Temporal Dynamics of Induced Enzymes in Finger Millet: The Impact of Neem Leaf Extract and Brevibacillus brevis in Blast Disease Management

Ragi or finger millet (Eleusine coracana (L.) Gaertner) is one of the common millets in several regions of India. The present study investigated enzymatic responses of finger millet leaves upon inoculation with the blast pathogen, Pyricularia grisea Sacc. and subsequent treatments with bio-agent, botanical, fungicide and salicylic acid. Enzymatic responses viz., β-1,3-glucanase, chitinase and lipoxygenase (LOX) were examined spectrophotometrically (at 24, 48 and 72 hours after treatment), which are pivotal components of the plant defense system. The pathogen was inoculated at twenty-one days old seedlings and immediately upon symptom development, the treatments were imposed. Treatments included seedling root dip and foliar spray with bacterial antagonist, Brevibacillus brevis; foliar spray with neem leaf extract (1500 ppm), carbendazim 12%+ mancozeb 63% (500 ppm) and salicylic acid (50 μM), challenged and unchallenged control. The results revealed that the enzymatic response of β-1,3-glucanase exhibited its highest activity at 24 hours post-treatment in foliar spray with neem leaf extract, whereas chitinase activity reached its maximum at 72 hours post-treatment with neem leaf extract, with a value of 0.75 µg glucose min-1 mg-1 protein. Lipoxygenase enzyme showed its peak activity at 48 hours post-treatment with neem leaf extract, showing a significant increase from 264.72 to 474.62 µmol/HPO/min compared to other treatments.