Resistant Potato Cultivars Research Articles

Increased virulence of Globodera pallida during repeated rearing on different resistant potato cultivars explained by a simple model

Selection for virulence of Globodera pallida on potato cultivars was studied for four generations under controlled conditions. The reproduction rate (Pf/Pi) of a mixed Pa2/3 population increased by a factor of 61 during rearing on the partially resistant potato cv. Darwina compared to rearing on the susceptible cv. Irene. This was a result of selection for virulence on cv. Darwina, and achieving the Hardy–Weinberg equilibrium on cv. Irene. Increased virulence also significantly raised the reproduction rate on several other Solanum genotypes. These changes could be explained reasonably well by the monogenic inheritance of a virulence factor breaking the Grp1 locus. The virulence changes were probably mainly evoked by this gene only, inherited from S. vernei 1‐3 or S. vernei 24/20. The Grp1 locus has probably provided the differential S. vernei hybrid (VTn)2 62‐33‐3 with its resistance to the Pa2 group and not to the Pa3 group. Alternation of cultivars did not halt selection if the cultivars highly differentiated between the Pa2 and Pa3 populations. Only when alternation was with cultivars that harboured a different resistance gene against Pa3 was selection for virulence delayed. Differences in virulence levels (i.e. reproduction rates) within the nematode population determined the rate of selection, not the resistance level itself. Selection of a Pa3 population for three generations on cv. Karakter not only increased the reproduction rate on cv. Karakter itself by a factor 4.2, but also raised the reproduction on other potato genotypes. A simple monogenic model could explain these changes in virulence.

PM 9/26 (1) National regulatory control system for Globodera pallida and Globodera rostochiensis

Specific scopeThis Standard describes a national regulatory control system for Globodera pallida and Globodera rostochiensis.

Resistance of Potato Cultivars as a Determinant Factor of Potato virus Y (PVY) Epidemiology

Potato virus Y (PVY) is considered the most economically damaging virus for seed-potato production. PVY isolates are usually divided into three historical PVY strains, namely PVYC, PVYO and PVYN. More recently, recombinant strains named PVYNTN and PVYN-Wi appeared in Europe and North America, rapidly spread into seed-potato production and gradually replaced historical strains. This progression can be explained by several factors, including the differential susceptibility of cultivars to PVY strains. This article presents the results of a Swiss survey of PVY strains conducted in 2012 in which the progressive increase of the prevalence of PVYN-Wi was observed. The occurrence of PVY strains in the two main potato cultivars grown in Switzerland, cv. Agria and cv. Charlotte, is described through the 2012 survey and one additional PVY strain survey conducted in 2014. Both surveys were completed with a mechanical-inoculation assay. The inoculation assay showed that cv. Agria is more susceptible to PVYN-Wi than to PVYNTN, whereas cv. Charlotte is susceptible to both strains. The inoculation assay also showed that the expression of symptoms on cultivars is strain-dependent. These results stress the major role of the resistance profile of cultivars to explain the balance of the PVY strains in potato crops.

Pest categorisation of Stagonosporopsisandigena.

The Panel on Plant Health performed a pest categorisation of Stagonosporopsis andigena, the causal agent of black blight of potato, for the EU. The pest is a well‐defined fungal species and reliable methods exist for its detection and identification. S. andigena is present in Bolivia and Peru. The pest is not known to occur in the EU and is listed in Annex IAI of Directive 2000/29/EC as Phoma andina, meaning its introduction into the EU is prohibited. The major cultivated host is Solanum tuberosum (potato); other tuber‐forming Solanum species and wild solanaceous plants are also affected. All hosts and pathways of entry of the pest into the EU are currently regulated. Host availability and climate matching suggest that S. andigena could establish in parts of the EU and further spread mainly by human‐assisted means. The pest affects leaves, stems and petioles of potato plants causing lesions and premature leaf drop but not the underground parts, including tubers. The disease causes yield reductions up to 80%, depending on the susceptibility of potato cultivars. Early application of fungicide sprays and cultivation of resistant potato cultivars are the most effective measures for disease management. The pest introduction in the EU would potentially cause impacts to potato production. The main uncertainties concern the host range, the maximum period the pest survives on host debris in soil, the maximum distance over which conidia of the pest could be dispersed by wind‐blown rain, and the magnitude of potential impacts to the EU. S. andigena meets all the criteria assessed by EFSA for consideration as potential Union quarantine pest. The criteria for considering S. andigena as a potential Union regulated non‐quarantine pest are not met, since the pest is not known to occur in the EU.

