotato gardens in Nakaseke District, Central Uganda at different stages of growth and adjacent to each other: vines from an old garden on the right were used to initiate the garden on the left allowing simultaneous transmission and perpetuation of viruses in the crop. Research Project Makerere University, Kampala, Uganda.
Sweetpotato gardens in Nakaseke District, Central Uganda at different stages of growth and adjacent to each other: vines from an old garden on the right were used to initiate the garden on the left allowing simultaneous transmission and perpetuation of viruses in the crop.

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.”

A vendor displaying sweetpotato for sale on a road-side in Masaka district, central Uganda
A vendor displaying sweetpotato for sale on a road-side in Masaka district, central Uganda

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:

  1. 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.
  2. 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.
  3. 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

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Natural Sciences

Equipping Students with Bioprospecting and Product Development Skills

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Dr. Alice Nabatanzi, Lecturer, Department of Plant Sciences, Microbiology and Biotechnology, School of Biosciences, College of Natural Sciences (CoNAS), Makerere University, Kampala Uganda.

By Dr. Alice Nabatanzi

As we train Scientists we ought to equip them with skills that will help them survive beyond the Laboratories, beyond University, and beyond Academia. Thus, the need to Bioprospect and acquire product development skills.

I am therefore proud of what my 2024 Biotechnology Product Development Class has been able to achieve.

Following bioprospecting and entrepreneurial training, students developed the following products: Exotic beard oil, Herbal cough mixture, Power candy, Laundry bar soap, Moringa snack bars, Prudy Organic hair dye, Hair food, Syphilis remedy, Cornstarch based bioplastic, Nash probiotic drink, Dental care herbal mouthwash, Rosemary – lemongrass infused vinegar, Tea tree hand wash, Scented candles, Aloe fruit jam, Herbal bloom shower gel, Custard, Beetroot yoghurt, Dewormer, Stomach pain killers, Liquid organic fertilizers, Face scrub, Mosquito repellant scented air diffuser, Underarm whitening oil, Essential oil deodorant, Ria hair conditioner, Shower gels, Crochet jacket among others.

I am confident that with subsequent incubation, start-ups will emerge.


“The future belongs to those who learn more skills and combine them in creative ways.”

Robert Greene


“Build your skills not your resume.”

Sheryl Sandberg

Dr. Alice Nabatanzi is a Lecturer of Phytomedicine and Nutraceuticals in the Department of Plant Sciences, Microbiology and Biotechnology, School of Bio-sciences, College of Natural Sciences (CoNAS), Makerere University.

Photo Gallery of some of the products

Pata Guard Herbal Dewormer. Products from Dr. Alice Nabatanzi's 2024 Biotechnology Product Development Class, Department of Plant Sciences, Microbiology and Biotechnology, School of Bio-sciences, College of Natural Sciences (CoNAS), Makerere University, Kampala Uganda, East Africa.
Pata Guard Herbal Dewormer.
Lemongrass-Rosemary Infused Vinegar. Products from Dr. Alice Nabatanzi's 2024 Biotechnology Product Development Class, Department of Plant Sciences, Microbiology and Biotechnology, School of Bio-sciences, College of Natural Sciences (CoNAS), Makerere University, Kampala Uganda, East Africa.
Lemongrass-Rosemary Infused Vinegar.
Avocorn. Products from Dr. Alice Nabatanzi's 2024 Biotechnology Product Development Class, Department of Plant Sciences, Microbiology and Biotechnology, School of Bio-sciences, College of Natural Sciences (CoNAS), Makerere University, Kampala Uganda, East Africa.
Avocorn.
Jackfruit Seed Juice. Products from Dr. Alice Nabatanzi's 2024 Biotechnology Product Development Class, Department of Plant Sciences, Microbiology and Biotechnology, School of Bio-sciences, College of Natural Sciences (CoNAS), Makerere University, Kampala Uganda, East Africa.
Jackfruit Seed Juice.
Pure Mint Mouthwash. Products from Dr. Alice Nabatanzi's 2024 Biotechnology Product Development Class, Department of Plant Sciences, Microbiology and Biotechnology, School of Bio-sciences, College of Natural Sciences (CoNAS), Makerere University, Kampala Uganda, East Africa.
Pure Mint Mouthwash.
Exotic Beard Oil. Products from Dr. Alice Nabatanzi's 2024 Biotechnology Product Development Class, Department of Plant Sciences, Microbiology and Biotechnology, School of Bio-sciences, College of Natural Sciences (CoNAS), Makerere University, Kampala Uganda, East Africa.
Exotic Beard Oil.
Crochet Jacket. Products from Dr. Alice Nabatanzi's 2024 Biotechnology Product Development Class, Department of Plant Sciences, Microbiology and Biotechnology, School of Bio-sciences, College of Natural Sciences (CoNAS), Makerere University, Kampala Uganda, East Africa.
Crochet Jacket.
AvoGlow. Products from Dr. Alice Nabatanzi's 2024 Biotechnology Product Development Class, Department of Plant Sciences, Microbiology and Biotechnology, School of Bio-sciences, College of Natural Sciences (CoNAS), Makerere University, Kampala Uganda, East Africa.
AvoGlow.
Luxe Guard Scented Candles. Products from Dr. Alice Nabatanzi's 2024 Biotechnology Product Development Class, Department of Plant Sciences, Microbiology and Biotechnology, School of Bio-sciences, College of Natural Sciences (CoNAS), Makerere University, Kampala Uganda, East Africa.
Luxe Guard Scented Candles.
Moringa Snack Bar. Products from Dr. Alice Nabatanzi's 2024 Biotechnology Product Development Class, Department of Plant Sciences, Microbiology and Biotechnology, School of Bio-sciences, College of Natural Sciences (CoNAS), Makerere University, Kampala Uganda, East Africa.
Moringa Snack Bar.
Power Candy. Products from Dr. Alice Nabatanzi's 2024 Biotechnology Product Development Class, Department of Plant Sciences, Microbiology and Biotechnology, School of Bio-sciences, College of Natural Sciences (CoNAS), Makerere University, Kampala Uganda, East Africa.
Power Candy.

