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Effect of ultraviolet-induced mutants of Trichoderma harzianum with altered antibiotic production on selected
1Department of Biology, Birkbeck College, London, United Kingdom.
Abstract:
Mutants of Trichoderma harzianum with altered antibiotic production were isolated using ultraviolet light mutagenesis. These included strains whose activity in a Fusarium oxysporum spore germination assay was greater than twice that of the parental strain and one that had no detectable antifungal activity. Characterisation of extracellular metabolites of these strains using thin-layer chromatography and gas-liquid chromatography showed that the strains with high activity produced only elevated levels of a 6-n-pentyl pyrone, the antibiotic produced by the parental strain, but two new antifungal compounds. One of these has been identified as an isonitrile antibiotic. The nature of the interactions of the mutants with Fusarium oxysporum, Rhizoctonia solani, and Pythium ultimum was examined in an in vitro dual-plating assay using two media. High antibiotic production by two T. harzianum strains, BC10 and BC63, did increase inhibition of hyphal growth of R. solani and P. ultimum, but there was no correlation between increased antibiotic production and colonisation ability. In some cases the increased antibiotic levels appeared to impede colonisation of F. oxysporum and R. solani by the mutants. Slow growth rate also affected colonising ability. The types of interactions showed great variability depending on the nature of the T. harzianum isolate and on the test fungus.
Insights
Mutants of Trichoderma harzianum were engineered to enhance antibiotic production. These modified strains showed altered interactions with plant pathogens, impacting disease control strategies.
Area of Science:
- Microbial Biotechnology
- Agricultural Science
- Mycology
Background:
- Trichoderma harzianum is a fungus known for its beneficial properties in agriculture, including antibiotic production.
- Understanding the genetic and metabolic basis of T. harzianum's antifungal activity is crucial for developing biocontrol agents.
Purpose of the Study:
- To isolate and characterize mutants of Trichoderma harzianum with altered antibiotic production.
- To investigate the impact of enhanced antibiotic production on the interactions between T. harzianum and key plant pathogenic fungi.
Main Methods:
- Ultraviolet light mutagenesis was employed to generate T. harzianum mutants.
- Extracellular metabolites were analyzed using thin-layer chromatography and gas-liquid chromatography.
- In vitro dual-plating assays were used to assess interactions with Fusarium oxysporum, Rhizoctonia solani, and Pythium ultimum.
Main Results:
- Mutants exhibited varied antifungal activity, including strains with significantly increased antibiotic levels and one with no detectable activity.
- High-activity mutants produced elevated levels of 6-n-pentyl pyrone and two new antifungal compounds, including an isonitrile antibiotic.
- Increased antibiotic production correlated with enhanced inhibition of Rhizoctonia solani and Pythium ultimum but not Fusarium oxysporum.
- Colonization ability was influenced by antibiotic production and growth rate, showing complex interactions with tested pathogens.
Conclusions:
- Genetic modification of T. harzianum can lead to strains with altered antibiotic profiles and biocontrol potential.
- The efficacy of T. harzianum as a biocontrol agent is influenced by a combination of antibiotic production, growth rate, and specific pathogen interactions.
- Further research into the identified novel antifungal compounds could lead to new disease management solutions.