Wild Potato Relatives Research Articles

Rapid Screening of Colorado Potato Beetle Resistance Derived from Solanum okadae

Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say) is a major insect pest of potato and development of resistant varieties is part of a strategy for management. Wild relatives of potato are resources for genetic improvement through breeding. Interspecies crosses to introgress CPB resistance will be facilitated with rapid and inexpensive selection methods. Solanum okadae is a novel source of feeding deterrence against the beetle and was associated with production of a naturally occurring leaf-specific lactone-containing metabolite in the foliage. The Baljet assay has been used for decades in pharmaceuticals for rapid screening of lactone-containing compounds. A modified Baljet assay was developed for potato foliar tissue to rapidly screen for lactone-containing compounds in plants from the field, greenhouse, and laboratory. Herein we report the screening of potato foliage for CPB resistance with a Baljet assay validated by CPB larval feeding studies. Foliage from wild accessions of S. okadae were tested using the Baljet assay and results showed that production of the leaf-specific lactones has a large range of variation in the species. In addition, tubers tested using the Baljet assay had negligible levels of lactone-containing metabolites, confirming leaf-specific production of lactones. This inexpensive method using leaf disk screening will allow potato breeders to quickly select for potential CPB resistant germplasms and advance the breeding of sustainable crops.

Diversity of the Rysto gene conferring resistance to potato virus Y in wild relatives of potato

BackgroundPotato virus Y (PVY) is among the economically most damaging viral pathogen in production of potato (Solanum tuberosum) worldwide. The gene Rysto derived from the wild potato relative Solanum stoloniferum confers extreme resistance to PVY.ResultsThe presence and diversity of Rysto were investigated in wild relatives of potato (298 genotypes representing 29 accessions of 26 tuber-bearing Solanum species) using PacBio amplicon sequencing. A total of 55 unique Rysto-like sequences were identified in 72 genotypes representing 12 accessions of 10 Solanum species and six resistant controls (potato cultivars Alicja, Bzura, Hinga, Nimfy, White Lady and breeding line PW363). The 55 Rysto-like sequences showed 89.87 to 99.98% nucleotide identity to the Rysto reference gene, and these encoded in total 45 unique protein sequences. While Rysto-like26 identified in Alicja, Bzura, White Lady and Rysto-like16 in PW363 encode a protein identical to the Rysto reference, the remaining 44 predicted Rysto-like proteins were 65.93 to 99.92% identical to the reference. Higher levels of diversity of the Rysto-like sequences were found in the wild relatives of potato than in the resistant control cultivars. The TIR and NB-ARC domains were the most conserved within the Rysto-like proteins, while the LRR and C-JID domains were more variable. Several Solanum species, including S. antipoviczii and S. hougasii, showed resistance to PVY. This study demonstrated Hyoscyamus niger, a Solanaceae species distantly related to Solanum, as a host of PVY.ConclusionsThe new Rysto-like variants and the identified PVY resistant potato genotypes are potential resistance sources against PVY in potato breeding. Identification of H. niger as a host for PVY is important for cultivation of this plant, studies on the PVY management, its ecology, and migrations. The amplicon sequencing based on PacBio SMRT and the following data analysis pipeline described in our work may be applied to obtain the nucleotide sequences and analyze any full-length genes from any, even polyploid, organisms.

Genetic diversity studies between Ipomoea wild species and cultivated sweet potato (Ipomoea batatas (L.) Lam.) using SSR markers

Sweet potato (Ipomoea batatas (L.) Lam) is one of the major tuber crops in Asian countries, including India, yet the interrelationship and genetic variability among the cultivar and its crop wild relatives remain obscure. The wild relatives of sweet potato represent a vital source of untapped genetic diversity in the breeding programs. In this study, a set of 12 Simple Sequence Repeats (SSR) markers were utilized to understand the extent of genetic diversity and relationship within and between 20 sweet potato accessions, 23 wild Ipomoea species and two Merremia species for utilization in breeding programmes. The SSR primers produced 84 polymorphic alleles within the range of 105–393 bp, collectively showing an average polymorphism of 94.5 %. The average Polymorphic Information Content (PIC) value of 0.67 showed that all the primers were polymorphic in nature. Similarity coefficient based dendrogram and Principal Component Analysis (PCA) scatter plot clearly differentiated all the cultivars and wild species. The cluster dendrogram analysis revealed the close relationship of cultivars with I. triloba and I. trifida at a similarity index of 0.75. Our analysis showed a high degree of genetic variability within and between hexaploid sweet potato and diploid wild species, whereas lower within the cultivars, which shows that there is a high level of genetic diversity exists within the Ipomoea species for its utilization in breeding programs. Thus, the two wild species, I. trifida and I. triloba could be used in hybridization for improvement of sweet potato through ploidy manipulation.

