Integrated transcriptomic and metabolomic analyses reveal hormone-mediated crosstalk during potato virus Y and potato spindle tuber viroid co-infection.

Potato virus X (PVX) and potato virus Y (PVY) are major pathogens that threaten seed potato quality and yield. To improve the efficiency of field screening, we developed monovalent PVX, monovalent PVY, and bivalent PVX/PVY nanozyme strips using Fe3O4 nanozymes as labels in a double-antibody sandwich lateral flow immunochromatographic assay. Western blot analysis demonstrated that four monoclonal antibodies (PVX 2, PVX 6, PVY 2, and PVY 5) specifically recognized their corresponding viral coat proteins. Specificity testing showed that the nanozyme strips reacted only with the target viruses and did not cross-react with other common potato viruses, including Potato virus A (PVA), Potato virus M (PVM), Potato virus S (PVS), and Potato leafroll virus (PLRV). The PVX nanozyme strip detected PVX-positive extracts diluted up to 103-fold, the PVY nanozyme strip up to 104-fold, and the bivalent strip detected PVX/PVY co-infected samples diluted up to 103-fold. In addition, detection results by strips from 12 samples of plantlets in vitro were fully consistent with RT-PCR. These nanozyme strips provide rapid, simple, specific, and sensitive methods that can be stored at ambient temperature, enabling field surveys, warehouse screening, and on-site testing and supporting early detection of potato virus diseases.

Cell-intrinsic restriction factors (CIRFs) negatively regulate plant virus infections and represent valuable resources for breeding virus-resistant crops. However, the potential for ribosomal proteins to function as CIRFs and the underlying mechanisms remains elusive. Our previous work demonstrated that the Nicotiana benthamiana chloroplastic ribosomal protein of the large subunit 1 (NbRPL1) promotes the infection of tobacco vein banding mosaic virus (TVBMV) by antagonizing the NbBeclin1-mediated degradation of the viral RNA-dependent RNA polymerase, NIb. Continuing this line of research, we explored the role of another nonchloroplastic ribosomal protein, large ribosomal protein 4 (RPL4), in TVBMV replication. We found that TVBMV NIb interacts with NbRPL4; however, the NIb proteins of 2 other related potyviruses, potato virus Y (PVY) and turnip mosaic virus (TuMV), did not interact with NbRPL4. Overexpression of NbRPL4 inhibited, whereas its downregulation promoted, TVBMV replication. NbRPL4 did not affect PVY or TuMV replication. The nuclear-cytoplasmic distribution of NbRPL4 positively correlated with its antiviral effect on TVBMV replication. NbRPL4 interfered with NbXPO1-mediated nuclear export of the NIb protein, subsequently affecting the translocation of NIb into the viral replication compartment. Our work indicates that NbRPL4 functions as a restriction factor for TVBMV by inhibiting NbXPO1-mediated nuclear export of NIb in a virus-specific manner.

ABSTRACT Aphid species that test positive for plant viruses in reverse transcription‐PCR (RT‐PCR) analysis are not necessarily vectors. This is because virus RNA can also be detected in non‐vector aphid species using this method. Potato virus Y (PVY) has been previously detected using RT‐PCR from three common weed‐infesting alate aphid species, Aphis fukii Shinji, Aphis oenotherae Oestlund, and Capitophorus hippophaes javanicus Hille Ris Lambers, trapped in potato fields in Hokkaido, northern Japan. However, these three taxa are not known as PVY vectors, and it remains unclear whether they acquired PVY from their respective host plants or other common weeds. Therefore, we conducted two experiments: (i) transmission experiments of these aphids using Myzus persicae (Sulzer), a species widely regarded as the most efficient PVY vector, as a reference species, and (ii) virus susceptibility experiments of typical host plant species of the three aphid species and other common weed species in and around potato fields in Hokkaido. The transmission experiments showed that the PVY‐transmission efficiency of A . fukii and A. oenotherae was not significantly different from that of M. persicae . In contrast, C. hippophaes javanicus did not transmit PVY. The estimated maximum transmission efficiency by one aptera was 7.5%. Mechanical inoculations and field sampling revealed that the tested weed species were not susceptible to PVY. These findings suggest that A . fukii and A. oenotherae serve as common and efficient PVY vectors in potato fields in Hokkaido, despite their individual transmission efficiency being < 7.5%. They likely acquire PVY from infected potato plants and/or unidentified reservoirs. These novel insights can advance our understanding of PVY epidemiology in Japan and contribute to the development of more effective vector‐based control strategies against PVY.

