In vitro shoot culture and cryopreservation (CP) are techniques essential for the ex situ preservation of genetic resources and the production of plant propagation material of clonally propagated horticultural crops. Changes in plant-associated microbiota diversity and composition induced by in vitro cultivation and CP treatment could have a negative effect on the growth and ex vitro adaptation of the in vitro propagated shoots. Therefore, the aim of the present study was to assess changes in endophytic bacteria diversity in domestic apple tissues induced by in vitro cultivation and CP treatment and to investigate the potential of the bacterial inoculum to improve the rooting and ex vitro acclimatisation of the propagated shoots. Metataxonomic analysis revealed a variation in the endophytic bacteria diversity and taxonomic composition between the field-grown tree dormant bud and the in vitro propagated or CP-treated shoot samples of apple cv. Gala. Whereas Sphingobacteriaceae, Sphingomonadaceae, Pseudomonadaceae, and Beijerinckiaceae families were the most prevalent families in the bud samples, Enterobacteriaceae, Bacillaceae, and Lactobacillaceae were dominant in the in vitro shoots. The bacterial inoculum effect on rooting and ex vitro acclimatisation was assessed using four isolates selected by screening the endophytic isolate collection. Bacillus sp. L3.4, B. toyonensis Nt18, or a combined inoculum resulted in a 21%, 36%, and 59% increase in cumulative root length and a 41%, 46%, and 35% increase in the biomass accumulation of ex vitro acclimatised plantlets, respectively. Root zone microbiota functional diversity analysis implied that growth stimulation was not related to improved nutrient uptake but could involve a pathogen-suppressing effect. The results demonstrate that the application of plant growth-promoting bacteria can potentially improve the performance of the in vitro propagated germplasm.

Abstract Background In vitro cultivation and cryopreservation techniques are essential tools for genetic diversity conservation and pathogen-free plant propagation of horticultural crops. The optimisation of cryopreservation protocols typically focuses on minimising the negative effects of pretreatment with cryoprotectors (CPs), cryogenic freezing (CF) treatment, and recovery procedures on explants. However, the impact of in vitro and CF techniques on plant-associated microbiota remains poorly understood, and their potential to improve plant adaptation after cryopreservation is underexplored. The aim of the present study was to investigate in vitro shoot culture and cryopreservation-induced changes in the endophytic bacterial diversity of two sweet cherry cultivars and to assess the potential of an inoculum of bacterial isolates to improve the growth of shoot culture after CF. Results Cultivars ‘Sunburst’ and ‘Mindaugė’ showed different responses to cold hardening preconditioning as well as different survival and regrowth rates after cryopreservation. Metataxonomic analysis revealed variation in the abundance and taxonomic composition of bacteria assigned to 35 families in samples of field-grown tree leaves, dormant buds, and in vitro shoot culture before and after CF treatment. Bacillaceae and Enterobacteriaceae bacteria were predominant in the leaf samples of both cultivars. For ‘Sunburst’, Pseudomonadaceae and Sphingomonadaceae bacteria were dominant in dormant buds and in vitro shoots, respectively, while Burkholderiaceae was largely predominant in the shoots following CF treatment. Conversely, ‘Mindaugė’ tissues exhibited more consistent colonisation by Bacillaceae and Enterobacteriaceae across the experimental groups, except for in vitro shoots where Mycobacteriaceae prevailed. A pure bacterial isolate inoculum was applied to the ‘Mindaugė’ shoot culture to counter the CF treatment-induced suppression of shoot growth (~ 40%). Cocultivation with Brevibacterium sp. S1-2, Bacillus cereus S1-3, or B. toyonensis Nt18 increased the shoot leaf area from 48 to 75%. Conclusions This study revealed that endophytic bacterial diversity is significantly reduced under in vitro conditions, often leading to a genotype-specific increase in the abundance and dominance of bacteria attributed to a single bacterial family. Moreover, shoot cocultivation with endophytic bacterial isolates has potential for improving the recovery of in vitro shoots after cryopreservation.

The aim of this study was to evaluate phenotypic traits and genetic diversity of the 13 tomato (Solanum lycopersicum L.) varieties and 6 hybrids developed at the Institute of Horticulture Lithuanian Research Centre for Agriculture and Forestry (LRCAF IH). For the molecular characterisation, seven previously published microsatellite markers (SSR) were used. A24 and 26 alleles were detected in tomato varieties and hybrids, respectively. Based on the polymorphism information content (PIC) value, the most informative SSR primers for varieties were TMS52, TGS0007, LEMDDNa and Tom236-237, and the most informative SSR primers for hybrids were SSR248 and TMS52. In UPGMA cluster analysis, tomato varieties are grouped in some cases due to genetic relationships, as the same cluster cultivars ‘Viltis’ (the parent of cv. ‘Laukiai’) and ‘Aušriai’ (the progeny of cv. ‘Jurgiai’) are present. The grouping of all hybrids in the dendrogram is related to the parental forms, and it shows the usefulness of molecular markers for tomato breeding, as they can be used to trace the origin of hybrids and, eventually, varieties accurately. The knowledge about the genetic background of Lithuanian tomato cultivars will help plan targeted crosses in tomato breeding programs.