A survey of the Sli gene in wild and cultivated potato.

Inbred-hybrid breeding of diploid potatoes necessitates breeding lines that are self-compatible. One way of incorporating self-compatibility into incompatible cultivated potato (Solanum tuberosum) germplasm is to introduce the S-locus inhibitor gene (Sli), which functions as a dominant inhibitor of gametophytic self-incompatibility. To learn more about Sli diversity and function in wild species relatives of cultivated potato, we obtained Sli gene sequences that extended from the 5'UTR to the 3'UTR from 133 individuals from 22 wild species relatives of potato and eight diverse cultivated potato clones. DNA sequence alignment and phylogenetic trees based on genomic and protein sequences show that there are two highly conserved groups of Sli sequences. DNA sequences in one group contain the 533 bp insertion upstream of the start codon identified previously in self-compatible potato. The second group lacks the insertion. Three diploid and four polyploid individuals of wild species collected from geographically disjointed localities contained Sli with the 533 bp insertion. For most of the wild species clones examined, however, Sli did not have the insertion. Phylogenetic analysis indicated that Sli sequences with the insertion, in wild species and in cultivated clones, trace back to a single origin. Some diploid wild potatoes that have Sli with the insertion were self-incompatible and some wild potatoes that lack the insertion were self-compatible. Although there is evidence of positive selection for some codon positions in Sli, there is no evidence of diversifying selection at the gene level. In silico analysis of Sli protein structure did not support the hypothesis that amino acid changes from wild-type (no insertion) to insertion-type account for changes in protein function. Our study demonstrated that genetic factors besides the Sli gene must be important for conditioning a switch in the mating system from self-incompatible to self-compatible in wild potatoes.

Plant necrotrophic bacterial disease resistance phenotypes, QTL, and metabolites identified through integrated genetic mapping and metabolomics in Solanum species.

Most food crops are susceptible to necrotrophic bacteria that cause rotting and wilting diseases in fleshy organs and foods. All varieties of cultivated potato (Solanum tuberosum L.) are susceptible to diseases caused by Pectobacterium species, but resistance has been demonstrated in wild potato relatives including S. chacoense. Previous studies demonstrated that resistance is in part mediated by antivirulence activity of phytochemicals in stems and tubers. Little is known about the genetic basis of antivirulence traits, and the potential for inheritance and introgression into cultivated potato is unclear. Here, the metabolites and genetic loci associated with antivirulence traits in S. chacoense were elucidated by screening a sequenced S. tuberosum x S. chacoense recombinant inbred line (RIL) population for antivirulence traits of its metabolite extracts. Metabolite extracts from the RILs exhibited a quantitative distribution for two antivirulence traits that were positively correlated: quorum sensing inhibition and exo-protease inhibition, with some evidence of transgressive segregation, supporting the role of multiple loci and metabolites regulating these resistance-associated systems. Metabolomics was performed on the highly resistant and susceptible RILs that revealed 30 metabolites associated with resistance, including several alkaloids and terpenes. Specifically, several prenylated metabolites were more abundant in resistant RILs. We constructed a high-density linkage map with 795 SNPs mapped to 12 linkage groups, spanning a length of 1,507 cM and a density of 1 marker per 1.89 cM. Genetic mapping of the antivirulence and metabolite data identified five quantitative trait loci (QTLs) related to quorum sensing inhibition that explained 8-28% of the phenotypic variation and two QTLs for protease activity inhibition that explained 14-19% of the phenotypic variation. Several candidate genes including alkaloid, and secondary metabolite biosynthesis that are related to disease resistance were identified within these QTLs. Taken together, these data support that quorum sensing inhibition and exo-protease inhibition assays may serve as breeding targets to improve resistance to nectrotrophic bacterial pathogens in potato and other plants. The identified candidate genes and metabolites can be utilized in marker assisted selection and genomic selection to improve soft- rot and blackleg disease resistance.

