Abstract

Isozyme analysis was carried out to determine whether Peroxidase (PO) and Polyphenol oxidase (PPO) activities were induced in groundnut (Arachis hypogaea L.) leaves by application of antagonistic Streptomyces sp. strains through seed and soil. PO isozyme analysis of protein extracts from control groundnut plants exhibited two isozymes (PO-1 and PO-2). Seed treatment or seed treatment plus soil application with Streptomyces sp. strain PDK strongly induced the activity of PO-2. In addition, two new PO isozymes (PO-3 and PO-4) were also appeared in the Streptomyces sp. strain PDK treated plants. No significant change in the PO isozyme profile of groundnut was observed in plants treated with other Streptomyces sp. strains viz., CBE and MDU through seed. However increase in the activity of PO-2 was observed in plants treated with MDU through seed plus soil. PPO isozyme analysis of protein extracts from control groundnut plants exhibited two isozymes (PPO-1 and PPO-2). An increase in the activities of both PPO-1 and PPO- 2 compared to control was observed in plants treated with all three strains of Streptomyces sp. through seed or seed plus soil. The increased activities of both PO and PPO in groundnut plants upon treatment with Streptomyces sp. might have contributed to resistance of groundnut against stem rot caused by Sclerotium rolfsii.

Keywords: Arachis hypogaea, Induced resistance, Peroxidase, Polyphenol oxidase, Streptomyces sp.