Necrotic Strain Of Potato Virus Research Articles

Ultrastructure of cytopathological responses in Solanum tuberosum cv. Spounta infected with necrotic strain of potato virus Y

Ultrastructural responses of plant cell organelles in leaf tissues of potato cv. Spounta towards potato virus Y (PVY-necrotic and ordinary strains) infection were investigated using an electron microscope. Numerous cytopathological alterations in cell wall, middle lamella, nucleus, chloroplast, mitochondria, endoplasmic reticulum and peroxisomes have been observed compared to healthy tissues. Splitting, destroying, joining to neighboring protoplasts and necrosis in cell wall were observed. Cell nucleus was changed to lobe-like shape; damage in envelope and enlargement of pore complexes were observed. Mitochondria were increased in number, elongated and destroyed. Many changes in chloroplasts such as deformation, reduction in size and number, damage of envelope and grana thylakoids were observed. Virus particles and cytoplasmic inclusions were observed in ultra-thin sections. To our knowledge, obtained results showed that only peroxisomes could be responsible organelles for induction of necrotic symptoms, because they were increased in number and frequently existed only in plant cells infected with PVY-necrotic strain.

Induction of potato systemic resistance against the potato virus Y (PVYNTN), using crude filtrates of Streptomyces spp. under greenhouse conditions

The potato virus Y (PVY) is considered one of the most important viruses in terms of both economical and biological impact. Potential of using three different Streptomyces spp. crude filtrates (SCF) to induce of resistance against tuber necrotic strain of potato virus Y (PVYNTN) in four potato cultivars namely, Spunta, Nicola, Selatar, and Diamant, were evaluated. Foliar spraying of Streptomyces netropsis DSM 40093 (SCF7), S. ambofaciens (SCF11) and S. actuosus (SCF20), applied separately on potato cultivated in pots, showed various inhibitory activities against PVYNTN infection in all the potato cultivars. SCF20 was the most effective one, as expressed by (100%) reduction of apical necrosis symptoms on potato cv. Spunta, Nicola, and Diamant leaves under greenhouse conditions. Application was done 7 days before virus inoculation with PVYNTN (DBVI) and 7 days after inoculation (DAVI). The concentration of PVYNTN in treatments was significantly reduced than in the untreated PVYNTN infected plants as detected by DAS-ELISA (expressed by decreasing in OD value). Expression of PR-1b gene was detected 21 (DAVI) in all SCF11-treated cultivars but was not expressed in healthy and infected control plants. Gas chromatography-mass spectrometry (GC-MS) analysis of S. actuosus (SCF20) ethyl acetate extract revealed the majority of fatty acids (FAs) and their derivatives, Citroflex A, Hexanoic acid, anhydride, Hexadecanoic acid, Hexadecanoic acid, ethyl ester, and Diisooctyl phthalate which suggested to act as elicitor molecules for induction of systemic acquired resistance (SAR). Overall, the application of culture filtrates of Streptomyces has the potentiality to be used as inducer against PVYNTN infection.

Expression and regulation of programmed cell death‐associated genes in systemic necrosis of PVYNTN susceptible potato tubers

Virus‐induced systemic necrosis accounts for great yield losses in potato (Solanum tuberosum) cultivars susceptible to the necrotic strain of potato virus Y (PVYNTN). To extend understanding of systemic necrosis, the tissue of healthy and PVYNTN‐infected potato tubers (necrotic and non‐necrotic) during storage was profiled for host gene expression using microarrays while virus concentration was determined using RT‐qPCR. Comparison of non‐necrotic tissue types revealed minor transcriptional differences, while tuber necrosis was characterized by high virus concentration and pronounced expression of defence response‐associated genes. Creation of programmed cell death‐associated gene ontology enabled assessment of expression and regulation of relevant differentially expressed genes implicated in the execution of plant programmed cell death. Vacuolar cell death and unfolded protein response to viral infection were implicated in the necrotic tuber tissue by transcriptional induction of genes possessing caspase‐like activity and genes coding for endoplasmic reticulum chaperones and folding proteins. A meta‐analysis, including all relevant publicly available gene expression datasets differing in genotype, pathogen interaction type and potato organ, revealed common defence responses associated with cell wall fortification, oxidative and biotic stress. The response in necrotic tissues of susceptible tubers resembled the hypersensitive response of resistant primary infected plants, but with hormonal signalling as an important differentiating factor. This study will be useful for in‐depth analysis of programmed cell death regulation in plants by providing gene ontology. It specifically addresses the issue of systemic necrosis formation in PVYNTN‐infected potato tubers during storage.

