Synergistic Effect of Plant Defense Elicitors and Biocontrol Agents on Induction of Defense Enzymes in Pea against Downy Mildew.

Background: Plant defense against the pathogens can be induced by using different defense inducers. Plants can be treated with elicitors for fast and more intense mobilization of defense responses which can enhance the resistance against biotic or abiotic stresses. Methods: The present study has been undertaken to evaluate the synergistic effect of different plant defense inducing chemical (Salicylic acid, Isonicotinic acid, Oxalic acid and Chitosan) and biological (Trichoderma harzianum and Pseudomonas fluorescens) elicitors. Enzyme activity was expressed as the increase in absorbance using spectrophotometer. Result: Among all the treatments the maximum PAL activity (35.58 mg/g of fresh weight) was found in case of oxalic acid but after 48 hrs its activity reduced drastically. Next to oxalic acid Pseudomonas fluorescens (31.38 mg/g of fresh weight), chitosan + Trichoderma harzianum (29.38 mg/g of fresh weight) and chitosan + Pseudomonas fluorescens (27.89 mg/g of fresh weight) showed the maximum enzyme activity. The PPO activity reached the highest at 96 hr after challenge inoculation in case of chitosan + Trichoderma harzianum (9.74 µmol/min/mg/protein) treated plants followed by Trichoderma harzianum (3.53 µmol/min/mg/protein) alone. the maximum PO activity (49.12 µmol/min/mg/protein) was found in case of chitosan + Pseudomonas fluorescens treated plants followed by chitosan (42.48 µmol/min/mg/protein) after 72 hrs. the maximum phenolics (27.53 mg/gm of fresh weight) was found in case of chitosan + Pseudomonas fluorescens after 48 hrs of treatment. [ABSTRACT FROM AUTHOR]