EGYPTIAN ISOLATES OF PAPAYA RINGSPOT VIRUS FORM A MOLECULARLY DISTINCT CLADE

A survey to determine the incidence in open field squash (Cucurbita pepo) of Papaya ringspot virus (PRSV) in Kafrelsheikh governorate regions (Balteem, Shabah, Kafrelsheikh and Sheno) was carried out in 2009 and 2010. The most commonly observed symptoms were mosaic, malformation such as blisters and narrow leaf blades and malformed fruits. The identification of PRSV by ELISA showed that the virus was highly distributed in squash fields with an incidence higher than 50%. Egyptian isolates of PRSV were easily transmitted by mechanical inoculation and by Myzus persicae. Flexuous particles were observed in leaf dip preparations and pinwheels and scrolls were seen in thin sections of diseased squash tissue. The RT-PCR amplified partial coat protein (CP) gene was sequenced from eight Egyptian PRSV isolates. Sequence comparisons and phylogenetic analysis revealed that the Egyptian isolates grouped together in a distinct clade. Comparison with PRSV sequences retrieved from GenBank presented nucleotide identities in the range of 87.5-97.1% and close relationships of the Egyptian isolates with the two Venezuelan isolates of the so-called type-P, Sucre-ElMuco and Merida6, and to the Mexican and USA isolates. This is the first report on the incidence and characterization of PRSV in Egypt.