The objective of this study was to analyse the genetic structure of the population of Phytophthora infestans in Poland, focusing on determining whether seed tubers play a role in pathogen migration and on the role of sexual recombination. In total, 858 isolates were collected from 2016 to 2018, 2020 and 2021 from 10 locations in different regions. The isolates were described in terms of mating type, mitochondrial haplotype, resistance to metalaxyl, virulence and polymorphism at 12 simple-sequence repeat (SSR) loci. Both mating types were found and often occurred in the same field. Among 858 P. infestans isolates, 309 multilocus genotypes (MLGs) were identified. Almost 24% (n = 204) of the sampled isolates were classified to European P. infestans genotypes: EU13, EU34, EU41, EU36 and EU37. The remaining 654 isolates of P. infestans had MLGs that were unique to Poland and strongly suggested sexual recombination and oospores as a source of inoculum. In parentage analysis, each European P. infestans genotype tested as a potential parent was assigned a different parent-offspring probability. Probable progeny isolates were identified for genotypes EU13 and EU34, which have been present in the Polish P. infestans population since 2005 and 2002, respectively. Detection of 2-16 P. infestans isolates of Polish genotypes in the same year but in different locations indicates seed potatoes as a migration route for the pathogen. Our study highlights sexual recombination and seed potato-related migrations as factors affecting the P. infestans population structure in Poland, increasing the pathogen's genetic adaptability.

In Serbia, potato and tomato are very important crops, often cultivated in open fields within the same areas. Phytophthora infestans, the causal agent of late blight, is the most devastating disease affecting these two crops worldwide. The distribution of P. infestans populations from potato and tomato was studied during the period 2018–2023 using genetic microsatellite markers. The resulting fingerprints were compared to other European data, identifying four major genotypes: EU_13_A2, EU_36_A2, EU_37_A2 and ‘Others’. It was shown that EU_13_A2 was the dominant genotype in Serbia on potato. However, the fluazinam insensitive EU_37_A2 genotype and the aggressive EU_36_A2 genotype were also detected at low frequencies during the 2018 period. During the 2019–2023 survey period, isolates collected from all potato fields were identified as EU_13_A2 genotype, indicating that this genotype is still well established in western and southern Serbia. In contrast, in the north region, previous P. infestans populations were displaced by new populations of EU_36_A2 which become dominant in this area. On tomato, more genetically diverse genotypes of P. infestans, classified as ‘Others’, were discovered and clustered into three populations. These populations showed geographic differentiation: one was found in Serbia as early as 2014 and in southern Italy in 2018, suggesting that it is a well-established tomato-adapted clone and mainly present in central Serbia. The second group of isolates belonged to a population occurring in the southern part of the country, while the third population was found only in western Serbia. Consequently, further investigation of the epidemiology of P. infestans is necessary to develop more effective and sustainable strategies for managing late blight disease.

India is the second largest potato producer in the world, with 80% of production on the Gangetic Plains from 3-month winter crops when cooler conditions are optimal for both potato growth and, at times, the concerning late blight disease that threatens food security. During the intercropping summer period, however, the average temperature remains above 35°C, which is unsuitable for the survival of the causal pathogen, Phytophthora infestans. This study investigated the source of potato late blight primary infections. Over 7,000 apparently healthy seed potatoes from a range of sources were planted under field and glasshouse conditions, and careful daily observation and sampling of the subsequent growing crops detected almost 120 primary infections. Overall, 1.6% of asymptomatic seed tubers resulted in late blight emerging as a stem lesion, with higher rates detected on blight-susceptible cultivars than on those more resistant. The rate also varied depending on the seed-production system, with formal systems generating fewer primary infections than seeds produced informally. Genotyping of P. infestans cultures revealed 31 multilocus genotypes of the locally dominant EU_13_A2 clonal lineage, with their tracking confirming overwintering of the pathogen in seed. This study provides clear evidence of seed tuber infection as the main source of primary inoculum driving late blight epidemics in Indian plain potato crops. Weaknesses in the seed-production systems are also flagged, which, if resolved through improved inspection and certification systems, would improve seed health, lower disease incidence, and improve socioeconomic outcomes in rural economies in India and neighboring regions.

