Changes in defence-related enzymes in rice responding to challenges by Rhizoctonia solani

Sheath blight disease caused by Rhizoctonia solani Kuhn is becoming a major constraint to rice production, especially in the intensified cultivation system. To know the in rice, it is important to get the knowledge of the activity of defence-related enzymes due to the fungal infection. The pathogen induced superoxide dismutase (SOD) and chitinase activities in rice plants, while suppressing peroxidase (POD) and phenylalanine ammonia-lyase (PAL) activities at 36 and 24 h after inoculation, respectively. Induction of two POD isozymes, POD-3 and -4, up to 48 h after inoculation and disappearance of the said isomers at 72 h onwards in rice–Rhizoctonia interaction implicated the role of these isomers in susceptible host–pathogen interaction. Apart from POD and SOD, the activities of other stress-related enzymes, viz. PAL, polyphenol oxidase (PPO) and β-1,3-glucanase were also studied. From this study, it was found that these defence-related enzymes are most significantly related to host–pathogenic interaction.