Abstract

CARDONA, Reinaldo  and  GONZALEZ, María Suleima. Characterization and pathogenicity of fungi of Helminthosporium complex associated to rice crop in Venezuela. Bioagro [online]. 2008, vol.20, n.2, pp.141-145. ISSN 1316-3361.

Rice is an important cereal in Venezuela with approximately 200,000 ha cropping area. The diseases caused by the fungi of the Helminthosporium complex are considered an important constraint in the production of the crop. Leaves and seeds of rice cv. INIA-017 coming from Portuguesa State, Venezuela, were placed on a plate with moistened filter paper and incubated at 26 ± 2°C, in laboratory conditions until fungal sporulation. Single spores were transferred to agar water and, when germinated, transferred to potato dextrose agar, preserving the resultant colonies for later used. Pathogenicity tests were performed on 21-day -old rice plants and four plants per bag were used by isolation. Before inoculation, the plants were placed in humid chamber for 48 h and inoculated with a suspension of 7x10⁴ spore·mL^-1; the control plants were sprinkled with distilled sterile water, placed in humid chamber for 72 h and taken to a greenhouse bench. The fungus Bipolaris oryzae was isolated from the leaves, and B.  oryzae and Exserohilum rostratum from the seeds. The inoculated plants showed symptoms of the disease between 5 and 7 days after inoculation, and the fungi could be reisolated from the affected tissues, thus showing their pathogenic capacity.

Keywords : Oryza; Bipolaris; Exserohilum; seed.