Resumo

MEDINA, Alessandra; GONZALEZ-VERA, Alex; PINEDA, Juan  e  HERNANDEZ, Alexander. Cultural characterization and pathogenic test of Ceratobasidium spp isolated from maize banded leaf. Bioagro [online]. 2012, vol.24, n.3, pp.197-204. ISSN 1316-3361.

The banded leaf of maize is the primarily disease in corn fields in Portuguesa State, Venezuela. The objectives of this study were to determine the incidence and carry out cultural and pathogenic characterization of binucleate Rhizoctonia strains isolated from typical symptoms of the banded leaf of maize. From samples collected in 2006, fungus strains were isolated in semi selective media and they were purified by growing hyphae tips. Nuclear staining was used to verify the number of nuclei per cell, and it allowed to find that 39.68 % of the isolates belonged to binucleate Rhizoctonia. Isolates were characterized by measuring the formation of sclerotia and growth velocity in PDA medium. Two pathogenicity tests were performed: a) in greenhouse, where agar-mycelium discs were inoculated in basal leaves of healthy maize plants, and b) in laboratory, where a grain of rice colonized by the fungus was placed on the adaxial part of healthy leaves in 2 ppm kinetin solution. The results in greenhouse indicated that the 16 tested strains caused symptoms in 100 % of the inoculated seedlings, being a response similar of the control Rhizoctonia solani AG1 IA. Only 31.2% of strains and isolates formed sclerotia, and the most aggressive isolates (M2C1, M4G4, M5B1, and M1F3) showed an average growth rate of 1.1 cm per day, under laboratory conditions. We conclude that Ceratobasidium (= binucleate Rhizoctonia) emerges as a pathogen of the complex banded leaf of maize, in Portuguesa State, Venezuela.

Palavras-chave : Zea mays; binucleate Rhizoctonia; nuclear stain.

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