Blight Resistant Potato Research Articles

Accumulation of dually targeted StGPT1 in chloroplasts mediated by StRFP1, an E3 ubiquitin ligase, enhances plant immunity.

Chloroplasts play a crucial role in essential processes, such as photosynthesis and the synthesis of primary and diverse secondary metabolites. Recent studies have also highlighted their significance linked to phytohormone production in plant immunity, especially SA and JA. Ubiquitination, a key posttranslational modification, usually leads to target protein degradation, which acts as a signal for remodeling the proteome via the induction of protein endocytosis or targeting to other membrane associated systems. Previously, the potato E3 ligase StRFP1 was shown to enhance resistance against Phytophthora infestans, but its mechanism remained unclear. Here, we demonstrate that StRFP1 interacted with the dually localized plastid glucose 6-phosphate transporter StGPT1 on the endoplasmic reticulum (ER). Transiently expressed StGPT1-GFP located on the chloroplast and ER in plant cells. Overexpression of StGPT1 enhances late blight resistance in potato and Nicotiana benthamiana, activates immune responses, including ROS bursts and up-regulation of PTI marker genes. The resistance function of StGPT1 seems to be related to its dual localization. Remarkably, StRFP1 ubiquitinates StGPT1 at the ER, possibly due to its merely transient function in peroxisomes, leading to apparent accumulation in chloroplasts. Our findings point to a novel mechanism by which a plant E3 ligase contributes to immunity via interacting with dually targeted GPT1 at the ER of plant cells.

Transcriptome analysis reveals genes associated with late blight resistance in potato

Late blight is a serious disease of potato worldwide. Our study aimed to unveil genes involved in late blight resistance in potato by RNA-seq analysis after artificial inoculation under controlled conditions. In this study, two potato somatic hybrids (P7 and Crd6) and three varieties such as Kufri Girdhari, Kufri Jyoti and Kufri Bahar (control) were used. Transcriptiome analysis revealed statistically significant (p < 0.05) differentially expressed genes (DEGs), which were analysed into up-regulated and down-regulated genes. Further, DEGs were functionally characterized by the Gene Ontology annotations and the Kyoto Encyclopedia of Genes and Genomes pathways. Overall, some of the up-regulated genes in resistant genotypes were disease resistance proteins such as CC-NBS-LRR resistance protein, ankyrin repeat family protein, cytochrome P450, leucine-rich repeat family protein/protein kinase family, and MYB transcription factor. Sequence diversity analysis based on 38 peptide sequences representing 18 genes showed distinct variation and the presence of three motifs in 15 amino acid sequences. Selected genes were also validated by real-time quantitative polymerase chain reaction analysis. Interestingly, gene expression markers were developed for late blight resistant genotypes. Our study elucidates genes involved in imparting late blight resistance in potato, which will be beneficial for its management strategies in the future.

Modern Breeding Strategies and Tools for Durable Late Blight Resistance in Potato.

Cultivated potato (Solanum tuberosum) is a major crop worldwide. It occupies the second place after cereals (corn, rice, and wheat). This important crop is threatened by the Oomycete Phytophthora infestans, the agent of late blight disease. This pathogen was first encountered during the Irish famine during the 1840s and is a reemerging threat to potatoes. It is mainly controlled chemically by using fungicides, but due to health and environmental concerns, the best alternative is resistance. When there is no disease, no treatment is required. In this study, we present a summary of the ongoing efforts concerning resistance breeding of potato against this devastating pathogen, P. infestans. This work begins with the search for and selection of resistance genes, whether they are from within or from outside the species. The genetic methods developed to date for gene mining, such as effectoromics and GWAS, provide researchers with the ability to identify genes of interest more efficiently. Once identified, these genes are cloned using molecular markers (MAS or QRL) and can then be introduced into different cultivars using somatic hybridization or recombinant DNA technology. More innovative technologies have been developed lately, such as gene editing using the CRISPR system or gene silencing, by exploiting iRNA strategies that have emerged as promising tools for managing Phytophthora infestans, which can be employed. Also, gene pyramiding or gene stacking, which involves the accumulation of two or more R genes on the same individual plant, is an innovative method that has yielded many promising results. All these advances related to the development of molecular techniques for obtaining new potato cultivars resistant to P. infestans can contribute not only to reducing losses in agriculture but especially to ensuring food security and safety.

