Solanum microdontum Bitter is a diploid wild Andean relative of potato that has shaped the domestication and adaptation of modern cultivated potato to diverse environments. S. microdontum has the potential to provide a wealth of untapped genetic material for use in addressing current challenges in potato breeding. Here, we report a high-quality 772 Mb reference genome sequence for S. microdontum that is anchored to 12 chromosomes. The resulting genome assembly has 99.0% complete benchmarking universal single copy orthologs and an N50 scaffold length of over 57 Mb, indicating a high level of completeness. Annotation of the assembly resulted in the identification of 37,324 protein-coding genes and 65% repetitive sequence. A total of 1,187 nucleotide-binding leucine-rich repeat genes were predicted from the assembly, of which, 93.1% overlapped an annotated high-confidence gene model. A k-mer-based kinship matrix derived from a 107-member S. microdontum diversity panel revealed an underlying population structure that corresponds to geographic proximity. The S. microdontum dataset enhances publicly available potato genome resources by providing breeders with genetic, molecular, and germplasm resources for newly developed diploid potato breeding programs.

Commercial potato (Solanum tuberosum) in North America is a clonal autotetraploid crop, which complicates breeding. Efforts are underway to convert potato to a diploid inbred-hybrid crop, allowing breeders to more quickly meet market and environmental demands. With the goal of preserving haplotypes developed over 200 years of selection, diploid potato breeding in the United States started with the creation of diploids from tetraploid commercial varieties and advanced breeding lines through prickle pollination. This is an effective but slow method, which presents a barrier to entry for individual breeding programs. Therefore, we developed 97 publicly available dihaploids (diploids from prickle pollination of tetraploids) as a resource for diploid breeding in the United States. These clones contain the majority of alleles in the US breeding population for three market classes: chips, russets, and fresh market reds. To facilitate genomic informed breeding, all clones have been resequenced, and we have developed de novo assemblies for 20 individuals. As an illustration of how these data will be used in breeding, we explored the maturity locus (StCDF1) and identified 15 different alleles. The majority of dihaploids were heterozygous for early and late alleles, resulting in intermediate maturity. Beyond informing breeding, these data facilitate investigations into potato genomics. The dihaploid population is both highly heterozygous and incredibly diverse on a population level. In particular, there is extensive structural diversity segregating within the population. This contrasts with a relatively low genome-wide historical recombination rate (ρ), indicating that much of potato's high diversity is found within long linkage blocks.

Common scab, caused by Streptomyces spp ., is worldwide an important skin disease of potato, capable of significant reductions in marketable value. Resistant varieties developed through phenotypic selection have been the most effective strategy thus far. Previous studies on the genetics of resistance have identified only minor-effect QTLs. In the current study, we explored the value of historical data for genetic analysis, derived from 52 sources. Based on partial replication of the 3500 + varieties, generalized (entry-mean) heritability was estimated at 0.67. For a subset of 292 varieties with genome-wide markers, the genomic (narrow-sense) heritability was only 0.10. The historical data was combined with a contemporary US dataset spanning 6 environments and 416 varieties. Genome-wide association studies identified four QTLs, which together explained 7.5% of the variation. The median reliability (r 2 ) of genomic-estimated breeding values for marker-based selection was higher for the contemporary US chip group (0.5) than for European varieties from the historical dataset (0.3). This difference can be explained by the higher genomic heritability of the contemporary US dataset (0.24), its larger population size and higher degree of relatedness. This study has illustrated the potential for leveraging historical data for genomics-assisted breeding, but genetic gain for potato common scab resistance continues to be limited by low heritability and high polygenicity.