Biological control of potato common scab by Bacillus amyloliquefaciens Ba01.

Potato common scab, which is caused by soil-borne Streptomyces species, is a severe plant disease that results in a significant reduction in the economic value of potatoes worldwide. Due to the lack of efficacious pesticides, crop rotations, and resistant potato cultivars against the disease, we investigated whether biological control can serve as an alternative approach. In this study, multiple Bacillus species were isolated from healthy potato tubers, and Bacillus amyloliquefaciens Ba01 was chosen for further analyses based on its potency against the potato common scab pathogen Streptomyces scabies. Ba01 inhibited the growth and sporulation of S. scabies and secreted secondary metabolites such as surfactin, iturin A, and fengycin with potential activity against S. scabies as determined by imaging mass spectrometry. In pot assays, the disease severity of potato common scab decreased from 55.6 ± 11.1% (inoculated with S. scabies only) to 4.2 ± 1.4% (inoculated with S. scabies and Ba01). In the field trial, the disease severity of potato common scab was reduced from 14.4 ± 2.9% (naturally occurring) to 5.6 ± 1.1% after Ba01 treatment, representing evidence that Bacillus species control potato common scab in nature.

Genome scans on experimentally evolved populations reveal candidate regions for adaptation to plant resistance in the potato cyst nematode Globodera pallida.

Improving resistance durability involves to be able to predict the adaptation speed of pathogen populations. Identifying the genetic bases of pathogen adaptation to plant resistances is a useful step to better understand and anticipate this phenomenon. Globodera pallida is a major pest of potato crop for which a resistance QTL, GpaVvrn , has been identified in Solanum vernei. However, its durability is threatened as G.pallida populations are able to adapt to the resistance in few generations. The aim of this study was to investigate the genomic regions involved in the resistance breakdown by coupling experimental evolution and high-density genome scan. We performed a whole-genome resequencing of pools of individuals (Pool-Seq) belonging to G.pallida lineages derived from two independent populations having experimentally evolved on susceptible and resistant potato cultivars. About 1.6million SNPs were used to perform the genome scan using a recent model testing for adaptive differentiation and association to population-specific covariables. We identified 275 outliers and 31 of them, which also showed a significant reduction in diversity in adapted lineages, were investigated for their genic environment. Some candidate genomic regions contained genes putatively encoding effectors and were enriched in SPRYSECs, known in cyst nematodes to be involved in pathogenicity and in (a)virulence. Validated candidate SNPs will provide a useful molecular tool to follow frequencies of virulence alleles in natural G.pallida populations and define efficient strategies of use of potato resistances maximizing their durability.

Yield and resistance of potato cultivars with colour flesh to potato late blight

The resistance to potato late blight (as AUDPC – the area under the disease progress curve) and yield were evaluated in precise field experiments with 13 colour-fleshed potato cultivars. Red Emmalie and Blaue Anneliese were the most profitable cultivars of potatoes with coloured flesh, the overall yield did not differ statistically from the control cv. Agria. Cv. Blaue Anneliese resistance to potato late blight was considerably better than both control cultivars, other 2 cultivars HB Red and Red Emmalie were similar to cv. Agria. Surprisingly, cv. Russet Burbank was found to be more resistant than most cultivars tested. A statistically significant weak dependence (r = 0.36) between the percentage of infestation of plants in the T6 evaluation date (6–8 August in individual years) and the yield was detected, the slightly stronger (r = 0.40) was the correlation between AUDPC values and total yields.

Evaluation of Solanum sisymbriifolium as a Potential Inoculum Source of Verticillium dahliae and Colletotrichum coccodes.

Solanum sisymbriifolium, the litchi tomato, is a perennial herbaceous plant from South America that is used as a trap crop to reduce soilborne populations of the pale cyst nematode Globodera pallida, an important potato pathogen. Possible interactions of soilborne potato pathogens Verticillium dahliae and Colletotrichum coccodes with litchi tomato are unknown, yet important for potato production if litchi tomato is to be planted as a trap crop. The goal of this research was to quantitatively assess if litchi tomato is a potential inoculum source for C. coccodes and V. dahliae by comparing colony forming units (CFU) observed in litchi tomato to susceptible and resistant potato cultivars. The potato cvs. Alturas (P = 0.0003), Ranger Russet (P = 0.0193), and Russet Norkotah (P = 0.0022) produced more CFUs of the potato pathotype of V. dahliae than litchi tomato the first of two years of greenhouse trials. Significantly more CFUs of the potato pathotype of V. dahliae were quantified from stems and roots of only cv. Russet Norkotah compared with litchi tomato (P = 0.0001) in the second year. The CFUs for C. coccodes varied between litchi tomato and the potato cvs., perhaps due to varying levels of resistance since litchi tomato is from a selected intermated seed source. Based on these data, the effect of litchi tomato in rotation with potato is likely to have limited effect on the proliferation of V. dahliae or C. coccodes populations in the soil when compared with a susceptible potato cultivar.