Phytophthora is a long-established, well-known, and globally important genus of plant pathogens. Phylogenetic evidence has shown that the biologically distinct, obligate biotrophic downy mildews evolved from Phytophthora at least twice. Because, cladistically, this renders Phytophthora "paraphyletic," it has been proposed that Phytophthora evolutionary clades be split into multiple genera (Crous et al. 2021; Runge et al. 2011; Thines 2023, 2024). In this letter, we review arguments for the retention of the generic name Phytophthora with a broad circumscription made by Brasier et al. (2022) and by many delegates at an open workshop organized by The American Phytopathological Society. We present our well-considered responses to the genus splitting proposals, both in general terms and in terms of the specific proposals for new genera, alongside new information regarding the biological properties and mode of origin of the Phytophthora clades. We consider that the proposals are mostly non-rigorous and not supported by the scientific evidence. Further, given (i) the apparent lack of any distinguishing biological characteristics (synapomorphies) between the Phytophthora clades; (ii) the fundamental monophyly of Phytophthora in the original Haeckelian sense (Haeckel 1877); (iii) the fact that paraphyly is not a justification for taxonomic splitting; and (iv) the considerable likely damage to effective scientific communication and disease management from an unnecessary breakup of the genus, we report that workshop delegates voted unanimously in favor of preserving the current generic concept and for seeking endorsement of this view by a working group of the International Commission on the Taxonomy of Fungi. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Invasive Phytophthora species infect a very broad range of herbaceous and woody hosts globally. The UK alone has experienced a particularly damaging series of outbreaks and epidemics of new, invasive Phytophthora species affecting the nation's trees over the last 30 years. The link between Phytophthora outbreaks and the importation and spread of infected nursery stock is well established across many countries worldwide. To understand better the pathways of spread of Phytophthora in the nursery trade in Britain, we applied a standardized nursery sampling method combined with a refined metabarcoding detection method to capture the diversity of Phytophthora species at 134 British plant nurseries representing a range of biosecurity and trading practices over multiple sampling years between 2016 and 2022. This included root and water samples collected from 17 nurseries sampled seasonally and root samples collected from 117 nurseries sampled once as part of plant health inspections. Based on analyses of 1894 pooled samples, DNA barcodes of 85 Phytophthora species or complexes were detected, with variation in species' relative frequencies across nurseries. We present the top 20 host-Phytophthora associations ranked by relative frequency and report five novel Phytophthora records for the UK. We identified surprisingly high-risk hosts (such as Douglas fir) with the greatest number of Phytophthora associations and revealed Phytophthora nursery niche preferences for water or roots. We discuss the implications of our findings in terms of pathogen diversity and abundance, high-risk hosts, our information dissemination approach and resulting advice on nursery practices aimed at reducing risk.

Estimates of invasion risk can support prioritisation of future threats from non-native species. Greater risk of invasion is expected when species occur in connected source regions and possess traits promoting successful transport, introduction or establishment. We compile a global database of first reports of Phytophthora de Bary species, a diverse oomycete genus attacking a broad range of plant hosts across multiple regions, sectors and ecosystem types with increasing frequency. Using Bayesian hierarchical zero-inflated models, we model global patterns of new detections since 2005 among 109 Phytophthora pathogens across 56 countries with at least two known Phytophthora species reported before 2005. We estimate the effects of trade connectivity, climate matching, national surveillance and pathogen traits on the probability of a new detection. We find that 69 (38%) Phytophthora species were either unknown or had no known source regions before 2005 and were therefore excluded from our analysis. Our study shows that invasion risk is increased for pathogens with broader thermal tolerance and the ability to produce survival structures linked to stress tolerance and asymptomatic infections. This knowledge can be used to enhance national horizon scanning and risk-based surveillance activities to better manage risks to plant health from emerging pathogens.

