Eight pre-selected bacterial strains were evaluated for control of rice sheath blight caused by Rhizoctonia solani, Pseudomonas synxatha, P. fluorescens, Bacillus subtilis, Bacillus sp. and Stenotrophomonas malthopilia. Rice seeds cv. El Passo L144 were treated by immersion in a bacterial suspension (A540=0.5) of each isolate under agitation at 10ºC for 30 min. Seeds immersed in saline solution and in saline plus fungicide (Carboxin + Thiran) were used as control. Ten seeds per pot were used, in four replications, in a completely randomized design. Three assays were performed, and in the first it was possible to select the three strains which reduced the severity of the disease, reaching 50, 33.3 and 16.7%, respectively. These isolates were used in the two last assays, which were maintained in greenhouse until the harvesting stage, where it was possible to observe the biocontrol effect, mainly by the strain of P. fluorescens DFs223, with significant reduction in the disease severity, reaching 88 and 91.7% in the second and third assays, respectively. There was an increase in the number of panicles, as well as in the number of tillers and dry mass of roots, reaching to 42.8, 81.2 and 113 % respectively, in plants treated with this isolate in both assays.
Rhizoctonia solani; Oryza sativa; biocontrol; rhizobacteria
