Blight Resistant Potato Research Articles

Transcriptome analysis reveals that exogenous ethylene activates immune and defense responses in a high late blight resistant potato genotype

Ethylene (ET) is one of the many important signaling hormones that functions in regulating defense responses in plants. Gene expression profiling was conducted under exogenous ET application in the high late blight resistant potato genotype SD20 and the specific transcriptional responses to exogenous ET in SD20 were revealed. Analysis of differentially expressed genes (DEGs) generated a total of 1226 ET-specific DEGs, among which transcription factors, kinases, defense enzymes and disease resistance-related genes were significantly differentially expressed. GO enrichment and KEGG metabolic pathway analysis also revealed that numerous defense regulation-related genes and defense pathways were significantly enriched. These results were consistent with the interaction of SD20 and Phytophthora infestans in our previous study, indicating that exogenous ET stimulated the defense response and initiated a similar defense pathway compared to pathogen infection in SD20. Moreover, multiple signaling pathways including ET, salicylic acid, jasmonic acid, abscisic acid, auxin, cytokinin and gibberellin were involved in the response to exogenous ET, which indicates that many plant hormones work together to form a complex network to resist external stimuli in SD20. ET-induced gene expression profiling provides insights into the ET signaling transduction pathway and its potential mechanisms in disease defense systems in potato.

Transformation using RNAi technology for developing potato lines resistance to late blight (Phytophthora infestans)

Phytophthora infestans (Mont.) de Bary causes late blight, a major disease of potato and tomato that causes production loss at about 10–100% in Indonesia. Breeding for late blight resistance in potato has been carried out in this country to minimize fungicide application. The objective of this study was to generate potato lines resistant to P. infestans through RNAi method. A series of studies were conducted, including confirmation of RNAi construct insertion in Agrobacterium tumefaciens and PCR analysis, transformation of two potato cultivars using A. tumefaciens carrying the RNAi fragment, in addition to selection and molecular analysis of selected plantlet using Polymerase Chain Reaction (PCR). The RNAi plasmid construct was confirmed via PCR analysis using specific primers for 35s and Tnos fragment, and resulted in 500 bp and 250 bp for fragment of 35s and Tnos, respectively. Transformation was performed on 733 Granola’s internode explants and 569 Atlantic’s internode explants. The transformation process produced 282 explants from Atlantic, while Granola did not produce any transformants. The level of transformation efficiency of Atlantic on selection medium containing hygromycin was 49.61%. Following regeneration step, the 282 selected explants produced 167 plantlets. Based on PCR reaction using specific primers for hpt gene, 14 plantlets were PCR positive and contained hpt fragment. Overall, Agrobacterium tumefaciens-mediated transformation on potato internode explants was successful. Therefore, the selected transformants should be further tested using bioassay for resistance to P. infestans.

Genetic engineering at the heart of agroecology

We discuss whether genetic engineering and agroecology are compatible. For this, we investigated three cases of genetically engineered crops and considered agroecology as scientific discipline as well as a social movement. One case was the use of cisgenic modifications to make potato durably resistant to late blight, the second was the use of CRISPR/Cas to make rice resistant to bacterial blight and as a third case, we evaluated experiences with cultivating transgenic Bt crops. These cases demonstrated that genetic engineering offers opportunities to grow crops in novel integrated pest management (IPM) systems with, as direct benefit, a decrease in the use of chemical crop protection agents, and as indirect effect that the role of predators and biological control agents can become more important than in present conventional systems based on pesticides. We used a framework based on four concerns (both cons and pros) that were gathered from an extensive societal interaction organized around the Dutch research project DuRPh, which produced a proof-of-concept of a cisgenic late blight-resistant potato. We concluded that genetic engineering and agroecology certainly have synergy in the context of agroecology as science, when applied to making crops less vulnerable to pests and diseases and when combined with cultivation using IPM. By contrast, within the movement context, genetically engineered varieties may be welcomed if they include traits that contribute to successful IPM schemes and are socially benign. Whether they would actually be deemed desirable or acceptable will, however, vary depending on the norms and values of the social movements. We propose that some concerns may be reconcilable in a dialogue. Deontological arguments such as naturalness are more difficult to reconcile, as they relate to deeply felt ethical or cultural values. A step forward would be when also for these arguments everyone can make an informed choice and when these choices can coexist in a respectful manner.

