Molecular analysis of the complete genomes of apricot and plum isolates of Plum pox virus detected in a Prunus germplasm collection in Almaty’s Pomological Gardens, Kazakhstan

Partial molecular characterization of isolates of Plum pox virus (PPV) from Kazakhstan was described in 2004 (Spiegel et al., 2004). The isolates were classified as members of the Dideron (D) strain based on; a) RFLP analysis of the 243 bp amplicon in the region of the C-terminus of the CP fragment, b) RFLP analysis of the 836 bp amplicon in the P3-6K1 coding region and c) analysis of the CP coding region. The plum isolates were detected in plum trees maintained in the plum selection-orchard of the Pomological Garden, Almaty, Kazakhstan. The apricot isolates were detected in wild apricot seedlings obtained originally from Zailiyski Alatou at the northern edge of the Tien-Shan Mountains, but maintained in the Pomological Garden, Almaty for about 15 years. Disease symptoms were observed on fruit from one of these infected apricot trees and on the leaves of the infected plum trees. PPV was never detected in any wild apricot plants growing in their natural habitat in Zailiyski Alatou. In this recent study, the virus genomes were sequenced completely and their analysis confirmed their identities as members of the D strain of PPV. Interestingly in some cases the genomes of the apricot and plum isolates were very similar, with identities of approximately 99.7% (nt and aa). Phylogenetic analyses seem to indicate a close relationship of the Kazakhstan apricot and plum isolates to each other, and to the PPV isolate BIII/2 (accession GU461890), a plum isolate from Slovakia. The Kazakhstan isolates and the Slovakia isolate are approximately 99% identical (nt and aa). The deletion event described by Spiegel et al., (2004) in the plum isolate P5R8 (KZPLa1) was confirmed.