Rizobactérias no controle in vitro de Pyricularia grisea

Abstract

Rice is the second most cultivated cereal in the world and the blast caused by Pyricularia grisea is a major disease of this crop, causing losses of up to 100% in production. The use of rhizobacteria has shown great potential to pathogens control, and an environmentally friendly alternative to the reduction of pesticide use in rice crops. This work aimed to obtain different rizobacterianos isolated from rice and soybeans plants and evaluate them in vitro for their antagonistic ability against fungus P. grisea. The tests were performed at the Laboratory of Soil Microbiology and Plant Pathology, Federal University of Pampa - Campus Itaqui. Isolation of rhizobacteria was made from roots of rice plants, taken at random from six different points from three crops of rice of the municipalities of Itaqui and Maçambará. The isolates with different shape and color were transferred to test tubes to obtain pure isolates. The isolates obtained was performed to evaluate the in vitro Mycelial Growth Speed Index (MGSI) and % inhibition of mycelial growth. The experimental design was completely randomized with four replications for each treatment. Each was isolated rizobacteriano peaked in the four ends of the petri dish, except the control treatment, and a disc with 0.5 cm of mycelium of the fungus was placed in the center of all cards. For evaluation of antagonistic rizobacteriano, measurements were made daily of the pathogen to the control reaches the edge of the plate. The data were subjected to analysis of variance and the means of each treatment, grouped by Scott-Knott test, at 5% probability. Rizobacterianos 39 isolates were obtained from rice and soybeans, where 89,7% had some degree of control as to MGSI compared with the control treatment and 94,9% showed antagonistic to P. grisea when evaluated the percentage inhibition of mycelial growth. The rhizobacterium BAC5 was the most effective, with 73,1% inhibition of mycelial growth of P. grisea. Rhizobacteria were obtained from the rhizosphere of rice plants that can act as antagonists to the pathogen Pyricularia grisea, where the isolated BAC5 is the most efficient among the isolates tested rizobacterianos.