Differentiation Among Three Egyptian Isolates of Citrus psorosis virus

This study was aimed to determined PCR product of the CP gene by electrophoresis. Three Egyptian isolates of Citrus psorosis virus (CPsV-EG), namely ARC, TB and TN were obtained from citrus cvs. Grapefruit, Balady and Navel, respectively. These isolates were differed in some of their external symptoms. The CPsV-EG isolates were detected by biological indexing, giving rise to Oak Leaf Pattern (OLP) on Dweet tangor. The three isolates were differentiated using Double Antibody Sandwich-Enzyme-Linked Immunosorbent Assay (DAS-ELISA), woody indicator plants, differential hosts, peroxidase isozymes and activity, total RNA content and Reserves Transcription-Polymerase Chain Reaction (RT-PCR). The severe isolate (ARC) gave the highest OD value (2.204) in ELISA, followed by the mild isolate (TB) (1.958) and the last latent isolate (TN) (1.669). These isolates differed also in incubation period, intensity of symptoms and response to sensitivity of woody indicator plants and differential hosts. The CPsV-EG isolates showed differences in isozymes fractions, R sub(F) value and intensity as compared with healthy plant. Results were confirmed by peroxidase activity where the level of peroxidase activity was considerably higher in ARC leaves than TB and the last TN. The total RNA content in infected leaves gave the highest content in ARC followed by TB isolate while the lowest was recorded in TN isolate. Finally, RT-PCR showed differences between CPsV-EG isolates of PCR products using specific primer (Ps66 and Ps65) where base number of coat protein gene ARC isolate 571 bp; TB isolate 529 bp and TN isolate 546 bp.