Eficiência de diferentes moléculas na redu o dos sintomas da queima das bainhas em arroz e no crescimento de Rhizoctonia solani in vitro Efficiency of different molecules on the reduction of sheath blight symptoms in rice and on Rhizoctonia solani growth in vitro

Este estudo verificou a eficiência da aplica o de diferentes moléculas em reduzir o comprimento relativo da les o (CRL) da queima das bainhas em arroz. Plantas dos cultivares BR-Irga 409 e Labelle foram cultivadas em solu o nutritiva e inoculadas com Rhizoctonia solani, no estádio de máximo perfilhamento. às 24 horas antes da inocula o, as bainhas das plantas foram pulverizadas com solu es de silicato de potássio (SP), silicato de potássio + fósforo (SP+F), Acibenzolar-S-Metil (ASM), fungicida Carbendazim, quitosana desacetilada (QD), etileno (ET) e fosfito de potássio (FP). Plantas cujas bainhas foram pulverizadas com água destilada serviram como testemunhas. O efeito das moléculas contidas nesses produtos no crescimento micelial de R. solani foi testado in vitro. Para BR-Irga 409, o CRL foi menor com a aplica o do FP, em rela o aos demais tratamentos, exceto o Carbendazim. A aplica o do Carbendazim reduziu em 86,1% o CRL, em rela o à testemunha. O CRL foi significativamente menor no cultivar BR-Irga 409 do que no 'Labelle', com aplica o do FP. O crescimento micelial de R. solani foi reduzido apenas pelo FP e Carbendazim, em compara o com os demais tratamentos. N o houve diferen a significativa entre os tratamentos testemunha, SP e SP+F para a concentra o de Si nas bainhas das plantas dos dois cultivares. This study aimed to test the efficiency of different molecules on the reduction of the relative lesion extension (RLE) of sheath blight in rice. Plants of cultivars BR-Irga 409 and Labelle were grown in nutrient solution and inoculated with Rhizoctonia solani at the maximum tillering stage. At 24 hours before inoculation, sheaths of plants were sprayed with solutions of potassium silicate (PS), potassium silicate + phosphorus (PS+P), Acibenzolar-S-Methyl (ASM), Carbendazim fungicide, deacetylated chitosan (DC), ethylene (ET) and potassium phosphite (PP). Sheaths from plants sprayed with water served as the control treatment. The effect of these products on R. solani mycelia growth was also studied in vitro. For BR-Irga 409, the RLE was lower with the application of PP compared with the other treatments, except the Carbendazim. The application of Carbendazim reduced in 86.1% the RLE in comparison with the control. The RLE was lower for BR-Irga 409 than for Labell with the application of PP. Mycelia growth of R. solani was inhibited only by PP and Carbendazim in comparison with the other treatments. There was no significant difference among the treatments control, PS, and PS+P for silicon concentration on sheaths of plants of the two cultivar