Potato (Solanum tuberosum) is the third-most important food crop in the world. Although the potato genome has been fully sequenced, functional genomics research of potato lags behind that of other major food crops, largely due to the lack of a model experimental potato line. Here, we present a diploid potato line, 'Jan,' which possesses all essential characteristics for facile functional genomics studies. Jan exhibits a high level of homozygosity after seven generations of self-pollination. Jan is vigorous, highly fertile and produces tubers with outstanding traits. Additionally, it demonstrates high regeneration rates and excellent transformation efficiencies. We generated a chromosome-scale genome assembly for Jan, annotated its genes and identified syntelogs relative to the potato reference genome assembly DMv6.1 to facilitate functional genomics. To miniaturize plant architecture, we developed two 'mini-Jan' lines with compact and dwarf plant stature through CRISPR/Cas9-mediated mutagenesis targeting the Dwarf and Erecta genes involved in growth. One mini-Jan mutant, mini-JanE, is fully fertile and will permit higher-throughput studies in limited growth chamber and greenhouse space. Thus, Jan and mini-Jan offer a robust model system that can be leveraged for gene editing and functional genomics research in potato.

Solanum verrucosum Schlechtendal (2x = 2n = 24) is unique among the clade 4 Solanum Sect Petota species. In addition to being one of the only fully self-compatible diploid potato species, S. verrucosum is the only clade 4 species that lacks prezygotic interspecific reproductive barriers. This allows S. verrucosum to accept pollen from a broad range of Solanum species and thereby serving as a genetic "bridge" between the cultivated or primary potato gene pool and distantly related wild relatives in the tertiary gene pool. The genetic mechanisms underlying self-compatibility in Solanum often underpin interspecific compatibility interactions, which in S. verrucosum, has been attributed to the lack of S-RNase expression. Using an interspecific F2 mapping population (n = 150), we investigated the genetic mechanisms responsible for the lack of interspecific reproductive barriers in S. verrucosum. This F2 population was evaluated for the ability to accept pollen from two clade 1, 1 EBN species (S. pinnatisectum and S. tarnii); from which two QTL for interspecific compatibility were identified on chromosomes 1 and 11, explaining 56.6% of the phenotypic variation observed. To identify the genetic basis of interspecific compatibility, we generated a chromosome-scale genome assembly of S. verrucosum MSII1813-2 and performed gene expression profiling of reproductive organs. Differential gene expression of S-RNase, located within the chromosome 1 QTL, confirmed the central role of the S-locus and specifically, S-RNase, in interspecific compatibility. Discovery of a non-S-locus QTL is consistent with previous findings that other non-S-locus factors are necessary for interspecific compatibility in S. verrucosum.

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.

CRISPR/Cas9 is the most popular genome editing platform for investigating gene function or improving traits in plants. The specificity of gene editing has yet to be evaluated at a genome-wide scale in seed-propagated Camelina sativa (L.) Crantz (camelina) or clonally propagated Solanum tuberosum L. (potato). In this study, seven potato and nine camelina stable transgenic Cas9-edited plants were evaluated for on and off-target editing outcomes using 55x and 60x coverage whole genome shotgun sequencing data, respectively. For both potato and camelina, a prevalence of mosaic somatic edits from constitutive Cas9 expression was discovered as well as evidence of transgenerational editing in camelina. CRISPR/Cas9 editing provided negligible off-target activity compared to background variation in both species. The results from this study guide deployment and risk assessment of genome editing in commercially relevant traits in food crops.

AbstractInbred‐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.

Common scab is an economically costly soilborne disease of potato endemic in many potato-growing regions. The disease is caused by species of Streptomyces bacteria that produce the phytotoxin thaxtomin A. The primary disease management tool available to growers is planting resistant cultivars, but no cultivar is fully resistant to common scab, and partially resistant cultivars are often not the preferred choice of growers because of agronomic or market considerations. Therefore, growers would benefit from knowledge of the presence and severity of common scab infestations in field soils to make informed planting decisions. We implemented a quantitative PCR diagnostic assay to enable field detection and quantification of all strains of Streptomyces that cause common scab in the United States through amplification of thaxtomin A biosynthetic genes. Greenhouse trials confirmed that pathogen abundance was highly correlated with disease severity for five distinct phytopathogenic Streptomyces species, although the degree of disease severity was dependent on the pathogen species. Correlations between the abundance of the thaxtomin biosynthetic genes from field soil with disease on tubers at field sites across four U.S. states and across 2 years were not as strong as correlations observed in greenhouse assays. We also developed an effective droplet digital PCR diagnostic assay that also has potential for field quantification of thaxtomin biosynthetic genes. Further improvement of the PCR assays and added modeling of other environmental factors that impact disease outcome, such as soil composition, can aid growers in making informed planting decisions.