Standardization of plant density and intra-row spacing to maximize seed size tubers in two potato cultivars (Solanum tuberosum) grown in northern hills

To overcome the problem of oversize tubers, three planting densities (80000, 100000 and 133333 plants/ha) were evaluated at 25, 20 and 15 cm intra-row and 50 cm inter-row spacing, in two late blight resistant potato (Solanum tuberosum L.) cultivars, viz. Kufri Himalini and Kufri Girdhari during the kharif season under hill conditions. At the maximum plant density (133333 plants/ha) obtained with closer spacing (50 × 15 cm), the proportion of extra large (>150 g) tubers was reduced from 23.5 to 12.4% in cv. Kufri Himalini and from 17.4 to 10.4% in cv. Kufri Girdhari. Besides, an increase in the proportion of seed size (20-80 g) tubers from 33.6 to 43.9% was also recorded. The yield of extra-large tubers (>150g) came down from 43 to 30% along with 10% increase in the yield of seed size (20-80 g) tubers.

Stacking three late blight resistance genes from wild species directly into African highland potato varieties confers complete field resistance to local blight races

SummaryConsidered responsible for one million deaths in Ireland and widespread famine in the European continent during the 1840s, late blight, caused by Phytophthora infestans, remains the most devastating disease of potato (Solanum tuberosum L.) with about 15%–30% annual yield loss in sub‐Saharan Africa, affecting mainly smallholder farmers. We show here that the transfer of three resistance (R) genes from wild relatives [RB, Rpi‐blb2 from Solanum bulbocastanum and Rpi‐vnt1.1 from S. venturii] into potato provided complete resistance in the field over several seasons. We observed that the stacking of the three R genes produced a high frequency of transgenic events with resistance to late blight. In the field, 13 resistant transgenic events with the 3R‐gene stack from the potato varieties ‘Desiree’ and ‘Victoria’ grew normally without showing pathogen damage and without any fungicide spray, whereas their non‐transgenic equivalent varieties were rapidly killed. Characteristics of the local pathogen population suggest that the resistance to late blight may be long‐lasting because it has low diversity, and essentially consists of the single lineage, 2_A1, which expresses the cognate avirulence effector genes. Yields of two transgenic events from ‘Desiree’ and ‘Victoria’ grown without fungicide to reflect small‐scale farm holders were estimated to be 29 and 45 t/ha respectively. This represents a three to four‐fold increase over the national average. Thus, these late blight resistant potato varieties, which are the farmers’ preferred varieties, could be rapidly adopted and bring significant income to smallholder farmers in sub‐Saharan Africa.

Field Screening and Marker Assisted Selection of Late Blight Resistant Potato Lines

Field Screening and Marker Assisted Selection of Late Blight Resistant Potato Lines

Development and validation of IPM strategies for the cultivation of cisgenically modified late blight resistant potato

Potato late blight disease remains the primary stressor of commercial potato production across the EU, typically requiring >10 fungicide applications per growing season to offset crop losses. In response, the goal of this study was to test and validate a novel, more durable, control strategy for potato late blight. This IPM2.0 strategy is based on the principles of Integrated Pest Management (IPM) which sees the deployment of a late blight resistant potato genotype, a cisgenically modified, Desiree based resistant potato line here, in conjunction with pathogen population monitoring for virulence to the resistance genes (R genes) deployed and a “do not spray unless”, low input fungicide spray strategy. Field evaluations were completed in the Netherlands and in Ireland in 2013, 2014 and in Ireland in 2015. Comparators used in this study included the original but susceptible potato variety Desiree and the conventional but highly resistant variety Sarpo Mira. The novel IPM2.0 strategy was compared to local common practice (fungicide applications on a near weekly basis) and an untreated control. Overall, the IPM2.0 control strategy validated here reduced the average fungicide input by 80–90% without compromising control efficacy. Corresponding environmental side-effects were reduced proportionally. The results underline the pragmatic role host resistance can provide to commercial potato production systems and to society at large if employed as part of an integrated late blight control system.

