Biology subjects

Stam, R.

Publications and source records attributed to Stam, R..

At least 19 recordsLinked to original sources

bioRxiv2026

PlantLRR-PRR:A Reproducible Annotation Pipeline Reveals Contrasting Evolution of Developmental and Defense Receptor-Like Proteins in Tomato

Plants perceive external and internal signals via receptors to modulate their growth, development, and defenses. Leucine-rich-repeat receptor-like-kinase (RLKs) and receptor-like-proteins (RLPs) are two major cell-surface receptors in plants. RLPs are a unique gene family (well-studied and characterized) and play an important role in plant development and defense activities against pests and pathogens. Yet their comparative analyses are hampered by a lack of reproducible and incomplete annotation tools. Here we present the PlantLRR-PRR, a reproducible and standardised RLP/RLK annotation pipeline. It outperforms previous tools and helps to dissect the RLP variation among Solanum spp. We investigated RLP diversity in eight genomes from five wild tomato Solanum sect Lycopersicum. We found limited intra- but moderate inter-specific copy number variation displaying a possible long-term diversification (gain and loss) of RLPs driven by host, environment, and pathogen interactions. Interestingly, we observed a dual-evolutionary pattern characterized by conservation and diversification of developmental- and defense-related RLPs, respectively. Overlapping with this, we found transposable elements (TEs) highly enriched around defense-related RLPs, supporting a strong role of TEs in promoting loss, gain, and structural variations. Further, zooming into the known Cf5 and CuRe1 RLP gene cluster revealed signatures of typical birth and death patterns. Comparative analysis of RLPs in wild tomato species revealed RLP diversity that is not apparent from cultivated tomato alone, highlighting the value of wild germplasm for understanding RLP family evolution. Together, our results provide a comparative framework for understanding the evolutionary divergence and conservation in the RLP family and establish a foundation for linking receptor evolution with functional resistance, and can form a stepping stone for translational applications in crop improvement.

bioinformatics↗

bioRxiv2026

Standing genetic variation buffers field populations of Zymoseptoria tritici against seasonal and fungicide selection

Zymoseptoria tritici is a fungal wheat pathogen whose exceptionally large effective population sizes and frequent sexual recombination enable rapid adaptation and the breakdown of disease control strategies, yet the relative contributions of demographic turnover and fungicide selection to within-season genomic change remain unresolved at the field scale. We analysed whole-genome sequences from five wheat fields sampled during epidemic progression, including paired untreated and fungicide-treated populations, to separate seasonal demographic change from fungicide effects on genome-wide diversity allowing us to compare minor allele frequency spectra and diversity statistics to disentangle these effectswithin individual fields. Field populations were locally differentiated yet nested within the broader European gene pool; within-season demographic turnover consistently shifted allele frequency spectra towards more shared, common alleles; whereas nucleotide diversity and adaptive potential remained largely unchanged. Seasonal demographic turnover accounted for most short-term genomic change, while fungicide effects were comparatively small, field-specific and acted primarily on pre-existing resistance alleles and standing genetic variation. Our results show that short-term adaptation is driven primarily by the redistribution rather than depletion of standing genetic variation, highlighting pathogen population biology as a key determinant of disease-control durability and emphasizing the value of population-informed genomic surveillance.

evolutionary biology↗

bioRxiv2026

Deletion of 29 cell death-inducing proteins and phytotoxin biosynthetic genes does not completely abolish virulence of Botrytis cinerea

Botrytis cinerea is a necrotrophic plant pathogen with an extremely wide host range. During invasion, the fungus induces rapid host cell death and proliferates in the necrotic tissue. Host killing involves secretion of lytic enzymes, phytotoxic metabolites and cell death inducing proteins (CDIPs), but their relative contributions are poorly understood. We have previously shown that the sequential knockout of up to 12 CDIPs leads to a substantial reduction of virulence of B. cinerea mutants. In this study, we identified additional CDIPs and generated an unprecedented series of multi-gene deletion mutants in a filamentous fungus, culminating in a 29x mutant carrying deletions of 27 CDIP-encoding genes and two genes required for the biosynthesis of the phytotoxins botrydial and botcinic acid. These multi-k.o. mutants were strongly reduced in virulence and almost unable to infect apple fruit tissue, but still induced slowly expanding necrosis on leaves, demonstrating that additional determinants of host killing remain to be identified. Overexpression of the highly phytotoxic Nep1 in a 22-fold CDIP mutant failed to increase its virulence. Reevaluation of several CDIPs previously described as virulence factors revealed for most of them only small or no significant contributions to pathogenesis. Generation of a mutant lacking all six predicted endo-polygalacturonases confirmed only for PG1 and PG2 a major role for cell wall degradation and infection. Our work demonstrates that necrotrophic pathogenesis in B. cinerea does not depend on a few primary virulence determinants, but rather on a highly redundant network of host damaging factors.