Despite their great agronomic interest and widespread occurrence in germplasm resources, the quantitative resistance and tolerance of plants to their parasites have rarely been studied in terms of durability potential. Using experimental evolution under controlled conditions for 9 months, we compared the evolution of potato virus Y (PVY) (Potyvirus yituberosi) virulence, measured by the effect of viral infection on plant fresh weight, and replicative fitness, measured by systemic viral load, in five pepper (Capsicum annuum) lines contrasting in their levels of quantitative resistance and tolerance. PVY evolutionary trajectories differed between pepper lines. Three lines revealed either an increase in PVY replicative fitness or an increase or decrease in PVY virulence. Two other lines did not reveal any significant change in PVY replicative fitness or virulence. The tolerance level of three pepper lines also differed significantly when measured with initial and evolved PVY populations, often associated with changes in PVY virulence. PVY evolutionary trajectories were partly explained by parameters linked to plant resistance operating at different stages of infection (inoculation, colonization of inoculated leaves and systemic infection). This study provides information on the durability potential of quantitative resistance and tolerance to PVY in pepper.

Identification of pesticide targets is of great significance for the development of new pesticides. The new compound GLY-15, containing a pyrimidine heterocycle and a moroxydine skeleton structure, has good anti-TMV activity, but the underlying molecular targets and mechanism of action remain elusive. Here, host malate dehydrogenase (MDH), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and tobacco mosaic virus (TMV) coat protein (CP) were identified as potential targets of GLY-15 using activity-based protein profiling (ABPP) and drug affinity responsive target stability (DARTS), and their interactions with GLY-15 were validated by microscale thermophoresis (MST) and pull-down analysis. Functional analyses demonstrate that MDH silencing significantly reduces TMV accumulation, while transient overexpression of MDH results in elevated viral infection. Meanwhile, yeast two-hybrid (Y2H), co-immunoprecipitation (Co-IP), and bimolecular fluorescence complementation (BiFC) analysis uncover that MDH interacts with CP, and their interaction is effectively inhibited by GLY-15. Site-directed mutagenesis identifies E225 as a critical residue for both GLY-15/MDH binding and MDH/CP interaction. Further investigations reveal that GLY-15 functions as an MDH inhibitor and affects its interaction with CP. Meanwhile, we showed that GLY-15 targeting MDH indicates broad antiviral activity against pepper mild mottle virus (PMMoV) and potato virus Y (PVY). This investigation systematically reveals novel insights into the anti-TMV mechanisms of GLY-15, establishing a valuable theoretical basis for antiviral target discovery and plant disease resistance breeding.

Potyvirus genomes are expressed as a single large open reading frame, which is translated into a polyprotein that is post-translationally cleaved by three virus-encoded proteases into 10 functional proteins. Several of these potyviral proteins, including nuclear inclusion protein b (NIb), are multifunctional. Here, using the classic GFP silencing in Nicotiana benthamiana gfp-transgenic plants, we show that potato virus Y (PVY) NIb, in addition to its canonical role as the viral RNA-dependent RNA polymerase (RdRP), functions as a suppressor of RNA silencing. Mutational analyses reveal a previously unreported NIb nuclear localization signal (NLS) consisting of a triple-lysine motif. NIb suppression of RNA silencing activity was lost when the NLS was mutated, suggesting that nuclear localization is required for NIb suppression of RNA silencing activity. Analysis of sequenced GFP siRNAs revealed three reproducible hotspot regions at ≈175 nt, ≈320-330 nt, and a broader 3'-proximal region spanning ≈560-700 nt that contains multiple local maxima. These data show differences in the positional distribution of siRNAs between samples expressing NIb and those expressing NIbDel3×2, the NIb null mutant that does not suppress RNA silencing. However, the positional distribution of GFP-derived small RNAs across the transgene differed modestly between NIb and NIbDel3×2, while both treatments showed the same three reproducible hotspot regions. Furthermore, NIb was found to interact with four key RNA silencing pathway proteins-AGO4, HSP70, HSP90, and SGS3. Except for HSP90, each of these proteins showed degradation products that were absent in NIb mutants that did not suppress RNA silencing. These findings support a role for NIb in countering host defense during virus infection.

