Induction of defense mechanisms with chemical elicitors and Alternaria brassicae in mustard (Brassica juncea)

Abstract

Induction of resistance in plants by the application of various biotic and abiotic agents is well known, however, our understanding on the impact ofsuch agents is still poor. Henceforth, effort has been made towards understanding ofinduced resistance in crop protection. Two promising combinations of benzothiadiazole (BTH) and salicylic acid (SA) viz., T1 (3.3ppmBTH + 33.3ppmSA) and T2 (6.6ppmBTH + 16.6ppm SA), were tested with/without avirulent biotic inducer, Alternaria brassicae for their ability to induce changes in the activities of defense enzymes (peroxidase, superoxide dismutase and phenylalanine ammonia lyase) and phenolics that may help in boosting the defense mechanism of Brassica juncea (var. RLM 619) against the attack of Alternaria blight. The results revealed that both the combinations of elicitors showed increase in the activity of defense enzymes and phenolics on all days of observation as compared to control in four and five weeks old plants. It was observed that the bio-control agent, A. brassicae induced higher level of defense enzymes and phenolics in inoculated leaves than that of uninoculated leaves on all days of observation. In conclusion, this study will be useful in formulating A. brassicae and elicitors based formulations which may have effective defense responses in mustard.