Abstract

                                Investigation was carried out at Horticultural College and Research Institute, TNAU, Coimbatore to understand the biochemical defense mechanism underlined in two virus tolerant hybrids namely H 24 x CLN 2123A and H 24 x LCR 1 in tomato (Lycopersicon esculentum Mill.). There existed significant differences in the activities of all the three host enzymes studied viz. peroxidase, polyphenol oxidase and phenylalanine ammonia lyase activity among different treatments. Both the hybrids recorded significantly higher peroxidase, polyphenol oxidase and phenylalanine ammonia lyase activity than their parents and susceptible check under both challenge-inoculated and control condition. Between the hybrids, rapid increase in phenylalanine ammonia lyase activity under challenge-inoculation of viruses was noticed only in H 24 x LCR 1. The possible reasons involved are discussed.

Key words : Tomato, peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, virus tolerance