molecular biology↗

bioRxiv2026

Alternaria atra from distinct ecological roles share functional genomic repertoires

Fungi, particularly ascomycetes, exhibit diverse ecological lifestyles, including endophytism, pathogenicity, and saprotrophy. Species of the genus Alternaria are taxonomically and ecologically diverse, yet the genomic determinants underlying different lifestyles remain poorly understood. Here, we investigate lifestyle-associated genomic variation in Alternaria atra using two newly collected isolates obtained as plant endophytes. We confirm their taxonomic identity and generate draft genome assemblies for both isolates. We assess their phenotypic behaviour under laboratory conditions and examine their genomic features alongside those of a previously published A. atra isolate described as pathogenic. Despite differing isolation histories, the endophytic and pathogenic isolates exhibit similar behaviour under laboratory conditions and possess highly comparable genomic repertoires, including predicted effector proteins, carbohydrate-active enzymes, and biosynthetic gene clusters. We detect no clear genomic signatures distinguishing endophytic and pathogenic origins or lifestyles. These findings suggest that A. atra harbours a shared genomic repertoire compatible with multiple ecological strategies, supporting a model of lifestyle plasticity rather than fixed genomic specialization. Our results add to growing evidence that genome content alone does not reliably predict ecological roles in ascomycete fungi.

genomics↗

bioRxiv2025

Distribution and Shared Pathogenicity of Small-Spored Alternaria on Solanaceous Crops in Europe

Small-spored Alternaria species such as A. alternata and A. arborescens are frequently isolated from diseased potato and tomato plants. However, their respective host ranges and pathogenic behaviours remain poorly resolved, and it is unclear whether their occurrence across hosts reflects true specialisation or ecological opportunism. Limited genetic differentiation among these closely related taxa further complicates their classification as primary necrotrophs or secondary colonisers. In this study, we analysed natural populations of small-spored Alternaria from Germany, Poland, and Serbia using molecular phylogenetics, morphological characterisation, and controlled infection assays to clarify species identity, host associations, and pathogenic potential. Both A. alternata and A. arborescens were detected across all regions and hosts, indicating broad distribution and ecological overlap. The two species were consistently isolated from foliar lesions and were each capable of causing characteristic Alternaria Brown-Spot (ABS) symptoms, thereby fulfilling Kochs postulates. Phylogenetic analyses based on Alt A1 and RPB2 loci resolved two well-supported species clades and revealed extensive haplotype sharing across more than 1300 km, multiple hosts, and diverse climates, suggesting high gene flow and limited population structure. The consistent co-occurrence and comparable pathogenicity of A. alternata and A. arborescens underscore their equal ecological relevance and redefine their roles in ABS epidemiology. These findings indicate that perceived differences in host specialisation may be overstated and that both species contribute equally to Alternaria Brown-Spot epidemics in solanaceous crops.

microbiology↗

bioRxiv2025

Evolutionary divergence in sympatric populations of the fungal pathogen Alternaria alternata across wild tomato hosts

Alternaria alternata is a globally distributed fungal pathogen with a broad host range, increasingly affecting both tomato crops and wild tomato relatives. The genomic basis of this ecological breadth in A. alternata remains poorly understood. Here we leverage the opportunity of wild pathosystems to study pathogen evolution and diversity beyond agricultural settings. We sampled isolates from wild tomato species across a 2,500 km range in South America, producing highly contiguous genomes, to investigate population structure. Our comparative genomics analyses reveal that A. alternata sensu stricto consists of two divergent clades. Strikingly, this divergence is not linked to host species, geography, or habitat type. Transposable elements contribute to variation within clades but do not explain their separation. Although some signs of recombination are present, reproductive mode appears stable across clades. Notably, global reference isolates cluster with one clade, while the other, more diverse clade is only found in wild populations. We hypothesize that these wild populations may act as reservoirs of evolutionary potential. These findings challenge prevailing assumptions about the population structure of necrotrophic pathogens and raise new questions about how genetic divergence can persist without ecological or geographic isolation. Media summary (lay abstract)The fungus Alternaria alternata is an emerging threat on tomato and potato crops. In a previous study, we found that it also infects wild tomato plants over a large range in Chile and Peru. Here we sequenced and compared full genomes of the fungi. Surprisingly, they formed two distinct groups that do not reflect different host plant species, geographical locations, or environments. One of those groups is related more closely to global reference samples, while the other group is more diverse. This suggests wild plants may quietly harbour forms of the fungus that could affect crops in the future.