Physiological, cytological and molecular analysis of PVYNTN-infected potato cultivars

The tuber necrotic strain of Potato Virus Y (PVYNTN) is considered the most aggressive strain of PVY. Effects of PVYNTN on some metabolic activities and cytological characteristics of three potato cultivars Lady Rosetta, Mondial and Santana were investigated. Virus concentration, infection percentage and disease severity were also estimated. Potato cultivars differed in their susceptibilities to PVYNTN infection, whereas various levels of apical necrosis with different disease severity 30, 60 and 100% were recorded for Mondial, Santana and Lady Rosetta cultivars respectively. The lowest amount of leaf pigments was found in PVYNTN-infected potato cv. Santana. Total phenolic and total soluble sugars contents were highly accumulated in PVYNTN-infected leaves compared to healthy ones. A noticeable increased level of sodium cation was detected in PVYNTN-infected leaves of potato cv. Lady Rosetta. Electron microscopy analysis showed changes in nuclei, mitochondria, cell walls, and chloroplasts in PVYNTN-infected cells of potato cultivars compared with healthy. Genetic variations among potato cultivars under PVYNTN infection were detected by Inter Simple Sequence Repeat-Polymerase Chain Reaction (ISSR-PCR) analysis. The ISSR primers amplified 57 bands, and 52 showed polymorphism (91.23%). According to our results, potato cvs. Lady Rosetta and Santana were highly susceptible to PVYNTN infection while, Mondial was moderately resistant.

Mapping Loci That Control Tuber and Foliar Symptoms Caused by PVY in Autotetraploid Potato (Solanum tuberosum L.).

Potato tuber necrotic ringspot disease (PTNRD) is a tuber deformity associated with infection by the tuber necrotic strain of Potato virus Y (PVYNTN). PTNRD negatively impacts tuber quality and marketability, and poses a serious threat to seed and commercial potato production worldwide. PVYNTN symptoms differ in the cultivars Waneta and Pike: Waneta expresses severe PTNRD and foliar mosaic with vein and leaf necrosis, whereas Pike does not express PTNRD and mosaic is the only foliar symptom. To map loci that influence tuber and foliar symptoms, 236 F1 progeny of a cross between Waneta and Pike were inoculated with PVYNTN isolate NY090029 and genotyped using 12,808 potato SNPs. Foliar symptom type and severity were monitored for 10 wk, while tubers were evaluated for PTNRD expression at harvest and again after 60 d in storage. Pairwise correlation analyses indicate a strong association between PTNRD and vein necrosis (τ = 0.4195). QTL analyses revealed major-effect QTL on chromosomes 4 and 5 for mosaic, 4 for PTNRD, and 5 for foliar necrosis symptoms. Locating QTL associated with PVY-related symptoms provides a foundation for breeders to develop markers that can be used to eliminate potato clones with undesirable phenotypes, e.g., those likely to develop PTNRD or to be symptomless carriers of PVY.

Elevated Ambient Temperature Differentially Affects Virus Resistance in Two Tobacco Species.

Antiviral defense of plants is usually enhanced by an elevated temperature under natural conditions. In order to better understand this phenomenon, we carried out temperature shift experiments with Nicotiana glutinosa plants that were infected with Potato virus X (PVX) or the necrotic strain of Potato virus Y (PVY(N)). The virus titer of the plants was found to be much lower when they were maintained at 30°C compared with 22°C, particularly in the upper leaves. PVX resistance at 30°C persisted for a short period even when temperature was shifted back to 22°C. In contrast, N. benthamiana lost the virus resistance immediately after the temperature dropped to 22°C. Expression analysis of two RNA-dependent RNA polymerases in N. glutinosa (NgRDR) showed that a 12-day treatment at 30°C increased the expression of NgRDR1, while NgRDR6 was not affected. In addition, the NgRDR6 mRNA level correlated with the PVX titer but was unaffected by PVY(N) infection. These observations indicate that PVX and PVY(N), although they are both RNA viruses, might trigger different defense responses at elevated temperatures. Our study provides valuable data for a better understanding of the temperature-regulated host virus interaction.