POPULATION STRUCTURE OF PHYTOPHTHORA INFESTANS ON WORLDWIDE SCALE: A REVIEW

Phytophthora infestans is a destructive pathogen that causes late blight of potato worldwide. Several sexually and asexually reproducing lineages of the pathogen have been identified and new lineages are more virulent as compared to their parental lineages. A new highly aggressive clonal lineage EU13_A2 has spread into potato fields of Europe, Africa and Asia in place of the older lineages. In North America, 24 clonal lineages US1to US24 have been identified. Despite of sexual reproduction, the overall population of P. infestans in potato and tomato fields is dominated by asexual lineages. Breeding has been done to transfer 'R' genes into commercial potato cultivars through classical breeding and by pyramiding of genes. Defender is the only potato cultivar that has foliar and tuber resistance to late blight. Genetically modified potato with RB gene from Solanum bulbocastanum has been developed but it lacks tuber resistance to disease. This review discusses population structure of P. infestans worldwide and breeding efforts to produce late blight resistant potato.

Environmental risk assessment of blight-resistant potato: use of a crop model to quantify nitrogen cycling at scales of the field and cropping system.

Environmental risk assessment of GM crops in Europe proceeds by step-wise estimation of effect, first in the plant, then the field plot (e.g. 10-100m-2), field (1000-10,000m-2) and lastly in the environment in which the crop would be grown (100-10,000km2). Processes that operate at large scales, such as cycling of carbon (C) and nitrogen (N), are difficult to predict from plot scales. Here, a procedure is illustrated in which plot scale data on yield (offtake) and N inputs for blight resistant (both GM and non-GM) and blight-susceptible potato are upscaled by a model of crop resource use to give a set of indicators and metrics defining N uptake and release in realistic crop sequences. The greatest potential damage to environment is due to loss of N from the field after potato harvest, mainly because of the large quantity of mineral and plant matter, high in N, that may die or be left in the field. Blight infection intensifies this loss, since less fertiliser N is taken up by plants and more (as a proportion of plant mass) is returned to the soil. In a simulation based on actual crop sequences, N returns at harvest of potato were raised from 100kgha-1 in resistant to 150kgha-1 in susceptible varieties subject to a 40% yield loss. Based on estimates that blight-resistant types would require ~20% of the fungicide applied to susceptible types, introduction of resistant types into a realistic 6-year cropping sequence would reduce overall fungicide use to between 72 and 54% depending on the inputs to other crops in the sequence.

Genotypic background of the recipient plant is crucial for conferring RB gene mediated late blight resistance in potato

BackgroundLate blight, caused by oomycetes pathogen Phytophthora infestans (Mont.) de Bary, is the most devastating potato disease in the world. RB gene from Solanum bulbocastanum has been shown to impart broad spectrum resistance against P. infestans races. In this study Katahdin transgenic event SP951 was used as male parent to cross with the popular Indian potato cultivars viz., Kufri Bahar (KB) and Kufri Jyoti (KJ) to enhance the late blight resistance.ResultsPopulations of 271 F1seedlings from the crosses KB × SP951 (87) and KJ × SP951 (184) were screened for inheritance of RB transgene through PCR and bioassay. Disease response based on AUDPC of different hybrid lines varied from immunity to complete susceptibility. High degree of resistance (<25% infection) was observed in KJ × SP951 derived seedlings (85.2%), whereas level of resistance in KB × SP951 (36.4% infection) derived seedlings was of low order.ConclusionThis study provides valuable genetic materials for development of potentially durable late blight resistant potato varieties. Besides, it also corroborates the fact that efficacy of R gene is not solely dependent on its presence in the variety but largely depends on the genetic background of the recipient genotype.

Why Organic Farming Should Embrace Co-Existence with Cisgenic Late Blight–Resistant Potato