Potato (Solanum tuberosum) is the third most important food crop in the world. Potato tubers must be stored at cold temperatures to minimize sprouting and losses due to disease. However, cold temperatures strongly induce the expression of the potato vacuolar invertase gene (VInv) and cause reducing sugar accumulation. This process, referred to as "cold-induced sweetening," is a major postharvest problem for the potato industry. We discovered that the cold-induced expression of VInv is controlled by a 200 bp enhancer, VInvIn2En, located in its second intron. We identified several DNA motifs in VInvIn2En that bind transcription factors involved in the plant cold stress response. Mutation of these DNA motifs abolished VInvIn2En function as a transcriptional enhancer. We developed VInvIn2En deletion lines in both diploid and tetraploid potato using clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated nuclease 9 (Cas9)-mediated gene editing. VInv transcription in cold-stored tubers was significantly reduced in the deletion lines. Interestingly, the VInvIn2En sequence is highly conserved among distantly related Solanum species, including tomato (Solanum lycopersicum) and other non-tuber-bearing species. We conclude that the VInv gene and the VInvIn2En enhancer have adopted distinct roles in the cold stress response in tubers of tuber-bearing Solanum species. An intronic enhancer is responsible for cold-induced expression of the vacuolar invertase gene in potato.

We find evidence of selection for local adaptation and extensive genotype-by-environment interaction in the potato National Chip Processing Trial (NCPT). We present a novel method for dissecting the interplay between selection, local adaptation and environmental response in plant breeding schemes. Balancing local adaptation and the desire for widely adapted cultivars is challenging for plant breeders and makes genotype-by-environment interactions (GxE) an important target of selection. Selecting for GxE requires plant breeders to evaluate plants across multiple environments. One way breeders have accomplished this is to test advanced materials across many locations. Public potato breeders test advanced breeding material in the National Chip Processing Trial (NCPT), a public–private partnership where breeders from ten institutions submit advanced chip lines to be evaluated in up to ten locations across the country. These clones are genotyped and phenotyped for important agronomic traits. We used these data to interrogate the NCPT for GxE. Further, because breeders submitting clones to the NCPT select in a relatively small geographic range for the first 3 years of selection, we examined these data for evidence of incidental selection for local adaptation, and the alleles underlying it, using an environmental genome-wide association study (envGWAS). We found genomic regions associated with continuous environmental variables and discrete breeding programs, as well as regions of the genome potentially underlying GxE for yield.

Plants defend themselves chemically against herbivory through secondary metabolites and phytohormones. Few studies have investigated how constitutive variation in secondary metabolites contributes to systemic herbivory response. We hypothesized that plants with lower constitutive defenses would induce a stronger phytohormone response to spatially separated herbivory than plants with high constitutive defense. We used growth chamber bioassays to investigate how aboveground herbivory by Colorado potato beetle (Leptinotarsa decemlineata, CPB) and belowground herbivory by northern root-knot nematode (Meloidogyne hapla, RKN) altered phytohormones and glycoalkaloids in roots and shoots of two lines of wild potato (Solanum chacoense). These lines had different constitutive levels of chemical defense, particularly leptine glycoalkaloids, which are only present in aboveground tissues. We also determined how these differences influenced the preference and performance of CPB. The susceptible wild potato line responded to aboveground damage by CPB through induction of jasmonic acid (JA) and OPDA. However, when challenged by both RKN and CPB, the susceptible line retained high levels of JA, but not OPDA. Beetles gained more mass after feeding on the susceptible line compared to the resistant line, but were not affected by nematode presence. Belowground, JA, JA-Isoleucine, and OPDA were higher in the resistant line compared to the susceptible line, and some compounds demonstrated response to local herbivory. In contrast, the susceptible line did not induce phytohormone defenses belowground. These findings allow us to predict that constitutive level of defense may influence the threshold of herbivory that may lead to plant-mediated effects on spatially separated herbivores.

