Unlike for plants, in animals especially humans, body mass index (BMI, which is a person’s weight divided by the square of height) is a measure of physical health and pre-disposure to conditions like obesity. BMI does not make sense in plant health because of differences between plant and animal physiological systems.
However, large body size in plants may have some advantages. Apart from controlling a larger proportion of available resources and space within crowded vegetation, what other advantage does a large plant body size offer to an individual plant?
The banana’s plant body architecture
From the botanical point-of-view, the banana plant is a gigantic herb. A plant that is a herb or “herbaceous” is unable to undergo “secondary growth” and cannot form wood during its vegetative development.
The banana plant springs from an underground “true stem”, also called the “corm” or “rhizome”, to form a false stem, also called a “pseudostem” of 2-7 m height. The pseudostem is composed of the basal portions of leaf sheaths and is crowned with a rosette of 10 to 20 oblong to elliptic leaves that sometimes attain a length of 2-4 m and a breadth of 70 cm.
In mature banana plants, true stem emerges at the top of the pseudostem and bends downward to become a bunch of 10 to 300 individual fruits, or fingers, grouped in clusters, or hands, of 3 to 22. The edible part of the bunch is the female. In contrast, the inedible distal part, including the purple-colored cone-shaped end (locally known in some Ugandan dialects as “omukanaana” or “empumumpu”) constitutes the male part of the bunch.
How is the giant banana size an advantage in disease control?
A new study, titled “Xanthomonas campestris pv. musacearum Bacterial Infection Induces Organ-Specific Callose and Hydrogen Peroxide Production in Banana” and led by a team of scientists at the Department of Plant Sciences, Microbiology and Biotechnology at Makerere University in collaboration with the University of California, Davis, USA, shows how the giant banana body size can be used to control banana Xanthomonas wilt (BXW) disease.
According to Prof. Arthur Tugume, the lead scientist of this study and expert in plant pathology, when plants get infected, they respond instantly by implementing different strategies that limit the multiplication and/or mobility of the disease agents (pathogens). “For example, plants rapidly produce reactive oxygen species (ROS) such as hydrogen peroxide, superoxide ions, and hydroxyl ions. These ROS act as rapid messengers in the plant tissues to activate additional responses spreading over the entire plant body. This helps the plant’s distant tissues or organs to be aware and prepare advance defenses against the intruding pathogens”.
Prof. Dinesh-Kumar the project’s research collaborator based at the University of California-Davis, USA and expert in plant biology explains that “disease is a form of stress in plants and plants cannot perform well their biological functions when they are sick since they have to spend a lot of energy fighting against the disease. This is why disease control is important to enable plants grow well and yield high.”
The research indicates that ROS set in motion additional processes to ensure limited impact of disease and pathogens on the plant. For example, Hydrogen peroxide (H2O2), which is a ROS, has direct bactericidal, fungicidal or other anti-effects on the pathogens. Also, following H2O2 production, a unique plant carbohydrate, named “callose” starts to accumulate in large quantities within plant cells as a means of fortifying plant tissues. Callose differs from the other usual plant carbohydrates such as starch or cellulose because of the way its structures are formed.
Increased production of callose acts as a roadblock to any pathogen e.g., bacteria by limiting bacterial movement that would otherwise allow ease of attack on other tissues or cells at distant locations in the plant. “Although these plant defense responses are rapid, plant organs that are distant from the site of pathogen attack can be instrumental and block progression of bacteria or other pathogens by depositing callose in advance at strategic points” Prof. Tugume explains.
However, Prof. Tugume notes that callose participates also in many other normal developmental processes of plants, and for that reason, there is always some “housekeeping” callose in the plant tissues even without pathogenic infection. “This means that one must be able to accurately and quantitatively distinguish between ‘stress-induced’ and normal ‘housekeeping’ callose”, he adds.
How was the study done?
In this study, the researchers used young (2.5-months old) banana plantlets that had been generated from tissue culture at Kawanda Agricultural Research Institute. They then infected the plantlets with a bacterium called Xanthomonas campestris pv. musacearum (Xcm). This bacterium is the causative agent of banana Xanthomonas Wilt (BXW), the most destructive disease of bananas in East and Central Africa (ECA).
The banana leaves, pseudostems, corms and roots were analyzed for callose and compared with the control plants that had been inoculated with water instead of bacteria. H2O2 production was monitored by “DAB staining”, and by “spectrophotometry” while the analysis of callose was done by two methods: staining and visualization of callose using florescence microscopy, and using “Sandwich Enzyme-Linked Immunosorbent Assay” methods.
What did the researchers discover and how can it be used in BXW disease control?
This study revealed that the underground corm tissues assemble the stiffest resistance against BXW by depositing the highest concentrations of callose, while the pseudostem produced the highest quantities of H2O2. This is interesting for three (3) main reasons:
- Firstly, Xcm bacteria often enter through the leaves in regular plantation husbandry; hence, the corm being distant from leaves gives it an anatomical advantage in promoting the ability of lateral plants to escape Xcm infection.
- Secondly, the corm is an organ of perennation supporting vegetative and perennial continuity of the crop across seasons; hence it is charged in ensuring a disease-free next generation by severely constraining “mother-child transmission” of Xcm bacteria.
- Thirdly, the control of BXW now becomes easy when farmers are observant to the first aerial disease symptoms because Xcm is strongly constrained by bottlenecks in the pseudostem and corm.
Therefore, at the onset of aerial symptoms, diseased peudostems should immediately be removed by aseptically cutting them off at the corm without interfering with symptomless lateral shoots, which allows continuous food production and disease control to go on simultaneously. This is facilitated by the large size of the banana plant because at the onset of leaf symptoms (2.5 to 5 meters away from the corm), the bacteria have not yet arrived at the base of the pseudostem where the diseased plant can be cut off from the corm. This gives chance to a farmer to eliminate the infected pseudostems early (in 1 to 7 days) since the appearance of leaf symptoms.
This research was part of the PhD studies for Mr. Abubakar S. Mustafa at Makerere University and University of California, Davis. According to Mr. Mustafa, these discoveries make the management of BXW in banana plantations easy as long as the farmers are observant and act fast by removing diseased plants aseptically.
This study has been published by the American Phytopathological Society (APS) in an open access journal, “PhytoFrontiers”, and is freely accessible on https://apsjournals.apsnet.org/doi/full/10.1094/PHYTOFR-11-21-0073-R.
This study was funded by the Bill and Melinda Gates Foundation through the National Agricultural Research Organization (NARO), Uganda. The project had partners including the International Institute of Tropical Agriculture (IITA), the Alliance for Bioversity International and International Centre for Tropical Agriculture (CIAT) and Centre for Agriculture and Bioscience International (CABI).
For more details, contact;
Prof. Arthur Tugume
College of Natural Sciences (CoNAS)
Mr. Abubakar S. Mustafa
Co-Author and PhD student on the study
Principal Communication Officer
College of Natural Sciences (CoNAS)
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
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