Potato virus Y (PVY) and potato leafroll virus (PLRV) are the most damaging viruses for potato production worldwide. Mixed infections not only result in additive detrimental effects on plant growth and tuber yield but also complicate the development of durable and broad-spectrum viral resistance. Heterologous protection against PVY can be achieved through the expression of the coat protein (CP) of lettuce mosaic virus (LMV) (CPLMV), conferring resistance via a capsid protein-mediated mechanism. On the other hand, we have previously demonstrated that transgenic lines expressing the PLRV ORF2 (RepPLRV) exhibit resistance to different PLRV isolates. In this study, potato transgenic lines of cv. Kennebec expressing CPLMV and RepPLRV were developed to confer dual virus resistance. Transgenic and non-transgenic control plants were molecularly and phenotypically characterized in greenhouse and field conditions. Across multiple growing seasons, two selected transgenic lines consistently displayed robust resistance to both major viruses, without exhibiting yield penalties or noticeable phenotypic alterations. These results constitute a significant advancement, demonstrating that dual resistance to PVY and PLRV can be achieved while preserving the original agronomic performance of the cultivar. This breakthrough not only contributes to long-term crop productivity but also provides a more sustainable strategy for managing viral diseases in potato production.

Abstract Whilst molecular methods for plant virus detection are usually based on PCR amplification, loop mediated isothermal amplification (LAMP) is a rapid and sensitive molecular diagnostic tool increasingly used for plant virus detection, particularly in field conditions and resource-limited laboratories. In this study, a novel LAMP primer set (ID: 334) was developed for the specific detection of Potato virus Y (PVY), a globally significant pathogen responsible for yield losses of up to 80% in potatoes. Primer set 334 was designed based on conserved regions identified across 30 complete PVY genomes. It was evaluated against 33 PVY isolates representing 5 strain groups. The assay demonstrated 100% inclusivity, successfully detecting all isolates, including both recombinant and non-recombinant strains. Specificity testing confirmed no cross amplification with related potyviruses (Potato virus A (PVA) and Potato virus V (PVV)) or unrelated potato viruses (Potato virus X (PVX), Potato leafroll virus (PLRV), and Potato mop-top virus (PMTV)), further validating the exclusiveness of the assay. Moreover, the assay was validated on multiple host matrices, including leaves and tuber tissues of potato. Compared to a previously published LAMP assay, primer set 334 exhibited 2.6-fold greater sensitivity, detecting PVY at four orders of magnitude lower concentrations, with performance comparable to qPCR but with faster time-to-result. This improved LAMP assay provides a rapid, specific, and sensitive tool for PVY detection in leaves and tubers, supporting both laboratory, field, and post-harvest diagnostics.

Sustainable nanotechnology, particularly chitosan (CS)-based biodegradable nanoparticles (NPs), offers an eco-friendly delivery system comparedto conventional techniques. Potato virus Y (PVY) causes severe potato yield losses and reduces tuber quality. Its control is challenging owing to nonpersistent aphid transmission, especially by Myzus persicae, the most efficient vector. Chemical insecticides lead to environmental pollution, health risks, and resistance, highlighting the need for alternatives. This study assessed pure CS, thyme essential oil (TEO)-loaded CS, CS-lecithin (LH) encapsulated TEO, and TEO alone for their ability to block PVY transmission by M. persicae. To the best of our knowledge, no prior studies have examined the CS + LH + TEO formulation's effect on aphid-mediated PVY transmission. The results clearly indicate that all NP formulations significantly reduced aphid vectored transmission of PVY to healthy plants and inhibited virus acquisition from infected sources. The CS + LH + TEO and pure TEO treatments were the most effective, with CS + LH + TEO reducing transmission by 50.0% and pure TEO suppressing acquisition by 57.5%. Moreover, these formulations, especially CS + LH + TEO, substantially enhanced antioxidant enzyme activities, increased proline levels, and upregulated expression of the defense genes PAL-1and PR-2. As a result, accumulation of post-PVY infection oxidative stress markers H₂O₂ and MDA was considerably lower in NP-treated plants, emphasizing their protective effect against membrane damage. In this study, TEO was successfully encapsulated using CS and LH. Although previous research has primarily focused on the individual effects of CS and TEO on aphids, the inhibitory effect of CS + LH + TEO NPs on PVY transmission and acquisition by aphids offers a promising avenue for developing novel integrated pest management strategies. © 2026 Society of Chemical Industry.

