Induced systemic resistance: an innovative control method to manage branched broomrape (Orobanche ramosa L.) in tomato

Abstract

The biochemical responses of tomato (Lycopersicon esculentum Mill.) roots to different concentrationsof the hormonal elicitors, salicylic acid (SA) and indole acetic acid (IAA), as presoaking treatments,on the healthy and Orobanche ramosa-infected plants were studied in pot experiment under controlconditions. Application of SA and IAA activate the production of proline and soluble proteins in tomatoroots, where their levels were more pronounced in the infected than the healthy plants. Moreover, bothelicitors increased the levels of phenolics and favonoids accompanied by stimulations in the activities ofphenylalanine ammonia lyase (PAL), peroxidase (POX) and polyphenol oxidase (PPO) in tomato roots,where the magnitude of induction were more obvious in infected plants than healthy one. Also, microscopicexamination revealed the anatomical differences observed in both untreated healthy and infected plants aswell as in plants treated with SA and IAA. The present results indicate the effectiveness of SA and IAAin enhancing resistance of tomato to retard the incidence of infestation by Orobanche. These biochemicaland histological changes involved in plant defense mechanisms may be one of the basic ways participatein the action of SA and IAA for increasing resistance in tomato against Orobanche ramosa.