Rice Resistance to Brown Spot Mediated by Silicon and its Interaction with Manganese

Abstract

AbstractBrown spot is one of the most devasting and prevalent disease of rice and its control is mainly dependent on fungicide application. Therefore, this study aimed to examine the effects of Si and Mn on the development of brown spot on rice plants grown in hydroponic culture. Rice plants (cv. ‘Metica‐1’) were grown in plastic pots containing 0 or 2 mm Si (−Si and +Si treatments, respectively) with three Mn rates (0.5, 2.5 and 10 μm). Plants were inoculated with B. oryzae 39 days after emergence. The following components of resistance were evaluated: incubation period (IP), number of lesions (NL) per cm2 of leaf area, real disease severity (RDS) and area under brown spot progress curve (AUBSPC). The content of Si and Mn in the plant tissues was also determined. Si content was significantly higher in rice tissue of plants of the +Si treatment than of the −Si treatment regardless of the Mn rates used. The Mn rates did not affect the Si content of the rice plants. The Mn content of the rice tissues was significantly higher in the −Si treatment than on +Si treatment, regardless of the Mn rate used. The Mn content was significantly lower at 0.5 μm Mn in comparison to the other rates for both −Si and +Si treatments. The IP of brown spot on rice leaves significantly increased in the +Si treatment; but the Mn rates in the presence of Si had no effect on IP. In the −Si treatment, the IP was significantly higher only at the rate of 2.5 μm. The NL, RDS and AUBSPC were significantly reduced in the +Si treatment regardless of the Mn rates. The Mn rates in the presence of Si had no effect on these components of resistance. Overall, Si dramatically impacted the development of brown spot regardless of the presence of Mn at either low or high rates. This may be useful in regions where the soil has either toxic or deficient levels of Mn and cultivars with brown spot resistance are not commercially available.