Tobacco leaf diseases significantly affect yield and quality, underscoring the need for rapid and non-destructive diagnostic tools. Although hyperspectral imaging (HSI) has been applied in tobacco pathology, most existing studies focus on single diseases and lack generalized, interpretable frameworks for multi-class identification. In this study, hyperspectral images of healthy leaves and four major diseases-brown spot, wildfire, Tobacco Mosaic Virus (TMV), and Potato virus Y (PVY)-were collected to construct a balanced, leaf-independent dataset. Pixels were grouped by leaf ID, and the entire dataset was strictly partitioned at the leaf level to prevent pixel-level data leakage and ensure generalization to unseen leaves. Multiple preprocessing techniques, wavelength-selection methods, and machine-learning classifiers were systematically compared. A compact ANN model integrating Savitzky-Golay preprocessing and SPA-based wavelength selection achieved the best overall performance while requiring only a small number of informative wavelengths. A Transformer model provided slightly stronger predictive capacity but depended on full-spectrum inputs and substantially higher computational cost. Pixel-level predictions enabled lesion-area-based severity estimation for the two leaf-spot diseases. SHAP analysis highlighted physiologically meaningful spectral regions associated with pigment absorption and structural variation. Overall, this study presents an efficient and interpretable HSI framework for multi-disease tobacco diagnosis, supporting the development of practical hyperspectral or multispectral systems.

Potato virus Y (PVY) exhibits a wide host range and significantly affects crop growth. Development of novel targets is an important way to discover highly active PVY inhibitors with novel structure. G-quadruplex (G4) structures formed by guanine-rich nucleic acid sequences, have emerged as validated therapeutic targets driving the development of novel antiviral and antitumor agents. The untranslated regions is a regulatory region for mRNA expression, and the G4s in this region can regulate gene expression. Ten G4 structures were identified in the genome of PVY, one of which is located in the 3'-untranslated regions (PQS10) and has the putative function of regulating gene expression. Further studies revealed that PQS10 may be folded into the dimeric G4 with two planar G-quartets. The binding affinity for G-quadruplex-ligands to PQS10 was evaluated by isothermal titration calorimetry, and the results indicated that BRACO-19, RHPS4, and TMPyP4 exhibited a higher binding affinity with PQS10. BRACO-19, RHPS4, and TMPyP4 were found to stabilize PQS10 G4 structure, thereby enhancing the inhibitory effect of PQS10 on expression of the dual luciferase reporter gene. These three compounds were found to interact with PQS10 through intercalation into its lateral external loops, and significantly inhibit the expression of the PVY gene with more than 75% inhibition rate. This study demonstrated that G4 structures in the PVY genome are essential regulatory elements for viral proliferation, and provided new strategies for suppressing PVY proliferation. © 2025 Society of Chemical Industry.

Potato virus Y (PVY), potato mop-top virus (PMTV), potato virus S (PVS), and tobacco rattle virus (TRV) can be difficult to identify based on visual foliar symptoms. Using tuber samples collected from seven locations and 12 cultivars during 2017 to 2019, we developed a molecular assay using customized Whatman Flinders Technology Associates Plantsaver cards (FTA cards) and a reverse-transcription PCR (RT-PCR) for efficient sample collection and nucleic acid extraction. PMTV and PVY were detected more frequently on the stem end, TRV on the rose end, and PVS was evenly detected across the stem-end to rose-end axis of the tubers. Differences were seen in virus species localization within a tuber, thereby a composite of samples taken from multiple locations on a tuber improved virus detection. Regardless of sampling location on the tuber, tissue excised from the surface to 0.5 cm deep provided the best detection for all four viruses. For PVY, PMTV, and TRV, the proportion of tubers with viruses detected from field samples was highest at 100, 150, and 175 days after harvest, respectively. However, the probability of detecting PMTV and PVY 25 days after harvest was not different than the probability of detection at their peak detection times after harvest. The probability of TRV detection was lower at 25 days after harvest than at 175 days after harvest (P < 0.05).

