Evaluation of Antifungal Activity of Trichoderma Isolates and Their Crude Extracts on Coffee Wilt Pathogen (Gibberella Xylarioides)
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Date
2018-05-05
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Addis Ababa University
Abstract
Coffee wilt disease (CWD) caused by the fungus Fusarium xylarioides is an important soil-borne disease reducing coffee (Coffea arabica L.) production yields at up to 60%. The present study aimed to evaluate, test and characterize potential biocontrol of rhizosphere Trichoderma isolates and their most active antifungal crude extracts against coffee wilt pathogen (Gibberella xylarioides). In vitro antagonistic bioassays were performed to evaluate and determine the potentiality of Trichoderma isolates as biocontrol agents against F. xylarioides. For extraction of antifungal crude extracts from fungal mycelia organic solvents such as chloroform, ethanol, methanol, ethyl acetate, n-hexane and acetone were used. A direct bioautographic procedure, involving spraying suspension of F. xylarioides on TLC plates developed in solvents of varying polarities to detect a number of antifungal substances present in the extracts. 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 54.8% to 83.2% after 10 days of incubation. The highest mean inhibitory effect on the growth of the test pathogen was achieved by Addis Ababa University Trichoderma isolate 71 (AUT-71) (83.2%) followed by AUT-03 (72.8%) and AUT-86 (67.2%), while AUT-89 isolate showed the lowest (54.8%) mean inhibitory effect restricting it almost completely in plates as compared to the control consisting of F. xylarioides growing alone. AUT-32 and AUT-66 isolates produced zones of inhibition which is an indicative of the production of secondary metabolite(s) inhibiting the mycelial growth of F. xylarioides. Bioautography assay revealed that 94 zones of inhibition spots and the highest inhibition zone was observed by SS1 in isolates AUT-21 (53 mm) at Rf (0.75), and AUT-66 and AUT-89 (35 mm) with chloroform extract at Rf (0.51) and at Rf (0.55), respectively. 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, Coffee Wilt Disease, TLC, Trichoderma Isolates