A freely available Monilinia spp. marker database was created, containing microsatellite (SSR) data of the three most essential European fungal pathogens: M. fructigena, M. laxa, and M. fructicola. These pathogens cause brown rot blossom blight. Microsatellites were identified using the bioinformatics tool Genome-wide Microsatellite Analyzing Toward Application (GMATA). The database provides information about SSR markers: forward and reverse sequences of the primers, fragment sizes, SSR motifs (and repeats), and the exact locations with the coordinates in the reference genome. This database currently contains information about 39,216 SSR motifs and 26,366 markers. In total, eight primers generated in silico were validated experimentally and they are marked in the database. All scientists can join this collaboration by adding their experimental data. This database is the initial start of organizing Monilinia spp. molecular data worldwide and, in the future, it could be extended by adding more molecular and genomic information.

Apple-tree (Malus × domestica Borkh.) belongs to the genus Rosaceae. Due to its adaptability and tolerance to different soil and climatic conditions, it is cultivated worldwide for fresh consump-tion. Therefore, the priorities of apple growers are the high-quality of fruits and stable yield for high production. In total about 90 to 95 percent of fruits should fall or be eliminated from apple trees to avoid overcropping and poor-quality fruits. Several technologies such as handwork, me-chanically or chemical substances are used for fruit and bud elimination. The most profitable in commercial orchards is the use of chemicals for elimination, but due to the European Green Deal more environmentally sustainable solutions are required. Elimination of fruitlets is influenced by several factors. Additionally, the apple trees have the self-elimination mechanism. This is de-termined by apple genotype, physiological futures and genetics. This review focuses on the bio-logical factors and genetics mechanisms in apple yield self-regulation for better understanding the regulatory mechanism of fruitlets abscission for future breeding programs targeted on self-regulating yield apple varieties

The apple tree (Malus × domestica Borkh.) belongs to the Rosaceae. Due to its adaptability and tolerance to different soil and climatic conditions, it is cultivated worldwide for fresh consumption. The priorities of apple growers are high-quality fruits and stable yield for high production. About 90 to 95 percent of fruits should fall or be eliminated from apple trees to avoid overcropping and poor-quality fruits. Apple trees engage in a complex biological process known as yield self-regulation, which is influenced by several internal and external factors. Apple buds develop in different stages along the branches, and they can potentially give rise to new shoots, leaves, flowers, or fruit clusters. The apple genotype determines how many buds will develop into fruit-bearing structures and the capacity for yield self-regulation. Plant hormones such as ethylene, cytokinins, auxins, and gibberellins play a crucial role in regulating the fruit set, growth, and development, and the balance of these hormones influences the flowering intensity, fruit size, and fruit number on the apple tree. Apple growers often interfere in the self-regulation process by manually thinning fruit clusters. Different thinning methods, such as by hand, mechanical thinning, or applying chemical substances, are used for flower and fruit thinning. The most profitable in commercial orchards is the use of chemicals for elimination, but more environmentally sustainable solutions are required due to the European Green Deal. This review focuses on the biological factors and genetic mechanisms in apple yield self-regulation for a better understanding of the regulatory mechanism of fruitlet abscission for future breeding programs targeted at self-regulating yield apple varieties.

Terminalia superba and T. ivorensis are difficult to identify with morphological markers. Molecular characterization is very effective to correct the delimitation of timber species, especially when the discriminatory power of morphological markers is weak. In this study, four amplified fragment length polymorphism (AFLP) marker combinations were used to determine the taxonomic relationship among a total of 33 accessions of the genus Terminalia, consisting of two species, Terminalia ivorensis (12 accessions) and T. superba (21). The primer combinations produced a total of 740 fragments out of which 619 (83.6%) were polymorphic. Among all the primer combinations used, E-ACT/M-CTC was the most informative, which generated 11 unique markers for clear identification of the two species. The average polymorphic information content (PIC) ranged from 0.24 (E-ACT/M-CAT) to 0.28 (E-ACT/M-CTC) while the resolving power (RP) varied from 40.73 (E-AAC/M-CTA) to 63.76 (E-ACT/M-CTC). The genetic difference between the two species was significant (PhiPT = 0.610, p<0.001). All 33 accessions were delimited by both the UPGMA cluster and principal component analysis. Based on the results, it was concluded that E-ACT/M-CTC is the best among the marker combinations used for molecular study of the two tree species and used significantly to distinguish them. STRUCTURE analysis identified two accessions of Terminalia superba with alleles derived from T. ivorensis as well as revealed five putative hybrid accessions, which requires further genetic investigation to substantiate the finding.