Potato is one of the most important plants in terms of yield potential, adaptability and nutritional content. Although potato breeding programs are integrated with many new technologies, they are intensively carried out by phenotypic observation and selection in field conditions. In the research, high dry matter content and PVY resistance were determined as the basic selection criteria in the development of new cultivars. The research was carried out between 2017-2022 using 30.000 F1 potato seeds as genetic material and by establishing comparative trials in different locations with commercial control cultivars. Selection and breeding studies were carried out considering PVY resistance according to the molecular marker test. As a result of the research, commercial candidate advanced lines suitable for PVY resistance, table, chip and French fry potato industries were developed by conducting phenotypic and genotypic selection and selection studies according to high dry matter content. Based on the findings of the present study, the lines 82-88-04, 82-45-24, 82-105-50, 82-78-16, 82-56-01, and 82-93-03, distinguished by their high yield potential and resistance to Potato virus Y (PVY), were identified as possessing significant potential for official registration and subsequent commercialization as candidate cultivars.

As one of the most widely consumed vegetables globally, the potato represents a nutritionally valuable crop, providing an important source of essential bioactive compounds beneficial to human health. The present research aimed to assess the total carotenoids content (TCC) in both the skin and flesh of ten Romanian potato cultivars exhibiting varying degrees of resistance to Potato Virus Y (PVY), cultivated in Brașov over a two-year period. The analysis revealed significant varietal differences. Overall, the flesh of the tubers showed lower TCC levels compared to the skin. Among the examined cultivars, the Romanian variety Sevastia (resistant to PVY) recorded the highest concentrations of carotenoids in both tissues. The findings contribute valuable insights into the micronutrient composition of recently developed Romanian potato varieties, characterized by high nutritional value and diverse PVYresistance

Potato virus Y (PVY) causes significant damage to crops worldwide. Nucleoside analogs and their derivative drugs are currently a research hot spot in antiviral medications. We designed and synthesized a nucleoside guanidine compound FluoroGuanidoNucleosin (FGN) with anti-plant virus effects by structural modification of the nucleoside scaffold. The structure of compound FGN was characterized by 1H NMR, 13C NMR, and HRMS, and is named (R)-N-(1-((2R,3R,4S,5R)-3,4-dihydroxy-5-(hydroxymethyl)tetrahydrofuran-2-group)-2-oxo-1,2-dihydropyrimidine-4-group)-3-guanidine-4-(2,4,5-trifluorophenyl)butanamide, and the molecular formula of compound FGN is C20H23N6O6F3. FGN achieved high antiviral activities against PVY in Nicotiana tabacum, with inactivation (82.13%), curative (72.69%), and protective (68.75%) activity at 500 μg/mL. Furthermore, RNA-seq revealed FGN-induced DEGs enriched in KEGG pathways such as plant-pathogen interaction, plant hormone signal transduction, and ribosome. In addition, molecular docking indicated that FGN potentially binds to PVY NIb and PVY NIa-Pro. The design and synthesis of the nucleoside guanidine compound FGN provides a theoretical basis for the development and application of antiviral drugs.

Goal. Screening of a collection of potato varieties using the polymerase chain reaction (PCR) method for the presence of three genes that provide extreme resistance (ER) to Potato virus Y (PVY) namely Ryadg , Rychc and Rysto. Methods. DNA was extracted from the leaves or tubers of potato varieties of Ukrainian and foreign origin using a silica-based method. The following primers were used to identify the genes: RY1648F24/R22 for the gene Rychc, YES3-A for the Rysto gene, and RYSC3 for Ryadg. The amplified products were analyzed by agarose gel electrophoresis. Results. Ukrainian varieties were studied for the first time using the direct molecular marker RY1648F24/R22. Sixty-eight samples of different origins were analyzed for this molecular marker of the Rychc gene, and the gene of interest was identified in 11 varieties. Using the YES3-A molecular marker, 34 potato samples were evaluated and the Rysto gene marker amplicon was detected in 5 samples. Among the 58 potato varieties analyzed, the Ryadg gene was detected by the RYSC3 marker only in the Resurs variety, which also had the Rysto gene marker. Conclusions. The presence of genes of extreme resistance to PVY, Ryadg , Rychc , and Rysto was detected in 16 Ukrainian and foreign potato varieties. The Resurs variety has a combination of Ryadg and Rysto genes. The varietis carrying the ER genes identified during the study as carriers of genes for extreme resistance to PVY can be used in the breeding process.