T-DNA characterization of genetically modified 3-R-gene late blight-resistant potato events with a novel procedure utilizing the Samplix Xdrop® enrichment technology.

Before the commercialization of genetically modified crops, the events carrying the novel DNA must be thoroughly evaluated for agronomic, nutritional, and molecular characteristics. Over the years, polymerase chain reaction-based methods, Southern blot, and short-read sequencing techniques have been utilized for collecting molecular characterization data. Multiple genomic applications are necessary to determine the insert location, flanking sequence analysis, characterization of the inserted DNA, and determination of any interruption of native genes. These techniques are time-consuming and labor-intensive, making it difficult to characterize multiple events. Current advances in sequencing technologies are enabling whole-genomic sequencing of modified crops to obtain full molecular characterization. However, in polyploids, such as the tetraploid potato, it is a challenge to obtain whole-genomic sequencing coverage that meets the regulatory approval of the genetic modification. Here we describe an alternative to labor-intensive applications with a novel procedure using Samplix Xdrop® enrichment technology and next-generation Nanopore sequencing technology to more efficiently characterize the T-DNA insertions of four genetically modified potato events developed by the Feed the Future Global Biotech Potato Partnership: DIA_MSU_UB015, DIA_MSU_UB255, GRA_MSU_UG234, and GRA_MSU_UG265 (derived from regionally important varieties Diamant and Granola). Using the Xdrop® /Nanopore technique, we obtained a very high sequence read coverage within the T-DNA and junction regions. In three of the four events, we were able to use the data to confirm single T-DNA insertions, identify insert locations, identify flanking sequences, and characterize the inserted T-DNA. We further used the characterization data to identify native gene interruption and confirm the stability of the T-DNA across clonal cycles. These results demonstrate the functionality of using the Xdrop® /Nanopore technique for T-DNA characterization. This research will contribute to meeting regulatory safety and regulatory approval requirements for commercialization with small shareholder farmers in target countries within our partnership.

Consumers' perceptions and acceptance of genome editing in agriculture: Insights from the United States of America and Switzerland

The terms “New Genomic Techniques” (NGTs) or “Genome Editing” refer to various methods that allow finding, cleaving, and repairing specific sequences in the genome. These techniques could contribute to managing various challenges in plant breeding and agriculture. Aside from regulatory uncertainties, the lack of consumer acceptance has frequently been cited as a significant barrier to the widespread use of NGTs in plant breeding and agriculture across the planet. This study was based on an anonymous online survey (N = 1202). It investigated what consumers from two countries that differ in gene technology regulation, namely the United States of America and Switzerland, thought about three specific applications of NGTs in plant breeding (i.e., blight-resistant potato, gluten-free wheat, cold-resistant soybean). The study highlights the importance of the affect heuristic for acceptance, as half of the participants in both countries expressed positive feelings regarding the three applications, a quarter of the participants expressed negative, and the remaining participants expressed torn or neutral emotions. Some evidence was provided that the regulatory context might have acted as a risk cue, as participants in Switzerland expressed more negative feelings, perceptions, and lower acceptance than participants from the United States of America. Lastly, our findings underscore the importance of a collaboration between the life sciences and social sciences in balancing technological innovations and public perceptions and acceptance, which have been shown in this study to be impacted by affect, values, and context.

Identification of QTL associated with plant vine characteristics and infection response to late blight, early blight, and Verticillium wilt in a tetraploid potato population derived from late blight-resistant Palisade Russet.

