Biological and molecular characterization of Prunus necrotic ringspot virus isolates from sweet and sour cherry

Abstract

Biological and molecular properties of six Prunus necrotic ringspot virus (PNRSV) isolates originating from sweet and sour cherry trees were studied. Double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) showed PNRSV infection in leaf samples from the respective source trees. While one of the infected source trees was symptomless, the other five showed symptoms, ranging from chlorotic to necrotic spots on the leaves. The reaction of greenhouse-grown seedlings of 22 herbaceous test plant species was investigated. The woody indicators Prunus serrulata cv. Kwanzan, wild cherry Prunus avium, P. cerasus, P. cerasifera and P. tomentosa were chip-budded. Chenopodium quinoa, Cucumis sativus cv. Amelia, C. sativus cv. Levina and P. tomentosa appeared as the most suitable test plants for the bioassay of the studied PNRSV isolates. The nucleotide sequences corresponding to the full-length coat (CP) and movement (MP) proteins were obtained. The nucleotide sequence identity among the studied isolates both in CP and MP genes was from 94% to 100%. The CP and MP amino acid sequence identities were from 95% to 100% and from 94% to 100%, respectively. Phylogenetic analyses performed with MP and CP nucleotide sequences showed that three isolates belonged to PV32-I and the other three to PV96-II phylogroups. Comparative amino acid analyses of MP and CP genes, together with the symptoms on naturally infected trees showed a higher affiliation of the studied isolates with the mild type than with the rugose types of isolates. The molecular variability correlated with the symptomatology on the naturally infected trees.