Abstract Potato cultivation in Bangladesh is severely constrained by potato virus Y (PVY), a non-persistent virus that causes major yield losses. This study aimed to develop PVY-resistant clones by introgressing the Ny-Smira resistance gene from the donor parent ‘Sarpo Mira’ into high-yielding breeding lines. Nine high-yielding advanced lines, derived from the cross Sarpo Mira × BARI Alu-53, were evaluated through molecular and phenotypic screening against PVY selected. Following RT-PCR confirmation, plants were inoculated with the prevalent PVY NTN strain. Clones C2-5 and C2-77 exhibited remarkable resistance with the lowest disease severity (5.1 and 8.5%, respectively), whereas C2-27 was highly susceptible (74.8%). Molecular analysis detected the presence of the Ny-Smira gene-linked marker (Ry186) in clones C2-5, C2-77, C2-33 and C2-80. In multi-location field trials, resistant clones C2-5 and C2-77 also demonstrated superior yield potential (46–48 and 42–46 t/ha, respectively), surpassing both parental lines. These elite clones represent valuable germplasm resources for breeding programmes aimed at developing PVY-resistant high-yielding potato varieties. Significance of the study What is already known on this subject? The Ny-Smira gene has been reported to confer resistance to Potato virus Y (PVY). What are the new findings? For the first time in Bangladesh, two advanced clones (C2-5 and C2-77) derived from Sarpo Mira × BARI Alu-53 were identified with the Ny-Smira gene, showing strong resistance to PVY NTN and significantly higher yields (42–48 t/ha) than their parental lines. What are the expected impacts on horticulture? These resistant, high-yielding clones provide valuable germplasm for breeding programmes, reducing pesticide reliance and enhancing yield stability in Bangladeshi potato production.

The potyvirus helper component proteinase (HcPro) is a multifunctional protein, with one of its most documented functions being host antiviral RNA silencing suppression. This study shows that the HcPro of potato virus Y (PVY), an important member of the potyvirus group, prevents the replication of a related competing secondary virus. This phenomenon, referred to as superinfection exclusion (SIE), is common in bacterial, human, and plant virus infections. We also report that HcPro's induction of SIE is strain-specific and that this specificity is provided by the first four amino acid residues of the protein. Consistent with the mechanism of SIE, the study found that HcPro does not exclude a resident virus. Additionally, HcPro's induction of SIE was observed to function independently of its ability to suppress antiviral RNA silencing. HcPro's induction of SIE is relevant given the prevalence of multiple PVY strains that routinely co-infect the same cell and that may lead to recombination and emergence of new and more virulent strains. Furthermore, cross-protection or systemic acquired resistance (SAR) that is employed in plant virus disease management occurs when SIE moves from the cellular level and spreads systemically, emphasizing the importance of studying SIE.

Potato virus Y (PVY) is one of the most significant pathogens in the production of cultivated potato Solanum tuberosum worldwide. The most efficient way to combat viral diseases is the use of resistant varieties. The Rychc gene was discovered in the tuber-bearing wild potato relative Solanum chacoense. This gene is able to confer extreme resistance to PVY by rapidly halting virus multiplication in plants without the development of visible symptoms. Two molecular markers were developed to predict the presence of the Rychc gene and PVY resistance with 100% accuracy. In this study, the diversity of the Rychc gene and its relationship with resistance to PVY were investigated in genotypes from the Russian potato genbank. A collection of 60 genotypes originating from different populations was examined for PVY resistance and for the presence of Rychc using molecular markers. The observed phenotypes ranged from susceptibility to hypersensitive reaction and extreme resistance to PVY. Irrespective of the type of resistance, all the PVY-resistant plants carried the Rychc gene, indicating the prevalence of this resistance mechanism in S. chacoense. Unexpectedly, two S. chacoense individuals with the Rychc gene were found to be completely susceptible to PVY. Rychc sequences were evaluated via long-read targeted sequencing in all Rychc-positive genotypes. Despite the low overall sequence variation observed in Rychc gene, identical polymorphisms were found in Rychc alleles from susceptible S. chachoense genotypes, demonstrating the existence of nonfunctional Rychc allele unable to confer PVY resistance.