EFFICACY OF ESSENTIAL OILS FROM THREE MEDICINAL AND AROMATIC PLANTS IN CONTROLLING WILT DISEASE OF ROSELLE (HIBISCUS SABDARIFFA L.)

Roselle (Hibiscus sabdariffa L.) is one of the most important medicinal plants. Root rot and wilt diseases of roselle attack either seedlings or adult plants. In this study, the isolation and identification of the pathogen associated with root rot and wilt symptoms of roselle in Assiut were studied during the seasons 2012-2014. The efficacy of essential oils from three plants i.e., sweet basil (Ocimum basilicum var. basilicum L.), marjoram (Majorana hortensis L.)and peppermint (Mentha piperita L.), at three concentrations (0.5, 1 and 2%) were tested against the most aggressive Fusarium isolate in vitro, as well as evaluation in vivo. Results showed that all tested isolates, Fusarium moniliform, F. solani and three isolates of F. oxysporum (No. 1, 2 and 3) were pathogenic to roselle plants while the highest pathogenicity was caused by F. oxysporum No. 3 followed by No. 1. In vitro, the three tested oils were found to have an inhibitory effect against the growth of the pathogenic fungus, the highest inhibition was observed at 2% of marjoram and peppermint (2.23 and 2.00 cm inhibition zone, respectively).Under open greenhouse conditions, results of seed coating with the threeessential oilsunder study suppressed infection with pathogenic F. oxysporum. Marjoram and peppermint were the most effective oils in reducing disease incidence, 0.5% concentration demonstrate the best protection of roselle seeds against F. oxysporum. Growth characteristics ie., plant height, No. branches and fruits/plant, fresh and dry weights of sepals were significantly higher at all treatments. Also, acidity and total anthocyanin increased significantly. Marjoram and peppermint oil at 0.5% and basil oil at 2% were the most effective concentrations in decreasing disease incidence in addition to increasing the quantity and quality of roselle yield.