STUDIES ON SWEET BASIL MOSAIC VIRUS DISEASE AND ITS CONTROL BY USING SOME ESSENTIAL OILS

The current study, the mosaic virus disease of Ocimum basilicum L. (sweet basil) was identified and the different effects of three essential oils on growth, oil content and composition as well as reducing CMV disease symptoms of sweet basil plants in vivo. During 2012 season, natural occurrence of mosaic virus disease was observed on sweet basil in Assiut, Egypt. The causal agent of basil mosaic disease was detected as cucumber mosaic virus (CMV) by PCR product that revealed presence of approximately expected size (~ 781 bp) in naturally infected basil. Therefore, a field experiment was carried out during two successive seasons 2013 and 2014 on sweet basil plants at the Experimental Farm of Arab El Awamer Agricultural Research Station, Assiut Governorate, Egypt. Ten treatments of three essential oils extracted from lemongrass (Cymbopogon citratus), rosemary (Rosemarinus officinalis) and peppermint (Mentha piperita L.) plants were applied as foliar spray at 1% concentration before and after inoculation with isolated virus and two controls (healthy and infected plants) were arranged in a randomized complete block design with three replicates. Results revealed that application of essential oils under field condition improved growth and yield (branches, weight of fresh and dry plant (g/plant) as well as essential oil percentage), reduced the CMV disease symptoms compared to untreated infected control. As well as significant increase in total identified of essential oil composition of basil plant. Whereas the treatment with rosemary oil before and after inoculation respectively, was increased in myrcene, linalool when applied before inoculation and with a great increase in 1, 8-cineole when applied after inoculation. Also a great increase was related to peppermint oil treatment for eugenol, myrcene and 1, 8-cineole % before inoculation comparable to untreated infected plants. While, using of peppermint oil significantlyincreased number of branches, fresh and dry weights, essential oil content and composition when applied before inoculation with virus compared to infected and healthy controls. Lemongrass essential oils exhibited a moderate protective effects. Generally, applying of rosemary essential oil as curative seemed to be superior for improving branches, weight of fresh and dry plant (g/plant), and essential oil percentage and composition comparing to other treatments.