Browsing by Subject "PVY"

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  • Pennanen, Laura (Helsingin yliopisto, 2018)
    The potato virus Y (PVY) is a type member of the family Potyvirus which infects the nightshade family (Solanaceae) plants. Economically it is considered to be the most siqnificant problem in seed potato production worldwide. Meaningful methods to prevent economical damage caused by PVY are the production of certified seed potato and breeding of PVY-resistant cultivars. The starting point of breeding is identifying different PVY strains. Sequence information from HCPro protein (HCPro) and coat protein (CP) regions are essential to be able to identify different PVY strains and their recombinant forms. The aim of this study was to express the variation in CP and HCPro regions of PVY. This was done by sequencing PVY data from Finlands seed potato fields from year 2015 and comparing it to Yanping Tians (Doctor of Science, Agriculture and Forestry) sequence data from the same area from the years 2006 and 2007. The PVY positive samples used in this study were collected in 2015 in a virus screening test executed by Evira. The screening was done by using ELISA test. The comparison in this study was executed by aligning CP and HCPro regions from all samples and examining the regions by nucleotide and aminoacid level. Comparison was also executed by creating phylogenetic trees from aligned sequences. On the findings of this study the recombinant strain PVY-NTN was the most common strain in Finlands seed potato fields in 2015. Occurence of PVY-O strain was reduced significantly when compared to data from 2006 and 2007. The seven PVY-NTN samples that were examined in this study had a typical aminoacid region to PVY-O strain. This region covers aminoacids R269–K270 and is absent from a known recombinant PVY-NTN ”Nevski” and it is also a singular finding when compared to Yangping Tians samples. However, this change in aminoacid structure did not seem to provoke resistant genes in known potato cultivars to recognize these samples. It is plausible that PVY profits from this new mutation in its aminoacid structure, but this cannot be point out on the bases of this study.
  • Saarela, Olli (Helsingfors universitet, 2016)
    The potato virus Y (PVY) is a member of the family Potyvirus, which is the largest plant pathogenic virus family. PVY is one of the most important pathogens of the nightshade family (Solanaceae) plants. PVY is a particular problem in seed potato production, as well as in tomato and pepper production. Some PVY races cause necrotic symptoms (PTNRD) in potato tubers, which will make the tubers unsuitable for use. This thesis studied the ability of several recombinant strains of PVY to infect these three plant species. First objective was to find out which recombinant strains can infect the plants systemically and whether some of them will cause PTNRD symptoms in potato tubers. Secondly, we wanted to find out what parts or even specific amino acids in the HCpro of PVY affect the infection ability of the virus. This was done by comparing the genomes of the recombinant and wild type viruses and based on the experimental data. Finally, we wanted to see if the mutations would persist in the virus genomes for the duration of the infection. The test plants were infected by applying virus contaminated plant juice and grinding powder on the plant leaves. Plants were first grown in growing chambers and then transferred to a greenhouse. The plants were tested for viral infection with DAS-ELISA for three times during different stages of growth. To investigate whether the mutations had persisted in the virus genome, the viral RNA was isolated, multiplied with RT-PCR and then sequenced. Most of the recombinant viruses were not able to systemically infect either of the potato cultivars tested (cv. ‘Nicola’ and cv. ‘Annabelle’). ‘Nicola’ was more susceptible than ‘Annabelle’. The Tyr323Phe-mutation in the HCpro seemed to have a positive effect on the viruses ability to infect ‘Nicola’ in recombinant O5ON-F. PTNRD was caused by recombinants O5NNO45, N605-F and O5ON-F only in ‘Nicola’. Tyr323Phe-mutation had persisted in the N605-F during the infection. Tomato cv. ‘Moneymaker’ was more resistant towards the recombinants than cv. ‘Ildi’, though both cultivars were considerably more susceptible towards the recombinants than either of the potato cultivars or the pepper cultivars. The pepper cultivars tested were resistant towards PVYN605 and PVYOUK.
  • Solarmo, Elina (Helsingfors universitet, 2011)
    Potato virus Y (PVY) is currently the most yield and quality limiting pathogen of the cultivated potato (Solanum tuberosum L.) globally. While yield losses specific to PVY are hard to measure in presence of other pathogens they are estimated as 20 to 80 %. The most important way by which the virus spreads are virus-infected seed potatoes. High quality seed potato is very important for food, food industry and starch potato production. Visual inspection of the potato plants underestimates usually the real percentage of PVY infection. Laboratory tests provide more accurate results about the incidence of infections. The problem with testing PVY is that the virus cannot be detected reliably from samples taken from dormant tubers. Different treatments have been used to break dormancy of tubers e.g. chemicals (Rindite, bromoethane), plant hormones (gibberellic acid) and adjusted storage temperatures (cold and heat treatment). The results have varied a lot. In this thesis an experiment with oxygen-carbon dioxide (O2 40 %-CO2 20 %) treatment with different periods of time was used to end dormancy of potato tubers. The aim was to test whether the treatment could end dormancy of tubers earlier than normally and to see if the treatment has an effect on detection of PVY. One aim was also to test how reliably PVY could be detected from tuber and sprout samples compared with potato leaf samples which are normally used for virus testing. Results from the sprouting treatment were variable and could not be readily generalized. The treatment had no effect on the detection of PVY incidence. When the different plant materials were compared with each other, tuber material showed the lowest PVY percentage when compared to sprouts and leaves. Testing sprouts also underestimated the incidence PVY. The best material for testing PVY in potatoes were the leaf samples.