Nutritional and anti-nutritional compositional analysis of transgenic potatoes with late blight resistance.

Late blight, caused by the pathogen Phytophthora infestans, is a devastating disease affecting potato production globally, with adverse effects in Africa where limited access to fungicides exacerbates its impact. Outbreaks of late blight lead to reduced yields and substantial economic losses to potato farmers and agricultural systems. The development of resistant potato varieties, tailored to African agroecological conditions, offers a viable solution in mitigating the devastating effects of late blight on potato cultivation. Leading to this study, two consumer-preferred varieties, Victoria and Shangi, with high susceptibility to late blight were targeted for conferring late blight resistance through genetic engineering. This was achieved by inserting R genes from wild relatives of potato displaying resistance to the disease. The intended effect of conferring resistance to the late blight disease has been consistently observed over twenty experimental field trials spanning 8years at three locations in Uganda and Kenya. In this study, we assessed whether the genetic transformation has led to any significant unintended effects on the nutritional and anti-nutritional composition of potato tubers compared to the non-transgenic controls grown under the same agroecological conditions. The compositional assessments were conducted on commercial-size potato tubers harvested from regulatory trials at three locations in Uganda and Kenya. Statistical analysis was conducted using two-way analysis of variance comparing transgenic and non-transgenic samples. Overall, the results showed that the transgenic and non-transgenic samples exhibited similar levels of nutritional and antinutritional components. Variations detected in the levels of the analysed components fell within the expected ranges as documented in existing literature and potato composition databases. Thus, we conclude that there are no biologically significant differences in the nutritional and anti-nutritional composition of transgenic and non-transgenic potato tubers engineered for resistance to late blight.

Wild relatives of potato (Solanum L. sec. Petota) poorly sampled and unprotected in Colombia

AbstractWild potato relatives (Solanum L. sec. Petota) play a vital role in crop improvement, understanding crop evolution, and conserving potato diversity. However, these invaluable resources are often neglected and underutilized and are susceptible to threats such as climate change, urbanization, and agricultural expansion. Little is known about the diversity, conservation status, and distribution of wild potato species in Colombia. To address this gap, we assessed the conservation status of five wild potato relatives conserved in the ex situ Colombian Central Collection. Five species were analyzed for their spatial patterns of biodiversity, conservation status, and conservation gaps. Colombia was found to have six centers of species richness, four areas of endemism, and six biogeographical regions. Of the five native species, only one was classified as adequately conserved for ex situ conservation, while the other four were considered low priority. In contrast, for in situ conservation, three species showed high priority, one was classified as medium priority, and one as low priority. In light of these findings, we propose three conservation strategies: (1) conducting collection missions to increase accessions in the national germplasm bank, prioritizing high‐priority species; (2) identifying and protecting unprotected natural habitats and engaging stakeholders to enhance in situ conservation efforts; and (3) establishing regional community genebanks to ensure localized conservation efforts.

Complete chloroplast genome sequence of Solanum iopetalum, one of the tuber-bearing wild potato relatives

Solanum iopetalum belongs to the Solanaceae family and is one of the tuber-bearing wild Solanum species. In this study, chloroplast genome sequencing of the species, completed with Illumina sequencing technology, is presented. The length of the chloroplast genome is 155,625 bp with a GC content of 37.86%. It comprises a large single copy (LSC) region of 86,057 bp, a small single copy (SSC) region of 18,382 bp, and two inverted repeat regions (IRa and IRb) of 25,593 bp. Additionally, 158 functional genes in the genome are identified, including 105 protein-coding genes, 8 ribosomal RNAs, and 45 transfer RNAs. Phylogenetic analysis revealed that S. iopetalum is grouped into a large clade with other Solanum species, including cultivated potatoes (S. tuberosum) and is closely related to Mexican Solanum species (S. stoloniferum, S. verrucosum, S. hougasii, S. hjertingii, and S. demissum). This study provides useful genomic information for future breeding and evolutionary studies of S. iopetalum and other Solanum species.

