Determination of Biological Properties of Cherry Virus Trakiya and Its Incidence on Sweet Cherry (prunus Avium L.) in Bulgaria

The bi-cistronic virus cherry virus Trakiya was detected recently and is related to a group of unclassified viruses in the order Picornavirales, typically with arthropod vectors/hosts. The virus was detected initially by next-generation sequencing (NGS) of total RNA extracts from leaves from symptomatic sweet cherry (Prunus avium L.) growing in Bulgaria. The aim of the current study was to ascertain some biological characteristics of CVT. The virus was successfully graft transmitted from Prunus to Prunus, with transmission confirmed using a two-step RT-PCR with the primer pair BuC-1657F/BuC-2095R that amplifies a CVT-coat protein coding region-specific fragment (443-bp product). Symptoms associated with graft transmission and CVT infection of sweet cherry include leaf chlorosis, leaf abnormality and phyllody. Interestingly, symptoms observed in the orchards were similar to symptoms observed on sweet cherry trees infected experimentally by grafting. CVT was mechanically sap-transmitted from sweet cherry to several herbaceous hosts with Chenopodium amaranticolor and Nicotiana clevelandii appearing to be suitable for use as indicator species. Survey analysis of 77 cherry samples collected from four districts of Bulgaria revealed 26 positive samples (34% infection) from three districts. The virus was detected only in symptomatic field trees of tested cherry cultivars and never in asymptomatic trees. Detection of CVT in buds, flowers and leaves from the four cardinal points of field-infected sweet cherry plants proved its systemic distribution in infected trees.