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.

Potato late blight, caused by Phytophthora infestans, is the most devastating disease affecting potatoes, leading to substantial annual yield losses. This study investigated the potential of three bacterial strains for the biological control of this disease under both in vitro and greenhouse conditions. In vitro, in a dual-culture test, Bacillus atrophaeus strain BaAZ2 demonstrated an antagonistic effect against P. infestans stronger than the Stenotrophomonas rhizophila strain SrAZ1 and Bacillus halotolerans strain BhAZ6. In planta, treatment with strain BaAZ2 led to a significant reduction in hydrogen peroxide accumulation in potato leaf tissue. Total phenolic content, and the activity of defense-related enzymes (polyphenol oxidase, and phenylalanine ammonia-lyase) as well as antioxidant enzymes (catalase, ascorbate peroxidase, and peroxidase) were significantly elevated in response to BaAZ2 treatment. Furthermore, the expression levels of stress and defense-related genes StuPR, StuMAPK4, StuWRKY1, StuPPO9, and StuPAL increased in strain BaAZ2-treated plants, while SrAZ1 showed moderate activity and BhAZ6 displayed comparatively limited responses. These findings highlight the strain-specific nature of bacterial biocontrol efficacy and emphasize the importance of evaluating individual isolates before their potential application in sustainable late blight management.

Key message Using a diploid potato diversity panel of 246 breeding lines, a genotyping-by-sequencing and a GWAS approach, we mapped QTL for ten traits important to potato breeders, including two previously unmapped traits: boiled tuber taste and pollen fertility. Abstract Potato breeding at the diploid level has a long history and has gained new impetus recently, when F1 hybrid breeding was made possible with the discovery of a dominant gene for self-compatibility. Our study deploys a unique diploid diversity panel with a broadened cultivated potato gene pool obtained as a result of introgressing valuable traits from wild potato relatives into the Solanum tuberosum background. Using historical phenotyping data collected between 1979 and 2017 for 246 diploid potato clones and high-density genotyping-by-sequencing, we mapped quantitative trait loci (QTL) for tuber yield, mean tuber weight, tuber shape and regularity, tuber eye depth, purple tuber skin colour, flesh colour, tuber starch content, boiled tuber taste (flavour) and pollen fertility. We found some QTL located in genomic regions described in earlier studies, e.g. the QTL for the tuber flesh colour on chromosome 3 overlapping with the location of beta-carotene hydroxylase gene. We identified novel QTL for mean tuber weight on chromosomes 8, 9 and 11 and for purple tuber skin colour on chromosomes 6, 7 and 8. QTL for boiled tuber taste and pollen fertility estimated by Lactofuchsin staining have not been mapped before. We found two regions on chromosome 10 affecting the boiled tuber taste, and QTL on chromosomes 2, 4, 5, 6, 9, and 12 for pollen fertility. Considering the increased interest in diploid hybrid potato breeding, the results presented here hold greater relevance and provide novel targets for potato breeding and research at the diploid level.

Globodera pallida is a major pest that is responsible for huge losses in potato yields worldwide. Expanding the gene pool of cultivated potatoes with clones resistant to this pest is made possible by searching for resistance genes in wild Solanum species. The aim of this study was to identify quantitative trait loci (QTLs) for potato resistance to Globodera pallida derived from Solanum gourlayi. A resistant diploid potato clone, Sg 2/7 (Solanum gourlayi, accession CGN17592), was crossed with a susceptible potato hybrid clone, DW 94-4235, to generate an F1 mapping population. All clones were tested for nematode resistance using G. pallida, pathotypes Pa2 and Pa3, in 2 or 3 years (2017–2019), respectively. Diversity Array Technology (DArTseq) was used for genotyping and genetic map construction. QTLs for nematode resistance were identified on potato chromosomes II, IV, V, VI, VII, X, XI, and XII, explaining from 10.1 to 21.5

The production of chips is an increasing part of the potato market. While the potato tubers are stored at low temperatures to minimize storage problems, they tend to accumulate reducing sugars, which negatively impact the quality and color of fried products. The goal of this study was to analyze the impact of cytoplasm type on chip color after harvest and after cold storage at 4 °C, as well as on proline content in cold-stressed potato tubers in a diploid potato population obtained from reciprocal crossing of parents with T- and D-type cytoplasm. Using 224 F1 progeny clones genotyped with Diversity Array Technology (DArTseq™), we mapped the Quantitative Trait Loci (QTL), treating cytoplasm type as a covariate. We detected five QTLs for chip color after harvest and six after cold storage, with the strongest QTL for both traits overlapping on chromosome III. Five QTL for proline content were detected on chromosomes V, X and XII, with the most significant one located on chromosome X. Although the progeny clones with T-type cytoplasm produced significantly lighter chips after cold storage, the cytoplasm type used as a covariate caused only minor modifications to the obtained QTL landscapes for chip color and proline content.

