Vol. 9, Special Issue 4, Part F (2025)

In the present investigation of induced defense mechanisms revealed significant accumulation of Phenol, Peroxidase and Polyphenol oxidase and Phenylalanine ammonialyase in rice plants challenge inoculated with bioagents M. graminicola. Phenolic compounds are known to play a major role in defense mechanism of plants against various externalinfectious agents. Accumulation of these enzymes after seven days challenge inoculation with the nematode and gradually increased up to 28 days. The highest accumulation of Phenol (2.36 μg catechol mg^-1 protein), Peroxidase (6.23 change inabsorbance m-1 mg-1 protein), Polyphenol oxidase (3.48 change in absorbance m-1 mg-1 protein) and Phenylalanine ammonialyase (34.13 nmol transcinnamic acid m-1mg-1 protein) was observed in case of Trichoderma isolates S13 at 14^th, 21^st, 21^st and 14^thdays after nematode inoculation respectively. Plants inoculated with the nematode alone also showed increased PO and PPO levels, but the increases were less than in P. fluorescens-treated plants.