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

The biochemical responses of tomato ( Lycopersicon esculentum Mill.) roots to different concentrations of 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 control conditions. Application of SA and IAA activate the production of proline and soluble proteins in tomato roots, where their levels were more pronounced in the infected than the healthy plants. Moreover, both elicitors increased the levels of phenolics and flavonoids accompanied by stimulations in the activities of phenylalanine 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, microscopic examination revealed the anatomical differences observed in both untreated healthy and infected plants as well as in plants treated with SA and IAA. The present results indicate the effectiveness of SA and IAA in enhancing resistance of tomato to retard the incidence of infestation by Orobanche. These biochemical and histological changes involved in plant defense mechanisms may be one of the basic ways participate in the action of SA and IAA for increasing resistance in tomato against Orobanche ramosa . Keywords : Orobanche ramosa ; tomato, Induced resistance, Phenolics, PR-proteins . *Corresponding author : Shahnaz Al-Wakeel (e-mail: shahnazalwakeel@yahoo.com) (Received: 12.04.2012 Accepted: 17.07.2012)