Expression of genes, encoded defense proteins, in potato plants infected with the cyst-forming nematode Globodera rostochiensis (Wollenweber 1923) Behrens, 1975 and modulation of their activity during short-term exposure to low temperatures

The expression of the principal genes providing an immune response in the roots of potato plants resistant and susceptible to the cyst nematode Globodera rostochiensis is investigated under conditions of infestation and with frequent variations in temperature. Differences in the immune status of resistant and susceptible potato cultivars are revealed in the level of expression of R-genes (H1 and Gro1-4), gene PAL, and defense genes of the PR-family (PR1, PR2, PR3, PR6). Varying the temperature changes the activity of transcriptome of susceptible plants towards activation of expression of R-genes, gene PAL, and defense genes; interactions between the plant and parasite are displaced towards induction of host resistance.

Risk Management Strategies using Precision Agriculture Technology to Manage Potato Late Blight

Core Ideas The benefits of adopting precision farming technology was investivated in scheduling fungicide applications to manage potato late blight. The precision farming technology is the preferred method to schedule fungicide applications in terms of disease suppression, net return per 0.41 ha, and risk‐adjusted net return. The increased adoption of the precision farming technology would help manage late blight, limit potential crop losses, and improve net returns. Precision agriculture has emerged as a revolutionary technology, which transforms farming related data into useful information for agricultural decision‐making. This paper compares precision farming technology with calendar‐based approach in scheduling fungicide applications to manage potato (Solanum tuberosum L.) late blight disease. Three fungicide scheduling strategies were evaluated: calendar‐based strategy, BlightPro decision support system based strategy (DSS‐based strategy), and unsprayed control. Using results from 14 yr of computer simulation experiments for 59 locations in the United States, we constructed distributions of net return to all costs excluding fungicide cost and application cost per 0.41 ha (net return per 0.41 ha) for the calendar‐based and DSS‐based strategies at each location. These distributions were then compared using three risk management methods: stochastic dominance, stochastic dominance with respect to a function, and stochastic efficiency with respect to a function. The DSS‐based strategy was identified as the most effective approach to manage late blight in terms of disease suppression, net return per 0.41 ha, and risk‐adjusted net return. Results indicate that the DSS‐based strategy is the preferred method to schedule fungicide applications. Under high disease pressure circumstances, the economic benefits to potato growers of adopting the precision agriculture technology ranged from US$30 to $573 per 0.41 ha. For risk neutral individuals, who are concerned about the difference between average net return per 0.41 ha, the benefits ranged from $30 to $305 per 0.41 ha. Except for growers raising the moderately resistant potato cultivars, more risk averse individuals tended to benefit more from adopting the precision agriculture technology, with benefits ranging from $38 to $573 per 0.41 ha.

Olfactory Response and Feeding Preference of Liriomyza huidobrensis (Diptera: Agromyzidae) to Potato Cultivars.

Liriomyza huidobrensis (Blanchard) is a serious invasive pest of potato in Korea. In sessile insect herbivores like leafminer flies, host plant choice is a critical decision made by adults for offspring survival, and one that is often influenced by host plant quality. In annual host plants like potato, leafminer choice is sometimes influenced by cultivar characteristics. To determine the basis of host selection, the odor and feeding preferences of adult L. huidobrensis were examined using a five-arm olfactometer offering a choice of five different potato cultivars: 'Chubeak', 'Seohong', 'Goun', 'Dejima', and 'Sumi'. Preferences of adult leafminers varied significantly among potato cultivars. Liriomyza huidobrensis showed a preference for the Goun cultivar in both olfactory and adult feeding tests. When measured 2 wk after release onto actual plants, plant damage ratings and the number of mines were consistent with the feeding preference results. Further studies should examine the influence of cultivar characteristics on larval fitness and adult longevity to develop a resistant potato cultivar through the selection behavior of leafminers.