genomics↗

bioRxiv2025

Temporal Shifts in Gene Expression Drive Quantitative Resistance to a Necrotrophic Fungus in a Tomato Crop Wild Relative

Resistance breeding against generalist necrotrophic pathogens heavily relies on quantitative disease resistance (QDR). Lesion growth dynamics involve distinct phases (e.g., lag phase duration or lesion doubling time), each independently affecting the overall symptom severity. While the genetic and regulatory basis of lesion growth rate has been studied, the host-derived regulation of the lag-phase duration remains largely uncharacterised. In this study, we tested the regulatory response of Solanum pennellii genotypes exhibiting different lag-phase durations. We conducted a time-series gene expression profiling experiment dissecting genotype-specific regulatory responses to Sclerotinia sclerotiorum inoculation. We observed genotype-specific regulatory trajectories, with resistant plants displaying early activation of defence-related genes during the asymptomatic phase. These genes, regulated by a WRKY6-centered gene regulatory network, exhibited elevated basal expression in resistant genotypes and a fine-tuned longitudinal expression with induction before lesion onset. In contrast, susceptible genotypes lacked this early response, showing gene induction only post-infection. This study is the first to link host regulatory dynamics to lag-phase duration, suggesting that elevated basal expression of receptor genes and a WRKY6-mediated gene regulatory network may enhance QDR. These findings provide insights into the regulatory foundation of QDR and establish a functional basis for more focused breeding of QDR traits.

plant biology↗

bioRxiv2025

Co-optation of Transcription Factors Drives Evolution of Quantitative Disease Resistance Against a Necrotrophic Pathogen.

Wild relatives of crop species possess diverse levels of quantitative disease resistance (QDR) to biotic stresses, yet the genomic and regulatory mechanisms underlying these differences are poorly understood. In particular, how QDR against a generalist necrotrophic pathogen evolved and whether it is driven by conserved or species-specific regulatory networks remains unclear. Here, we examined the transcriptomic responses of five diverse wild tomato species that span a gradient of QDR. We initially hypothesised that conserved regulatory modules might control QDR. Instead, we use differential gene expression analysis and weighted gene co-expression network analysis (WGCNA) to find that species-specific regulatory features, encompassing both infection-induced and constitutively expressed genes, predominantly shape QDR levels. Although we identified an ethylene response factor among candidate genes for QDR-regulation, it did not fully account for the phenotypic variation. To further dissect the evolutionary basis of these regulatory patterns, we performed phylotranscriptomic analyses on gene regulatory networks. Notably, our findings reveal that the conserved NAC transcription factor 29 is pivotal in developing disease resistance only in S. pennellii. The differential regulation and altered downstream signalling pathways of NAC29 provide evidence for its co-option in the resistance mechanisms of S. pennellii. This finding highlights the species-specific rewiring of gene regulatory networks by repurposing a conserved regulatory element to enhance resistance against pathogens effectively. These results offer new insights into the evolutionary and regulatory complexity underlying QDR and emphasise the significance of species-specific gene regulation in shaping resistance against a cosmopolitan necrotrophic pathogen.

plant biology↗

bioRxiv2025

Zymoseptoria tritici show local differences in within-field diversity and effector variation

Zymoseptoria tritici is a cosmopolitan hemibiotrophic wheat pathogen with a high mutation rate and a mixed reproduction system, leading to challenges in traditional farming management. For successful integration of pest management, especially for early diagnostics of new aggressive or fungicide-resistant lineages, it is critical to understand population diversity in the field. We look at whole-genome sequence data for three datasets to differentiate within field diversity in fields of similar size: one dataset from a newly sampled field population from the United Kingdom and two publicly available datasets from fields from the United States and Switzerland. Inspection of population structure and diversity features, such as minor allele frequency distribution and clonality, show no within-field structure, the most abundant SNPs are present in low frequency, and European fields have higher clonality. Knowing that effectors play particularly important roles in (a)virulence, we specifically assess effector diversity characteristics. Whereas on a whole-genome scale, we can see separation of the populations at the regional scale, we do not find such separation for the effectors. Moreover, we find that multiple effector haplotypes can be found interspersed within the field and even occur within what has been considered clonal isolates or isolates from a single lesion. Our analyses highlight that within-field Z. tritici diversity is higher than previously reported. Our finding that multiple effector haplotypes can be found within a single lesion might explain the large resistance gene-breaking potential of Z. tritici.

microbiology↗

bioRxiv2024

Horizontal transfer of accessory chromosomes in fungi - a regulated process for exchange of genetic material?