Potato late blight (causal agent Phytophthora infestans) is a disease of potatoes with economic importance worldwide. Control is primarily through field monitoring and the application of fungicides. Control of late blight with fungicides and host plant resistance is difficult, with documented cases of such control measures failing with the advent of new pathotypes of P. infestans. To better understand host plant resistance and to develop more durable late blight resistance, Quantitative Trait Locus/Loci (QTL) analysis was conducted on a tetraploid mapping population derived from late blight-resistant potato cultivar Palisade Russet. Additionally, QTL analyses for other traits such as Verticillium wilt and early blight resistance, vine size and maturity were performed to identify a potential relationship between multiple traits and prepare genetic resources for molecular markers useful in breeding programs. For this, one hundred ninety progenies from intercrossing Palisade Russet with a late blight susceptible breeding clone (ND028673B-2Russ) were assessed. Two parents and progenies were evaluated over a two-year period for response to infection by the US-8 genotype of P. infestans in inoculated field screenings in Corvallis, Oregon. In Aberdeen, Idaho, the same mapping population was also evaluated for phenotypic response to early blight and Verticillium wilt, and vine size and maturity in a field over a two-year period. After conducting QTL analyses with those collected phenotype data, it was observed that chromosome 5 has a significant QTL for all five traits. Verticillium wilt and vine maturity QTL were also observed on chromosome 1, and vine size QTL was also found on chromosomes 3 and 10. An early blight QTL was also detected on chromosome 2. The QTL identified in this study have the potential for converting into breeder-friendly molecular markers for marker-assisted selection.

Hemibiotrophic Phytophthora infestans Modulates the Expression of SWEET Genes in Potato (Solanum tuberosum L.).

Sugar Efflux transporters (SWEET) are involved in diverse biological processes of plants. Pathogens have exploited them for nutritional gain and subsequently promote disease progression. Recent studies have implied the involvement of potato SWEET genes in the most devastating late blight disease caused by Phytophthora infestans. Here, we identified and designated 37 putative SWEET genes as StSWEET in potato. We performed detailed in silico analysis, including gene structure, conserved domains, and phylogenetic relationship. Publicly available RNA-seq data was harnessed to retrieve the expression profiles of SWEET genes. The late blight-responsive SWEET genes were identified from the RNA-seq data and then validated using quantitative real-time PCR. The SWEET gene expression was studied along with the biotrophic (SNE1) and necrotrophic (PiNPP1) marker genes of P. infestans. Furthermore, we explored the co-localization of P. infestans resistance loci and SWEET genes. The results indicated that nine transporter genes were responsive to the P. infestans in potato. Among these, six transporters, namely StSWEET10, 12, 18, 27, 29, and 31, showed increased expression after P. infestans inoculation. Interestingly, the observed expression levels aligned with the life cycle of P. infestans, wherein expression of these genes remained upregulated during the biotrophic phase and decreased later on. In contrast, StSWEET13, 14, and 32 didn't show upregulation in inoculated samples suggesting non-targeting by pathogens. This study underscores these transporters as prime P. infestans targets in potato late blight, pivotal in disease progression, and potential candidates for engineering blight-resistant potato genotypes.

Screening of wild species and transcriptome profiling to identify differentially regulated genes in response to late blight resistance in potato.

Late blight (Phytophthora infestans) is a serious disease of potatoes. The aim of this study was to screen wild potato species and identify differentially expressed genes (DEGs) associated with late blight resistance. Wild potato species such as PIN45 (Solanum pinnatisectum), CPH62 (Solanum cardiophyllum), JAM07 (Solanum jamesii), MCD24 (Solanum microdontum), PLD47 (Solanum polyadenium), and cv. Kufri Bahar (control) were tested by artificial inoculation of P. infestans under controlled conditions. Transcriptomes of the leaf tissues (96h post-inoculation) were sequenced using the Illumina platform. Statistically significant (p < 0.05) DEGs were analyzed in wild species by comparison with the control, and upregulated (>2 log2 fold change, FC) and downregulated (<-2 log2 FC) genes were identified. DEGs were functionally characterized with Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Selected genes were validated by real-time PCR analysis to confirm RNA-seq results. We identified some upregulated genes associated with late blight resistance in wild species such as cytochrome P450, proline-rich protein, MYB transcription factor MYB139, ankyrin repeat-containing protein, and LRR receptor-like serine/threonine-protein kinase in PIN45; glucosyltransferase, fructose-bisphosphate aldolase, and phytophthora-inhibited protease 1 in CPH62; steroid binding protein and cysteine proteinase 3 in JAM07; glycine-rich cell wall structural protein 1 and RING finger protein in MCD24; and cysteine proteinase 3 and major latex protein in PLD47. On the other hand, downregulated genes in these species were snakin-2 and WRKY transcription factor 3 in PIN45; lichenase and phenylalanine ammonia-lyase 1 in CPH62; metallothionein and LRR receptor-like serine/threonine-protein kinase in JAM07; UDP-glucoronosyl/UDP-glucosyl transferase family protein and steroid binding protein in MCD24; and cytoplasmic small heat shock protein class I and phosphatase PLD47. Our study identified highly resistant wild potato species and underlying genes such as disease resistance, stress response, phytohormones, and transcription factors (e.g., MYB, WRKY, AP2/ERF, and AN1) associated with late blight resistance in wild potato species.

