Molecular characterisation of little cherry virus 1 infecting apricots in the Czech Republic

Little cherry virus 1 is one of the pathogens associated with little cherry disease of cherries. The host range of the virus is widening and recently it has been detected in apricot trees in the Czech Republic, Hungary, and Morocco. To obtain a view about the importance of apricots in the epidemiology of the virus, a survey was conducted in Czech apricot-growing areas. Little cherry virus 1 was detected in seven out of 13 locations, and the infection was noted predominantly in old orchards, but its frequency was low. During the survey, an infected almond tree developing severe leaf mosaic was also detected. Using high-throughput sequencing and Sanger sequencing, five near-complete genome sequences and another 20 partial ORF8 sequences were obtained. Phylogenetic analysis showed a close relationship of most of the apricot isolates to the phylogenetic group G3 with UW2, UW1, and ITMAR isolates. Three apricot isolates, including the almost complete Apr 184R isolate and almond isolate Alm138, showed homology within the phylogenetic group G5. The analysis clearly demonstrates the presence of isolates of this type in Europe. The 4-year-long survey of selected pomological characteristics showed that infection with the virus is generally latent, but the infection could significantly affect the ripening of the fruit of some apricot genotypes. A significant decrease in the fruit yield was noticed for ‘Magyar Kajszi’. The potential routes of the transmission of little cherry virus 1 to apricots are discussed in the context of propagation practice.