Occurrence of Bipolaris maydis leaf spot on tanzania guineagrass in the north region of the Mato Grosso state

Abstract

The monoculture associated with the intensification of livestock results on appearance of diseases in forages, which can lead to significant losses. Symptomatic leaves of Tanzania guineagrass (Panicum maximum) collected in Alta Floresta and Nova Guarita, Mato Grosso State, Brazil, were analyzed in the Plant Pathology Laboratory of UNEMAT/Alta Floresta. Fragments of diseased tissues previously disinfected in 70% ethanol and sodium hypochlorite to 1000 ppm solutions, were plated in a potato dextrose agar culture medium. The plates were stored at 25 °C and 12-hours photo period, for seven days. After this period Tanzânia guineagrass (Panicum maximum) plants were inoculated with the pathogen from infected plants collected on both cities. To complete Koch's postulate, after the onset of symptoms, the pathogen was reisolated. The fungus Bipolaris maydis, causal agent of leaf spot was identified, based on the observation of fungal structures in the light microscope, the use of sort keys and the of Koch’s postulate