Two isolates of PNRSV were isolated from peach and apricot trees at the Experimental Station of the Faculty of Agriculture, Cairo Univer sity, Giza, Egypt. The peach isolate of PNRSV (PNRSV-PF) was differentiated from the apricot isol ate (PNRSV-AP) by ten differential host species. Both isolates were purified successfully w ith the electro-elution technique. Both isolates had A max and A min at 260 and 240 nm respectively. The A260/280 ratios were 1.55 and 1.6 0 for the AP and the PF isolates, respectively. Electron mic roscopy examination showed spherical virions with ca 27-29 nm in diameter. Both isolates had mo lecular weight of coat protein subunits of 29 kDa, determined by polyacrylamide gel electrophores is (SDS-PAGE). Antisera raised against the two isolates detected their counter antigens in pea ch and apricot trees. Both antisera cross reacted with their homologous and heterologous antigens in dot blot immunoassay (DBIA) and agar-double diffusion (ADD) tests. The two virus isolates appea red to belong to the same sero-group and represent two different pathotypes. PNRSV-AP varie d in sero-grouping of that of beet necrotic ringspot ilarvirus, a tentative isolate of PNRSV, w hen examined in ADD test. Indirect ELISA showed that 64.2 % of 210 tested apricot trees were infected, while 150-inspected peach trees showed 29.5 % infection. Four sets of primers were used to amplify both movement protein (MP) and coat protein (CP) genes of the two Egyptian iso lates of PNRSV isolated from apricot and peach trees. Amplicons of the correct size (~ 894 bp) fo r the MP gene and (~ 704 bp) for the CP gene were obtained from the two examined isolates of PNR SV. Nested PCR using specific primers for both the MP and the CP genes confirmed the authenti city of the PCR amplified products. RT-PCR detected successfully the presence of PNRSV in the pollen grains of infected apricot and peach trees. Nucleotide sequences of the MP genes of the two isolates were revised by the GenBank and given the accession # EU100388 for the peach isolate and EU106649 for apr icot isolate. Phylogenetic analysis of RNA 3-MP showed ca 65 % si milarity between PNRSV-AP and PNRSV- PF; indicating that the two isolates of PNRSV are d istantly related. The relatedness between the two isolates and other PNRSV isolates is discussed.

An isolate of tobacco ringspot virus (TRSV) was isolated from potato (Solanum tuberosum L.) plants showing calico symptoms and growing in commercial fields in El-Dakahlia govenorate. The isolated virus was designated as TRSV-DAK. The virus was transmitted mechanically to several hosts including Capsicum annuum L., Physalis floridana Thdb., Cucumis sativus L., and some cultivars of Nicotiana tabacum L. Symptoms ranged between chlorosis, ringspot, and necrosis. TRSV-DAK induced local lesions upon its inoculation on Vigna unguiculata Walp. The isolated virus was purified using an electro- elution technique. The purified virus has Amax at 260, Amin, at 245 and A260/280 of 1.34. Virus yield was 0.5 mg/ml. TRSV-DAK reacted scrologically with two authentic antisera for TRSV from the USA and France. A third locally induced antiserum for TRSV- DAK detected its presence in potato leaves, stems and tubers grown in both field and greenhouse upon using different immuno-sorbent techniques. Distribution of the virus was uneven in infected- potato plants. Ten potato cultivars were tested for pathogenecity to TRSV-DAK. Generally, plants infected under field conditions were more susceptible to TRSV-DAK infection when compared to those under greenhouse conditions. Cydon and Gigent potato cvs. were the least infected under greenhouse conditions showing 10 and 20% infection, respectively. The same two cvs. exhibited 60, 70% infection respectively in the field. EIectron microscopy examination of purified virus showed the presence of spherical particles with 27 nm in diameter. In tissue culture experiments, four tested antiviral compounds, namely salicylic acid (SA), benzoic acid (BA), jasmonic acid (JA) and linolcnic acid (LA), exhibited variable abilities to remove TRSV- DAK from infected potato explants. Increased concentrations of all used substances were positively correlated with the percentages of TRSV-free potato plantlets. JA induced the highest percentages of virus-free plantlets (being 96.7% at 0.3 mg/l) compared with other tested chemicals.