Tuber Flesh Colour, Enzymatic Discolouration, Dormancy and Late Blight Resistance of 29 Tuber-Bearing Accessions of Solanum spp.

Potato relatives adapted to many different habitats are promising sources of desirable agricultural traits for potato breeding. Wild potato relatives are preserved in different collections around the world, and their detailed description is key to their exploitation in practice. We described 29 seed accessions of 26 Solanum species originating from the VIR potato collection (Institute of Plant Industry – VIR, Saint Petersburg, Russia) and preserved in Poland. The description included resistance to Phytophthora infestans, tuber flesh colour, enzymatic discolouration and tuber dormancy (sprouting). Up to 13 genotypes were evaluated per accession. The evaluation was repeated in three years for each trait. Two P. infestans isolates were used in late blight resistance tests. Amongst all the tested accessions, five were resistant to both P. infestans isolates, including genotype 13_A2. Twenty-one accessions had white tuber flesh, and 13 accessions showed a lack of or weak enzymatic discolouration. Additionally, we found accessions that were whiter than the standard white-fleshed Polish potato cultivar Irys. In our material, we observed a large variation in the length of the sprouts after storage, indicating differences in the dormancy period length. Four accessions showed a lack of sprouting after 28 weeks of storage at 5–6 °C. The tested material is preserved as in vitro plants in the National Centre for Plant Genetic Resources: Polish Genebank (IHAR-PIB, Radzików, Poland), which will facilitate their use in breeding programs.

GISH Analysis of the Introgression of the B Subgenome Genetic Material of Wild Allotetraploid Species Solanum stoloniferum into Backcrossing Progenies with Potato

Wild relatives of cultivated potato are used in breeding to increase the genetic diversity of Solanum tuberosum (AAAA genome) varieties. Wild Mexican allotetraploid species Solanum stoloniferum (AABB genome) was used in breeding for extreme resistance to viruses and late blight. In this study, genomic in situ hybridization (GISH) was used for visualization of introgression of genetic material of the B subgenome of S. stoloniferum into the genome of backcross hybrids. The fertile hexaploid hybrid had 48 chromosomes of the A genome and 24 chromosomes of the B subgenome. Plants of the BC1 generation were pentaploid having the AAAAB genome constitution and three selected BC2 hybrids were aneuploid, containing one to six chromosomes of the B subgenome and 48 chromosomes of the A genome. The B subgenome of S. stoloniferum was inherited in the backcross generations as single chromosomes and in rare cases as recombinant chromosomes. GISH showed that chromosome pairing in the backcross hybrids was predominantly intragenomic. Most chromosomes of the B subgenome remained as univalents in backcross hybrids. Rare homeologous A/B chromosome pairing was detected in all analyzed hybrids. The obtained data indicate that the B subgenome of S. stoloniferum was able to recombine with the A genome.

Allelic variants of a potato HEAT SHOCK COGNATE 70 gene confer improved tuber yield under a wide range of environmental conditions.

Previously, we developed and applied a glasshouse screen for potato tuber yield under heat stress and identified a candidate gene (HSc70) for heat tolerance by genetic analysis of a diploid potato population. Specific allelic variants were expressed at high levels on exposure to moderately elevated temperature due to variations in gene promoter sequence. In this study, we aimed to confirm the results from the glasshouse screen in field trials conducted over several seasons and locations including those in Kenya, Malawi and the UK. We extend our understanding of the HSc70gene and demonstrate that expression level of HSc70 correlates with tolerance to heat stress in a wide range of wild potato relatives. The physiological basis of the protective effect of HSc70 was explored and we show that genotypes carrying the highly expressed HSc70 A2 allele are protected against photooxidative damage to PSII induced by abiotic stresses. Overall, we show the potential of HSc70 alleles for breeding resilient potato genotypes for multiple environments.

