Occurrence of Ilarviruses in sweet and sour cherry in Bulgaria

Kamenova, I., Borisova, A. & Popov, A. (2020). Occurrence of Ilarviruses in sweet and sour cherry in Bulgaria. Bulg. J. Agric. Sci., 26 (3) , 590-597 Sweet cherry is an important fruit crop in Bulgaria. Field surveys were conducted in 43 commercial and three collection sweet and sour cherry orchards in ten locations of six regions of Bulgaria. Single home-grown sweet and sour cherry trees were included, too. Leaf samples were collected from 2090 trees with and without virus -like symptoms. These samples were tested by DAS-ELISA for three Ilarviruses including Prunus necrotic ringspot virus (PNRSV), Prune dwarf virus (PDV) and Apple mosaic virus (ApMV). While ApMV was not found, 269 and 111 samples tested positive for PDV and PNRSV, respectively and 22 samples for both viruses, showing that 19.2% of the trees were infected with at least one of the two viruses. PDV was the most abundant virus in sweet cherry detected in 87.1% of infected trees. PNRSV was prevalent in sour cherry. Visual ob- servations were made in order to connect the expressed symptoms with the respective virus infection. In 56.2% of infected with PDV trees symptoms as chlorotic spots and rings or chlorosis in the base of central and secondary veins were observed, and 43.8% of infected trees were asymptomatic. PNRSV infection was associated both with and without symptoms. Symptomatol- ogy only is not enough for determination of PNRSV or PDV infections due to similar symptoms, thus imposing the need of serological or molecular detection. The almost equal rate of PDV and PNRSV infections found in differently aged orchards suggests their introduction by infected propagating materials.