A total of 3,860 accessions from the global in trust clonal potato germplasm collection w3ere genotyped with the Illumina Infinium SolCAP V2 12K potato SNP array to evaluate genetic diversity and population structure within the potato germplasm collection. Diploid, triploid, tetraploid, and pentaploid accessions were included representing the cultivated potato taxa. Heterozygosity ranged from 9.7% to 66.6% increasing with ploidy level with an average heterozygosity of 33.5%. Identity, relatedness, and ancestry were evaluated using hierarchal clustering and model-based Bayesian admixture analyses. Errors in genetic identity were revealed in a side-by-side comparison of in vitro clonal material with the original mother plants revealing mistakes putatively occurring during decades of processing and handling. A phylogeny was constructed to evaluate inter- and intraspecific relationships which together with a STRUCTURE analysis supported both commonly used treatments of potato taxonomy. Accessions generally clustered based on taxonomic and ploidy classifications with some exceptions but did not consistently cluster by geographic origin. STRUCTURE analysis identified putative hybrids and suggested six genetic clusters in the cultivated potato collection with extensive gene flow occurring among the potato populations, implying most populations readily shared alleles and that introgression is common in potato. Solanum tuberosum subsp. andigena (ADG) and S. curtilobum (CUR) displayed significant admixture. ADG likely has extensive admixture due to its broad geographic distribution. Solanum phureja (PHU), Solanum chaucha (CHA)/Solanum stenotomum subsp. stenotomum (STN), and Solanum tuberosum subsp. tuberosum (TBR) populations had less admixture from an accession/population perspective relative to the species evaluated. A core and mini core subset from the genebank material was also constructed. SNP genotyping was also carried out on 745 accessions from the Seed Savers potato collection which confirmed no genetic duplication between the two potato collections, suggesting that the collections hold very different genetic resources of potato. The Infinium SNP Potato Array is a powerful tool that can provide diversity assessments, fingerprint genebank accessions for quality management programs, use in research and breeding, and provide insights into the complex genetic structure and hybrid origin of the diversity present in potato genetic resource collections.

Potato mop top virus (PMTV) and Tobacco rattle virus (TRV) are significant soil borne pathogens of potato vectored by powdery scab and stubby-root nematodes, respectively. These viruses adversely impact tuber quality with infected tubers displaying brown streaks in the flesh and/or necrotic arcs on the surface contributing to the rejection of tubers in commercial settings. Currently, limited agricultural control methods for PMTV are available to farmers outside of planting resistant genotypes and avoiding fields with its vector; however, for TRV chemical control of the nematode vector is an option. Field screening for susceptibility to PMTV and TRV identified ‘Castle Russet’ to be resistant to both PMTV and TRV. In order to localize virus resistance genes for the development of marker assisted selection, a tetraploid mapping population (A15001) was developed by hybridizing ‘Castle Russet’ x A06084-1TE (susceptible to both viruses) and its progeny were subsequently trialed for two years in fields known to be infested with PMTV and TRV (two separate disease trial sites) near Larimore, ND. The population was phenotyped for PMTV and TRV incidence and severity of necrotic tubers at two time points post-harvest (approximately 19 days after harvest and 89 days after storage) with several genotypes in the population showing little or no virus induced necrosis over the years of evaluation, making them useful as parents in hybridizations by the potato breeding community. Tubers produced from the population were further assayed for PMTV and TRV infection by testing tuber core samples with a quantitative polymerase chain reaction (qPCR) assay. The A15001 population and the parents, 241 individuals, were genotyped with the Illumina Infinium SolCAP V2 12K Potato SNP Array yielding 6,704 quality-filtered, informative SNP markers. A genome wide association study (GWAS) analysis revealed SNP markers on multiple chromosomes (1, 2, 3, 5, and 11) that were significantly associated with PMTV incidence and negative qPCR suggesting polygenic inheritance. Conversely, GWAS revealed a significant QTL on chromosome 9 associated with all TRV phenotypes indicative of a major gene contributing to TRV resistance. These data can guide the development of molecular markers to select genotypes resistant to PMTV and TRV in potato breeding programs.