Characterization of host-effector transcription dynamics during pathogen infection in engineered late blight resistant potato.

Phytophthora infestans, the etiologic agent of late blight, is a threat to potato production in areas with high humidity during the growing season. The oomycete pathogen is hemi-biotrophic, it establishes infection on living plant cells and then spreads, kills, and feeds off the necrotized plant tissue material. The interaction between host and pathogen is complex with dynamic pathogen RXLR effectors and potato NB-LRR resistance proteins actively competing for dominance and survival. Late blight protection was brought to several cultivars of potato through insertion of the wild potato (Solanum venturii) NB-LRR resistance gene Rpi-vnt1.1. We have established that the late blight protection trait, mediated by Rpi-vnt1.1, is effective despite low expression of RNA. The RNA expression dynamics of Rpi-vnt1.1 and the cognate pathogen RXLR effector, Avr-vnt1, were evaluated following spray inoculation with up to five different contemporary late blight isolates from North America and South America. Following inoculations, RXLR effector transcript profiles provided insight into interaction compatibility in relation to markers of the late blight hemi-biotrophic lifecycle.

Will genetically modified late blight resistant potatoes be the first GM crops to be approved for commercial growing in Norway?

Last decade's advances in biotechnology, with the introduction of CRISPR, have challenged the regulatory framework for competent authorities all over the world. Hence, regulatory issues related to gene editing are currently high on the agenda both in the EU and in the European Economic Area (EEA) Agreement country of Norway, particularly with regards to sustainable agriculture. During the negotiations on the EEA Agreement, Norway was allowed to retain three extra aims in the Gene Technology Act: "That the production and use of GMO happens in an ethical way, is beneficial to society and is in accordance with the principle of sustainable development". We argue the case that taking sustainability into the decisions on regulating gene edited products could be easier in Norway than in the EU because of these extra aims. Late blight is our chosen example, as a devastating disease in potato that is controlled in Norway primarily by high levels of fungicide use. Also, many of these fungicides are being banned due to negative environmental and health effects. The costs of controlling late blight in Norway were calculated in 2006, and since then there have been new cultivars developed, inflation and an outbreak of war in Europe increasing farm input costs. A genetically modified (GM) cisgenic late blight resistant (LBR) potato presents a possible solution that could reduce fungicide use, but this could still be controversial. This paper aims to discuss the advantages and disadvantages of approving the commercial use of a GM LBR potato cultivar in Norway and compare these against currently used late blight management methods and conventional potato resistance breeding. We argue that a possible route for future regulatory framework could build upon the proposal by the Norwegian Biotechnology Advisory Board from 2019, also taking sustainability goals into account. This could favour a positive response from the Competent Authorities without breeching the European Economic Area (EEA) Agreement. Perhaps the EU could adopt a similar approach to fulfil their obligations towards a more sustainable agriculture?

Dissection of the Plant Hormone Signal Transduction Network in Late Blight-Resistant Potato Genotype SD20 and Prediction of Key Resistance Genes.

