Foliar application of Bacillus subtilis AUBS1 reduces sheath blight and triggers defense mechanisms in rice

Foliar application of Bacillus subtilis strain AUBS1 significantly reduced the sheath blight disease of rice (Oryza sativa L.) under greenhouse conditions. Treatment with B. subtilis led to an increase in the activities of phenylalanine ammonia-lyase (PAL) and peroxidase (PO) and an accumulation of pathogenesis-related (PR) proteins in rice leaves. Application of B. subtilis also induced an accumulation of a thaumatin-like protein (17 kDa) and two β-1-3-glucanases (30 kDa and 33 kDa). Western blotting analysis for chitinase revealed the induction of two chitinases with apparent molecular masses of 30 kDa and 35 kDa in the induced plants. The coordinate upregulation of different defense mechanisms in induced plants suggests that these defense responses may be involved in the restriction of Rhizoctonia solani.