We describe a protocol to amplify DNA barcodes of known and unknown taxa of Phytophthora and related plant pathogenic oomycetes from a range of environments. The methods focus on sampling pathogen propagules from water using in situ sampling and filtration equipment and buffers that enable efficient storage and DNA extraction for later downstream processing.

Phytophthora species pose a significant threat to citrus production in the Mediterranean, particularly in Sicily, a major citrus-producing region. This study explores the diversity and distribution of Phytophthora taxa in Sicilian citrus orchards, addressing the urgent need to tackle increasing agricultural challenges, such as climate change. Specifically, it aimed to evaluate how environmental factors, such as the type of management (organic vs. conventional) and geographical area influence the composition of Phytophthora communities in Sicilian citrus orchards, and whether these communities correlate with tree health. An additional objective was to compare the effectiveness of traditional baiting and high-throughput metabarcoding techniques (targeting the ITS1 region and RPS10 gene) in capturing this diversity, as well as to assess potential shifts in community structure resulting from climate change by comparing current data with historical records. Soil samples were collected from ten citrus-producing areas under two distinct agronomic management and tree health conditions. Traditional baiting recovered 556 isolates of three already described Phytophthora species, while ITS1 metabarcoding identified ten additional taxa, demonstrating higher specificity (99.5% of ITS1 reads classified as Phytophthora compared to 82.5% for RPS10 ). Our findings indicate that geographical location is a key driver of community composition. Although statistical analyses did not reveal significant differences in Phytophthora diversity between organic and conventional management systems, these results provide valuable insights into the factors shaping pathogen communities. These insights are crucial for developing targeted disease management strategies and for understanding how environmental stressors, including climate change, impact pathogen dynamics in Mediterranean citrus orchards. Graphical Abstract

The microbial oomycete pathogen Phytophthora infestans causes severe epidemics of potato late blight in crops globally. Disease management benefits from an understanding of the diversity of pathogen populations. In this study, we explore the dynamics of P. infestans populations in the late blight-potato agro-ecosystem across the Indian subcontinent. Investigations of the macroecological observations at the field level and microbial ecological principles provided insights into future pathogen behavior. We use a comprehensive simple sequence repeat allele dataset to demonstrate that an invasive clonal lineage called EU_13_A2 has dominated populations over 14 years across India, Bangladesh, and Pakistan. Increasing levels of subclonal variation were tracked over time and space, and, for the first time, populations in Asia were also compared with the source populations from Europe. Within India, a regional pathogen population structure was observed with evidence for local migration, cross-border movement between surrounding countries, and introductions via imports. There was also evidence of genetic drift and between-season transmission of more strongly pathogenic subclones with a complete displacement of some subclonal types. The limited introduction of novel genotypes and the use of resistant potato cultivars could contribute to the dominance of the 13_A2 lineage. The insights will contribute to the management of the pathogen in these key global potato production regions.

Phytophthora diversity was examined in eight forest and ornamental nurseries in the Czech Republic. A leaf baiting isolation technique and, in two nurseries, also Illumina DNA metabarcoding were used to reveal the diversity of Phytophthora in soil and irrigation water and compare the efficacy of both approaches. In total, baiting revealed the occurrence of 12 Phytophthora taxa in 59.4% of soil samples from seven (87.5%) nurseries. Additional baiting of compost was carried out in two nurseries and two Phytophthora species were recovered. Irrigation water was examined in three nurseries by baiting or by direct isolation from partially decomposed floating leaves collected from the water source, and two Phytophthora species were obtained. Illumina sequencing of soil and water samples was done in two and one nurseries, respectively. Phytophthora reads were identified as 45 Phytophthora taxa, 15 of them previously unknown taxa from Clades 6, 7, 8 and 9. Another 11 taxa belonged to known or undescribed species of the oomycete genera Globisporangium, Hyaloperonospora, Nothophytophthora, Peronospora and Plasmopara. Overall, with both techniques 50 Phytophthora taxa were detected with five taxa (P. taxon organica, P. plurivora, P. rosacearum, P. syringae and P. transitoria) being exclusively detected by baiting and 38 only by DNA metabarcoding. Particularly common records in DNA barcoding were P. cinnamomi and P. lateralis which were not isolated by baiting. Only seven species were detected by both techniques. It is recommended to use the combination of both techniques to determine true diversity of Phytophthora in managed or natural ecosystems and reveal the presence of rare or unknown Phytophthora taxa.

