Prunus necrotic ringspot virus (PNRSV) andPrune dwarf virus (PDV) are the most common pathogens in stone crop orchards. These diseases are easily transmitted with pollen and hence rapidly spread in orchards leading to stunting of trees, their increased susceptibility to abiotic stress factors and, eventually, to significant yield losses. In Ukraine, only monitoring studies on the spread of these viruses were conducted until now. However, phylogenetic comparison of Ukrainian isolates was lacking. In this work, total RNA was isolated from plant samples tested positive for PNRSV and PDV by ELISA. The part of viral CP gene sequences were amplified and sequenced with their subsequent phylogenetic analysis. It was determined that PNRSV isolates from Ukraine analyzed in this study belong to different groups -PV-96 (MT828889) and PV-32 (MT892676) with a maximum identity level of 100 % with known isolates from NCBI GenBank. PDV isolates (MT828888 and MT828887) showed high identity with each other (99.6 %), and Slovakian isolate from sweet cherry was shown as the most related to them with identity of 95.3 %.

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Prune dwarf virus (PDV) and Prunus necrotic ringspot virus (PNRV) are most widespread pathogens in sour cherry orchards in Ukraine. The study is aimed to select the optimal season and tissues of sour cherry plants for the detection of PDV and PNRV in the climatic condition of Ukraine. The experiment was performed by DAS-ELISA using certified test kits manufactured by Loewe Biochemica GmbH (Germany). Trees of cherry cultivars 'Bohuslavka' (PDV infected) and 'Kseniia' (PNRV infected) were selected for testing. Healthy plants of the same cultivars were selected as the negative controls. Samples of various tissue (young leaves, dorman leaves, flower petals, fruits and cambium) were taken at different terms of the vegetation period. The young leaves demonstrated the highest absorbance levels of PDV and PNRV in April when А 405 nm was at least 19 times higher comparing to negative control. Also reliable results were recorded at the beginning of the growing season when flower petals were used. So leaves and flowers were the most reliable source for the detection of these viruses from April till August. Instead, in October there was a high possibility of false-negative results as the results didn't exceed the negative control value more then 2.5 times. This study will contribute to the optimization of DAS-ELISA PDV and PNRV detection in Ukraine.

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