Horizontal transfer of entire chromosomes has been reported in several fungal pathogens, often significantly impacting the fitness of the recipient fungus. All documented instances of horizontal chromosome transfers (HCTs) showed a marked propensity for accessory chromosomes, consistently involving the transfer of an accessory chromosome while other chromosomes were seldom, if ever, co-transferred. The mechanisms underlying HCTs, as well as the factors regulating the specificity of HCTs for accessory chromosomes, remain unclear. In this perspective, we provide an overview of the observed propensity in reported cases of horizontal chromosome transfers. We hypothesize the existence of a signal that distinguishes mobile, i.e., horizontally transferred, accessory chromosomes from the rest of the donor genome. Recent findings in Metarhizium robertsii and Magnaporthe oryzae, suggest that a mobile accessory chromosome may contain putative histones and/or histone modifiers, which could generate such a signal. Based on this, we propose that mobile accessory chromosomes may encode the machinery required for their own horizontal transmission, implying that HCT could be a regulated process. Finally, we present evidence of substantial differences in codon usage bias between core and accessory chromosomes in 14 out of 19 analysed fungal species and strains. Such differences in codon usage bias could indicate past horizontal transfers of these accessory chromosomes. Interestingly, HCT was previously unknown for many of these species, suggesting that the horizontal transfer of accessory chromosomes may be more widespread than previously thought and, therefore, an important factor in fungal genome evolution.

evolutionary biology↗

bioRxiv2024

High-resolution disease phenotyping reveals distinct resistance strategies of wild tomato crop wild relatives against Sclerotinia sclerotiorum

Besides the well-understood qualitative disease resistance, plants possess a more complex quantitative form of resistance: quantitative disease resistance (QDR). QDR is commonly defined as a partial but more durable form of resistance and, therefore, might display a valuable target for resistance breeding. The characterization of QDR phenotypes, especially of wild crop relatives, displays a major bottleneck in deciphering QDRs genomic and regulatory background. Moreover, the relationship between QDR parameters, such as infection frequency, lag phase duration, and lesion growth rate, remains elusive. High hurdles for applying modern phenotyping technology, such as the low availability of phenotyping facilities or complex data analysis, further dampen progress in understanding QDR. Here, we applied a low-cost phenotyping system to measure lesion growth dynamics of wild tomato species (e.g., S. pennellii or S. pimpinellifolium). We provide insight into QDR diversity of wild populations and derive specific QDR strategies and their crosstalk. We show how temporally continuous observations are required to dissect end-point severity into functional resistance strategies. The results of our study show how QDR can be maintained by facilitating different defense strategies during host-parasite interaction and that the capacity of the QDR toolbox highly depends on the hosts genetic context. We anticipate that the present findings display a valuable resource for more targeted functional characterization of the processes involved in QDR. Moreover, we show how modest phenotyping technology can be leveraged to help answer highly relevant biological questions.

plant biology↗

bioRxiv2023

Contrasting patterns of presence-absence variation of NLRS within S. chilense are mainly shaped by past demographic history

Understanding the evolution of pathogen resistance genes (nucleotide-binding site-leucine-rich repeats, also known as NLRs) within a species requires a comprehensive examination of factors that affect gene loss and gain. We present a new reference genome of Solanum chilense, that leads to an increased number and more accurate annotation of NLRs. Next, using a target-capture approach, we quantify the presence-absence variation (PAV) of NLR loci across 20 populations from different habitats. We build a rigorous pipeline to validate the identification of PAV of NLRs, then show that PAV is larger within populations than between populations, suggesting that maintenance of NLR diversity is linked to population dynamics. Furthermore, the amount of PAV is not correlated with the NLR presence in gene clusters in the genome, but rather with the past demographic history of the species, with loss of NLRs in diverging populations at the distribution edges and smaller population sizes. Finally, using a redundancy analysis, we find limited evidence of PAV being linked to environmental gradients. Our results contradict the classic assumptions of the important selective role of PAV for NLRs, and suggest that NLRs PAV is driven by random processes (and weak selection) in an outcrossing plant with high nucleotide diversity.