In South Africa, potato (Solanum tuberosum) late blight epidemics from 1996 to 2007 were caused by Phytophthora infestans clonal lineage US-1 (McLeod et al. 2001; Pule et al. 2013). Similarly, surveys on tomatoes in the mid-1990s only identified the US-1 clonal lineage in South Africa (McLeod et al., 2001). On potatoes, populations from the Southern Cape and Western Cape regions consisted of persistent mefenoxam-resistant populations (McLeod et al. 2001; Pule et al. 2013). Limited mefenoxam (R-enantiomer of metalaxyl) screening in 2021 in the Western Cape showed that potato isolates were sensitive, which prompted our study. Potato late blight samples were collected in 13 potato fields in the 2021 to 2023 seasons in the Western Cape (n = 4), Free State (n = 7), Limpopo (n = 1) and Kwazulu-Natal (n = 1) Provinces, and one tomato sample in 2022 in the Limpopo Province. Fourteen samples, one per field, were simple sequence repeat (SSR) genotyped for 12 loci (Li et al. 2013) using as DNA template, FTA cards, or genomic DNA extracted from cultures. P. infestans isolations from lesions and DNA culture extractions were conducted as previously described (Pule et al. 2013). SSR genotyping revealed that all 14 P. infestans samples belonged to clonal lineage EU_23_A1 (EU23), which has a phenotype (A1 and metalaxyl sensitive) and SSR genotype matching the US-23 lineage (Saville et al., 2021). As expected, minor polymorphisms were detected among the samples at loci Pi02, G11, D13 and SSR4. Mefenoxam sensitivity testing of seven potato isolates from the Free State (n = 3) and Western Cape (n = 4), and one tomato isolate was conducted as previously described (Mcleod et al. 2001). All isolates were sensitive to mefenoxam since no infection and sporulation occurred at 3 µg/ml. This was expected since EU23 has been reported as mefenoxam sensitive in other countries (Kawchuk et al., 2011; McGrath et al., 2015). Replacement of the US-1 clonal lineage by EU23 suggests that the latter lineage is more aggressive or fit than US-1, but this must be verified especially on potatoes. On tomatoes, on the other hand, EU23 is known as a highly aggressive lineage (Kawchuk et al., 2011; McGrath et al., 2015; Saville et al., 2021). Therefore, population displacements may have first occurred on tomatoes from where the lineage spread to potatoes. In the Cape coastal potato production regions, population displacement may have been supported by the withdrawal of mefenoxam/metalaxyl from the region since 1996 because the EU23 lineage is mefenoxam sensitive, as opposed to the previously prevailing US-1 mefenoxam-resistant lineage. More severe potato late blight epidemics has not been observed in recent years in South Africa. However, tomato late blight has increased and is more prevalent in the Limpopo province. The source of the introduction of EU23 into South Africa is unknown. Only test-tube plants and/or greenhouse tubers may be imported into South Africa since 1997. Therefore, the illegal importation of planting material may have introduced the new genotype. Whether this could have occurred from neighbouring African countries is unknown since P. infestans genotyping has not been conducted in these countries. In Africa, EU23 has been reported in northern African countries (Tunisia, Algeria and Egypt) (Saville et al., 2021; El-Ganainy et al., 2023). Mefenoxam and metalaxyl applications will likely be effective again in the Western Cape, but more samples will have to be tested to confirm this. This will provide growers with a more cost-effective fungicide (metalaxyl) since alternative actives with comparable systemic and curative activity are more expensive.