Potassium phosphite combined with reduced doses of fungicides provides efficient protection against potato late blight in large-scale field trials

Potato late blight caused by the oomycete Phytophthora infestans is a devastating disease of potato worldwide. Most of the potato cultivars grown in conventional agriculture are susceptible, or at best moderately resistant, and require frequent applications of fungicides to avoid heavy yield losses.In field trials spanning four years, we have investigated the effect of potassium phosphite, an inorganic salt on potato late blight. Potassium phosphite is known to induce defence responses in potato and to also have direct toxic effects on oomycetes, which in turn counteract late blight and tuber blight development. However, the use of this salt is not yet implemented and approved in European potato cultivation. We compared the effect of phosphite alone with fungicides currently used in Swedish potato cultivation. We also investigated the combined use of potassium phosphite and reduced doses of fungicides. Table potato cultivars and starch potato cultivars with different levels of resistance were used.We found that potassium phosphite in combination with reduced doses of fungicides results in the same level of protection as treatments with the recommended full dose of fungicides. These combined treatments reduce the need of traditional fungicides and may also decrease the selection pressure for fungicide resistance development in the pathogen. In relatively resistant starch potato cultivars using phosphite alone gave sufficient protection against late blight. Furthermore, in starch potato a combination of phosphite and fungicides at two-week intervals provided similar protection to weekly applications of fungicide at the recommended dose. Foliar treatment with phosphite also gave protection against tuber blight at similar levels to that of the best-performing fungicide. Our data suggests that potassium phosphite could be used in potato cultivation in temperate regions such as in Sweden, at least in combinations with reduced rates of fungicides. The implementation of the use of phosphite in practical potato crop protection as part of an IPM strategy is discussed. Doses, intervals and combinations could be adjusted to the level of cultivar resistance.

Evaluation of cultural methods for the management of the golden nematode (Globodera rostochiensis) in Quebec, Canada

Potato cyst nematodes are a major threat to potato production worldwide. In 2006, the isolation of the golden nematode, Globodera rostochiensis, in Quebec, Canada, led to the establishment of a quarantine area and the initiation of a research programme for the sustainable management of this regulated pest. In this study, the field efficacy of crop rotations and soil amendments was assessed in microplots for their potential to reduce populations of G. rostochiensis in the quarantine area. Crop rotation with a resistant potato cultivar was very effective in decreasing the population density of G. rostochiensis in soil. A single year with a cultivar carrying the H1 resistance gene reduced nematode populations by 62–95%. After 3 consecutive years of cropping to resistant potato, the number of viable eggs was zero in several microplots, and the overall population reduction was around 95%. Natural population decline with the cultivation of a non-host crop such as corn was around 30% per year. Trap cropping also showed reduced G. rostochiensis populations with results similar to the resistant cultivar. Sticky nightshade could not be established under Quebec’s climatic conditions and therefore was not a viable alternative for managing golden nematode in Quebec. Soil amendment with high rates of urea provided some reduction in populations but was not an economically viable option for managing potato cyst nematodes. Chicken manure and pig slurry did not provide a significant reduction of G. rostochiensis under Quebec field conditions.

Variation in Susceptibility to Potato Psyllid, Bactericera cockerelli (Hemiptera: Triozidae), among Solanum verrucosum Germplasm Accessions

Potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), is a key pest of potato and the vector of “Candidatus Liberibacter solanacearum,” the pathogen associated with zebra chip disease. Development of potato cultivars with genetic resistance to potato psyllid would enable cost-effective control of this pest with reduced use of insecticides. To facilitate the development of resistant cultivars, the objective of our study was to screen germplasm accessions of Solanum verrucosum for resistance to potato psyllid. The susceptibility of S. verrucosum germplasm accessions to potato psyllid was highly variable in choice prescreening assays and no-choice performance assays. Compared with the susceptible potato cultivar, ‘Russet Burbank,’ several S. verrucosum populations exhibited strong resistance to potato psyllid. The S. verrucosum accession, PI 195170 was highly resistant to potato psyllid, and is a potential source of genetic resistance for the development of resistant potato cultivars.

