Abstract
The effective in vitro screening tests of Trichoderma viride for antagonism against post harvest pathogens of cassava roots (Manihot esculenta Crantz) rot together with its competitive and mycoparasitic abilities informs its selection as the most promising candidate for the biocontrol of post harvest cassava root rot pathogens. While the percentage germination of the spores were observed to increase with increasing dilution of the culture filtrate (100, 50, 25, and 10% ) at a concentration of 20,000 spores/ml, the percentage rot recorded amongst the untreated cassava roots ranged from 4% (Rhizopus oryzae) to 44% (Aspergillus flavus). Treatment with the antagonist and the subsequent storage resulted in a remarkable reduction in the frequency of occurrence of the normal root surface mycoflora and the pathogens over a 3 weeks storage period. Botryodiplodia theobromae and R. oryzae were isolated only in the first week of storage and at a frequency of 3 and 2% rot, respectively, after treatment whereas A. flavus and Fusarium solani persisted throughout the whole storage period with 2 and 3% rot on the third week, respectively. The observed results suggest that T. viride is root surface competent and highly antagonistic.
Highlights
Trichoderma viride is a filamentous soil fungus known to be an effective biocontrol agent of a range of important airborne and soil borne pathogens
The result suggests that the inoculated B. theobromae and R. oryzae did not survive beyond 1 week of storage whereas A. flavus and F. solani persisted throughout the whole period (Table 2)
The idea of a sustainable agricultural practice and environmental protection enhances the importance of biocontrol
Summary
Trichoderma viride is a filamentous soil fungus known to be an effective biocontrol agent of a range of important airborne and soil borne pathogens. Trichoderma spp. is the most widely studied biocontrol agents (BCAs) against plant pathogens. Weindling and Emerson (1936) observed that they could excrete extracellular compound which was named gliotoxin. Many antibiotics and extracellular enzymes were isolated and characterized later, and the biocontrol mechanisms became clearer (Haran et al, 1996; Zhihe et al, 1998). The first to appear, named “Primary deterioration” consist of physiological changes characterized by an internal root discoloration called vascular streaking. Wounds and bruises are the major points of entry for micro-organisms after harvest leading to the second stage of cassava root spoilage, known as “Secondary deterioration”
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