Wild relatives of potato may bolster its adaptation to new niches under future climate scenarios

AbstractFood production strategies and patterns are being altered in response to climate change. Enhancing the adaptation of important food crops to novel climate regimes will be critical to maintaining world food supplies. Climate change is altering the suitability of production areas for crops such as potato (Solanum tuberosum L.) making future productivity, resilience, and sustainability of this crop dependent on breeding for climate adaptation, including through the introgression of novel traits from its wild relatives. To better understand the future production climate envelopes of potatoes, and the potential of its wild relatives to contribute to adaptation to these environments, we estimated the climate of potato in four future climate scenarios and overlapped the current climate of 72 wild relative species and potato with these future climates. We discovered a shift of up to 12.5% by potato from current to novel climate by 2070 and varying magnitudes of overlap by different wild relatives with potato, primarily driven by the extent of endemism. To address the threat of novel climate on potato production and with the wealth of data available for the agrobiodiversity in potato wild relatives, we systematically developed a prioritization value inspired by the logic of the breeder's equation for locating potentially beneficial species possessing local adaptability, climatic plasticity, and interspecific crossability. In doing so, 26 unique species by discrete climate combinations are found, highlighting the presence of unique species to use in adapting potato to changing local climates. Further, the 20 highest prioritized values belong to diploid species, enforcing the drive to shift into diploid breeding by the potato research community, where introgression of the local climate adaptability traits may be more streamlined.

Genome-Wide Identification and Analysis of NAC Transcription Factor Family in Two Diploid Wild Relatives of Cultivated Sweet Potato Uncovers Potential NAC Genes Related to Drought Tolerance.

NAC (NAM, ATAF1/2, and CUC2) proteins play a pivotal role in modulating plant development and offer protection against biotic and abiotic stresses. Until now, no systematic knowledge of NAC family genes is available for the food security crop, sweet potato. Here, a comprehensive genome-wide survey of NAC domain-containing proteins identified 130 ItbNAC and 144 ItfNAC genes with full length sequences in the genomes of two diploid wild relatives of cultivated sweet potato, Ipomoea triloba and Ipomoea trifida, respectively. These genes were physically mapped onto 15 I. triloba and 16 I. trifida chromosomes, respectively. Phylogenetic analysis divided all 274 NAC proteins into 20 subgroups together with NAC transcription factors (TFs) from Arabidopsis. There were 9 and 15 tandem duplication events in the I. triloba and I. trifida genomes, respectively, indicating an important role of tandem duplication in sweet potato gene expansion and evolution. Moreover, synteny analysis suggested that most NAC genes in the two diploid sweet potato species had a similar origin and evolutionary process. Gene expression patterns based on RNA-Seq data in different tissues and in response to various hormone, biotic or abiotic treatments revealed their possible involvement in organ development and response to various biotic/abiotic stresses. The expression of 36 NAC TFs, which were upregulated in the five tissues and in response to mannitol treatment, was also determined by real-time quantitative polymerase chain reaction (RT-qPCR) in hexaploid cultivated sweet potato exposed to drought stress. Those results largely corroborated the expression profile of mannitol treatment uncovered by the RNA-Seq data. Some significantly up-regulated genes related to drought stress, such as ItbNAC110, ItbNAC114, ItfNAC15, ItfNAC28, and especially ItfNAC62, which had a conservative spatial conformation with a closely related paralogous gene, ANAC019, may be potential candidate genes for a sweet potato drought tolerance breeding program. This analysis provides comprehensive and systematic information about NAC family genes in two diploid wild relatives of cultivated sweet potato, and will provide a blueprint for their functional characterization and exploitation to improve the tolerance of sweet potato to abiotic stresses.