Camelina sativa (L.) Crantz, a member of the Brassicaceae, has potential as a biofuel feedstock which is attributable to the production of fatty acids in its seeds, its fast growth cycle, and low input requirements. While a genome assembly is available for camelina, it was generated from short sequence reads and is thus highly fragmented in nature. Using long read sequences, we generated a chromosome-scale, highly contiguous genome assembly (644,491,969 bp) for the spring biotype cultivar ‘Suneson’ with an N50 contig length of 12,031,512 bp and a scaffold N50 length of 32,184,682 bp. Annotation of protein-coding genes revealed 91,877 genes that encode 133,355 gene models. We identified a total of 4,467 genes that were significantly up-regulated under cold stress which were enriched in gene ontology terms associated with “response to cold” and “response to abiotic stress”. Coexpression analyses revealed multiple coexpression modules that were enriched in genes differentially expressed following cold stress that had putative functions involved in stress adaptation, specifically within the plastid. With access to a highly contiguous genome assembly, comparative analyses with Arabidopsis thaliana revealed 23,625 A. thaliana genes syntenic with 45,453 Suneson genes. Of these, 24,960 Suneson genes were syntenic to 8,320 A. thaliana genes reflecting a 3 camelina homeolog to 1 Arabidopsis gene relationship and retention of all three homeologs. Some of the retained triplicated homeologs showed conserved gene expression patterns under control and cold-stressed conditions whereas other triplicated homeologs displayed diverged expression patterns revealing sub- and neo-functionalization of the homeologs at the transcription level. Access to the chromosome-scale assembly of Suneson will enable both basic and applied research efforts in the improvement of camelina as a sustainable biofuel feedstock.

The relationships of interspecific compatibility and incompatibility in Solanum section Petota are complex. Inquiry into these relationships in tomato and its wild relatives has elucidated the pleiotropic and redundant function of S-RNase and HT which tandemly and independently mediate both interspecific and intraspecific pollen rejection. Our findings presented here are consistent with previous work conducted in Solanum section Lycopersicon showing that S-RNase plays a central role in interspecific pollen rejection. Statistical analyses also demonstrated that HT-B alone is not a significant factor in these pollinations; demonstrating the overlap in gene function between HT-A and HT-B, as HT-A, was present and functional in all genotypes used. We were not able to replicate the general absence of prezygotic stylar barriers observable in S. verrucosum, which has been attributed to the lack of S-RNase, indicating that other non-S-RNase factors play a significant role. We also demonstrated that Sli played no significant role in these interspecific pollinations, directly conflicting with previous research. It is possible that S. chacoense as a pollen donor is better able to bypass stylar barriers in 1EBN species such as S. pinnatisectum. Consequently, S. chacoense may be a valuable resource in accessing these 1EBN species regardless of Sli status.

