Plant Extract Treatments Induce Resistance to Bacterial Spot by Tomato Plants for a Sustainable System

• Main Authors: Kamal A.M. Abo-Elyousr, Najeeb M. Almasoudi, Ahmed W.M. Abdelmagid, Sergio R. Roberto, Khamis Youssef
• Format: Article
• Language: English
• Published: MDPI AG 2020-06-01
• Series: Horticulturae
• Subjects: Induced resistance; polyphenol oxidase; peroxidase; plant extract; bacterial spot
• Online Access: https://www.mdpi.com/2311-7524/6/2/36

The aim of this study is to assess the effect of extracts of <i>Nerium oleander, Eucalyptus chamadulonsis </i>and <i>Citrullus colocynthis</i> against bacterial spot disease of tomato and to investigate the induction of resistance by tomato (<i>Solanum </i>l<i>ycopersicum</i>) in order to promote a sustainable management system. The antibacterial activity of aqueous and ethanol plant extracts was tested against <i>Xanthomonas axonopodis </i>pv. <i>vesicatoria</i>, isolate PHYXV3, <i>in vitro</i> and <i>in vivo</i>. The highest antibacterial activity in vitro was obtained with <i>C. colocynthis, N. oleander </i>and<i> E. chamadulonsis,</i> respectively. <i>In vivo</i>, ethanol extracts of <i>N. oleander </i>and <i>E. chamadulonsis </i>were more effective than aqueous extracts in reducing pathogen populations on tomato leaves. Under greenhouse conditions, application of the plant extracts at 15% (v/v) to tomato plants significantly reduced disease severity and increased the shoot weight of ‘Super Marmande’ tomato. In most cases, plant extracts significantly increased total phenol and salicylic acid content of tomato plants compared to either healthy or infected ones. In addition, <i>C. colocynthis</i>and<i> E. chamadulonsis </i>extracts significantly increased peroxidase activity while only <i>E. chamadulonsis </i>increased polyphenol oxidase after infection with the causal agent. The results indicated that the plant extracts showed promising antibacterial activity and could be considered an effective tool in integrated management programs for a sustainable system of tomato bacterial spot control.