ジャガイモにおける青枯病抵抗性<i>in vitro</i>検定法を利用した青枯病菌phylotype IおよびIVの温度による発病特性

We examined the pathogenic differences between Ralstonia solanacearum phylotypes I and IV. R. solanacearum phylotypes I （MAFF327001） and IV （MAFF327032） were inoculated to potato using an in vitro screening assay at 22, 24, 26 and 28℃ incubation temperatures after inoculation. As a result, phylotype IV showed high pathogenicity for potato at a lower temperature than phylotype I. The most suitable temperature for evaluating the degree of resistance in potato cultivars and breeding lines was clearly different between phylotypes Ⅰand Ⅳ, with phylotype Ⅰat 28℃，and phylotype Ⅳ at 26℃. However, the degree of resistance in potato cultivars and breeding lines for both phylotypes had a similar tendency at the most suitable temperature conditions. In conclusion, phylotype IV showed pathogenicity at a lower temperature than phylotype Ⅰ, but the results suggested resistance was shown in the potato cultivars and breeding lines regardless of the phylotype（Ⅰ and Ⅳ）.

Quantitative Gene Expression of Peroxidase, Polyphenoloxidase and Catalase as Molecular Markers for Resistance against <i>Ralstonia solanacearum</i>

Brown rot or bacterial wilt of potato caused by Ralstonia solanacearum, is an economically important disease. Potato, cv. Nicola, was found to be relatively highly resistant to the infection with R. solanacearum and showed 15.12% wilt disease index, meantime, cv. Kara showed intermediate resistance with 37.40% disease index while, cv. Spunta was susceptible and showed 80.33% disease index. The role of defense-related enzymes in imparting resistance in potato against R. solanacearum was investigated by quantifying enzymes activity and gene expression of three defense- related enzymes, peroxidase, polyphenol oxidase and catalase. Peroxidase showed maximum activity 0.488 min-1&middotg-1 early at 12 h after pathogen inoculation in the cv. Nicola, whereas in susceptible cultivar Spunta showed lower activity of maximum 0.226 min-1&middotg-1 later at 48 h after inoculation. While, the moderately resistant cultivar Kara showed intermediate activity for the peak and its time. Meanwhile, polyphenol oxidase showed similar trends to that of peroxidase. On the contrary, catalase showed the highest activity values in the susceptible, cv. Spunta, while, in relatively highly resistant (cv. Nicola) and the moderately resistant (cv. Kara) showed lower values of activity and up to 96 h after inoculation. Meanwhile, gene expression of related enzymes the RT-PCR was used. At zero time, the relatively highly resistant potato cultivar, Nicola, showed the highest values of gene expression for both Peroxidase (POD) and Poly Phenol Oxidase (PPO). While, the susceptible potato cultivar, Spunta showed the lowest values. On the contrary, Catalase (CAT) gene expression was the highest in the susceptible, cv. Spunta, and was the lowest in the relatively highly resistant, cv. Nicola, while, was of intermediate values in the intermediate resistance, cv. Kara. Results show that peroxidase and polyphenol oxidase activities can be used as biochemical markers to reveal the resistance and susceptibility nature of potato cultivars against bacterial wilt disease of potato caused by R. solanacaerum.

Breeding of Pest and Disease Resistant Potato Cultivars in Japan by Using Classical and Molecular Approaches

Solanum tuberosum L.) is among the most important upland crops cultivated for many end uses throughout Japan. Potatoes are consumed in different ways, such as table use, food processing, starch production, and others. At the same time, various cropping systems are adopted according to environmental conditions. Although potato-breeding programs in Japan are conducted by consider- ing these demands, pest and disease resistance is one of the most important traits required for all modern cultivars. There are many pests and diseases affecting potato production in Japan, where conferring resistance against potato cyst nematodes, late blight, common scab, bacterial wilt, and viral diseases has become a main target of breeding. Artificial inoculation tests and cultivation in infested fields were traditionally conducted, in order to evaluate the levels of resistance among breed- ing materials. However, several DNA markers for pest and disease resistance genes have recently been developed for the selection of resistant genotypes. We have taken both approaches toward the selection of pest and disease resistant genotypes at each breeding step. This review introduces our approaches to develop new pest and disease resistant potato cultivars by using classical and molecular approaches.

