Serological and molecular characterization of isolates of Plum pox virus El Amar strain to better understand its diversity, evolution, and unique geographical distribution

Abstract

Sixteen isolates of Plum pox virus (PPV) were collected during a survey in the Egyptian areas of Sinro and Apoxa (El Fayoum) and El Amar (Nile Delta). All isolates reacted with the universal PPV monoclonal antibody MAb 5B and were identified as PPV strain EA by phylogenetic analysis of the full-length sequence of the coat protein (CP) gene. This classification was confirmed by detection with the strain-specific MAb EA24, except for an isolate denoted APR 50. Detailed analysis of the CP amino acid sequence of the EA isolates and epitope mapping revealed that histidine at amino acid position 65 of the CP sequence is an essential component of the epitope required for MAb EA24 recognition. APR 50 has an arginine substitution at this position. Five EA serogroups were identified, serogroup I being the prevailing one with 10 of the 14 isolates characterized. Moderate serological and relatively high genetic diversity was observed among isolates of PPV-EA. The most variable isolate, APR 48, contained a deletion of 33 nucleotides at the 5’ terminus of the CP gene. The relatively high genetic diversity of PPV-EA suggests that it is not a recent introduction.