Preferential acquisition and inoculation of PVYNTN over PVYO in potato by the green peach aphid Myzus persicae (Sulzer).

In the past decade, the incidence and distribution of the recombinant, tuber necrotic strain of Potato virus Y (PVYNTN) has been increasing in the US seed potato crop while the ordinary strain (PVYO) has been decreasing. The transmission efficiency of both strains was determined from two potato cultivars when acquired sequentially by the same aphid or when acquired by separate aphids and inoculated to the same plant. PVYNTN was transmitted more efficiently than PVYO and the order of acquisition or inoculation did not affect the preferential transmission of PVYNTN. When a recipient plant became infected with both strains, PVYNTN maintained higher titre than PVYO and would facilitate the acquisition of PVYNTN. Furthermore, the acquisition and transmission of PVYNTN over PVYO was enhanced in the potato cultivar that expressed a strain-specific Ny-like resistance gene that confers partial resistance to PVYO.

First Report of Potato mop top virus Causing Potato Tuber Necrosis in Colorado and New Mexico.

Potato mop top virus (PMTV) is considered the type member of the genus Pomovirus. PMTV is an important pathogen of potato vectored by the plasmodiophorid Spongospora subterranea f. sp. subterranea (Sss), which causes powdery scab of potato (1). Sss and PMTV are usually associated with cool and humid environments. PMTV-infected potato tubers generally exhibit internal hollow necrotic spots or concentric rings, and the virus is known to cause significant economic losses in Northern Europe, North and South America, and Asia (4). PMTV in the United States was first reported in Maine (2). Potato (Solanum tuberosum L.) tubers cv. FL2048 and cv. Atlantic were sent to our laboratory from fields in Saguache County in Colorado and in San Juan County in New Mexico, respectively, during the spring of 2013. The tubers from both locations had multiple, internal, concentric, necrotic arcs and circles. Internal tissue with necrotic lesion from six symptomatic tubers from each location were crushed in liquid nitrogen followed by ribonucleic acid extraction using a Total RNA Isolation kit (Promega Corp., Madison, WI). These extracts were tested by reverse transcription (RT)-PCR using three different sets of previously published primers for molecular detection of PMTV. The primer set H360/C819 targeting the coat protein (CP) on RNA 3 of PMTV yielded an amplicon (H360-CO and H360-NM) of 460 bp (4). The second set of primers, pmtF4/pmtR4 (5), amplified a 417-bp product (PMTF-CO and PMTF-NM) in RNA 2, and the third set, PMTV-P9/PMTV-M9 (3), designed to amplify the region encoding an 8-KD cysteine-rich protein in RNA 3 of PMTV, yielded a 507-bp amplicon (PMTV9-CO and PMTV9-NM). The amplicons generated from RT-PCR using all three sets were cloned (PGEMT-easy) and sequenced. Since the sequences from symptomatic tuber extracts from each location were identical to their respective primer sets, a consensus sequence from each primer set was submitted to National Center for Biotechnology Information (NCBI) GenBank. Sequences obtained from the H360/C819 primer set (GenBank Accession Nos. KM207013 and KM207014 for H360-CO and H360-NM, respectively) were 100% identical to the corresponding CP regions of PMTV isolates from North Dakota (HM776172). Sequences from the pmtF4/pmtR4 primer set (KM207015 and KM207016 for PMTF-CO and PMTF-NM, respectively) were 100% identical to the corresponding protein in RNA2 of PMTV isolates from North Dakota (GenBank HM776171), and sequences from the PMTV-P9/PMTV-M9 primer set (KM207017 and KM207018 for PMTV9-CO and PMTV9-NM respectively) were 99% identical to the corresponding protein in RNA3 of PMTV isolates (AY187010). The 100-99% homology of the sequences from this study to the corresponding PMTV sequences published in NCBI confirmed the occurrence of symptoms in the tubers from both Colorado and New Mexico due to PMTV. None of the symptomatic tubers tested positive for Tobacco rattle virus, Tomato spotted wilt virus, Alfalfa mosaic virus, Potato leafroll virus, or the necrotic strains of Potato virus Y by RT-PCR. To our knowledge, this is the first report of PMTV in potato in states of Colorado and New Mexico.