Phytophthora infestans (Mont.) de Bary is an oomycete plant pathogen that causes late blight in potato (Solanum tuberosum L.) and tomato (Solanum lycopersicum L.). This review documents the population structure of P. infestans in northern and eastern Europe, and aims to explain the differences between populations of P. infestans in this region and in western Europe. Populations of P. infestans are influenced by many factors, e.g., migrations related to the movement of potato seed tubers, possibility of sexual reproduction, changes in climate, and agricultural management practices. All the presented factors may have a significant impact on the P. infestans population structure. The knowledge on P. infestans populations varies strongly depending on country and time, even within the rather intensively studied region of eastern and northern Europe. Our review indicates some knowledge gaps, such as a lack of data for some countries and gaps in some years in population monitoring. This indicates the need to continue the monitoring of P. infestans populations.

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

Phytophthora infestans is the causal agent of late blight in potato. The occurrence of P. infestans with both A1 and A2 mating types in the field may result in sexual reproduction and the generation of recombinant strains. Such strains with new combinations of traits can be highly aggressive, resistant to fungicides, and can make the disease difficult to control in the field. Metalaxyl-resistant isolates are now more prevalent in potato fields. Understanding the genetic structure and rapid identification of mating types and metalaxyl response of P. infestans in the field is a prerequisite for effective late blight disease monitoring and management. Molecular and phenotypic assays involving molecular and phenotypic markers such as mating types and metalaxyl response are typically conducted separately in the studies of the genotypic and phenotypic diversity of P. infestans. As a result, there is a pressing need to reduce the experimental workload and more efficiently assess the aggressiveness of different strains. We think that employing genetic markers to not only estimate genotypic diversity but also to identify the mating type and fungicide response using machine learning techniques can guide and speed up the decision-making process in late blight disease management, especially when the mating type and metalaxyl resistance data are not available. This technique can also be applied to determine these phenotypic traits for dead isolates. In this study, over 600 P. infestans isolates from different populations—Estonia, Pskov region, and Poland—were classified for mating types and metalaxyl response using machine learning techniques based on simple sequence repeat (SSR) markers. For both traits, random forest and the support vector machine demonstrated good accuracy of over 70%, compared to the decision tree and artificial neural network models whose accuracy was lower. There were also associations (p < 0.05) between the traits and some of the alleles detected, but machine learning prediction techniques based on multilocus SSR genotypes offered better prediction accuracy.

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

Using late blight resistance genes targeting conservative effectors of Phytophthora infestans and the constructing gene pyramids may lead to durable, broad-spectrum resistance, which could be accelerated through genetic engineering. Potato (Solanum tuberosum L.) is one of the most important food crops worldwide. In 2020, potato production was estimated to be more than 359 million tons according to the Food and Agriculture Organization (FAO). Potato is affected by many pathogens, among which Phytophthora infestans, causing late blight, is of the most economic importance. Crop protection against late blight requires intensive use of fungicides, which has an impact on the environment and humans. Therefore, new potato cultivars have been bred using resistance genes against P. infestans (Rpi genes) that originate from wild relatives of potato. Such programmes were initiated 100 years ago, but the process is complex and long. The development of genetic engineering techniques has enabled the direct transfer of resistance genes from potato wild species to cultivars and easier pyramiding of multiple Rpi genes, which potentially increases the durability and spectrum of potato resistance to rapidly evolving P. infestans strains. In this review, we summarize the current knowledge concerning Rpi genes. We also discuss the use of Rpi genes in breeding as well as their detection in existing potato cultivars. Last, we review new sources of Rpi genes and new methods used to identify them and discuss interactions between P. infestans and host.

Damage to the plant's photosynthetic system is known as the main symptoms of sensitivity to environmental stresses. Little is known about beneficial role of new chitosan compounds such as Kitoplus (R), and chitosan-coated nanomaterials on alleviation of adveres effects of drought stress in plants. In the present study, a factorial experiment was conducted in a split-plot manner based on a randomized complete block design (RCBD) with three replications to evaluate the effects of Kitoplus (R) growth stimulant and Chitosan-Coated Iron Oxide Nanoparticles (Fe-CTs NPS) on peppermint growth, chlorophyll fluorescence and essential oil biosynthesis under drought stress conditions. Treatments included three levels of drought stress (irrigation at soil moisture levels of 30%, 60%, and 90%), three concentrations of Kitoplus (R)(control without Kitoplus (R), 0.5% and 1%), and three concentrations of Fe-CTs NPs (control without Fe-CTs NPs, 5 and 10 mu M). Drought stress, growth stimulation treatment with Kitoplus (R), and Fe-CTs NPs had significant dual and triple effects on the studied physiological traits. According to the results, chlorophyll index and stomatal conductance were significantly lower in control plants than in those undergoing drought stress. Under 60% field capacity moisture conditions, the chlorophyll index was increased with 1% Kitoplus (R) treatment. The maximum fluorescence (Fm) and variable fluorescence (Fv) raised as the drought stress intensity increased. The highest Fm and Fv were observed in plants treated with 1% Kitoplus (R) and 10 mu M Fe-CTs NPS under 30% soil moisture stress. Results also showed that the highest value of menthone (33.31%) was obtained in plants treated with Kitoplus (R) at 1% and Fe-CTs NPs at 10 mu M under drought stress of 60% field capacity. In addition, the highest amount of menthol (26.5%) was observed in plants treated with 0.5% Kitoplus (R) under drought stress of 30% field capacity. The overall importance of the study lies in devising the simultaneous application of biostimulants and nanomaterials in enhancing essential oils production in the mint plant under drought stress challenges.