Identification of potato cyst nematode resistant genotypes using molecular markers

At present the resistant potato cultivars under cultivation do not possess enough resistance to wide range of potato cyst nematode (PCN) pathotypes (Ro1 to Ro5 of Globodera rostochiensis and Pa1 to Pa3 of Globodera pallida). Therefore, development of varieties having resistance against different PCN pathotypes is must however, large scale phenotypic evaluation for PCN is difficult and costly. Identification of resistance genes using DNA markers may be an alternative approach. In the present study, we have evaluated advanced generation breeding material along with five popular varieties grown in the Nilgiris (Kufri Jyoti, Kufri Giriraj, Kufri Girdhari, Kufri Swarna and Kufri Neelima) with known DNA markers for identification of PCN resistance genes (H1 gene against Ro1 and Ro4, Gro 1-4 and GroVI gene against Ro1, Grp1_QTL against Ro5, Pa2,3 and Gpa5 & Gpa6_QTL against Pa2,3). The results revealed that nearly 60% of the breeding lines and varieties tested possessed H1 gene whereas, no genotype was positive for the Gro1-4. The marker TG432 associated with QTL conferring resistance to G. pallida amplified in 24 genotypes. The SNP marker HC was amplified for 40 genotypes and four varieties. For G. pallida, marker SPUD 1636 associated with the QTL Gpa5 and Gpa6 was amplified in four breeding lines and variety Kufri Swarna. Hence, the result of the study will facilitate breeding of novel resistant varieties by efficient selection of ideal genotypes and pyramiding of resistant loci in a single genotype.

Efficiency of a computerised decision support system as a tool to reduce fungicide input for the control of potato late blight

VNIIFBlight decision support system is intended to identify weather conditions favourable or unfavourable for the late blight outbreaks on potato. To provide an improved choice of fungicide treatment dates, we investigated the use of a standard five-day weather forecast based disease management decision support system VNIIFBlight as well as the use of information about the late blight resistance level of the cultivars used. The efficiency of this decision support system was compared with a seven-day routine program of fungicide treatments in the course of four-year field trials in Moscow region and six-year virtual trials in four regions of Russia, three regions of Lithuania, and single regions of Canada, Ukraine, Poland, and the Netherlands. According to the results of field experiments, in the case of a high infection pressure (2004 and 2008), yield losses caused by late blight in the untreated control made up 62% and 39%, respectively, whereas the losses for both compared schemes of protection did not exceed 8.2% for both years. In the case of weak disease development (2005 and 2007), for all studied treatments, including the untreated control, yield losses did not exceed 3%. In all years, the use of the VNIIFBlight decision support system significantly reduced the number of fungicidal treatments as compared to the routine scheme of protection; this reduction in 2004, 2005, 2007 and 2008 made up 62, 50, 50 and 17 %, respectively. According to the results of virtual trials, the use of the VNIIFBlight decision support system reduced the number of fungicide treatments of susceptible and resistant potato cultivars by 50% and 60% on average, respectively, as compared with the routine program.

RAPD marker linked Potato Virus Y resistant potato cultivars and treated with ribosome inactivating proteins (RIPs)

Ribosome inactivating proteins (RIPs) isolated from Phytolacca sp. and Mirabilis jalapa, which inhibit the necrotic tuber necrosis strain of potato virus Y (PVYNTN) infection by catalytically removing a specific adenine residue from the 28S RNA. The primary objective of this study was the development of a simple and novel strategy for controlling PVYNTN by using of leaf extracts from Phytolacca sp., and M. jalapa plants. In addition, assessment of genetic variability among PVYNTN resistant, susceptible, and the healthy control potato plants was carried out by Random amplified polymorphic DNA (RAPD). Spraying extracts on five potato cultivars ('Selan', 'Spunta', 'Cara', 'Diamond' and 'Nicola') before virus inoculation resulted in 100% inhibition of PVYNTN infection; these results were confirmed by DAS-ELISA. Analysis of variance showed there were no significant differences in number, weight and volume of tubers between extract-treated potato plants and healthy control in all five potato cultivars. RAPD marker generated by five arbitrary decamers was used to determine DNA polymorphism among the PVYNTN resistant, infected and healthy control potato plants. A total of 65 reproducible fragments ranging from 100 – 1200 bp were scored using five primers. Thirty-three out of 65 (50.77%) bands were polymorphic, and the remaining 32 (49.23%) were monomorphic. The number of bands for each primer varied from 5 to 22 fragments. Among the 65 fragments, 18 (27.69%) turned out to be reproducible and regarded as reliable RAPD markers for further analyses. Extract treated potato cultivars and the PVYNTN resistance varied considerably using the five primers of RAPD-PCR, whereas the 'Selan' cultivar appeared to have the highest number of markers (7), followed by 'Spunta' (6), while 'Cara' scored the lowest number from unique markers (1). This information should be taken into consideration in future breeding programs. The use of leaf extract sprays as those from P. americana, P. acinosa and M. jalapa on various crops are expected to prevent or control viral infection.