Biologically mediated systemic resistance against Marssonina leaf blotch of apple caused by Marssonina coronaria (Ellis & J.J. Davis) J.J. Davis

Abstract

In order to determine the effect of biocontrol agents used for inducing resistance in plants against Marssonina leaf blotch caused by the fungus Marssonina coronaria (Ellis & J.J. Davis) J.J. Davis two polyhouse trials were conducted using scion bud wood of cultivars Starking Delicious, Tydeman’s Early Worcester and Granny Smith apple. Three biocontrol agents, Trichoderma viride, Pseudomonas fluorescens and Bacillus subtilis, at three different dilution i.e. 10-3, 10-4, 10-5 for fungi and 10- 3, 10-5 and 10-7 for bacteria were applied on the test cultivars 48 hrs before inoculation. Distilled sterilized water was sprayed on control plants. All the biocontrol agents significantly lowered the disease intensity as compared to control. Pseudomonas fluorescens and Bacillus subtilis and Trichoderma viride, reduced disease severity by 15.50 – 33.50 per cent on the leaves Starking Delicious cultivar. Similarly, disease severity data in cultivar Tydeman’s Early Worcester ranged from 5.33-16.66 per cent and on the leaves of cultivar Granny Smith it ranged from1.68-6.00 per cent against 28 and 9 per cent in Tydeman’s Early Worcester and Granny Smith respectively. The activity of the defense enzymes peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL) was found maximum in Pseudomonas fluorescens treated leaves in all the test cultivars. Thus biocontrol agents have potential for the control of Marssonina leaf blotch of apple in the field.