Virulence, Diversity and Management of Fusarium Oxysporum F.Sp. Cubense Infecting Bananas in Selected Counties in Central and Eastern Kenya
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Date
2023-10
Authors
Malaka, Musime Samuel
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Banana belongs to Musaceae family and is cultivated worldwide supporting the 1ivelihood.s
of many people and the economies of many countries. One of the pathogens that is
significantly reducing banana yield in Kenya is Fusarium oxysporum f.sp. cubense (Foc)
that causes Fusarium wilt of bananas (panama disease). There are currently no_long—term
control mechanisms for panama disease. Critically, there is very little information on the
distribution of Foc races in Kenya. Carbendazim based fungicides have been used as a
control measure but they have not given a reliable and long term management effect.
Carbendazim has a single mode of action, hence high chances of Foc developing resistance.
This study determined the pathogenicity, physiological races of Foc and the in vitro and
greenhouse efficacy of Trichoderma harzianum, T. asperellum and 7. viride for
management of Foc. Laboratory experiments were done at the Horticulture Research
Institute (HRI) in Kandara, Kenya in May 2022. The tissue culture and greenhouse
experiments were done at Coffee Research Institute. The molecular work was conducted at
Kenyatta University Plant Transformation Laboratory. The genomic DNA was extracted
from the 7 days old monosporic fungal cultures. The PCR amplification was done using
Foc specific primers for the three Foc races by targeting hypothetical protein, TEF-1a, and
SIX8a gene respectively. A total of 57 isolates were collected. Conidia for pathogenicity
test were harvested from 14 days old Fusarium cultures on PDA media using two layered
cheese cloth, the greenhouse pathogenicity experiment was done using the root dipping
method. For management in the greenhouse, the test products and Foc were applied directly
into the soil. All isolates were tested in four replicates of one plant per isolate. Disease
severity was recorded weekly for 20 weeks. A disease scale of 1-5 was used during data
collection. In vitro efficacy of fungicides was evaluated using poisoned food technique.
The fungal radial growth for in vitro efficacy was recorded daily for one week. The data on
plant biomass, biological and chemical control treatments and the data on pathogenicity test
experiment were subjected to one-way ANOVA. The results were compared using
Student—-Newman—Keuls (SNK) test at P<0.05. All the tested isolates were virulent. The
isolates that were highly pathogenic based on data on external and internal symptoms
included, AP009, CV005, KL002, KL004, AP007, EM001, AP006, CV001, CV004, and
AP002. Data on plant biomass revealed that the discase caused by the pathogens also
decreased the plant biomass. All the test fungicides; 7. asperellum at 0.1% rate, T. viride at
0.6% rate, T. harzianum 0.1% rate, and Carbendazim (500g/1) were effective in
management of Foc. The results indicated that 7. viride, T. harzianum, T. asperellum and
Carbendazim (500g/1) recorded a significantly (P<0.05) higher control of Foc compared to
the negative control at 58.57 %, 61.38 %, 72.68 %, and 78.94 % respectively. The
percentage control of Foc using T. viride, T. harzianum, and T. asperellum, was
significantly p < 0.05 lower compared (0 Carbendazim (500g/1). A total of 31 isolates
collected were confirmed to belong to Foc racel. This study generated new knowledge on
the diversity of Foc in banana growing regions of Central and Eastern Kenya as well as
identifying potential biological control agents against panama disease. These findings will
enable farmers to access a wider range of management strategies for long-term control of
panama disease.
Description
A Thesis Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Science in Crop Protection (Plant Pathology Option) in the School of Agriculture and Environmental Sciences of Kenyatta University, October 2023
Keywords
Virulence, Diversity and Management, Fusarium Oxysporum F.Sp. Cubense, Bananas, Counties, Central and Eastern, Kenya