Omhashem Mohamed Ibrahim El-Banna

Tobacco Rattle Virus (TRV) was isolated from naturally infected onion (Allium cepa L.) plants growing in the fields of onion plants during the survey carried out in two successive seasons (2007-2008 and 2008-2009) in seven Egyptian Governorates. Plants showing yellowing, malformation, yellow stripping, white necrotic stripes and stunting symptoms were collected and subjected to identification studies that based on host range, symptomatology, modes of transmission, serological tests, inclusion bodies and morphology of virus particles. The virus was transmitted by mechanical inoculation and by seeds. On the other hand, cytological changes accompanied with the infection were investigated. Different methods of serological detection of the virus were also tested. The obtained results indicated that the host range of the expanded to 7 different plant families. The virus was transmitted mechanically and by seeds with percentages ranged between 8-13%. Different serological methods were used successfully for detection of TRV i.e., DAS-ELISA, TBIA and DIBA. Infection of tobacco leaves with TRV resulted in the formation of amorphous inclusion bodies in the cytoplasm. Light microscopy examination of semi thin sections in both healthy and artificially infected onion leaves showed anatomical changes which reflecting on the external symptoms on infected plants. Also, electron microscopy observed tubular particles with two main dimensions (length 48-114 nm and 180-197 nm and 22 nm width). Investigation of ultrathin sections by transmission electron microscopy revealed changes in both nucleus and chloroplast. According to the available data, TRV was isolated and identified for the first time in Egypt from onion plants during the present study.