Determination of Wilt Disease Resistance, Performance and Environmental Safety of Transgenic Bananas Expressing Hrap-Pflp and Espflp Genes under Field Conditions
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Date
2024-04
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Kenyatta University
Abstract
Banana Xanthomonas wilt (BXW) disease is caused by the bacterium Xanthomonas campestris pv musaceae. Transgenic banana expressing the genes hypersensitive reactive associated protein (Hrap), plant ferredoxins-like protein (Pflp), and extracellular secreted plant ferredoxin-like protein (EsPflp) have been developed and shown to control BXW in glasshouse in Uganda. However, the transformed banana lines have not been evaluated in Kenya for BXW disease resistance, field performance, and environmental safety. BXW disease causes over 50% losses of production in farmer’s fields. Banana production is essential to Kenya and the region as it provides food, fodder, and income. In Uganda, these transgenes have been used to transform banana cultivars of Sukali Ndiizi (AB) and found to be resistant to BXW under glasshouse and field trials. Non-target effect studies of the transgenes have also been conducted in Uganda for non-target soil bacteria colonization. As demonstrated in the trials, the technology has potential, so conducting field trials for the transgenic banana events in Kenya is important to generate data on disease resistance, performance and environmental safety before they are incorporated into agricultural production. With respect to this, a confined field trial was established in Busia County at Kenya agricultural and livestock research organization (KALRO) Alupe research station. Randomized complete block design (RCBD) with 30 banana events replicated 12 times was used. Bananas were planted at a spacing of 3m by 3m from each other and a hole size of 2.5 cubic feet. During planting, 20 kg of well-composted manure and 100 g of double ammonium phosphate (DAP) were used for each banana stool. At 5 months after planting, molecular characterization of the plants was carried out. The plants were then physically infected with the wilt-causing cultures. Disease resistance was carried out by scouting for disease symptoms post-infection. Morphological/Agronomical data was collected on traits such as height, girth, and leaf total area. Soil studies were also conducted by analyzing plant litter decomposition rate and carbon readings. Environmental studies were conducted by analyzing the numbers of soil nematodes, flying insects, and banana weevils. All the data were analyzed using one-way ANOVA, and significance levels were read at α=0.05. In the BXW disease resistance evaluation and agronomy, the effects of the transgenes could not be determined, as the study ended prematurely because both transgenic and non-transgenic plants died within 12 months. The differences between transgenic and non-transgenic control in soil qualities, soil nematodes, flying insects, and banana weevils did not differ significantly (p˃0.05). The study implies that Hrap-Pflp and EsPflp are environmentally safe as they did not affect non-target organisms and soil quality. The transgenes can, therefore, be selected for multilocation assessment to collect more data on safety.
Description
A Thesis Submitted in Fulfilment of the Requirements for the Award of the Degree of Doctor of Philosophy (Biotechnology) in the School of Pure and Applied Sciences of Kenyatta University April, 2024
Supervisors:
1. Richard O. Oduor
2. Leena Tripathi