Trichoderma spp. are used for biocontrol of several plant pathogens. However, their efficient interaction with the host needs to be accompanied by production of secondary metabolites and cell wall-degrading enzymes. Three parameters were evaluated after interaction between four Trichoderma species and plant-pathogenic fungi: Fusarium solani, Rhizoctonia solani and Sclerotinia sclerotiorum. Trichoderma harzianum and T. asperellum were the most effective antagonists against the pathogens. Most of the Trichoderma species produced toxic volatile metabolites, having significant effects on growth and development of the plant pathogens. When these species were grown in liquid cultures with cell walls from these plant pathogens, they produced and secreted β-1,3-glucanase, NAGAse, chitinase, acid phosphatase, acid proteases and alginate lyase.
Some species of Trichoderma have successfully been used in the commercial biological control of fungal pathogens, e.g., Sclerotinia sclerotiorum, an economically important pathogen of common beans (Phaseolus vulgaris L.). The objectives of the present study were (1) to provide molecular characterization of Trichoderma strains isolated from the Brazilian Cerrado; (2) to assess the metabolic profile of each strain by means of Biolog FF Microplates; and (3) to evaluate the ability of each strain to antagonize S. sclerotiorum via the production of cell wall-degrading enzymes (CWDEs), volatile antibiotics, and dual-culture tests. Among 21 isolates, we identified 42.86% as Trichoderma asperellum, 33.33% as Trichoderma harzianum, 14.29% as Trichoderma tomentosum, 4.76% as Trichoderma koningiopsis, and 4.76% as Trichoderma erinaceum. Trichoderma asperellum showed the highest CWDE activity. However, no species secreted a specific group of CWDEs. Trichoderma asperellum 364/01, T. asperellum 483/02, and T. asperellum 356/02 exhibited high and medium specific activities for key enzymes in the mycoparasitic process, but a low capacity for antagonism. We observed no significant correlation between CWDE and antagonism, or between metabolic profile and antagonism. The diversity of Trichoderma species, and in particular of T. harzianum, was clearly reflected in their metabolic profiles. Our findings indicate that the selection of Trichoderma candidates for biological control should be based primarily on the environmental fitness of competitive isolates and the target pathogen.
Genetic engineering has brought improvements of Trichoderma species for biotechnological processes such as agriculture. It has previously been reported that sm1 and aquaglyceroporin genes from Trichoderma harzianum are strongly expressed during pathogens biocontrol. We have previously shown that Sm1 plays a significant role in plant disease resistance and aquaporin (AQP) regulate physiological processes and responses related to water stress. Here, we report the evaluation of mutant lines with sm1 (deleated) and aqp (overexpressed) in Phaseoulus vulgaris growth promotion and disease resistance induction. It was investigated plants physiological and biochemical responses, plant growth promotion and biocontrol of Sclerotinia sclerotiorum, the causal agent of white mold. Treatments included Trichoderma harzianum wyld type, mutant line overexpressing aquaporin (Aqua), and deleted ΔEpl1mutant line. Our results demonstrated that Aqua mutant line increased leaf area in 25%, in comparison to non-treated plants. It also differed from other treatments, in comparison to plants with treatments ALL-42 and ΔEpl1, which increased 28% and 91%, respectively (Isso é abstract, ta confuse e extensor. Specific activity of β-1.3 glucanase was higher in plants treated with T. harzianum ΔEpl1 mutant isolate, in leaves and roots respectively with 2.07 Umg-¹ and 2.57 Umg-¹. Plants inoculated or not with S. sclerotiorum presented with 2.27 Umg -1 and 2.34 Umg -1 of β-1.3 glucanase on average, respectively, but enzymatic activity was higher on leaves when compared to the roots. The Aqua mutant demonstrated excellent growth promoting properties. Both mutants of T. harzianum do not induce resistance to white mold on common bean plants.
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