Hormones play an important role in plant disease resistance and defense. Transcriptome data of late blight-resistant potato genotype SD20 treated by ethylene (ET), jasmonate (JA), salicylic acid (SA), and Phytophthora infestans CN152 was analyzed to assess the role of the ET/JA/SA regulatory network in plant disease resistance and defense and predict key resistant genes. The results show that there was significant crossover of differentially expressed genes among all treatments, and common and specific plant disease interaction genes for the ET, JA, and SA treatments were differentially expressed in the CN152 treatment. The resistance and defense genes of the potato genotype SD20 could be induced to regulate metabolic and hormone signaling pathways by alternative splicing in all treatments. Further analysis found that JA and ET pathways can work together synergistically. JA/ET and SA pathways antagonize each other to initiate the expression of calmodulin-domain protein kinases and calmodulin/calmodulin-like and RPM1-interacting protein 4 genes, and they activate HSP-mediated hypersensitive response and defense-related genes. Meanwhile, nine defense genes, including wound-responsive AP2-like factor, glutathione-s-transferase, serine/threonine-protein kinase BRI1, and Avr9/Cf-9 rapidly elicited protein genes, were obtained using weighted gene coexpression network analysis, which provided reliable targets for functional verification. This study provides a theoretical reference for the comprehensive application of plant hormones to improve resistance to potato late blight disease.

Analysis of Genetic Diversity, Population Structure and Association Mapping for Late Blight Resistance in Potato (Solanum tuberosum L.) Accessions Using SSR Markers

The allelic variations in a diversity panel of 353 potato accessions, including 256 accessions belonging to Solanum tuberosum sub spp. tuberosum, 49 accessions belonging to Solanum tuberosum sub spp. andigena, and 48 Indian potato varieties were analysed using 25 simple sequence repeat (SSR) markers. The SSR allelic profiles revealed high levels of polymorphism and distinctness among the accessions studied. A total of 343 alleles of 25 SSR markers were observed in the diversity panel of 353 highly diverse tetraploid potato accessions. The number of alleles produced per SSR varied from 8 for the marker STM1053 to 25 for the marker STIKA. The polymorphic information content (PIC) ranged from 0.66 (STG0010) to 0.93 (STM1106) with an average of 0.82. The cluster analysis using the SSR allelic profiles of 353 accessions divided the population into five major groups. The association mapping for late blight resistance identified six markers with the general linear model (GLM), and out of these six markers significance of three markers was reconfirmed with the mixed linear model (MLM). The findings of this study suggest that SSRs are the appropriate markers for evaluating genetic diversity and population structure within different potato germplasm collections. A significant diversity across the tetraploid potato accessions was observed. Moreover, the markers identified in this study could be useful in marker-assisted selection (MAS) breeding in potato for late blight resistance (LBR).

Status and way-forward in breeding potato (Solanum tuberosum) for resistance to late blight

Improving host resistance to late blight (Phytophthora infestans) has been a major concern of potato breeders since the Irish famine of 1840s. Since then, a number of late blight resistant potato (Solanum tuberosum L.) cultivars have been developed using both conventional and molecular techniques. However, resistance to late blight did not last long and broke down due to the emergence of more virulent races of Phytophthora infestans. This perspective paper presents the status of sources of resistance to late blight, defence mechanism of host against the pathogen and late blight resistance genes mapped, cloned, and transferred to cultivated potato. Considerable progress has been made in all aspects of breeding potato for resistance to late blight. However, a critical appraisal of the status of potato breeding for resistance to late blight suggests the continued need to identify new sources of resistance, transfer of resistance genes from diverse sources and stacking them in maximum number into individual plants. Other breeding strategies to combat this dreaded disease are also discussed.

Genetically modified (GM) late blight-resistant potato and consumer attitudes before and after a field visit

ABSTRACT Late blight, caused by Phytophthora infestans, is the most devastating disease in potato production. Here, we show full late blight resistance in a location with a genetically diverse pathogen population with the use of GM potato stacked with three resistance (R) genes over three seasons. In addition, using this field trials, we demonstrate that in-the-field intervention among consumers led to change for more favorable attitude generally toward GM crops.