Virus resistance of transgenic potato plants (Solanum tuberosum L.) bearing PVY NTN -CP gene of potato virus Y coat protein

The PVY NTN -CP coat protein gene from a necrotic strain of potato virus Y (PVY NTN ) has been transferred into two potato Solanum tuberosum L. cultivars, Mindenes and Somogyi kifli, via agrobacterial transformation. Expression of the PVY NTN -CP gene was revealed in 33 (89%) of 37 and 3 (75%) of 4 kanamycin-resistant regenerates of these cultivars, respectively. The level of virus resistance against two virus strains (PVY O , PVY NTN ) of independent lines of transgenic potatoes varied from extreme resistance to full susceptibility. The three independent lines of transgenic potatoes proved to be extreme resistant to both PVY strains.

First Report of Potato mop-top virus in North Dakota.

Potato mop-top virus (PMTV) is the type member of the genus Pomovirus. PMTV is an important pathogen of potato, causing significant economic losses in Northern Europe, North and South America, and Asia (3). PMTV in the United States was first reported in Maine (2). PMTV is vectored by the plasmodiophoromycete Spongospora subterranea cv. subterranea, which causes powdery scab of potato (1). S. subterranea and PMTV are usually associated with cool and humid environments. In the spring of 2010, six potato tubers of cv. Russet Burbank were received from a commercial potato farm in Grand Forks County in North Dakota. The tubers had multiple, internal, concentric, necrotic arcs and circles. The presence of PMTV in the necrotic lesions was verified by a positive double-antibody sandwich-ELISA (Agden Ltd., Ayr, Scotland). The tuber lesions had an absorbance value (405 nm) at least two times greater than that of the negative control sample, which consisted of a healthy tuber. Total RNA was extracted from lesions of six different tubers that tested positive by ELISA using a Total RNA Isolation kit (Promega Corp. Madison, WI). These extracts were tested for PMTV by reverse transcription (RT)-PCR using two different sets of primers. The primer set H360/C819 targeted the coat protein (CP) of PMTV and yielded an amplicon of 460 bp (4). The amplicons generated from the necrotic lesions were cloned (TOPO Cloning; Invitrogen, Carlsbad, CA) and sequenced. Another set of primers, pmtF4/pmtR4, designed to bind to a region in RNA 2 of PMTV, yielded a 417-bp amplicon that also was cloned and sequenced (3). The sequences from all six tuber lesions were identical for the respective primer sets. A consensus sequence for each primer pair was submitted to GenBank (Accession No. HM776171 for primers pmtF4/pmtR4 and No. HM776172 for primers H360/C819). The sequences obtained from the H360/C819 and pmtF4/pmtR4 amplicons were 99% identical to the corresponding regions of PMTV isolates from Northern Europe (GenBank Accession Nos. AM503629 and AJ277556, respectively). Freeze-dried, necrotic tuber tissue from all six tubers was also tested at a USDA Laboratory in Prosser, WA by RT-PCR with the H360/C819 primer pair (4), confirming the results above. Cloning and sequencing of one of the amplicons revealed 100% similarity to the sequence described above for these primers (GenBank Accession No. HM776172), confirming the presence of PMTV in the symptomatic tubers. None of the symptomatic tubers tested positive for Tobacco rattle virus, Tomato spotted wilt virus, Alfalfa mosaic virus, Potato leafroll virus, or the necrotic strains of Potato virus Y by RT-PCR. To our knowledge this is the first report of PMTV in North Dakota.

Inhibiting Virus Infection by RNA Interference of the Eight Functional Genes of the Potato Virus Y Genome

