ABSTRACT
Two isolates of PNRSV were isolated from peach and apricot trees at the Experimental Station of the Faculty of Agriculture, Cairo University, Giza, Egypt. The peach isolate of PNRSV [PNRSV-PF] was differentiated from the apricot isolate [PNRSV-AP] by ten differential host species. Both isolates were purified successfully with 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 1.60 for the AP and the PF isolates, respectively. Electron microscopy examination showed spherical virions with ca 27-29 nm in diameter. Both isolates had molecular weight of coat protein subunits of 29 kDa, determined by polyacrylamide gel electrophoresis [SDS-PAGE]. Antisera raised against the two isolates detected their counter antigens in peach 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 appeared to belong to the same sero-group and represent two different pathotypes. PNRSV-AP varied in sero-grouping of that of beet necrotic ringspot ilarvirus, a tentative isolate of PNRSV, when 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 isolates of PNRSV isolated from apricot and peach trees. Amplicons of the correct size [ 894 bp] for the MP gene and [ 704 bp] for the CP gene were obtained from the two examined isolates of PNRSV. Nested PCR using specific primers for both the MP and the CP genes confirmed the authenticity 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 apricot isolate. Phylogenetic analysis of RNA 3-MP showed ca 65% similarity between PNRSV-AP and PNRSV-PF; indicating that the two isolates of PNRSV are distantly related. The relatedness between the two isolates and other PNRSV isolates is discussed