The EU regulation on organic farming does not allow the use of genetically modified organisms (GMOs) which are subject to Directive 2001/18/EC. Mutagenesis using irradiation or chemicals is genetic modification, but the organisms obtained through these techniques are not subject to the provisions of the GMO directive. Such mutants can therefore be used in organic agriculture. Derived from its basic principles, organic farming can only use natural substances to control disease and crops should be resilient, which, in the case of disease resistance, means that durable (horizontal) resistance is preferred to vertical (single gene) resistance. Cisgenesis can achieve such a durable resistance by introducing multiple resistance genes in one step. These multiple-resistant plants only contain natural genes that can also be introduced by breeding. In case cisgenic plants are not subject to the provisions of the GMO legislation, they can even be legally used in organic agriculture. In case they are not exempted from the GMO regulation, the question is: why obstruct a cisgenic potato crop that can hardly be distinguished from a potato crop that is the result of conventional breeding? Among the reasons why organic agriculture does not allow the use of GMOs it is mentioned that genetic engineering is unpredictable, it causes genome disruption and it is unnatural. However, our knowledge of plant genome evolution and breeding has increased dramatically. We now know that breeding is more unpredictable and causes more genome disruption than genetic engineering. Recent field trials have shown the efficacy of cisgenic late blight–resistant potatoes carrying multiple resistance genes. Large-scale growing of such durably resistant potatoes would not only be environmentally beneficial by it would strongly reducing the need for fungicide sprays in conventional potato cultivation and it would also reduce the disease pressure in organic potato cultivation.

Effects of a genetically modified potato on a non-target aphid are outweighed by cultivar differences

Insect–plant interactions may be unintentionally affected when introducing genetically modified (GM) crops into an agro-ecosystem. Our aim was to test the non-target effects of a late blight-resistant GM potato on Myzus persicae in greenhouse and climate room experiments and understand how position and number of R gene insertions can affect non-targets in GM events. We also aimed to compare results to baseline differences among three conventional potato varieties varying in resistance to late blight. Aphid development and survival were affected by some GM events in the first generation, though effects disappeared in the second generation. Effects were not dependent on the presence of a marker gene or the insertion of a second resistance gene. Positional effects of gene insertion influenced aphid performance on certain GM events. However, aphid fitness varied considerably more between conventional potato varieties than between Désirée and the GM events. Comparing different GM events to the non-transformed variety is relevant, since unintended effects of insertion can occur. Our protocols can be recommended for in planta risk assessments with aphids. Ecological perspective is gained by selecting several measured endpoints and by comparing the results with a baseline of conventional cultivars.

DNA Markers for Selection of Late Blight Resistant Potato Breeding Lines

Potato late blight, caused by the oomycete Phytophthora infestans, is one of the most devastating diseases in the agricultural sector around the world. Many genes (R genes) conferring resistance to late blight have been identified in various potato species and most of these R genes have been used in potato breeding. The aim of this study was to develop and validate PCR-based assays for the R genes Rpi-blb1, Rpi-blb2, Rpi-blb3 and Rpi-bt1, to distinguish between late blight resistant and late blight susceptible potato progeny in the given breeding background. A total of 100 breeding progeny were screened for the presence of these R genes and tested for resistance against P. infestans mating type A2, genotype US-8 strain, using detached leaf and tuber rot assays. PCR products for the Rpi-blb1 and Rpi-bt1 resistance genes were identified in the resistant progeny but were absent in the susceptible ones; therefore these PCR assays could differentiate between late blight resistant and susceptible plants. Genotypic data from the DNA markers derived from the Rpi-blb1 and Rpi-bt1 genes was found to correlate with the phenotypic data for foliar late blight but not with data for tuber rot. Our results demonstrate that markers derived from these two R genes could be useful for marker-assisted selection (MAS) for foliar late blight resistance in potato breeding programs.

Consumer Willingness‐to‐Pay for Genetically Modified Potatoes in Ireland: An Experimental Auction Approach

ABSTRACTIt is recognized that many consumers are skeptical about genetically modified (GM) foods. Yet less is known about the extent to which consumers may purchase GM food products given suitable price positioning and marketing information on nonprice attributes of the products. In this study, we examine consumer acceptance of GM late blight resistant potatoes in Ireland. Our analysis uses an experimental auction methodology that facilitates positive and negative bids to provide a more complete revelation of preferences. Results show that a majority of participants preferred conventional potatoes to GM potatoes. Favorable information about GM increased subjects’ valuations of GM potatoes. After being informed about potential economic and health benefits, up to two‐thirds of our subjects indicated that they would choose GM potatoes at a 20% price discount, while 14% of subjects would still reject GM potatoes at any price. Higher levels of education, greater familiarity with GM, and the presence of children in the household were associated with lower valuation of the GM product. [EconLit citations: C91; D12].

