Effect of silicon and fungicide on photosynthetic responses in barley leaves challenged by Bipolaris sorokiniana

Abstract

The effect of silicon (Si) amendment in the soil, combined with fungicide application 7 or 15 days before plant inoculation, was evaluated on barley plants challenged by Bipolaris sorokiniana. For this, the disease control, the gas exchange parameters, and the concentration of photosynthetic pigments were evaluated on two barley cultivars (AnaG01 and BRS Cauê). The higher spot blotch severity occurred on plants not supplied with Si and without fungicide application. The disease reduced the net assimilation of CO2 (A), the stomatal conductance (gs), internal CO2 concentration (Ci) and transpiration rate (E). The concentration of photosynthetic pigments was significantly altered in inoculated leaves. The plants supplied with Si showed an increase in leaf Si concentration, which was associated with a reduction of up to 15% in spot blotch, and increase in A, gs, Ci, and E, and concentration of pigments (Chlorophylls a and b, and carotenes). The fungicide reduced disease intensity and increased A and gs, and the concentration of pigments. Higher control of the disease by fungicide occurred on plants supplied with Si, especially when application occurred at 15 day before inoculation. In conclusion, the association of Si and fungicide provided a greater reduction in spot blotch and maintained a better physiological state of the plant when affected by B. sorokiniana.