Genome-Wide Identification and Analysis of NAC Transcription Factor Family in Two Diploid Wild Relatives of Cultivated Sweet Potato Uncovers Potential NAC Genes Related to Drought Tolerance

NAC (NAM, ATAF1/2, and CUC2) proteins play a pivotal role in modulating plant development and offer protection against biotic and abiotic stresses. Until now, no systematic knowledge of NAC family genes is available for the food security crop, sweet potato. Here, a comprehensive genome-wide survey of NAC domain-containing proteins identified 130 ItbNAC and 144 ItfNAC genes with full length sequences in the genomes of two diploid wild relatives of cultivated sweet potato, Ipomoea triloba and Ipomoea trifida, respectively. These genes were physically mapped onto 15 I. triloba and 16 I. trifida chromosomes, respectively. Phylogenetic analysis divided all 274 NAC proteins into 20 subgroups together with NAC transcription factors (TFs) from Arabidopsis. There were 9 and 15 tandem duplication events in the I. triloba and I. trifida genomes, respectively, indicating an important role of tandem duplication in sweet potato gene expansion and evolution. Moreover, synteny analysis suggested that most NAC genes in the two diploid sweet potato species had a similar origin and evolutionary process. Gene expression patterns based on RNA-Seq data in different tissues and in response to various hormone, biotic or abiotic treatments revealed their possible involvement in organ development and response to various biotic/abiotic stresses. The expression of 36 NAC TFs, which were upregulated in the five tissues and in response to mannitol treatment, was also determined by real-time quantitative polymerase chain reaction (RT-qPCR) in hexaploid cultivated sweet potato exposed to drought stress. Those results largely corroborated the expression profile of mannitol treatment uncovered by the RNA-Seq data. Some significantly up-regulated genes related to drought stress, such as ItbNAC110, ItbNAC114, ItfNAC15, ItfNAC28, and especially ItfNAC62, which had a conservative spatial conformation with a closely related paralogous gene, ANAC019, may be potential candidate genes for a sweet potato drought tolerance breeding program. This analysis provides comprehensive and systematic information about NAC family genes in two diploid wild relatives of cultivated sweet potato, and will provide a blueprint for their functional characterization and exploitation to improve the tolerance of sweet potato to abiotic stresses.

Potato landraces and their wild relatives in 3 micro-centers of diversity in Ecuador: farmers' perception and ecogeography

Ecuador is one of the centers of diversity for wild and cultivated potatoes. Three micro-centers of diversity were previously identified based on germplasm collecting passport data of potato landraces and their wild relatives. The objective of this study was to understand the potential hybridization dynamic of the genetic diversity present in situ in these micro-centers (provinces of Carchi, Chimborazo and Loja in Ecuador) by means of assessing the possibility of an eventual genetic cross within intercropped potato landraces, or among potato landraces to their wild relatives; besides the mapping of actual geographic location of recent collections of potato landrace and wild potato relatives in the study areas. Information from farmers and eco-geographic data demonstrated that there is no potential crossing between wild and cultivated potato species. Probably the existing genetic variability in Ecuador has been accumulated since the historical movement of potato landraces by American ancestors from the center of origin in Peru and Bolivia and the continuum knowledge and seed sharing besides the conscious and unconscious selection of potato landraces by local farmers for centuries. Additionally, we discuss options to conserve both cultivated and wild potato species in Ecuador due to apparent current genetic erosion processes.

Genome assembly of primitive cultivated potato Solanum stenotomum provides insights into potato evolution.

Genetic diversity is the raw material for germplasm enhancement. Landraces and wild species relatives of potato, which contain a rich gene pool of valuable agronomic traits, can provide insights into the genetic diversity behind the adaptability of the common potato. The diploid plant, Solanum stenotomum (Sst), is believed to have an ancestral relationship with modern potato cultivars and be a potential source of resistance against disease. Sequencing of the Sst genome generated an assembly of 852.85 Mb (N50 scaffold size, 3.7 Mb). Pseudomolecule construction anchored 788.75 Mb of the assembly onto 12 pseudochromosomes, with an anchor rate of 92.4%. Genome annotation yielded 41,914 high-confidence protein-coding gene models and comparative analyses with closely related Solanaceae species identified 358 Sst-specific gene families, 885 gene families with expansion along the Sst lineage, and 149 genes experiencing accelerated rates of protein sequence evolution in Sst, the functions of which were mainly associated with defense responses, particularly against bacterial and fungal infection. Insights into the Sst genome and the genomic variation of cultivated potato taxa are valuable in elaborating the impact of potato evolution in early landrace diploid and facilitate modern 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.

