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Articles by Rehab A. Dawoud
Total Records ( 3 ) for Rehab A. Dawoud
  Entsar A. Nassar , Kh. A. El-Dougdoug , M.E. Osman , Rehab A. Dawoud and Aliaa H. Kinawy
  An Egyptian isolate of a Tobamovirus was isolated and identified from Chrysanthemum cultivation in Egypt. Both biological, serological and sequence analysis of the coat protein gene demonstrated that the virus represents an isolate of the Tobamoviridae family. The isolated virus was nominated as TMV Chrysanthemum Egyptian isolate (TMV-Ch-EG). This virus isolate caused severe disease symptoms in Chrysanthemum plants with mosaic, mottling and flower discoloration. The virus was purified biologically using serial transfer of the single local lesion technique on Nicotiana gultinosa. The induced antiserum for the isolated virus had a titer 1\1024. 600 bp DNA fragments from the coat protein gene (CP) of TMV-Ch-EG was amplified with Rt-PCR technique. Phylogenetic analysis of the TMV-Ch-EG/CP- gene showed 89% nucleotide sequence homology with other published strains of TMV in GenBank and 81% amino acid sequence homology. Tissue culture approach was used to permit the recovery of TMV-Ch-free micropropagated shoots via application of 20 mg L-1 virazole followed by thermotherapy at 38°C for two weeks and early screening to facilitate the efficient production of virus-free tissue culture derived propagules using the produced antiserum against TMV-Ch-EG.
  Kh.A. El-Dougdoug , Rehab A. Dawoud , A.A. Rezk and A.R. Sofy
  Direct tissue printing on membranes has been applied on a large scale for an initial detection of CEVd, HSVd and PLMVd in fruit trees in Egypt. CEVd was detected mainly in sweet orange trees and occasionally in grapevine and mango. The principal characteristics of the disease on sweet orange trees. It was incidence with 15.4, 4.5 and 1.5%, respectively. HSVd was detected mainly in sweet orange trees and occasionally in apple, apricot, mandarin, grapevine, mango, peach, pear and plum trees with 25.2, 2.2, 7.2, 10.5, 12.4, 15.7, 65.6, 40.5 and 5.7%, respectively. The principal characteristics of the disease on sweet orange trees. PLMVd was detected mainly in peach and occasionally in apple, apricot, grapevine, mango, pear and plum with 45.0, 5.4, 2.5, 0.5, 13.5, 23.4 and 3.5% incidence. The principal characteristics of the disease on peach trees. The three viroids; CEVd, HSVd and PLMVd were detected frequently in sweet orange and peach occasionally in grapevine, pear, mango, plum and apricot in Egypt.
  Aly Mohamed Mamoun Abdel-Salam , Adel A. Rezk and Rehab A. Dawoud
  Background and Objective: Tomato Chlorosis Virus (ToCV) is a white fly-transmitted and phloem-limited crinivirus reported in this study for the first time in Egypt. ToCV caused drastic reduction in tomato yield since 2013. The aim of this study is to characterize the virus incidence using biological, serological and molecular tools. Materials and Methods: The B. tabaci MEAM1 white fly was used for virus isolation and propagation. Identity of ToCV , its natural hosts were confirmed with RT-PCR using a specific primer pair for ToCV-heat shock protein 70 homologue (HSP70h) gene, sequencing and phylogenetic studies. ToCV was purified using the innovative electro-elution technique. The induced antiserum for the Egyptian isolate of the virus (ToCV-Giza) was used for DAS-ELISA and dot blotting immuno-assays to evaluate the virus presence in tomato and other natural hosts. Results: The ToCV-Giza isolate was donated an accession number “MH667315.1” from the GenBank. Blastx sequence analysis of the HSP70h gene indicated 97-99% of amino acid similarities with many tested ToCV isolates. Phylogenetic studies showed the clustering of all ToCV isolates including ToCV-Giza in a separate group from the other tested criniviruses. The virus had a UV spectrum of a nucleoprotein with Amax and Amin at 260 and 240 nm, respectively and A260/280 ratio of 1.33. Out of 52 different tested plant species within 22 families, 44 were positive hosts for ToCV. Thirty seven out of these 44 plant species were considered as new hosts for ToCV in the present study. These included Ammi majus and Coriandrum sativum (Apiaceae), cabbage (Brassicaceae), sweet potato (Convolvulaceae), melon, cucumber, luffa (Cucurbitaceae), soybean, cowpea, faba bean (Fabaceae), Egyptian and American Cotton (Malvaceae). Several ornamentals either herbal type or woody trees belonging to Acanthaceae, Amaranthaceae, Euophorbiaceae, Moraceae and Rubiaceae were also recognized for the first time as hosts for ToCV. Conclusion: The obtained results confirmed the wide distribution of ToCV in its natural hosts in Egypt. Hygienic measures including control of the virus vector and removing of natural hosts should be strictly implicated.
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