Combining ability analysis of yield and late blight [Phytophthora infestans (Mont.) de Bary] resistance of potato germplasm in Rwanda

Designed crosses among complementary parents and combining ability analysis are essential to recombine traits of economic importance and to select novel genotypes. The objective of this study was to estimate combining ability effects for yield and yield related traits and late blight resistance in potato. Crosses were performed using a 10 10 half diallel mating design to generate 45 F1s. Only 28 families with sufficient individuals and eight parents were field evaluated in experiments laid out in a 6 6 lattice design with two replications across two sites (Kinigi and Nyamagabe) in Rwanda. Late blight resistance was estimated using the relative area under the disease progress curve (rAUDPC: 100 % max). Furthermore, data on total tuber yield, total tuber number, and average tuber weight were collected and subjected to combining ability analyses. Results showed that additive gene action and non-additive gene action were present affecting yield and late blight resistance in potato. Additive gene action was predominant over non-additive gene action for both traits. All the families selected for further evaluation showed improved levels of late blight resistance and high yields. The study identified ten top families with high tuber yield and resistance to late blight for further evaluation and release.

The Solanum demissum R8 late blight resistance gene is an Sw-5 homologue that has been deployed worldwide in late blight resistant varieties.

Key messageThe potato late blight resistance geneR8has been cloned.R8is found in five late blight resistant varieties deployed in three different continents. R8 recognises Avr8 and is homologous to the NB-LRR protein Sw-5 from tomato.The broad spectrum late blight resistance gene R8 from Solanum demissum was cloned based on a previously published coarse map position on the lower arm of chromosome IX. Fine mapping in a recombinant population and bacterial artificial chromosome (BAC) library screening resulted in a BAC contig spanning 170 kb of the R8 haplotype. Sequencing revealed a cluster of at least ten R gene analogues (RGAs). The seven RGAs in the genetic window were subcloned for complementation analysis. Only one RGA provided late blight resistance and caused recognition of Avr8. From these results, it was concluded that the newly cloned resistance gene was indeed R8. R8 encodes a typical intracellular immune receptor with an N-terminal coiled coil, a central nucleotide binding site and 13 C-terminal leucine rich repeats. Phylogenetic analysis of a set of representative Solanaceae R proteins shows that R8 resides in a clearly distinct clade together with the Sw-5 tospovirus R protein from tomato. It was found that the R8 gene is present in late blight resistant potato varieties from Europe (Sarpo Mira), USA (Jacqueline Lee, Missaukee) and China (PB-06, S-60). Indeed, when tested under field conditions, R8 transgenic potato plants showed broad spectrum resistance to the current late blight population in the Netherlands, similar to Sarpo Mira.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-016-2740-0) contains supplementary material, which is available to authorized users.

Enhanced resistance to late blight pathogen conferred by expression of rice oxalate oxidase 4 gene in transgenic potato

Phytophthora infestans is the pathogen responsible for late blight disease of potato. Multiple spraying of crop protection chemicals is so far the only means to control the disease. Despite the continuous effort from breeders, late blight resistant potato varieties are not available to farmers. In this context, development of genetic resistance by incorporating new genes through genetic engineering is an attractive way to combat the pathogen. Here, we report the development of transgenic potato cultivars overexpressing the rice oxalate oxidase 4 gene (Osoxo4). Transgenic lines showed higher activity of oxalate oxidase enzyme and were able to degrade externally applied oxalic acid. The levels of reactive oxygen H2O2 were elevated in transgenic plants. The transcription of defense related genes (anionic peroxidase and phenylalanine ammonia lyase) was found to be elevated after pathogen inoculation. Detached leaf bioassays with spore suspension and in vitro plantlet bioassays with mycelia of P. infestans showed enhanced resistance in transgenic plants. Interestingly, constitutive overexpression of Osoxo4 did not show any effect on the morphology and yield of transgenic potato plants as evident from agronomic performance studies. Thus, constitutive expression of Osoxo4 represents an efficient strategy for engineering late blight resistance in potato.