Knowledge of a pathogen's genetic variability and population structure is of great importance to effective disease management. In this study, 193 isolates of Phytophthora infestans collected from three Estonian islands were characterized over 3 years using simple sequence repeat (SSR) marker data complemented by information on their mating type and resistance to metalaxyl. In combination with SSR marker data from samples in the neighboring Pskov region of Northwest Russia, the impact of regional and landscape structure on the level of genetic exchange was also examined. Among the 111 P. infestans isolates from Estonian islands, 49 alleles were detected among 12 SSR loci, and 59 SSR multilocus genotypes were found, of which 64% were unique. The genetic variation was higher among years than that among islands, as revealed by the analysis of molecular variance. The frequency of metalaxyl-resistant isolates increased from 9% in 2012 to 30% in 2014, and metalaxyl resistance was most frequent among A1 isolates. The test for isolation by distance among the studied regions was not significant, and coupled with the absence of genetic differentiation, the result revealed gene flow and the absence of local adaptation. The data are consistent with a sexual population in which diversity is driven by an annual germination of soilborne oospores. The absence of shared genotypes over the years has important implications when it comes to the management of diseases. Such population diversity can make it difficult to predict the nature of the outbreak in the coming year as the genetic makeup is different for each year.

Late blight, caused by Phytophthora infestans, is a serious disease of potatoes worldwide and is predominantly controlled by repeated prophylactic use of fungicides throughout the growing season. Effective blight management and integrated pest management strategies rely on knowledge of the efficacy of available fungicides to control contemporary genotypes of P. infestans. Between 2019 and 2022, representative isolates of the newer dominant genotypes EU36, EU37 and the older dominant genotype EU6 were sampled from GB crops and tested for sensitivity to seven commonly used fungicide active ingredients (cyazofamid, fluopicolide, mandipropamid, propamocarb, oxathiapiprolin, amisulbrom and mancozeb) used preventatively in detached leaf tests and zoospore motility assays where appropriate. Dose–response curves based on lesion area (mm2) were constructed, and EC50 values calculated. Isolates of P. infestans genotype EU37 were insensitive to fluazinam as previously reported. No insensitivity, or progression towards resistance over time, to any of the other fungicides was observed in any isolates of the genotypes tested, and EC50 values were generally in line with previous testing. Zoospore motility tests with fluopicolide revealed significantly higher MIC values for isolates of genotype EU36 compared with EU37 and EU6, which, whilst not indicative of resistance at the low concentrations of active ingredient tested, may be a factor contributing to the overall dominance of that genotype in the wider population of P. infestans. The evidence suggests that the fungicides tested, with the exception of fluazinam and EU37, are effective for the control of P. infestans genotypes dominant in the GB population up until 2022.

Mandipropamid is an active ingredient in the carboxylic acid amide group of fungicides and plays a key role in current potato late blight (Phytophthora infestans) management programmes. However, reports from Danish potato growers in 2022 suggested that mandipropamid had lost its efficacy. A study was therefore conducted to investigate the sensitivity of isolates collected from fields in which mandipropamid had been reported to be ineffective. Seventy-two isolates of P. infestans collected from potato fields in Denmark were genotyped using microsatellite markers, revealing a dominance of the clonal lineage EU43 and fewer isolates of EU41 and 'other' genetically distinct genotypes. Isolates belonging to the EU43 and EU41 lineages were selected, in addition to representative isolates of clones EU36 and EU37 from Scotland, and tested for sensitivity to mandipropamid at five concentrations ranging from 0.1 to 10 mu g/mL on potato leaf discs (cultivar Maris Piper). The EU43 genotype infected leaf discs at all tested concentrations, and therefore no dose-response curve could be calculated. A dose response was observed for isolates of genotypes EU36, EU37 and EU41 with EC50 values ranging from 0.35 to 0.75 mu g/mL. Field experiments confirmed resistance of tested isolates of genotype EU43 to mandipropamid, with no significant difference in the area under the disease curve between the untreated and mandipropamid treatments. Analysis of the Danish population of P. infestans showed that EU43 was widely distributed across the country. To our best knowledge, this is the first report of resistance to mandipropamid in P. infestans.

