The dissertation is devoted to viral diseases of sour and sweet cherries.
The work studied the distribution of 10 viral pathogens from the standard PM (4)29(1) "Certification scheme for cherry ", as well as the plum pox virus on the territory of Ukraine.
The main testing method was serologic diagnosis.
Over the years of research, 291 samples have been tested, including 134 sweet cherries, 103 sour cherries, and 54 root-stock ones. Serologic diagnosis of the samples showed a high infection level of the material — 28,6 %. The largest share of infected samples was recorded in the sour cherry material — 33 %, sweet cherry — 30,6 %, and the smallest - in the tested root-stock samples — 13 %. Among the viruses detected, PNRV prevailed, namely, in sour cherry samples — 14 %. The cultures under study within 5,5—9,7 % are infected with two or more viruses.
It was found that the infection rate of the tested sweet cherry varieties ranges from 23 to 45,5 %, depending on the cultivar; sour cherries — from 7,1 to 42,9 %, and root-stock — 4,2 % (VSL-2) and 33,3 % (Prunus mahaleb).
For true serologic diagnosis of PNRV and PDV, the optimal timing and types of plant material tissues have been selected for effective pathogens detection.
For phylogenetic analysis, we selected isolates of PNRV, PDV and PPV. Based on the analysis of the PNRV nucleotide sequence, it was found that the recovered isolates belong to different groups: PV-96 (MT828889) and PV-32 (MT892676), circulating in the Kyiv and Zaporizhzhia regions.
Phylogenetic analysis of PDV established that domestic isolates MT828888 and MT828887 have a high identity — 99,6 %. During clustering, two groups were formed with division into two subgroups.
Since the PPV isolates selected are 100 % similar to each other, only one, MW055900, was deposited with GenBank. It was found that this isolate belongs to strain D.
To improve the certification scheme, it was proposed to amend the existing documents, namely: national standard DSTU 4791:2007 «Rootstocks of fruit crops. Quality Determination Methods» and DSTU 4792: 2007 «Saplings of fruit crops. Quality Determination Methods».
In the process of studying variety-rootstock combinations, the response of sensitive rootstocks to grafting with infected oculants was investigated. Within the rootstock of VSL-2 and LC-52, the gummosis was observed at the site of inoculation, and subsequently a change in the color of the leaves to an anthocyanin coloration. Also in the spring, 100% of attacks were observed in the second field of the nursery on these rootstocks. Unlike previous rootstocks, no such reactions were recorded at VC-13. The survival rate of infected oculants was 50 % with the Nizhnist` cultivar and 76,6 % with the Bohuslavka and Kseniia varieties, while in uninfected control plants this indicator was equal 90 %.
The negative effect of the virus on the state of the plant's photosynthetic apparatus was revealed. In general, there was a decrease in chlorophyll a from 20,9 to 38 %, chlorophyll b from 31 to 43,9 %, depending on the cultivar and the virus that infected the plant. It was also found that PNRV and PDV have a negative effect on the frost resistance of the studied varieties reproductive buds. It was determined that the viral load on the plant entailed damage to the bourgeons of infected of Kseniia varieties (PNRV) amounting to 3,5—4,5 points, and Bohuslavka (PDV) — 4,5. At the same time, in healthy plants, the level damage was from 1,7 to 3,5 points, depending on temperature, pathogen and variety. When studying the effect of a viral infection on the quality of one-year-old seedlings, a decrease in the area of the leaf blade by 7,6—31 % was recorded, depending on the pathogen and plant variety. The specific surface density of the infected cultivars Bohuslavka (PDV) and Nizhnist (PDV + PNRV) was 5,5 and 39,9 % higher, respectively, while in cultivar Kseniia (PNRV) this indicator was less than the control by 27,4 %. An increase in the specific surface density of leaves in some variants influenced an increase in the water content in the cells: by 1,4 % in the Bohuslavka samples, 5,7 % in Kseniia ones, with a complex infection of the variety, while with a complex infection of the Nizhnist` variety, a decrease in hydration by 20,2 % was recorded.
When analyzing the parameters of the grown seedlings, there is a tendency to a decrease in the average diameter of the stem under the influence of viral infection. In sweet cherry saplings of the Nizhnist` variety, the diameter of the bole decreases by 18,8 %, in the Bohuslavka sour cherry variety — by 13,3 %. At the same time, the average height of seedlings decreases by 3,1 and 13 % in the Bohuslavka and Kseniia sour cherry varieties, respectively, and in the Nizhnist` sweet cherry — by 36,3 %.
As the research progressed, we have calculated that using infected material for growing seedlings reduces their yield when compared to using virus-free material.