AbstractThe genome of Potato virus Y is a single‐stranded, positive‐sense RNA molecule that encodes a single large polypeptide that is cleaved by self‐encoded proteases into 10 functional proteins. Using specific primers designed based on the cloned genome sequence of the necrotic strain of Potato virus Y (PVYN), we amplified 400 bp and 500 bp cDNA fragments from the 3′ ends of P1, HC‐Pro, P3, CI, Vpg, NIa, NIb and CP genes. These cDNA fragments were then inserted into the binary vector pROKII to construct the vectors pROK‐P1, pROK‐HC‐Pro, pROK‐P3, pROK‐CI, pROK‐NIa‐Vpg, pROK‐NIa‐Pro, pROK‐NIb and pROK‐CP, all of which contained hairpin RNAs (hpRNAs). These recombinant binary vectors were introduced into Agrobacterium tumefaciens strain LBA4404 and then into Nicotiana tabacum L. var. NC89 plants, respectively. Virus challenge inoculation indicated that the plants transformed with each construct were resistant to PVY infection, and the percentage of resistant plants obtained ranged from 33–64%. Northern blot showed an inverse correlation between transgenic transcript accumulation and virus resistance. siRNAs could be detected in all the resistant plants. We also studied the relationship between the secondary structure and the gene‐silencing efficiency and found a positive correlation between local free energies (ΔGloc) and the virus‐resistance ratio. For each construct, one line of progeny T1 was randomly selected to analyse the inheritance of the transgene and the resistance. All transgenic single locus lines were completely resistant, and this resistance could be stably inherited.

Ultrastructural events during hypersensitive response of potato cv. Rywal infected with necrotic strains of potato virus Y

Potato plants cv. Rywal with hypersensitivity gene Ny-1 infected with PVYN or PVYNTN reacted in local necroses 3 days after infection. Potato virus Y (PVY) particles were found in epidermis, mesophyll, phloem and xylem cells in inoculated leaves. Noncapsidated virus particles (without capsid protein) were observed already 10 h after infection by using electron microscopy in situ. Capsid protein on one terminus of noncapsidated virus particles was located 5 days after inoculation with the use of immunogold labeling method. Whereas cytoplasmic inclusions were observed for the first time 24 days after infection during hypersensitive response. Ultrastructural studies showed that ER may take part in PVY RNA replication and capsidation of Potyvirus particles. Observed cytopathological changes and virus particles indicate that cell nucleus and mitochondrion might participate in PVY life cycle. During hypersensitive response PVY particles were found in plasmodesmata as well as in phloem and xylem.

PVYNTN-CP coat protein gene mediated virus resistance of transgenic potato plants

PVYsup style="line-height:1.6em"NTN/sup-CP span style="line-height:1.6em"coat protein gene from a necrotic strain of potato virus /spanY (pvysup style="line-height:1.6em"ntn/sup) span style="line-height:1.6em"has been transferred into two potato /spanSolanum tuberosum L. span style="line-height:1.6em"cultivars /spanMindenes span style="line-height:1.6em"and /spanSomogyi kifli via Agrobacterium tumefaciens span style="line-height:1.6em"transformation. Expression of integrated PVY/spansup style="line-height:1.6em"NTN/supspan style="line-height:1.6em"-CP gene were confirmed for 33 (89 %) of 37 and 3 (75 %) of 4 kanamycin-resistant regenerants of potato cultivars Mindenes and Somogyi kifli respectively. The level of virus resistance against two virus strains /span(PVY°, PVYsup style="line-height:1.6em"NTN/sup) span style="line-height:1.6em"of independent lines of transgenic potatoes varied between extreme resistance to susceptibility. The three independent lines of transgenic potatoes proved to be extreme resistant against both PVY strains./span

First Report of Tomato spotted wilt virus Causing Potato Tuber Necrosis in Texas.