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Natural Sciences

15 PhD Positions: Human River Systems in the 21st century

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15 New Positions Open in the FWF PhD Program "Human River systems in the 21st century (HR21)". Application Deadline: 2nd April 2024. Austria. Europe

Highly qualified applicants from all over the world are invited to apply for the PhD Program “Human River systems in the 21st century (HR21)”. The 15 positions are fully funded and the Doctoral Programme is providing additional resources for conference presentations, retreats etc.

The 15 PhD research topics are:

  • Topic 1: Role of hydrological extremes (floods) for sediment transport and morphodynamics in the human-river system
  • Topic 2: Material resources demand and flows of hydraulic structures to prevent societal impact of extreme events (social ecology, environmental history)
  • Topic 3: Intermittent flow – hydrological effects and impacts on benthic communities, ecological state and functioning of riverine systems
  • Topic 4: Drought, low flow and warming – hydrological effects and impacts on the ecological state and functioning of river systems
  • Topic 5: Water transit time distributions as indicators for the vulnerability of riverine ecosystems under different pressures from social metabolism
  • Topic 6: Analyzing possible contributions of re-activated former watercourses towards a more sustainable transformation of industrialized riverine landscapes in urban areas
  • Topic 7: The role of the latest industrial revolutions on instream processes and ecological vulnerability of IRL
  • Topic 8: The effects of infrastructure development on ecological and ecosystem service network properties in river systems
  • Topic 9: The impact of urban settlements on organic matter and nutrient flows in industrialized riverine landscapes – What can we learn from the past?
  • Topic 10: Urban metabolism, a river’s ecohydrology and industrialization: Vienna and the Danube, 1800-2000
  • Topic 11: Impact of external organic matter sources on nutrient, sediment and water transport from cropland into streams
  • Topic 12: Impacts of bioenergy crops used as riparian buffer strips on stream ecosystems’ functioning
  • Topic 13: Sustainable hydropower & and the water-energy-food nexus in multi-stressed IRLs: Challenges and solutions for science & management
  • Topic 14: Integrated modelling of farmers’ climate change impact and adaptation appraisal to inform regional human river nexus management
  • Topic 15: Strategic planning approaches to territorial governance of industrialized riverine landscapes

For more information, please visit: https://short.boku.ac.at/q9ry2k

Application deadline: 2nd April 2024

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Natural Sciences

Dr. Tugume Patience Wins OWSD Early Career Fellowship

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Dr. Tugume Patience, Department of Plant Sciences, Microbiology and Biotechnology, College of Natural Sciences (CoNAS), Makerere University, Kampala Uganda, East Africa.

Dr Tugume Patience, a Lecturer in the Department of Plant Sciences, Microbiology and Biotechnology at the College of Natural Sciences (CoNAS), Makerere University is one of the 28 women who have been granted the 2023 OWSD Early Career Fellowship.  These scientists will receive up to USD50,000 to lead research projects and establish research groups at their home institutions in 16 countries in the developing world, to maintain an international standard of research and attract scholars from all over the world to collaborate. Funding for the fellowships is generously provided by Canada’s International Development Research Centre (IDRC).

During the 3-year fellowship, fellows will receive specific training to build on their leadership and management skills and develop connections with a variety of public and private sector partners to potentially convert their research into marketable products or guarantee its impact on a broader scale. By improving their communication and outreach skills, fellows will also learn to effectively present their research to various audiences, thus attracting new collaborators and potential funders to ensure the sustainability of the research project.

Dr Tugume’s Project – Biological Systems and Organisms

This project will use various forms of bio-wastes from households and urban centres in Uganda as raw materials for production of biogas, as well as an eco-friendly bio-fertilizer and bio-pesticide. Large amounts of unconsumed food are often thrown away in homes and urban centres that could be converted into useful products that would supply energy, enhance agricultural productivity and reduce deforestation. This project will construct anaerobic bio-digester tanks to process different kinds of bio-waste into biogas, a renewable energy source, and evaluate yields of biogas from different bio-wastes and combinations of bio-wastes. It will additionally produce a bio-fertilizer to enrich soil and a bio-pesticide to manage agricultural pests. The project will also equip households with the skills to biologically convert wastes into value-added products, training women and youth in biogas production and usage.

Details on the fellowships at: https://owsd.net/news/news-events/introducing-2023-owsd-early-career-fellows

Congratulations Dr Tugume

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