A breeding approach to enhance late blight resistance in potato

ABSTRACT A study was conducted at the Advanced Seed Research and Biotech Centre, ACI Limited from 2017 to 2020 for developing late blight (LB) resistant potato clones where BARI Alu 77 was used as the female parent and BARI Alu 53 was the male parent. Thirty-two potato clones out of 330 were selected based on plant vigour, tuber shape, size and colour. Finally, a putative clone, C2-5, was selected as a LB resistant, in which 0.4–0.5% foliage destruction was observed after 90 days of planting under artificial inoculation and natural infection of Phytophthora infestans. On an average, a maximum of 10.6 tubers/hill was recorded. Maximum 713.7 g of tubers per hill was found along with the highest yield potential of 59.5 metric tons per hectare, when no fungicide was applied. Besides, it was PCR positive for different LB-resistance genes/QTLs, such as Rpi-abpt1, R3b, R1, Rpi-sto1, Rpi-blb1, and Rpi-Smira1 from R2-F1R3, R3b-F4/R5, CosA, Ssto-448, 1521/518 and 45/XI primers, respectively. Therefore, this developed clone, C2-5, can be a potential candidate as a cultivar, as well as an elite germplasm for further LB resistance potato breeding programmes.

Comparative Metabolomic Profiling of Compatible and Incompatible Interactions Between Potato and Phytophthora infestans.

Late blight is one of the main biological stresses limiting the potato yield; however, the biochemical mechanisms underlying the infection process of Phytophthora infestans remain unrevealed. In this study, the late blight-resistant potato cultivar Ziyun No.1 (R) and the susceptible cultivar Favorita (S) were inoculated with P. infestans. Untargeted metabolomics was used to study the changes of metabolites in the compatible and incompatible interactions of the two cultivars and the pathogen at 0, 48, and 96 h postinoculation (hpi). A total of 819 metabolites were identified, and the metabolic differences mainly emerged after 48 hpi. There were 198 and 115 differentially expressed metabolites (DEMs) in the compatible and incompatible interactions. These included 147 and 100 upregulated metabolites during the compatible and incompatible interactions, respectively. Among them, 73 metabolites were identified as the P. infestans-responsive DEMs. Furthermore, the comparisons between the two cultivars identified 57 resistance-related metabolites. Resistant potato cultivar had higher levels of salicylic acid and several upstream phenylpropanoid biosynthesis metabolites, triterpenoids, and hydroxycinnamic acids and their derivatives, such as sakuranetin, ferulic acid, ganoderic acid Mi, lucidenic acid D2, and caffeoylmalic acid. These metabolites play crucial roles in cell wall thickening and have antibacterial and antifungal activities. This study reports the time-course metabolomic responses of potatoes to P. infestans. The findings reveal the responses involved in the compatible and incompatible interactions of potatoes and P. infestans.

Dual RNA Sequencing Reveals the Genome-Wide Expression Profiles During the Compatible and Incompatible Interactions Between Solanum tuberosum and Phytophthora infestans.

Late blight, caused by Phytophthora infestans (P. infestans), is a devastating plant disease. P. infestans genome encodes hundreds of effectors, complicating the interaction between the pathogen and its host and making it difficult to understand the interaction mechanisms. In this study, the late blight-resistant potato cultivar Ziyun No.1 and the susceptible potato cultivar Favorita were infected with P. infestans isolate SCPZ16-3-1 to investigate the global expression profiles during the compatible and incompatible interactions using dual RNA sequencing (RNA-seq). Most of the expressed Arg-X-Leu-Arg (RXLR) effector genes were suppressed during the first 24 h of infection, but upregulated after 24 h. Moreover, P. infestans induced more specifically expressed genes (SEGs), including RXLR effectors and cell wall-degrading enzymes (CWDEs)-encoding genes, in the compatible interaction. The resistant potato activated a set of biotic stimulus responses and phenylpropanoid biosynthesis SEGs, including kirola-like protein, nucleotide-binding site-leucine-rich repeat (NBS-LRR), disease resistance, and kinase genes. Conversely, the susceptible potato cultivar upregulated more kinase, pathogenesis-related genes than the resistant cultivar. This study is the first study to characterize the compatible and incompatible interactions between P. infestans and different potato cultivars and provides the genome-wide expression profiles for RXLR effector, CWDEs, NBS-LRR protein, and kinase-encoding genes.

