Resumo

PUNO, Ramon et al. Assessment of metabolic capacity of Trichoderma inhamatum Bol12 QD biocontrol on native strains of Phytophthora infestans in vitro. J. Selva Andina Res. Soc. [online]. 2011, vol.2, n.1, pp.26-33. ISSN 2072-9294.

Plant pathogen Phytophthora infestans is a cause of decreased crop yield of tomato, to control these losses, farmers use chemicals. This has consequences for the environment, human health and beneficial organisms in the ecosystem. The objective was to obtain and identify native isolates of Trichoderma spp. In soil planted with tomato Tlayacapan, Morelos (Mexico), Alternaria solani problems and Phytophthora infestans, also determine their antagonistic capacity in vitro. Trichoderma was isolated directly from soil by dilution in culture medium plate with potato dextrose agar (PDA). On the other side plate dilutions of yeast T. QD Bol12 inhamatum crops produced in batch for 30 days to compare the effectiveness of biocontrol. The filtered yeast inhibited mycelial growth kinetic of the agent in laboratory with the 1:2 dilution growth was 32.5% for the 1:4 dilution mycelial growth was 69.1% and finally to the dilution of 1:8 of the yeast biocontrol mycelium grew to 95.2%. To demonstrate the inhibitory activity on the pathogen in field crops, there were 3 L batch for four months. The application of three doses (undiluted, diluted 1:2 and 1:4 plus a control dilution water only) was performed in a complete block design with four replications randomly with the tomato crop, belonging to the variety Santa Cruz Kada Gigante in the plots of the Academic Rural United Campesina Carmen Pampa. Statistical analysis by Duncan's test showed that the pure leaven reduce infection by Phytophthora infestans significantly in tomato. Appeared another tomato plant pathogen, Septoria lycopersici, in the course of fieldwork. We also evaluated the effect of the dose of yeast to this disease, and also noticed a significant reduction with all doses of yeast. These experiments demonstrated that the seeds of T. QD Bol12 inhamatum have biocontrol effect on the tomato crop. The antagonistic capacity was assessed using the cellophane and the kind of antagonism with the dual culture technique. Data were subjected to analysis of variance and Tukey tests. We obtained 20 isolates of Trichoderma. The range of percentage inhibition of mycelial growth of plant pathogens by isolates ranged from 38.8 to 81.3% in A. solani, and from 16.3 to 85.5% in P. infestans. We selected 10 isolates inhibited at least 65% growth, which belong to the species: T. harzianum (THz), T. longibrachiatum (Tl) and T. koningii (Tk). The isolated Tl-17, TI-19, TI-20, TI-21, THz-16 and Tk-4, selected from A. solani, have antagonistic class 1, overgrowing the plant pathogen and fruiting on it. Isolates-17 THz, THz-18, TI-17, TI-18 and TI-19 selected against P. infestans, present antagonism antagonism Class 2 and Class 3 Thz19. Because of its antagonistic action in vitro on P. infestans and A. solani, can be considered as a promising agent Trichoderma in biological control of diseases brought about by these pathogens.

Palavras-chave : Phytophthora infestans; Trichoderma spp; secondary metabolites; antagonist activity; biological control.

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