Microbiolização de sementes para o controle da mancha-parda e da escaldadura em arroz irrigado

Abstract

The potential of isolates DFs185 (Pseudomonas synxatha), DFs223 (Pseudomonas fluorescens), DFs306 (unidentified), DFs416, DFs418 and DFs419 (Bacillus sp.), DFs422 (Bacillus subtilis) and DFs471 (Stenotrophomonas maltophilia) was evaluated for the control of rice brown spot (Bipolaris oryzae) and leaf scald (Gerlachia oryzae). Rice seeds cv. El Passo L144 were immersed in a suspension (107 a 108 CFU/mL) of each of the isolates, agitated for 30 min at 10°C and sowed in pots, in complete randomized design with four replications. Two controls were used: one with seeds treated with saline solution, and the other with saline solution plus fungicide (Carboxin+Thiran). Two assays for each of the pathogens were carried out. Plants were inoculated by spraying and their disease severity was evaluated at 7, 14 and 21 days after inoculation for the calculation of the area under disease progress curve. The best result for brown spot biocontrol in the first assay was provided by isolates DFs185, DFs223 and DFs306, which presented 80, 86 and 70% of control. In the second assay, isolate DFs306 was the most efficient, with reduction in disease severity reaching 74% in relation to control. The isolates DFs223, DFs185 and DFs306 provided a rise in grain yield of 74, 70 and 59%, respectively. For the control of leaf scald, in the first assay, the isolates that presented the best results were DFs416 and DFs418, which showed 65 and 59% of control, respectively. In the second experiment, isolates DFs416 and DFs185 reduced the disease severity, respectively, by 64 and 60%, without increasing the yield.