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
Department of Plant Sciences, Microbiology and Biotechnology
College of Natural Sciences (CoNAS)
Dr. Deusdedith Mbanzibwa
Tanzania Agricultural Research Institute (TARI),
Biosciences Centre, Dodoma, Tanzania
Email: Tel: +255755881758
Dr. Titus Alicai
Root Crops Research Program
National Crops Resources Research Institute (NaCRRI)
National Agricultural Research Organization (NARO)
Principal Communication Officer
College of Natural Sciences
Mak Paves Path to Biodiversity Leadership: Inaugural ABS Project Workshop Strengthening Uganda’s Nagoya Protocol Capacity
By Laban Lwasa
In a groundbreaking event that unfolded at Makerere University‘s Telepresence Center on November 7, 2023, the Inception Workshop for the ABS Project took center stage, hosted by the College of Natural Sciences (CoNAS), Department of Plant Sciences, Microbiology, and Biotechnology. Prof. Tumps Ireeta, Principal of CoNAS, set the tone with a warm welcome, highlighting Uganda’s rich biodiversity and the pivotal role of the Nagoya Protocol in ensuring the legal utilization of genetic resources. The collaboration between NEMA and Makerere University, supported by the GEF, aims to equip professionals with ABS knowledge and position Makerere at the forefront of Nagoya Protocol compliance.
Prof. Arthur Kajungu Tugume, Dean of the School of Biosciences, emphasized the project’s significance in institutional capacity strengthening for the Nagoya Protocol’s implementation in Uganda, showcasing the School of Biosciences as a hub for genetic resource research and training. The pilot project, in collaboration with NEMA, GEF, and UNEP, aims to expand countrywide and potentially across the African continent. It seeks to empower a skilled workforce informed on ABS issues, contributing to economic development and poverty eradication as aligned with SDG 1.
Mr. Achuu Peter, Project Manager from NEMA, highlighted Uganda’s extraordinary biodiversity and the need to explore the benefits of genetic resources for medicines, food, and more. He emphasized the importance of the Nagoya Protocol in mitigating biodiversity loss and highlighted challenges faced by Uganda in terms of weak institutional capacity, inadequate policies, and lack of coordination for ABS. The project focuses on strengthening ABS frameworks, capacity building, community-level management, and raising awareness to ensure equitable benefits from genetic resource utilization.
Mr. Daniel Abowe, UNCST ABS Project Officer, shed light on the complex landscape of national ABS laws in Uganda, resulting in legal complexity and high transaction costs for users. He also detailed the Uganda research approval process, emphasizing UNCST’s role in ABS implementation, which includes issuing access permits and ensuring benefit-sharing agreements. The multifaceted project aims to align Uganda with the Nagoya Protocol’s goals and foster collaboration between higher institutions and local communities for the management of genetic resources.
Dr. Katuura Esther, the Project Principal Investigator at Makerere University, highlighted the institution’s pivotal role in training and research. Makerere University aspires to be a thought leader, committed to providing transformative teaching, learning, research, and services that cater to dynamic national and global needs. The institution’s strategic goals encompass leadership in high-quality programs, knowledge dissemination, research, scholarship promotion, and corporate social responsibility. Dr. Esther also addressed the challenges and opportunities in preserving indigenous knowledge, emphasizing the role of digital technologies and collaboration between research institutions and local communities.
The programs designated for updating at Makerere University are a comprehensive effort to align with the Nagoya Protocol. Notable among these programs are BSc Applied and Economic Botany, BSc in Conservation Biology, Bachelor of Biotechnology, Masters in Botany, Masters in Genetics, Masters in Plant Pathology and Crop Science, and Masters in Economic Botany. This holistic approach aims to contribute to the conservation and equitable utilization of genetic resources.
Dr. Cyprian Misinde, the Director of Quality Assurance at Makerere University, emphasized the importance of incorporating international and global standards into the academic curriculum. He underscored the crucial role of projects like ABS in enhancing the capacity of professionals and equipping them to become part of a globally competitive workforce. This workshop marked a significant stride in Uganda’s journey towards sustainable biodiversity management and conservation, creating a ripple effect that extends far beyond its borders, leaving a lasting impact on the world stage.
Laban Lwasa is the Senior Administrative Assistant, Makerere University, Grants Administration and Management Support Unit (GAMSU)
Ugandan student Dorothy Akoth wins 2023 GBIF Graduate Researchers Award
Ms. Dorothy Akoth, a Master’s student at the College of Natural Sciences (CoNAS), Makerere University has been named one of two winners of the 2023 GBIF Graduate Researchers Award. An expert jury selected Akoth, who was nominated by the Uganda National Council for Science and Technology together with National Fisheries Resources Research Institute (NaFIRRI), for the instrumental role of her research in improving the knowledge of the distribution and imperilment status of 110 native fish species outside the iconic Haplochromine tribe of East African cichlids. The student was supervised by Prof. Fredrick Muyodi and Dr. Jackson Efitre
from the Department of Zoology, Entomology and Fisheries Sciences at CoNAS, Makerere University, and Dr Vanny Natugonza of Busitema University.
Since its inception in 2010, the annual GBIF Graduate Researchers Award (previously the Young Researchers Award) has sought to promote and encourage innovation in biodiversity-related research using data shared through the GBIF network.
CARTA Fellow Anywar Selected as Fellow of ASLP
Godwin Anywar (cohort 6 graduate, Makerere University) was selected as a fellow of the Africa Science Leadership Programme (ASLP) based at the Future Africa Campus at the University of Pretoria, South Africa, on September 8, 2023.
Within the month, he:
- Will be participating in the Uganda-Swiss Museum Cooperation Workshop from September 24 – October 4, 2023, in Kampala, Uganda, and will present on ‘Traditional Medicine in Transition.’
- Presented a keynote paper on ‘Mental Health and Wellbeing during the PhD Journey’ at the Makerere University Business School (MUBS) 27th Annual International Management Conference (AIMC) under the theme “Leveraging Governance, Human Capital and Technology for Sustainability in Kampala – Uganda on September 25 – 27, 2023.
- Presented a paper on ‘The Cannabis/Marijuana (Cannabis sativa L.) Landscape in Africa: An Overview of its Cultivation and Legal Aspects’ at the 20th International Napreca Conference on Natural Network for East and Central Africa (NAPRECA) in Harare, Zimbabwe on September 20, 2023.
- Attended the German Academic Exchange Service (DAAD) Science Forum at the University of Nairobi on September 20, 2023, to celebrate 50 years of DAAD in East Africa.
Source: CARTA Newsletter Issue 69
General5 days ago
Application Forms for Admission to Public Universities 2024/2025
General6 days ago
African Universities urged on developing comprehensive safeguarding policies with critical elements of safety & protection
Agriculture & Environment2 weeks ago
RUFORUM 19th AGM Urges Africa to Take the Lead on Climate Action
Agriculture & Environment5 days ago
Soybean Breeders Deliberate Strategies for Improving Productivity
Humanities & Social Sciences2 weeks ago
Anthems of the World Concert for the United Nations Day, 2023, in Uganda