Tuber dry rot is an important disease of potato caused by soil and seed-borne pathogens of the Fusarium genus leading to losses that may reach 60% of the yield. The goal of this work was to study the inheritance of the dry rot resistance in two diploid potato hybrid populations (11–36 and 12–3) with complex pedigrees, including several wild Solanum spp. We used an aggressive isolate of F. sambucinum for phenotyping both progenies, parents, and standard potato cultivars in laboratory tuber tests, in three subsequent years. The QTL for dry rot resistance were mapped by interval mapping on existing genetic maps of both mapping populations. The most important and reproducible QTL for this trait was mapped on chromosome I and additional year- and population-specific QTL were mapped on chromosomes II, VII, IX, XI, and XII, confirming polygenic control of this resistance. This is the first study mapping the loci affecting tuber dry rot resistance in potato genome that can contribute to better understanding of potato-F. sambucinum interaction and to more efficient breeding of resistant potato cultivars.

The goal of this research was to identify quantitative trait loci (QTLs) for potato tuber resistance to the soil- and seedborne bacterium Dickeya solani and for tuber starch content, to study the relationship between these traits. A resistant diploid hybrid of potato, DG 00-270, was crossed with a susceptible hybrid, DG 08-305, to generate the F-1 mapping population. Tubers that were wound-inoculated with bacteria were evaluated for disease severity, expressed as the mean weight of rotted tubers, and disease incidence, measured as the proportion of rotten tubers. Diversity array technology (DArTseq) was used for genetic map construction and QTL analysis. The most prominent QTLs for disease severity and incidence were identified in overlapping regions on potato chromosome IV and explained 22.4% and 22.9% of the phenotypic variance, respectively. The second QTL for disease severity was mapped to chromosome II and explained 16.5% of the variance. QTLs for starch content were detected on chromosomes III, V, VI, VII, VIII, IX, XI, and XII in regions different from the QTLs for soft rot resistance. Two strong and reproducible QTLs for resistance to D. solani on potato chromosomes IV and II might be useful for further study of candidate genes and marker development in potato breeding programmes. The relationship between tuber resistance to bacteria and the starch content in potato tubers was not confirmed by QTL mapping, which makes the selection of genotypes highly resistant to soft rot with a desirable starch content feasible.

AbstractSoft rot is a bacterial disease that causes heavy losses in potato production worldwide. The goal of this study was to identify quantitative trait loci (QTLs) for potato tuber resistance to bacteriumDickeya solaniand for tuber starch content to study the relationship between these traits. A highly resistant diploid hybrid of potato was crossed with a susceptible hybrid to generate the F1 mapping population. Tubers that were wound-inoculated with bacteria were evaluated for disease severity expressed as the mean weight of rotted tubers, and disease incidence measured as the proportion of rotten tubers. Diversity array technology (DArTseq™) was used for genetic map construction and QTLs analysis. The most prominent QTLs for disease severity and incidence were identified in overlapping regions on potato chromosome IV and explained 22.4% and 22.9% of the phenotypic variance, respectively. The second QTL for disease severity was mapped to chromosome II and explained 16.5% of the variance. QTLs for starch content were detected on chromosomes III, V, VI, VII, VIII, IX, XI, and XII in regions different than the QTLs for soft rot resistance. Two strong and reproducible QTLs for resistance toDickeya solanion potato chromosomes IV and II might be useful for further study of candidate genes and marker development in potato breeding programs. The relationship between tuber resistance to bacteria and the starch content in potato tubers was not confirmed by QTL mapping, which makes the selection of genotypes highly resistant to soft rot with a desirable starch content feasible.

