Potentiation of defense-related gene expression by silicon increases wheat resistance to leaf blast

It is well known that silicon (Si) increases the resistance of many plant species to several pathogens, including Pyricularia oryzae , the causal agent of blast on wheat, but the mechanisms underlying such resistance remain elusive. This study was carried out to investigate whether Si-mediated wheat resistance to blast could be linked to host defense responses at the histopathological level as well as with greater expression of defense-related genes. Wheat plants (cv. BR 18) were grown in hydroponic cultures containing 0 (−Si) or 2 mM (+Si) Si and were either non-inoculated or inoculated with P. oryzae . The foliar Si concentration was 0.4 and 4.5 dag/kg, and blast severity was 29.5 and 8.8 % for the −Si and +Si plants, respectively. Colonization of P. oryzae in leaf tissue for +Si plants was greatly limited and was associated with the deposition of phenolic compounds. The expression of all defense-related genes studied was significantly increased in response to P. oryzae infection. However, expression levels were 2- to 3-fold higher for the +Si plants relative to their −Si counterparts at 96 h after inoculation. This study provides further evidence that Si plays an active role in wheat resistance to leaf blast through the expression of some defense-related genes.