الفهرس 
introduction and aim of workOnly 14 pages are availabe for public view
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Abstract
The present study is conducted to detect this virus following by carrying out some biological, serological and molecular studies for designing a high sensitive, rapid and specific diagnostic tool as well as discover the defense response of the onion plant for IYSV. Results of this study can be summarized as follows: 1.from the whole sample collection (280) from 11 Governorates in Egypt they was about, 259 samples were positive while 21 samples gave negative result. Incidence varied from 50 % to 100 %. 2.The virus transmitted biologically by thrips. 3.The use of electron microscope to investigate the presence of the virus particles of IYSV in the purified virus preparations showed that the dimension size of spherical particles about 80 nm. Western blot revealed a strong band of about 30 kDa, which was indicating for the expected molecular weight of IYSV N protein. 4.The IYSV antiserum titer was 1:4000 in indirect (I)-ELISA after first bleeding and 1:2000 after both second and third bleeding. The antiserum produced was subjected to DBIA analysis showed that the antiserum was specific and gave similar results comparably to a commercially available antibody. 5.Sequencing and phylogenetic analysis resulted from the RT-PCR fragment of N gene indicated that the Egyptian IYSV isolate was having 95% identity at the amino acid level with Israeli isolate. 6.By using Real-time Quantitative PCR method the statistical analysis revealed that there is a significant difference in the peak of expression for both PR1 after 8 dpi and PR3 after 9dpi. The overall analysis showed that, β-actin is the most suitable gene served as internal control for quantitative gene expression. 7.Results of differential display PCR, eleven up-regulated and down-regulated genes were isolated and sequenced. All of the investigated genes were of plant origin and this was supported by the high similarities and identities demonstrated to known genes from onion plant species.