Resumo

LOPEZ, Yuleidy; PINEDA, Juan B; HERNANDEZ, Alexander  e  ULACIO, Dilcia. Differential effect of six Trichoderma isolates on root development, plant growth and severity of Rhizoctonia solani on mayze. Bioagro [online]. 2010, vol.22, n.1, pp.37-42. ISSN 1316-3361.

The banded leaf spot disease on maize, Rhizoctonia solani Kuhn, has increased its incidence in Venezuela, causing considerable damages and yield reduction. In many cases, soil microbiota can protect the plant from the pathogen attack and contributes to better plant development. In order to study forms of biocontrol of R. solani, six isolations of Trichoderma obtained from maize plant rizosphere  were collected in several localities of Portuguesa and Yaracuy States;  the  isolations  were  used  in  antagonism tests on a sterilized substrate in nursery. Two orifices were made in the substrate and sterilized grains of rice were placed on them, covering with 2 mL of spore solution of the antagonist (3-7x10⁶ conidia mL^-1). Later, one maize of seed hybrid D2000 and two esclerotia of R. solani was placed in each hole and added 3 mL of the solution of the antagonist, covering with sterilized soil. In relation to plant survival, there was a positive effect of the treatments where Trichoderma was used, obtaining values between 70 and 90 %. As far as plant disease severity up to 60 days, it was obtained a value of 82.5 % in the control and 16.2 % in the best treatment with Trichoderma.  For  the  isolation coming from Píritu-Portuguesa State, the advance of the disease was the smallest. This isolation, followed by the one coming from Yaritagua-Yaracuy State, promoted a greater plant growth and better root development.

Palavras-chave : Plant pathology; banded leaf spot; infection level; Zea mays.