Standardized rosemary extract induces host plant defenses and suppresses rice leaf blast

Abstract

The efficiency of rosemary (Rosmarinus officinalis L.) liquid extract (RLE), standardized as rosmarinic acid (RA) on the suppression of rice (Oryza sativa) leaf blast (Magnaporthe oryzae) (LB) were determinate. RLE (3.3, 6.6, and 10 mg·mL−1), SRA (3.1, 4.2, and 6.3 mg·mL−1), and water (control) were sprayed on leaves of Primavera rice cultivar, at 48 hours before inoculation with M. oryzae (MO). The activities of chitinase, β-1, 3-glucanase, peroxidase, lipoxygenase, phenylalanine ammonia-lyase, and phenolic compounds and of salicylic acid levels were determined in samples collected before and after inoculation with MO. The highest concentrations of RLE and RA reduced the LB severity by more than 92%. Except for Peroxidase, all enzymes increased their activity after spraying RLE and RA, prior and after the challenge inoculation. Our results suggest that RLE standardized as RA can induce the activity of enzymes related to plant defense.