evolutionary biology↗

bioRxiv2023

Network analyses reveal D clade ethylene response factors as major regulators of jasmonic acid-mediated resistance to early blight disease complex in tomato

Resistance mechanisms to early blight disease complex (EBDC) in tomato remain obscure given its polygenic and quantitative nature. We investigated the early defense responses of Heinz 1706 tomato to EBDC using RNA-seq. We observed distinct transcriptional reprofiling upon exposure to two EBDC isolates and the PAMP chitin. Avirulent isolate CS046 (Alternaria alternata) elicited a vigorous defense response in the host, whilst the virulent isolate 1117-1 (Alternaria sect. Porri) showed subdued gene expression, suggesting a suppression of defense responses during compatible pathogenesis. We emphasize the specific roles of ETHYLENE RESPONSE FACTORs (ERFs) in defense against EBDC, with a particular focus on the D clade ERFs. Co-expression network analysis revealed the principal genes in early defense responses to EBDC are secondary metabolite biosynthesis genes, transcription factors, and hormone response genes. We constructed a gene regulatory network and predicted novel hub genes as putative global regulators of the defense response, including the D clade ERFs, WRKY, and NAC transcription factors. Our work highlights the failure of virulent EBDC pathogenesis to elicit hormone responses that suppress cell death. Additionally, we found a selective induction for specific ERFs that strongly influence the topology of the EBDC defense transcriptional network.

plant biology↗

bioRxiv2023

Copy number variations shape genomic structural diversity underpinning ecological adaptation in the wild tomato Solanum chilense

Copy Number Variation (CNV) is a prevalent type of variation affecting large genomic regions which contributes to both genetic diversity and ecological adaptation in plants. The target genes involved in adaptation through CNV in tomato and its wild relatives remain unexplored at the population level. Therefore, we characterized the CNV landscape of Solanum chilense, a wild tomato species adapted to dry habitats, using whole-genome short-read data of 35 individuals from seven populations. We identified 212,207 CNVs, including 160,926 deletions and 51,281 duplications. We found a higher number of CNVs in diverging populations occupying stressful habitats. CNVs and single nucleotide polymorphisms analyses concordantly revealed the known species population structure, underscoring the impact of historical demographic and recent colonization events shaping genome-wide CNVs. Furthermore, we identified 3,539 candidate genes with highly divergent CNV profiles across populations. Interestingly, these genes are functionally associated with response to abiotic stress and linked to multiple pathways of flowering time regulation. Gene CNVs in S. chilense exhibit two evolutionary trends: gene loss in ancestral lineages distributed in central and southern coast populations and gene gain in the most recent diverged lineage from the southern highland region. Environmental association of the CNVs ultimately linked the dynamics of gene copy number to six climatic variables. It suggests that natural selection has likely shaped CNV patterns in stress-response genes promoting the colonization of contrasting habitats. Our findings provide insights into the role of CNV underlying adaptation during recent range expansion.

evolutionary biology↗

bioRxiv2023

Untargeted metabolomics reveals PTI-associated metabolites in cultivated tomato

Plants employ a multi-layered innate immune system to detect and fend off invading fungal pathogens. In one such layer, recognition of Pathogen- or Microbe-Associated Molecular Patterns or elicitors, triggers a signaling cascade that leads to defence against the pathogen and ultimately Pattern-Triggered Immunity (PTI). Secondary Metabolites (SMs) are expected to play an important role in this kind of resistance, because they are potentially mycotoxic compounds. Tomato plants inoculated with Alternaria solani show clear symptoms of infection 5 days after inoculation. Whereas plants inoculated with Alternaria alternata remain symptomless. We hypothesized that pattern-triggered induction of resistance-related metabolites in Solanum lycopersicum contribute to the resistance against A. alternata, yet such SMs are suppressed in a compatible interaction. We compared the metabolomic profile (metabolome) of S. lycopersicum at two time points (3 and 24 hours) after treatments with A. alternata, A. solani and the fungal elicitor chitin and identified SMs that are involved in the early defence response of tomato plants. Our study revealed differential metabolome fingerprints and shows that the molecular composition of A. alternata and chitin-induced indeed show larger overlap with each other than with the A. solani-induced metabolome. We identify 65 candidate metabolites possibly associated with pattern-triggered resistance in tomato plants, including the alkaloid, trigonelline, for which we can confirm that it inhibits fungal growth in vitro when supplied at physiological concentrations. Our findings show that a true, pattern-triggered, chemical defence is mounted against A. alternata and that it contains mycotoxin compounds previously unidentified in tomato, that could be interesting for future crop protection strategies.