Fusarium is one of the most important genera of phytopathogenic fungi, causing potato wilt in the field and potato tuber dry rot during storage. The objectives of this study were to identify Fusarium species associated with both potato diseases in different growing regions in Algeria, and to assess their pathogenicity. Among the 152 isolates collected from symptomatic potato plants and tubers in different provinces in Algeria, 13 species of Fusarium and Neocosmospora were identified. Among these three species were isolated only from plants showing symptoms of Fusarium potato wilt (F. oxysporum, F. venenatum, Neocosmospora solani). Two species (F. culmorum, N. tonkinensis) and an isolate of Neocosmospora sp. were found exclusively in tubers with potato dry rot and the remaining ones (F. redolens, F. cf. tricinctum, F. sambucinum, F. cf. incarnatum-equiseti, F. nygamai, F. brachygibbosum and N. falciformis) were associated with both sample types. Fusarium sambucinum was the most frequent species (52.6% of isolates). Fusarium oxysporum and F. nygamai isolates were the most aggressive in the potato wilt pathogenicity test, and F. sambucinum isolates were the most aggressive in the potato tuber pathogenicity test. This is the first study identifying and characterizing potato dry rot and potato wilt pathogens in Algeria.

Interspecific somatic hybridization is a noteworthy breeding strategy that allows the production of novel genetic variability when crossing barriers exist between two parental species. Although the genetic consequences of somatic hybridization have been well documented, little is known on its impact at the epigenetic level. The objective of our research was to investigate the epigenetic changes, in particular DNA methylation, occurring in a population of potato somatic hybrids. The analysis of 96 Solanum × michoacanum (+) S. tuberosum somatic hybrids from five fusion combinations and their parents was carried out by methylation-sensitive amplified polymorphism (MSAP) and high-performance liquid chromatography (HPLC) methods. Six MSAP primer combinations generated 622 unique bands, of which 295 were fully methylated. HPLC analysis showed from 15.5% to 16.9% total cytosine methylation within the parental forms. Overall, the MSAP and HPLC methods indicated an increase in DNA methylation in the somatic hybrids in comparison to their parents. Among the latter, a lower degree of DNA methylation in the wild S. × michoacanum species than S. tuberosum was found. Our findings indicated that somatic hybridization changed the level of cytosine methylation in the studied potato somatic hybrids.

Among different types of potato cytoplasmic genomes, some are associated with male sterility or affect agronomic traits. The goal of this study was to analyze types of chloroplast and mitochondrial genomes of selected potato relatives originating from collection of the Institute of Plant Industry, Saint Petersburg, Russia, and preserved in Poland. Using chloroplast and mitochondrial markers the cytoplasm types were determined for 401 genotypes belonging to 43 seed accessions of 28 Solanum species. Among characterized genotypes, 201 (50.1%), 156 (38.9%) and 44 (11%) had cytoplasm types W, D, M, respectively. No accessions with the T, P or A cytoplasm were found. Within cytoplasm W, genotypes with the subtypes: W/α and W/β were identified, but not with W/γ. In S. famatinae, we detected unusual product of the T marker with 65 bp insertion earlier seen exclusively in S. vernei. Among the genotypes of S. leptophyes, two profiles of the ALM_4/ALM_5 marker were observed. S. famatinae and S. vernei come from Argentina, provinces Catamarca and Tucumán. Possibly the insertion in marker T occurred independently in two species, or the accessions were misidentified. Segregation of the ALM_4/ALM_5 marker within S. leptophyes indicates that potato seed accessions are heterogeneous not only due to nuclear DNA polymorphisms but have diversified cytoplasm, too. Our findings are important for exploitation of the tested material in potato breeding. Male-fertile cytoplasm types give a chance of avoiding fertility problems and widening the range of crosses in future generations of breeding materials.

Late blight is a disease with the biggest economic impact on potato cultivation worldwide. Pyramiding of the resistance genes originating from potato wild relatives is a breeding strategy that has a potential to produce potato cultivars durably resistant to late blight. Growing such cultivars would allow limiting the intensive chemical control of the disease. The goal of this work was to transfer the late blight resistance gene Rpi-rzc1 from Solanum ruiz-ceballosii to the tetraploid level of cultivated potato and to pyramid it with the Rpi-phu1 gene . We obtained two diploid and, through 4x-2x cross, a tetraploid potato population segregating for the Rpi-rzc1 presence, as well as one diploid and one tetraploid population where both genes were introgressed. In total, 754 progeny clones were tested for resistance to late blight in detached leaflet assays. Pathogen isolates avirulent on plants with both genes and virulent on plants with the Rpi-phu1 were used. The selection was assisted by two PCR markers flanking the Rpi-rzc1 gene and a newly designed, highly specific intragenic marker indicating the Rpi-phu1 gene presence. We obtained 26 diploid and 49 tetraploid potato clones with pyramid of both genes that should enhance the durability and spectrum of their late blight resistance and that can be exploited in potato breeding. The specificity of the marker for the Rpi-phu1 gene and the precision of the Rpi-rzc1 mapping were improved in this work.