The eastern region of Kazakhstan is an important territorial district producing seed potatoes. Since 2022, the region has been divided into the Abay region (administrative center in Semey city) and the East Kazakhstan region (administrative center in Ust-Kamenogorsk city). One of the largest elite seed farms producing potatoes is East Kazakhstan Agricultural Station LLP (Ust-Kamenogorsk). Potato Virus Y (PVY) was reported as problem for the production of Solanum tuberosum L. in Kazakhstan more than 25 years ago, however, over the past 5 years the spread of recombinant strains of PVY has become more serious problem (Loebenstein, Manadilova 2003). The purpose of this study was to find out the prevalence of PVY strains in the fields of the eastern region of Kazakhstan, including the fields of elite seed farm and commercial potato fields of the Glubokovsky district for the period from 2020 to 2021. Previously, the presence of recombinant strains (PVYN, PVYNTN, PVYN-Wi, PVYO) was shown in the west of Kazakhstan (Khassanov et al. 2020), but there is no data on the variety of PVY strains in the east region of Kazakhstan. Considering the geographical remoteness of these regions by more than 2000 km, the study of the prevalence of PVY in the fields of Kazakhstan needs to be supplemented with new data. PVY strains show a range of symptoms in different potato cultivars. The most damaging of these symptoms is tuber necrosis (Karasev and Gray 2013) associated with PVYNTN and some other recombinant strains. The pathogenesis of a viral infection of the PVYN strain and its recombinants is associated with the development of severe necrotic lesions of the tuber material, because of which yield losses can reach 60% (Chikh-Ali at al., 2020). In July 2021 leaf samples of 240 plants of two local regional potato varieties (Tavria and Izolda) were randomly selected to study PVY strains circulating in seed potatoes. 120 samples of the Tavria variety (seed material of the Elita class) and 120 samples of the Izolda variety (seed material of the Elita class) grown on seed potato fields of the East Kazakhstan Agricultural Experimental Station (GPS: N50.03324°, E82.53346°) were tested for the presence of potato viruses (PVA, PVS, PVM, PLRV, PVY) using commercial ELISA test systems (Russian Potato Research Center, Russia). In most samples (43 leaf samples), PVY is identified in the presence of a number of other potato viruses, mainly with PVM and PVS viruses. In order to type of PVY recombinant strains, samples containing PVY monoinfection have been selected. According to the results of ELISA, 21 PVY monoinfection positive samples have been detected: 14 plants of the Tavria variety, 7 plants of the Izolda variety. Serotype analysis using anti-rabbit polyclonal antibodies (Bioreba Ag, Switzerland) specific for PVYO, PVYC and PVYN serotypes identified PVYO serotype in 14 samples of the Tavria variety and in 7 samples of the Izolda variety, PVYN serotype in 2 samples of the Tavria variety and in 2 samples of the Izolda variety. All 21 PVY-positive samples were tested for strain by reverse transcription polymerase chain reaction (RT-PCR) using the strain-specific primers described by Chikh Ali et al. (2010). The products of PCR analysis showed the presence of bands characteristic of the recombinant N:O strain, 853, 633, and 441 bp - in 17 samples and characteristic of the NTNa strain, 1307, 633 and 441 bp in 4 samples. After determining the results of the analysis of leaf material samples, PVY-infected plants were removed from the soil and the tuber material was visually analyzed for signs of necrosis. According to the results of visual diagnostics, the symptoms of tuber necrosis were found in 80% of cases of infection with recombinant strains of PVYNTNa. In terms of severity, the symptoms of tuber necrosis were identical in both strains and caused to the damage of 35-50% of tubers on each plant of the Tavria and Isolda varieties, which indicates the absence of resistance to these recombinant strains. As is known, at present, many potato varieties have strain-specific resistance to PVYO (Funke at al. 2017). However, N:O and NTNa recombinant strains are the most difficult to develop resistance (Green et al. 2017). This is the first report on the Tavria and Izolda potato varieties as a susceptible host to recombinant strains of PVYN:O and PVYNTNa. Over the past five years, recombinant strains PVYN:O and PVYNTNa were introduced in two regions of Kazakhstan. In this regard, research and development of effective strategies to reduce the spread of recombinant strains PVYN:O and PVYNTNa in Kazakhstan, is particularly relevant. The authors declared no conflicts of interest. Funding: research was carried out within the framework of the scientific project "Development and implementation of innovative technology aimed at imparting antiviral resistance to crop varieties", funded by the Ministry of Education and Science of the Republic of Kazakhstan, Individual registration number (IRN): AP08052163.
Keywords: Causal Agent; Crop Type; Epidemiology; Field crops; PVY; Solanum tuberosum L.; Subject Areas; Viruses and viroids; disease development and spread.