Breeding Late Blight Resistant Potatoes for Organic Farming—a Collaborative Model of Participatory Plant Breeding: the Bioimpuls Project

AbstractIn organic potato production, the need for varieties with durable late blight resistance developed through classical breeding programmes is urgent. Besides late blight resistance, other variety characteristics needed in organic potato production are early canopy closure for weed suppression and good tuber dormancy to eliminate the need for (chemical) sprouting inhibition during storage, amongst others. This paper is a unique example of collaboration between researchers, farmers and professional breeders of both large, medium and small breeding companies. The aim of the resulting breeding project, Bioimpuls, was to provide a substantial impulse to both the organic and conventional potato breeding sector by enlarging the access to various sources of late blight resistance. The Bioimpuls activities include providing true seed populations for variety selection with five available sources ofR-genes againstPhytophthora infestans, early and advanced introgression breeding with six newR-genes, and education and communication. The results achieved over the 11-year period (2009–2019) are analysed. Many true seed populations containing multiple resistance genes are produced and selected, and a constant flow of breeding clones is entering the evaluation and positioning trials of companies. However, it will still take a considerable amount of time before varieties with stacked resistance genes will replace the new resistant single gene varieties entering the market in the next few years. Five out of six new sources ofR-genes need more years of backcrossing before they are ready for commercial use. Bioimpuls successfully introduced a training course for farmer breeders, and published a manual for potato breeding.

Resistencia a lancha de papas nativas ecuatorianas: evaluación en campo y percepción de agricultores

Late blight, caused by Phytophthora infestans (Mont.) de Bary, is one of the most devastating diseases of potato world-wide. A field experiment, in a location under high P. infestans pressure, was carried out in Ecuador to assess resistance or susceptibility to late blight of 31 potato landraces collected in Carchi, Chimborazo and Loja. Resistant commercial varieties (I-Fripapa) and a susceptible (Superchola) were included as references. Based on the Area Under the Disease Progress Curve (AUDPC) three categories were scored: resistant, intermediate and susceptible. The landraces under study showed different responses to late blight in the experimental field. Only, five landraces showed the best field resistance: Uva, Chaucha roja, Guata amarilla, Coneja and Chaucha ratona. Additionally, a survey to 150 farmers growing potato landraces in these three provinces identified the main diseases affecting their potatoes. Informal conversations with these farmers both during the collections and during farmer meetings provided additional information regarding late blight and their perception of landrace resistance. Similar to farmers growing commercial varieties also farmers currently cultivating landraces consider late blight as the main disease in their potatoes. Probably the broad crop diversity on their farms and the planting of potato landrace mixtures reduces the late blight severity effects within their potato fields. Possible strategies to improve late blight resistance in potato in Ecuador could include the identification of accessions with resistance among local landraces, wild potato relatives and/or the introduction of new sources of resistance from other origins.

Molecular characterization for food safety assessment of a genetically modified late blight resistant potato: an unusual case

Standard food safety assessments of genetically modified crops require a thorough molecular characterization of the novel DNA as inserted into the plant that is intended for commercialization, as well as a comparison of agronomic and nutritional characteristics of the genetically modified to the non-modified counterpart. These characterization data are used to identify any unintended changes in the inserted DNA or in the modified plant that would require assessment for safety in addition to the assessment of the intended modification. An unusual case of an unintended effect discovered from the molecular characterization of a genetically modified late blight resistant potato developed for growing in Bangladesh and Indonesia is presented here. Not only was a significant portion of the plasmid vector backbone DNA inserted into the plant along with the intended insertion of an R-gene for late blight resistance, but the inserted DNA was split into two separate fragments and inserted into two separate chromosomes. One fragment carries the R-gene and the other fragment carries the NPTII selectable marker gene and the plasmid backbone DNA. The implications of this for the food safety assessment of this late blight resistant potato are considered.