RESUMO
Silicon (Si) is considered to be a plant growth and development regulator element as well as provide the regulatory response against various biotic stressors. However, the potential mechanism of Si enhancement to regulate plant disease resistance remains to be studied. Therefore, the current study evaluated the effects of Si application on the performance of sugarcane against Xanthomonas albilineans (Xa) infection. Si was applied exogenously (0, 3.85 and 7.70 g Si/kg soil) and the results show that plant height, stem circumference and leaf width of siliconized sugarcane have been improved, which effectively reduced the disease index (0.17-0.21) and incidence (58.2%-69.1%) after Xa infection. Lowest values of MDA (348.5 nmol g-1 FW) and H2O2 (3539.4 mmol/L) were observed in 7.70 g Si/kg soil followed by in 3.85 g Si/kg soil (MDA: 392.6 nmol g-1 FW and H2O2: 3134.6 mmol/L) than that of the control. Whereas, PAL enzyme activity (50.8 mmol/L), JA (230.2 mmol/L) and SA (2.7 ug mL-1) contents were significantly higher in 7.70 g Si/kg soil followed by in 3.85 g Si/kg soil (PAL: 46.3 mmol/L, JA: 182.7 mmol/L and SA: 2.4 ug mL-1) as compared to control. The lower MDA, H2O2 level and higher enzymatic activities were associated with the highest expression levels of their metabolic pathway associated genes i.e., ShMAPK1, ShLOX, ShPAL, ShAOS, ShAOC, ShC4H, ShCAT, Sh4CL and ShNPR1 (22.08, 15.56, 10.42, 3.35, 2.54, 2.14, 1.82, 1.67 and 1.22 folds, respectively) in 7.70 g Si/kg soil as compared to other experimental units and control. Overall, the results of current study indicates that siliconized sugarcane more actively regulates disease resistance through modulation of growth and MDA, H2O2, SA and JA associated metabolic pathways.