Stakeholder views on issues to consider when assessing the sustainability of genetically modified potato

The importance of assessing socio-economic and sustainability aspects of genetically modified (GM) crops is increasingly recognized by policy-makers, both within the EU and internationally. Nevertheless, experience has shown that it is challenging to assess and implement these aspects in actual decision-making processes. This paper argues that stakeholder engagement may provide valuable insights when developing frameworks for sustainability assessment of GM crops. We organized two stakeholder workshops with the aim to gather perspectives on the sustainability of cultivating late blight resistant (LBR) GM potato in Norway. Sixteen Norwegian stakeholders involved in potato production and in agriculture in general took part in the workshops. Here, we present and discuss the outcomes of this participatory approach. The stakeholders identified several conditions that an LBR GM potato ought to satisfy in order to contribute to sustainable development. These conditions concerned environmental and health safety aspects of cultivating LBR GM potato, potential for fungicide reductions, durability of the LBR GM potato plant's resistance, farmers' profitability and consumer acceptance. In addition, the stakeholders considered issues such as maintenance of a diversity of potato cultivars, transparency during product development and risk assessment processes, ownership and control and opportunity for independent risk research as important considerations in a sustainability assessment. While focusing on a specific application of agricultural biotechnology, we believe that these findings are useful contributions to the ongoing efforts to develop frameworks and guidelines for assessing sustainability and socio-economic considerations of GM crops in general.

Durable Late Blight Resistance in Potato Through Dynamic Varieties Obtained by Cisgenesis: Scientific and Societal Advances in the DuRPh Project

Abstract From 2006 through 2015, a research project on Durable Resistance in potato against Phytophthora (DuRPh) was carried out at Wageningen University and Research Centre. Its objective was to develop a proof of principle for durable resistance against late blight by cisgenesis. This public-funded project aimed at stimulating research on genetic modification and public debate on innovative genetic techniques. It was decided to clone and transfer late blight resistance (R) genes of crossable wild potato species (cisgenes) by Agrobacterium tumefaciens-mediated transformation without non-potato genes. A stack of multiple R genes were planned to be inserted into established varieties, thereby creating a dynamic variety in which the composition of the stacks may vary over space and time. Cisgenic plants were selected based on the expression of all inserted R genes and trueness-to-type. Within the project, 13 R genes from wild potato species were genetically mapped and three of them were cloned. Four varieties were transformed with one to three R genes. This was initially done using kanamycin resistance provided by a selectable marker gene of synthetic origin in order to quickly test the performance and stability of the introduced R genes and stacked R gene combinations. Once the functioning thereof was confirmed, marker-free transformations were conducted; thus, true cisgenic events were selected. The results about the different R genes, their chromosomal location, their specificity, the background dependence, the maximum size of a stack, its regeneration time and associated somaclonal variation frequency and its stability were studied. After selection and characterisation in the laboratory, the best cisgenic events were assessed in field trials for late blight resistance. This showed that inserted R genes were capable of turning a susceptible variety into a resistant one. Maximising longevity of the resistance was assured through resistance management research. It was shown that stacking of multiple R genes and monitoring how to deploy these stacks spatially and temporally could reduce fungicide use by over 80%. Communications through media and field demonstrations were manifold to allow public and policymakers to decide if cisgenesis is an acceptable tool to make potato farming more sustainable. Future deployment of the DuRPh strategy will depend largely on its status as a genetically modified crop or its exemption thereof. Worldwide near eradication of late blight would increase global annual potato production by close to 80 million tons, thereby contributing considerably to the needed additional global future food supply.

Demystification of GM crop costs: releasing late blight resistant potato varieties as public goods in developing countries

A few studies have reported some of the costs associated with bringing to market genetically-modified (GM) crops but no comprehensive studies exist on the real cost of the entire process of developing and releasing one GM variety by a not-for-profit institution in a developing country for sustainable agriculture. Despite the lack of documented studies, it is commonly assumed that such an undertaking is cost prohibitive, based on mere hearsay, and on two private sector cost assessments. The present study assesses the costs and the time expenditures to two not-for-profit programs, one lead by CIP and the other by Cornell University, of developing a late blight resistant (LBr) potato variety for release in one developing country. CIP's costs run to $1.6 million over eight years, while Cornell's costs amount to $1.4 million over nine years. Exogenous disturbances might result in insignificant increases in cost, but can increase time expenditure significantly. A sensitivity analysis revealed that the total cost is markedly influenced by technical parameters determining the production and identification of the pre-commercial LBr transgenic event.