In the summer of 2008, potato (Solanum tuberosum L.) tubers (cvs. FL1867, FL2053, and FL1922) from commercial fields near Dalhart, TX were observed with distinct external erumpent rings and severe internal discolorations including blotches, spots, and dry, cork-like tissue. The presence of rings suggested the possible involvement of one or more viruses. Nucleic acid from seven of eight symptomatic tubers received in Washington (cvs. FL1867 and FL1922) tested positive for Tomato spotted wilt virus (TSWV) by reverse transcription (RT)-PCR with primers TSWV 1 and 2 (3). Similarly, tubers (cvs. FL1867 and FL2053) received in North Dakota tested positive for TSWV with forward (S1983) and reverse (S2767) primers of Tsompana et al. (4). The 777-bp amplicon obtained with primers TSWV 1 and 2 and the 803-bp amplicon obtained with primers S1983 and S2767 were cloned and three clones of each were sequenced. Analysis of the consensus sequences and BLAST comparisons confirmed the Washington and North Dakota sequences were indeed TSWV in origin and were each 98 to 99% identical to the corresponding nucleocapsid region of a number of TSWV isolates and most closely related to an isolate detected in eastern black nightshade from Colorado (GenBank No. AY777475). The deduced amino acid sequences of the 777-bp nucleocapsid open reading frame differed from AY777475 at only two residues in each of the Washington and North Dakota sequences. The Washington and North Dakota derived sequences were deposited with GenBank (Nos. FJ882069 and FJ882070, respectively). None of the eight symptomatic tubers tested positive for Tobacco rattle virus (TRV), Alfalfa mosaic virus (AMV), or the necrotic strains of Potato virus Y (PVY) by RT-PCR. Mechanical transmission tests were conducted by grinding symptomatic tissue of a TSWV-positive FL1867 tuber in 10 volumes of 30 mM potassium phosphate buffer, pH 8.0, containing 10 mM of sodium diethyldithiocarbamate and 10 mM of sodium thioglycollate and rub inoculated onto Carborundum-dusted leaves of Samsun NN tobacco. Approximately 10 days after inoculation, chlorotic-necrotic rings were present on the inoculated leaves and circular necrotic lesions developed on the upper leaves. Dark stem lesions were also present on inoculated tobacco, and after 3 weeks, the upper leaves developed severe, spreading lesions. Tissue from the symptomatic tobacco tested positive for TSWV by RT-PCR (primers TSWV 1 and 2) and also with a TSWV-specific ImmunoStrip (Agdia, Inc., Elkhart, IN), but tested negative for TRV, AMV, and PVY by RT-PCR. TSWV has been reported on field-grown potatoes in North Carolina (1) and has been reported on potatoes in Australia (2) and in other parts of the world (referenced in 1). To our knowledge, this is the first report associating TSWV with tuber necrosis on potatoes in Texas.

Presence of necrotic strains of Potato virus Y in Mexican potatoes.

As part of a routine screening for the possible presence of the necrotic strains of potato virus Y affecting potatoes in Mexico, five PVY isolates were submitted to biological and molecular analysis. Considering their serological properties, two belong to the common strain (O) and three to the necrotic strain (N). All the isolates induced vein necrosis in Nicotiana tabacum. To characterize the isolates, 5' NTR and P1 genes were sequenced and compared with sequences from GenBank database. Nucleotide sequence similarity ranged from 47–100% in the 5' NTR and from 63–100% in the P1 coding region. The lowest amino acid similarity between sequences of P1 gene was 55%. In phylogenetic trees of 5'NTR analysis, two PVYO Mexican isolates clustered with other PVYO isolates. In turn, the three PVYN isolates grouped with PVYN-NTN isolates. The phylogenetic analysis of P1 sequences (nucleotide and amino acid) showed two PVYO isolates grouping next to N-NTN cluster. A detailed analysis of the PVYO isolates showed two potential recombination regions in the P1 gene, in contrast to 5'NTR where no recombination was detected.

Starch, protein, glycoalkaloids, and l-ascorbic acid content in tubers of genetically modified potato cv. Irga

Changes in contents of protein, starch, ash, l-ascorbic acid, and glycoalkaloids in tubers of 15 clones of cultivar Irga transformed with viral genome sequences in order to improve their resistance to a necrotic strain of potato virus Y (PVYN) were investigated. The influence of modification type and year of cultivation on the contents of all chemical compounds examined for particular modified clones appeared to be irregular over the 3-year period of examination, and the clone of the best and stable content of chemical compounds was not found. Stable tendencies in the chemical compounds of tubers composed into groups and subgroups of clones representing the same modification type were not confirmed either. An essential stable decrease in glycoalkaloid content and an increase in starch content (compared with parental cultivar Irga) were found in almost all genetically modified clones. Glycoalkaloid content in green tubers of modified clones was usually (except three clones) higher than this for parental cultivar Irga. Correlation between glycoalkaloid content and tuber size for all, normal and green tubers of selected clones and parental cultivar Irga was examined as well.

Nutritional properties of tubers of conventionally bred and transgenic lines of potato resistant to necrotic strain of Potato virus Y (PVYN).

