Seleção de rizobactérias para o tratamento de sementes de arroz

Abstract

The use of treated or healthy seeds is important to avoid introducing new pathogens into new areas. Treatment with fungicides is the most used method, however, also increases the risk of environmental contamination. An alternative to chemical control is biological control using rhizobacteria that have potential in reducing pathogens. This study aimed to select rhizobacteria to fungi control transmitted by seeds and to promote germination and seedling growth of rice. The experiment was conducted at the Laboratory of Plant Pathology, Federal University of Pampa - UNIPAMPA / Campus Itaqui. For the execution of this work was used to cultivate the puita INTA-CL rice. Rice seeds were treated with 21 rhizobacteria isolated from rice roots, which are deposited in a freezer at temperature of -20 °C in the Laboratory of Phytopathology. The rhizobacterianas suspensions were prepared with NaCl solution at 0.85%, and the concentrations were adjusted to A₅₄₀ = 0.5. For microbiolization, seeds were immersed in the bacterial suspension for 30 minutes under stirring at 25º C. After microbiolization, 25 seeds were placed in clear plastic boxes on two sheets of paper germination. The experimental design was completely randomized, with four replicates of 25 seeds. The evaluation of incidence and identification of pathogens was performed after seven days individually by examining the seeds in magnifier. Evaluation of seed germination was held on the 5th and 14th days. For assessing the Germination Speed Index (GSI), the seeds were evaluated daily until day 14th. The evaluation of growth promotion was held on the 14th day, where measurements of roots length and shoots were held. The results were subjected to analysis of variance and means were compared by the Scott & Knott test at 5% probability. All isolates tested reduced the incidence of fungi in seeds. However, only 14 isolates concomitantly reduced the incidence of the fungus Pyricularia grisea, Phoma sp. and Bipolaris oryzae in rice seeds. All isolates tested reduced the incidence of fungi in seeds. All rhizobacterianas isolates tested not increased the rate of germination speed and germination. The BAC 06, BAC 28, BAC 40.1 and BAC 40.2 isolates promoted the reduction of the incidence of Pyricularia grisea, Phoma sp. and Bipolaris oryzae and the highest growth of shoots and roots of rice seedlings, concomitantly. Therefore, the tested rhizobacteria have the potential to control pathogens in seeds and promote growth of rice seedlings.