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CACIQUE, Isaías Severino; DOMICIANO, Gisele Pereira; RODRIGUES, Fabrício Ávila  and  VALE, Francisco Xavier Ribeiro do. Silicon and manganese on rice resistance to blast. Bragantia [online]. 2012, vol.71, n.2, pp.239-244. ISSN 0006-8705.

Blast, caused by the fungus Pyricularia oryzae, is the most important fungal disease of rice. The effect of silicon (Si) and manganese (Mn), and their interaction, on rice resistance to blast was investigated. Rice plants (cultivar "Metica 1") were grown in hydroponic solution with 0 or 2 mmol L-1 of Si and with 0.5, 2.5, and 10 mmol L-1 of Mn. Sixty-day-old plants were inoculated with a conidial suspension of P. oryzae and the incubation period (IP), the number of lesions (NL) per cm2 of leaf area, the lesion size (LS), and blast severity were evaluated. Blast severity was scored at 48, 72, 96, and 144 hours after inoculation and data were used to obtain the area under blast progress curve (AUBPC). Silicon concentration was significantly higher in leaf tissues of plants supplied with this element than on its absence, regardless of Mn rates. There was no significant difference in Si concentration among the Mn rates for both - Si and +Si treatments. The Mn concentration was significantly higher in the tissues of plants from the - Si treatment as compared to plants of the +Si treatment, but only at the rate of 10 mmol L-1 of Mn. There was a significant increase in Mn concentration as the rates of this micronutrient increased from 0.5 to 10 mmol L-1 regardless of the Si treatments. The IP significantly increased in the +Si treatment. The Mn rates had no effect on the IP regardless of the Si treatments. The NL was significantly lower in the presence of Si regardless of the Mn rates. The Mn rates had no effect on NL regardless of the Si treatments. The addition of Si to the nutrient solution significantly reduced both LS and AUBPC regardless of Mn rates. However, in the absence of Si, the values for LS and AUBPC were significantly lower at the Mn rate of 10 µmol L-1 as compared to the rate of 0.5 µmol L-1. Overall, the results from this study showed the potential of Si to decrease blast development on rice regardless of the foliar concentration of Mn.

Keywords : Oryza sativa; Pyricularia oryzae; leaf spot; mineral nutrition.

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