The potential effect of genetic modification on nutritional properties of potatoes transformed to improve resistance to a necrotic strain of Potato virus Y was determined in a rat experiment. Autoclaved tubers from four transgenic lines were included to a diet in the amount of 40% and compared with the conventional cv. Irga. The experiment lasted 3 weeks and special attention was paid to nutritional properties of diets, caecal metabolism and serum indices. Genetic modification of potato had no negative effect on the chemical composition and nutritional properties of tubers, ecosystem of the caecum, activity of serum enzymes and non-specific defence mechanism of the rats. Obtained results indicate that transgenic potato with improved resistance to PVY(N): line R1F (truncated gene coding for PVY(N) polymerase in sense orientation), R2P (truncated gene coding for PVY(N) polymerase in antisense orientation), and NTR1.16 (non-translated regions of PVY(N) genome in sense orientation) are substantial and nutritional equivalence to the non-transgenic cultivar. Tubers of transgenic line NTR2.27 (non-translated regions of PVY(N) genome in antisense orientation) increased the bulk of caecal digesta and the production of SCFA as compared to tubers of the conventional cultivar and the other transgenic clones. Taking into account some deviations, it seems reasonable to undertake a long-term feeding study to confirm the nutritional properties of tubers of transgenic lines.

Potato virus Y induced changes in the gene expression of potato ( Solanum tuberosum L.)

The tuber necrotic strain of Potato virus Y (PVY NTN) causes potato tuber necrotic ringspot disease in sensitive potato cultivars. Gene expression in the disease response of the susceptible potato ( Solanum tuberosum L.) cultivar Igor was investigated at different times after infection, using subtractive hybridization, cDNA microarrays and real-time PCR. The most pronounced change in the expression pattern of functionally diverse groups of genes was detected in systemically infected leaves 14 days after inoculation, and in leaves of plants grown from infected tubers. The expression of several stress-related genes during the infection process, including those for heat shock proteins, catalase 1, β-1,3-glucanase, wound inducing gene, and genes involved in photosynthesis, suggests their role in the susceptible potato–PVY NTN interaction.

Effect of antiviral genetical modification on softening of potato tubers during cooking

An investigation into the influence of genetical modification on potato tubers should include also an estimation of their technological usability. Potato tubers of 15 clones of cultivar Irga transformed with viral genome sequences in order to improve their resistance to a necrotic strain of potato virus Y (PVYN) were examined. The effect of cooking on tissue texture, expressed by fracture stress (F) and strain (D), and elastic modulus (E) from a compression test, was investigated. Although the influence of the modification type appeared to be statistically significant but irregular in particular years of cultivation, a detailed statistical analysis (variance and discrimination analyses) did not confirm any repeatable nor statistically significant differences in F, D, and E over the three-years period of examinations. While the effect of cultivation year was unmistakable, the order of F, D, and E values for particular clones was not constant in the successive years. The lack of stable tendencies in average values of the mechanical parameters for both groups and subgroups of clones representing the same modification model was also found. The statistical analysis of the variability of mechanical parameters of raw and heat-treated potatoes measured during the three successive years enabled classifying Irga and its genetically-modified clones as similar and did not allow to distinguish clones of the quickest softening.

Differentiation and molecular detection of Canadian necrotic strains of Potato virus Y

Isolates of Potato virus Y (PVY) from potatoes grown in Canada were identified as tuber necrotic strains on the basis of biological, serological, and molecular characteristics. Only one isolate, however, caused symptoms of potato tuber necrotic ringspot disease (PTNRD) in progeny tubers of inoculated potato plants Solanum tuberosum 'Nadine' under greenhouse conditions. None of the isolates caused symptoms of PTNRD in potato plants 'Russet Burbank' or 'Saco'. A primer set based on the NIb gene for detection of PVYO by RT-PCR was modified to include detection of the Canadian necrotic isolates of PVY. Restriction analysis of amplicons generated from suspected PVYNTN isolates with primers based on the P1 protein gene differentiated two sets of isolates. Subsequent comparison of the P1 gene sequence of the Canadian isolates with published sequences confirmed that the isolates corresponded to North American and European types of PVYNTN. A new primer pair, based on the NIb gene sequence amplified by RT-PCR, allowed the amplification by RT-PCR of a gene fragment from all PVYN and PVYNTN isolates but not from PVYO strains. These primers proved to be useful for detecting the virus in composite samples of potato leaves, sprouts, and tubers.