Prunus necrotic ringspot virus (PNRSV) is a stone fruit tree pathogen. Field surveys were conducted in the spring of 2018 and 2019 in 58 commercial and four collection sweet and sour cherry orchards in six regions of Bulgaria. Leaf samples from 3214 trees showing and not showing virus-like symptoms were tested by enzyme linked immunosorbent assay (ELISA) for PNRSV infection. The average infection level of 5.1% was higher in sour cherry (15.5%), than in sweet cherry trees (1.8%). The coat protein (CP) sequences of 25 isolates were determined. The obtained sequences were 596 or 675–681 nucleotides (nts) in length, translated to 198 or 225–227 amino acids (aa), respectively. Sequence comparisons showed 94–100% nucleotide and 90–100% amino acid identities among the 25 isolates. Phylogenetic analysis using nucleotide and amino acid sequences of Bulgarian isolates and cherry isolates retrieved from the GenBank database confirmed clustering into the previously reported PV96-II, PV32-I, PE5-III and CH30 phylogroups. Twenty Bulgarian isolates belonged to PV96-II and five isolates to PV32-I phylogroup. No correlation was noted between PV96-II phylogrouping and the sampling region/and or symptoms of infected trees of studied isolates, while a connection to a certain degree with geographical origin of the isolates in PV32-I phylogroup, but not with the symptomatology was observed.

中文翻译：

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保加利亚酸樱桃李坏死环斑病毒外壳蛋白基因的分子变异性

李子坏死环斑病毒 (PNRSV) 是一种核果树病原体。于 2018 年和 2019 年春季在保加利亚六个地区的 58 个商业和四个收集糖醋樱桃园进行了实地调查。来自 3214 棵树的叶子样本显示和不显示病毒样症状，通过酶联免疫吸附测定 (ELISA) 检测 PNRSV 感染。酸樱桃（15.5%）的平均感染水平为 5.1%，高于甜樱桃树（1.8%）。确定了 25 个分离株的外壳蛋白 (CP) 序列。获得的序列长度为 596 或 675-681 个核苷酸 (nts)，分别翻译为 198 或 225-227 个氨基酸 (aa)。序列比较显示 25 个分离株中有 94-100% 的核苷酸和 90-100% 的氨基酸同一性。使用从 GenBank 数据库中检索到的保加利亚分离株和樱桃分离株的核苷酸和氨基酸序列进行的系统发育分析证实聚类到先前报告的 PV96-II、PV32-I、PE5-III 和 CH30 系统群中。20 个保加利亚分离株属于 PV96-II，5 个分离株属于 PV32-I 系统群。PV96-II 系统群与被研究分离株的感染树的采样区域/和或症状之间没有发现相关性，而在一定程度上与 PV32-I 系统群中分离株的地理起源有关，但与症状无关.