In Bangladesh, the third largest producer of potatoes in Asia, late blight, caused by Phytophthora infestans , is the major constraint to production. Nevertheless, there is a lack of published information on the pathogen population. A collection of 69 isolates obtained from samples of infected potato foliage collected in 2018–2019 varied significantly in their aggressiveness to detached potato leaflets and tuber slices of cv. Diamant. On leaflets, most isolates were highly aggressive, colonizing more than half the surface in 7 days. On tuber slices, while some isolates were highly aggressive, those collected in 2019 were less so. There was a significant effect of the locations from which the isolates were obtained on aggressiveness to both leaflets and tuber slices, but aggressiveness to leaflets and to tuber slices was not significantly correlated. All isolates were A2 mating type and either intermediate (38%) or resistant (62%) in sensitivity to the fungicide metalaxyl . A subset of 24 isolates all had mitochondrial DNA haplotype Ia. Samples of P. infestans DNA (124) from infected potato foliage obtained from Bangladesh (2014–2019) were genotyped by 12-plex SSR. The vast majority (95%) were assigned to EU_13_A2, which was present in every year in which samples were collected. Numerous EU_13_A2 variants were identified, many specific to Bangladesh. Six samples (from 2017 to 2019) had genotypes distinct from EU_13_A2 and with no close match to known European lineages. It is concluded that the current P. infestans population of Bangladesh is dominated by the aggressive lineage EU_13_A2, also dominant in India and Pakistan. The implications of this for control of late blight are discussed.

Since the mid-2010s, Phytophthora infestans clones that have been dominant in Western Europe from the beginning of the 21st century, for example, EU_13_A2, EU_6_A1 and EU_1_A1, are being replaced by several other emerging clones, including EU_37_A2. The objective of this study was to determine whether the main drivers for the success of EU_37_A2 in Western Europe are associated with decreased fungicide sensitivity, increased virulence and/or aggressiveness. Axenic P. infestans cultures were sampled in the 2016 and 2017 growing seasons from potato crops in France and the United Kingdom. Amongst these, four genotypes were identified: EU_37_A2, EU_13_A2, EU_1_A1 and EU_6_A1. Although a wide range of fluazinam sensitivity was found amongst individual isolates, clonal lines EU_13_A2 and EU_37_A2 showed decreased sensitivity to fluazinam. EU_37_A2 overcame the R5 differential cultivar more often than isolates of EU_1_A1 or EU_6_A1. However, this does not explain the competitive advantage of EU_37_A2 over the virulent EU_13_A2. The fittest genotype, as measured by aggressiveness under controlled conditions, was EU_6_A1, followed by EU_37_A2, EU_13_A2 and then EU_1_A1. EU_37_A2 isolates also showed a shorter latent period than either EU_6_A1 or EU_13_A2, which could favour its long-term persistence. Overall, the data suggest that the emergence of EU_37_A2 in Western Europe was driven by its resistance to a then-major fungicide and shorter generation time. This conclusion is further supported by the fact that EU_37_A2 emergence was slowed by the progressive reduction in the use of fluazinam as a single active ingredient in the years following its initial detection.

