Banana Rhizosphere Microbial Diversity, Low-Cost Tissue Culture Bananas (Musa spp.) Micropropagation, Genetic Fidelity and Acclimatization Using Arbuscular Mycorrhizal Fungi
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Date
2024-05
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Kenyatta University
Abstract
Banana production in Kenya predominantly involves smallholder farmers, yet current
yields fall short of meeting local and international market demands due to constraints
faced by these farmers among them being soil health and lack of clean planting materials.
To address this issue, the study assessed banana cultivation practices in Kisii, Nyamira,
and Embu counties, aiming to understand strengths and challenges within these regions.
In this study, rhizospheric soil physicochemical properties and the diversity of microbial
communities was assessed, shedding light on soil health status. Furthermore, the efficacy
of a cost-effective micro-propagation technique for local banana cultivars was
determined, considering contamination susceptibility and acclimatization efficacy of
arbuscular mycorrhizal fungi on micropropagated banana plantlets. The study revealed a
reliance on ineffective traditional propagation methods, with over 30% of the smallholder
farmers facing a banana seedlings shortage. The soil physic-chemical parameters
indicated signs of degradation, with low pH and nutrient deficiencies raising concerns
with Embu County having the lowest pH measured (4.43). Soil metagenomic studies by
NGS showed that proteobacteria and basidiomycota were the two most prevalent
bacterial and fungus divisions, respectively. Based on the Shannon diversity indices, the
highest bacterial and fungal community diversity was in soil samples obtained from
Embu County and Kisii County respectively. To evaluate efficacy using low cost tissue
culture technology, selected banana cultivars were utilized and results indicated the
highest survival rate of 100 % in Kiganda, Muraru and Kienyeji banana cultivars
established in BAP and IAA. Ng’ombe cultivar best responded to low cost
micropropagation with the highest shoot establishment (80.5 %) and shoot emergence
rates (75.5 %) producing the highest number of shoots per culture (10.61). To investigate
clonal fidelity of the tissue culture plantlets Inter Simpler Sequence Repeats (ISSR) and
the research demonstrated genetic homogeneity in banana seedlings generated via low cost tissue culture to the mother plant. During the micropropagation process the presence
of bacterial and fungal contaminants in the tissue culture laboratory was noted with the
most predominant bacterial and fungal contaminants being Microccoccus luteus and
Cladosporium sp respectively. Additionally, broad-spectrum antimicrobial agents
nalidixic acid (30 µg) and carbendazim+ triadimefom (0.3 µg and 0.6 µg) exhibited
100% inhibition rates against these contaminants. To determine the response of the
micropropagated plantlets to AMF acclimatization, it was observed that Kiganda cultivar
responded best to Rhizophagus irregularis which showed the highest recorded biomass at
0.97. There is need to emphasize collaborative efforts among various stakeholders in
establishing sustainable practices. Additionally, low-cost TC is a viable tool for
producing disease-free seedlings and intergrating antimicrobial agents is recommended to
minimize contamination risks. Finally, the use of AMF treatment in acclimatization with
further research needed for validation across different agroecological conditions. These
recommendations aim to enhance productivity, sustainability, and resilience in banana
farming systems.
Description
A Thesis Submitted in Fulfillment of the Requirements for the Award of the Degree of Doctor of Philosophy (Microbiology) in the School of Pure and Applied Sciences of Kenyatta University, May 2024
Supervisors
1. John Maingi
2. Omwoyo Ombori
3. Ezekiel Mugendi Njeru