Isolation and Characterization of Endophytic Trichoderma Isolates for Antagonistic Activity Against Coffee Wilt Disease (Gibberella Xylarioides) in Keffa Zone, Southwestern Ethiopia
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Date
2018-09-04
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Addis Ababa University
Abstract
The present study aimed to evaluate, test and characterize potential biocontrol of endophytic
Trichoderma isolates against coffee wilt pathogen (Gibberella xylarioides). In this study we
examined the effect of pH and temperature on the mycelia growth and spore yield of Trichoderma
isolates in batch culture. Coffee root samples were collected from different ecological habitat of
Kaffa zone for the isolation of endophytic Trichoderma isolates. The ability of Trichoderma
isolates to grow at pH 4.5, 6.5 and 7.5 were tested in liquid potato dextrose broth (PDB) medium.
The effect of volatile and non-volatile compounds produced by Trichoderma isolates on radial
growth of pathogenic fungi, F. xylarioides was also determined. In vitro antagonistic bioassays
were performed to evaluate and determine the potentiality of Trichoderma isolates as biocontrol
agents against F. xylarioides. The pH and temperature had significant effect on the growth and
sporulation of Trichoderma isolates. It was observed that the optimum pH for maximum mycelial
growth and spore yield produced by Trichoderma isolates in batch cultures was pH 7.5 while the
optimum temperature for mycelial growth and the maximum spore yield was produced at optimum
temperature was 25OC. This work has revealed the important role that environmental conditions
plays in the mycelia growth and spore yield of Trichoderma isolates, a biocontrol agent. In in-vitro
bioassay the experimental results showed that all isolates of Trichoderma were able to inhibit the
growth of F. xylarioides under in vitro experiment at rates ranging from 42.2 % to 69 % after 10
days of incubation. The highest mean inhibitory effect on the growth of the test pathogen was
achieved by Gimbo Trichoderma isolate 05 (Gim-T05) (69%) followed by Gim-T10 (67.6%) and
Gim-05 (66.7%), while Gowata Trichoderma isolate 01 (Gow-01) isolate showed the lowest
(42.2%) mean inhibitory effect restricting it almost completely in plates as compared to the control
consisting of F. xylarioides growing alone. Gimbo Trichoderma isolate 05 (Gim-T05) produced
zones of inhibition which is an indicative of the production of secondary metabolite(s) inhibiting
the mycelial growth of F. xylarioides. Thus, the use of novel isolates of Trichoderma with efficient
antagonistic capacity against F. xylarioides is a promising alternative strategy to pesticides for
coffee wilt disease management.
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Keywords
Antagonism, Coffee Arabica, Endophytes, Ph, Temperature