plant biology↗

bioRxiv2023

Barley shows reduced Fusarium Head Blight under drought and modular expression of differential expressed genes under combined stress

Plants often face simultaneous abiotic and biotic stress conditions. However, physiological and transcriptional responses of plants under combined stress situations are little understood. Spring barley is susceptible to Fusarium Head Blight (FHB), which is strongly affected by weather conditions. We therefore studied the potential influence of drought on FHB severity and responses in three differently susceptible spring barley varieties and found strongly reduced FHB severity in susceptible varieties under drought. Quantity of differentially expressed genes (DEGs) and strength of transcriptomic regulation reflected the concentration of physiological stress markers such as abscisic acid or fungal DNA contents. Infection-related gene expression associated rather with susceptibility than resistance. Weighted gene correlation network analysis uncovered 18 modules of co-expressed genes, which reflect the pathogen or drought response in the used varieties. A generally infection-related module contained co-expressed genes for defence, programmed cell death and mycotoxin-detoxification indicating that diverse genotypes use a similar defence strategy towards FHB albeit with different success. Further DEGs showed co-expression in drought or genotype-associated modules correlating with measured phytohormones or the osmolyte proline. The combination of drought stress with infection lead to highest numbers of DEGs and provoked a modular composition of single stress responses rather than a specific transcriptional readout. HighlightCo-expression network analysis reveals association of physiological stress markers and gene expression modules under biotic and abiotic stress

plant biology↗

bioRxiv2022

Small-spored Alternaria spp. (section Alternaria) are common on wild tomato species

The wild relatives of modern tomato crops are native to South America. These plants occur in habitats as different as the Andes and the Atacama Desert and are to some degree all susceptible to fungal pathogens of the genus Alternaria. Alternaria is a large genus. On tomato, several species cause early blight, leaf spot, and other diseases. We collected Alternaria-like infection lesions from the leaves of eight wild tomato species from Chile and Peru. Using molecular barcoding markers, we characterized the pathogens. The infection lesions were caused predominantly by small-spored species of Alternaria of the section Alternaria, like A. alternata, but also by Stemphylium spp., Alternaria spp. from the section Ulocladioides, and other related species. Morphological observations and an infection assay confirmed this. Comparative genetic diversity analyses show a larger diversity in this wild system than in studies of cultivated Solanum species. As A. alternata has been reported to be an increasing problem on cultivated tomato, investigating the evolutionary potential of this pathogen is not only interesting to scientists studying wild plant-pathosystems. It could also inform crop protection and breeding programs to be aware of potential epidemics caused by species still confined to South America.

microbiology↗

bioRxiv2021

Whole genome sequencing elucidates the species-wide diversity and evolution of fungicide resistance in the early blight pathogen Alternaria solani

Early blight of potato is caused by the fungal pathogen Alternaria solani and is an increasing problem worldwide. The primary strategy to control the disease is applying fungicides such as succinate dehydrogenase inhibitors (SDHI). SDHI-resistant strains, showing reduced sensitivity to treatments, appeared in Germany in 2013, five years after the introduction of SDHIs. Two primary mutations in the Sdh complex (SdhB-H278Y and SdhC-H134R) have been frequently found throughout Europe. How these resistances arose and spread, and whether they are linked to other genomic features, remains unknown. We performed whole-genome sequencing for A. solani isolates from potato fields across Europe (Germany, Sweden, Belgium, and Serbia) to better understand the pathogens genetic diversity in general and understand the development and spread of the genetic mutations that lead to SDHI resistance. We used ancestry analysis and phylogenetics to determine the genetic background of 48 isolates. The isolates can be grouped into 7 genotypes. These genotypes do not show a geographical pattern but appear spread throughout Europe. The Sdh mutations appear in different genetic backgrounds, suggesting they arose independently, and the observed admixtures might indicate a higher adaptive potential in the fungus than previously thought. Our research gives insights into the genetic diversity of A. solani on a genome level. The mixed occurrence of different genotypes and apparent admixture in the populations indicate higher genomic complexity than anticipated. The conclusion that SDHI tolerance arose multiple times independently has important implications for future fungicide resistance management strategies. These should not solely focus on preventing the spread of isolates between locations but also on limiting population size and the selective pressure posed by fungicides in a given field to avoid the rise of new mutations in other genetic backgrounds.

evolutionary biology↗