Status of the Ex Situ and In Situ Conservation of Brazilian Crop Wild Relatives of Rice, Potato, Sweet Potato, and Finger Millet: Filling the Gaps of Germplasm Collections

This study presents the status of ex situ and in situ conservation for the crop wild relatives of rice, potato, sweet potato, and finger millet in Brazil, and the subsequent germplasm collection expeditions. This research is part of a global initiative entitled “Adapting Agriculture to Climate Change: Collecting, Protecting, and Preparing Crop Wild Relatives” supported by the Global Crop Diversity Trust. Species of the primary, secondary, and tertiary gene pools with occurrences reported in Brazil were included: Oryza alta Swallen, O. grandiglumis (Döll) Prod., O. latifolia Desv., O. glumaepatula Steud., Eleusine tristachya (Lam.) Lam., E. indica (L.) Gaertn., Solanum commersonii Dunal, S. chacoense Bitter, Ipomoea grandifolia (Dammer) O’Donell, I. ramosissima (Poir.) Choisy, I. tiliacea (Willd.) Choisy, I. triloba L., and I. cynanchifolia Meisn. The status of the ex situ and in situ conservation of each taxon was assessed using the gap analysis methodology, and the results were used to plan 16 germplasm collection expeditions. Seeds of the collected material were evaluated for viability, and the protocols for seed germination and cryopreservation were tested. The final conservation score, resulting from the gap analysis and including the average of the ex situ and in situ scores, resulted in a classification of medium priority of conservation for all the species, with the exception of I. grandifolia (high priority). The total accessions collected (174) almost doubled the total accessions of these crop wild relatives incorporated in Embrapa’s ex situ conservation system prior to 2015. In addition, accessions for practically absent species were collected for the ex situ conservation system, such as Ipomoea species, Eleusine indica, and Solanum chacoense. The methods used for dormancy breaking and low temperature conservation for the Oryza, Eleusine, and Ipomoea species were promising for the incorporation of accessions in the respective gene banks. The results show the importance of efforts to collect and conserve ex situ crop wild relatives in Brazil based on previous gap analysis. The complementarity with the in situ strategy also appears to be very promising in the country.

Resisting Potato Cyst Nematodes With Resistance.

Potato cyst nematodes (PCN) are economically important pests with a worldwide distribution in all temperate regions where potatoes are grown. Because above ground symptoms are non-specific, and detection of cysts in the soil is determined by the intensity of sampling, infestations are frequently spread before they are recognised. PCN cysts are resilient and persistent; their cargo of eggs can remain viable for over two decades, and thus once introduced PCN are very difficult to eradicate. Various control methods have been proposed, with resistant varieties being a key environmentally friendly and effective component of an integrated management programme. Wild and landrace relatives of cultivated potato have provided a source of PCN resistance genes that have been used in breeding programmes with varying levels of success. Producing a PCN resistant variety requires concerted effort over many years before it reaches what can be the biggest hurdle—commercial acceptance. Recent advances in potato genomics have provided tools to rapidly map resistance genes and to develop molecular markers to aid selection during breeding. This review will focus on the translation of these opportunities into durably PCN resistant varieties.

Potato improvement through genetic engineering

ABSTRACT Potato (Solanum tuberosum L.) is the third most important crop worldwide and a staple food for many people worldwide. Genetically, it poses many challenges for traditional breeding due to its autotetraploid nature and its tendency toward inbreeding depression. Breeding programs have focused on productivity, nutritional quality, and disease resistance. Some of these traits exist in wild potato relatives but their introgression into elite cultivars can take many years and, for traits such as pest resistance, their effect is often short-lasting. These problems can be addressed by genetic modification (GM) or gene editing (GE) and open a wide horizon for potato crop improvement. Current genetically modified and gene edited varieties include those with Colorado potato beetle and late blight resistance, reduction in acrylamide, and modified starch content. RNAi hairpin technology can be used to silence the haplo-alleles of multiple genes simultaneously, whereas optimization of newer gene editing technologies such as base and prime editing will facilitate the routine generation of advanced edits across the genome. These technologies will likely gain further relevance as increased target specificity and decreased off-target effects are demonstrated. In this Review, we discuss recent work related to these technologies in potato improvement.