THAPBI PICT is an open source software pipeline for metabarcoding analysis of Illumina paired-end reads, including cases of multiplexing where more than one amplicon is amplified per DNA sample. Initially a Phytophthora ITS1 Classification Tool (PICT), we demonstrate using worked examples with our own and public data sets how, with appropriate primer settings and a custom database, it can be applied to other amplicons and organisms, and used for reanalysis of existing datasets. The core dataflow of the implementation is (i) data reduction to unique marker sequences, often called amplicon sequence variants (ASVs), (ii) dynamic thresholds for discarding low abundance sequences to remove noise and artifacts (rather than error correction by default), before (iii) classification using a curated reference database. The default classifier assigns a label to each query sequence based on a database match that is either perfect, or a single base pair edit away (substitution, deletion or insertion). Abundance thresholds for inclusion can be set by the user or automatically using per-batch negative or synthetic control samples. Output is designed for practical interpretation by non-specialists and includes a read report (ASVs with classification and counts per sample), sample report (samples with counts per species classification), and a topological graph of ASVs as nodes with short edit distances as edges. Source code available from https://github.com/peterjc/thapbi-pict/ with documentation including installation instructions.

Phytophthora infestans (causal agent of potato late blight) populations are mainly clonal in Great Britain (GB), but sexual reproduction of the pathogen leads to the emergence of novel (non-clonal) genotypes that may have traits such as new virulence or fungicide insensitivity that can make them more challenging to control. In this study, spatiotemporal variation in diversity of P. infestans across GB was mapped and investigated using ArcGIS software. Analysis of >2000 late blight outbreaks during 2006-2018 revealed 169 non-clonal outbreaks in different postcode districts across GB. Statistically significant hot and cold spots of diversity were identified, as well as areas with an increasing trend in the occurrence of high diversity through time. These analyses provide the first quantitative evidence of space-time clustering of non-clonal outbreaks of late blight in GB. The results will be used to guide future efforts to identify the drivers associated with increased genetic diversity of the late blight pathogen and improve management programmes for late blight in GB.

Potato (Solanum tuberosum L.) and tomato (S. lycopersicum L.) are the most economically important vegetable crops in Egypt and worldwide. The winter crop in Egypt is particularly prone to late blight caused by Phytophthora infestans. A total of 152 P. infestans isolates were isolated from the 2013, 2014, 2016 and 2018 winter crops with 82 isolates from potato, 69 from tomato and one isolate from eggplant (S. melongena L.). All isolates belonged to the A1 mating type with no evidence of A2 or self-fertile strains. The majority of isolates (53%) were sensitive to metalaxyl, 32% were intermediate and 15% were resistant. Variation in aggressiveness between three P. infestans isolates EG-005 (13_A2) and EG-276 (23_A1) from potato, and EG-237 (23_A1) from eggplant was determined on tuber slices and leaflets of 10 potato cultivars. The eggplant isolate EG-237 showed higher sporulation capacity compared with the other tested isolates and was able to infect potato (Lady Rosetta cv) and tomato (Super Strain B cv). The simple sequence repeat (SSR) genotyping data showed that in contrast to our previous work (3-year period 2010–12) in which the proportion of 13_A2 lineage was 35%, all isolates belonged to the 23_A1 lineage. There was no evidence for the existence of the A2 mating type or 13_A2 lineage even in the destroyed field crops of some cultivars (Cara, Bellini and Valor) that had been reported as resistant to 23_A1. The data have been submitted into the Euroblight database to allow temporal and spatial genetic diversity to be examined in comparison with other regional P. infestans populations. The AVR2 and AVR2-like RXLR effector genes were amplified and sequenced. In the avirulent AVR2 gene, only one heterozygous SNP was detected at position 31 in the N terminus in six isolates out of eleven, whereas two heterozygous SNPs were detected at position 29 in the N-terminus and ninety-two in the C- terminus of the AVR2-like gene. This suggests that changes in the previously reported virulence profile of 23_A1 are not related to commercial cultivars carrying the R2 gene. In addition, this is the first report of P. infestans on eggplant in Egypt.