Availability of readily transformable germplasm, as well as efficient pipelines for gene discovery are notable bottlenecks in the application of genome editing in potato. To study and introduce traits such as resistance against biotic and abiotic factors, tuber quality traits and self-fertility, model germplasm that is amenable to gene editing and regeneration is needed. Cultivated potato is a heterozygous autotetraploid and its genetic redundancy and complexity makes studying gene function challenging. Genome editing is simpler at the diploid level, with fewer allelic variants to consider. A readily transformable diploid potato would be further complemented by genomic resources that could aid in high throughput functional analysis. The heterozygous Solanum tuberosum Group Phureja clone 1S1 has a high regeneration rate, self-fertility, desirable tuber traits and is amenable to Agrobacterium-mediated transformation. We leveraged its amenability to Agrobacterium-mediated transformation to create a Cas9 constitutively expressing line for use in viral vector-based gene editing. To create a contiguous genome assembly, a homozygous doubled monoploid of 1S1 (DM1S1) was sequenced using 44 Gbp of long reads generated from Oxford Nanopore Technologies (ONT), yielding a 736 Mb assembly that encoded 31,145 protein-coding genes. The final assembly for DM1S1 represents a nearly complete genic space, shown by the presence of 99.6% of the genes in the Benchmarking Universal Single Copy Orthologs (BUSCO) set. Variant analysis with Illumina reads from 1S1 was used to deduce its alternate haplotype. These genetic and genomic resources provide a toolkit for applications of genome editing in both basic and applied research of potato.

The Gametophytic Self-Incompatibility (GSI) system in diploid potato (Solanum tuberosum L.) poses a substantial barrier in diploid potato breeding by hindering the generation of inbred lines. One solution is gene editing to generate self-compatible diploid potatoes which will allow for the generation of elite inbred lines with fixed favorable alleles and heterotic potential. The S-RNase and HT genes have been shown previously to contribute to GSI in the Solanaceae family and self-compatible S. tuberosum lines have been generated by knocking out S-RNase gene with CRISPR-Cas9 gene editing. This study employed CRISPR-Cas9 to knockout HT-B either individually or in concert with S-RNase in the diploid self-incompatible S. tuberosum clone DRH-195. Using mature seed formation from self-pollinated fruit as the defining characteristic of self-compatibility, HT-B-only knockouts produced little or no seed. In contrast, double knockout lines of HT-B and S-RNase displayed levels of seed production that were up to three times higher than observed in the S-RNase-only knockout, indicating a synergistic effect between HT-B and S-RNase in self-compatibility in diploid potato. This contrasts with compatible cross-pollinations, where S-RNase and HT-B did not have a significant effect on seed set. Contradictory to the traditional GSI model, self-incompatible lines displayed pollen tube growth reaching the ovary, yet ovules failed to develop into seeds indicating a potential late-acting self-incompatibility in DRH-195. Germplasm generated from this study will serve as a valuable resource for diploid potato breeding.

Late blight, caused by Phytophthora infestans, is an economically important disease of potato that causes significant yield losses, with severe outbreaks regularly occurring in Bangladesh. The objective of this study was to do a large-scale survey of potato fields in the main potato-growing divisions of Bangladesh examining genotypic diversity of P. infestans populations. A total of 160 samples were collected in 2018 from both potato (n = 140) and tomato (n = 20). Isolates were mainly collected on FTA cards (n = 143), but 17 were also collected and isolated into pure culture. Microsatellite analysis revealed high levels of subclonal diversity in P. infestans populations with 116 multilocus genotypes recorded from 160 samples. Comparisons with standards of European and US isolates showed that 74% of samples could be categorized as genotype EU_13_A2, 7% clustered near EU_6_A1 and EU_1_A1, and 19% were unique. Discriminant analysis of principal components showed that the P. infestans population clustered into four distinct groups: a main group that contained most of the samples from potato, two distinct tomato groups and one group of samples originating from the division of Mymensingh. Of 17 isolates from cultures, 16 were EU_13_A2 and one was EU_6_A1; 15 were insensitive to metalaxyl-M. Out of 160 samples, 158 were categorized as mating type A2 and two as mating type A1. These results indicate that Bangladesh populations of P. infestans from potato, like those from neighbouring countries, are dominated by genotype EU_13_A2. However, populations from tomato were distinct and appear to be specific to tomato.