Abstract

REYES, Yusimy; MARTINEZ, B  and  INFANTE, Danay. EVALUATION OF THE ANTAGONISTIC ACTIVITY OF THIRTEEN Trichoderma spp. isolates ON Rhizoctonia sp.. Rev. Protección Veg. [online]. 2008, vol.23, n.2, pp. 112-117. ISSN 2224-4697.

The sheath blight or blot easterly is considered the second important disease on rice in Cuba and worldwide. The methods used to control this disease have not been effective and, at present, there is a tendency to use the biological control. Trichoderma is recognized as a potential antagonist of soil pathogens, with positive results as an antagonist to Rhizoctonia . The objective of this work was to select promising strains of Trichoderma spp . according to their in vitro antagonism and effectiveness to control Rhizoctonia sp. under semicontrolled conditions. Antagonism was evaluated using the dual culture method, where the competition for the substrate, mycoparasitism and antibiosis could be observed. The colony radial growth was measured with a graduated ruler and the inhibition percentage was calculated after 96 hours. Micoparasitism was also observed using an optic microscope with 400x magnification, where the interaction between strains was evaluated. Strains showing a radial growth inhibition higher than 50 % and at least two types of hyphae interaction were selected to be tested under semicontrolled conditions for evaluating the technical effectiveness on the pathogen in stainless steel trays of 0,30cm². The 100 % of the strains had high antagonism capabilities with different types of hyphal interactions, lysis , vacuolization, rolling, and penetration. Five strains were selected, three of them showing a technical effectiveness of 50% under semicontrolled conditions. Strains 39, 56 and 78 resulted promising to control the disease under field conditions.

Keywords : Trichoderma; Rhizoctonia; rice; biological control.

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