This study aimed to understand the differences in the performance of diploid and tetraploid daylily cultivars under water deficit conditions, which are essential indicators of drought tolerance. This research revealed that tetraploid daylilies performed better than diploid varieties in arid conditions due to their enhanced adaptability and resilience to water deficit conditions. The analysis of the results highlighted the need to clarify the specific physiological and molecular mechanisms underlying the enhanced drought tolerance observed in tetraploid plants compared to diploids. This research offers valuable knowledge for improving crop resilience and sustainable floricultural practices in changing environmental conditions. The morphological and physiological parameters were analyzed in 19 diploid and 21 tetraploid daylily cultivars under controlled water deficit conditions, and three drought resistance groups were formed based on the clustering of these parameters. In a high drought resistance cluster, 93.3% tetraploid cultivars were exhibited. This study demonstrates the significance of ploidy in shaping plant responses to drought stress. It emphasizes the importance of studying plant responses to water deficit in landscape horticulture to develop drought-tolerant plants and ensure aspects of climate change.

Plants inhabiting environments with suboptimal growth conditions often have a more pronounced capacity to attract and sustain microbial communities that improve nutrient absorption and expand abiotic stress tolerance. Rhodiola rosea L. is a succulent plant of the Crassulaceae family adapted to survive in sandy or rocky soils or dry tundra. The aim of the present study was to investigate the diversity and plant growth-stimulating potential of R. rosea endophytic microbiota. Metataxonomic analysis of the bacterial diversity in the rhizome of R. rosea revealed 108 families. Among these, three families were found exclusively in the core microbiome of 1-year-old plants, while nine families were unique to the core microbiome of mature plants grown in the field for more than 4 years. Seventy-three endophytic bacteria isolates were obtained from the rhizome of R. rosea plants and were assigned into 14 distinct bacterial genera of Firmicutes (26%) or Proteobacteria (74%) phyla. Screening for functional genes related to the nitrogen cycle, phosphorus mineralisation or dissolution, and traits associated with nitrogen fixation (56% of isolates), siderophore production (40%), inorganic phosphorus solubilisation (30%), and production of indole-related compounds (51%) led to the classification of the isolates into 16 distinct clusters. Co-cultivation of 45 selected isolates with germinating Arabidopsis seedlings revealed 18 and 5 isolates that resulted in more than a 20% increase in root or shoot growth, respectively. The study results established the complexity of the succulent R. rosea endophytic microbiome and identified isolates for potential plant growth-stimulating applications.

Six sweet cherry cultivars and two advanced selections of Gisela 5 rootstock were tested in 2015–2021 at the Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry. Fruit trees were planted at distances of 4.5 × 2.5 m and trained as spindles. Orchard floor management included frequently mown grass in alleyways with herbicide strips along tree rows. Cultivars ‘Mindaugė’ and ‘Irema BS’ were the most vigorous at the end of the seventh leaf. Their trunk diameter achieved 11.6 cm. The ‘Merchant’ cultivar had the smallest trunk diameter—9.3 cm. The average yield in 2018–2021 ranged from 2.75 t/ha for ‘Vega’ to 8.73 t/ha for ‘Regina’. Cultivars ‘Regina’, ‘Sunburst’, ‘Irema BS’ and ‘Merchant’ had the highest cumulative yield efficiency of 0.440–0.503 kg/cm2 with respect to the trunk cross-section area (TCSA). The least productive cultivar ‘Vega’ produced fruits of the highest average weight—9.9 g. Fruits of ‘Regina’ and ‘Sunburst’ were large as well—8.8–9.1 g. ‘Irema BS’ fruits had the highest soluble solids content (SSC)—20.2%. The lowest SSC was recorded in ‘Merchant’ and ‘Sunburst’ fruits—14.7–15.8%. The yield of advanced selection, No. 102, equaled to the yield of cv. ‘Regina’. No. 102 had a high fruit weight, and fruits were distinguished by attractiveness and taste.

This work aims to characterize the genetic diversity of species, early hybrids, and cultivars using microsatellite simple sequence repeat (SSR) markers, as well as analyze and identify the origin of Hemerocallis spp. early hybrids. For this research, samples were collected from different types of daylily species, early hybrids (known or hypothetically first-generation hybrids from Hemerocallis species), foreign, and Lithuanian varieties. An initial screening of SSR primers developed for Hemerocallis citrina was performed, and their suitability for testing other daylily species and hybrids was evaluated. The genetic diversity was assessed with the selected eight-primer set, and molecular SSR profiles were created. Primer SAU00097 is the most informative according to heterozygosity (0.95) and polymorphism information content (PIC) (0.17). The highest heterozygosity was observed in Lithuanian cultivars (0.713), the lowest in species (0.583). Genetic relationships between species show that only fulvous daylilies are separated into a different cluster. The highest variation among genotypes was observed in the species group (18%), while modern cultivars had the slightest variation among genotypes (1%). The putative origin of early hybrids was analyzed using a likelihood heatmap of all genotypes. Results show what species might be used in breeding for early hybrids. Several modern diploid and tetraploid daylily cultivars have triploid species as ancestors.

Chromosome doubling in ornamental plants, as shown by our study in daylilies (Hemerocallis spp.), has great potential to increase tolerance to abiotic stress. Drought is the most critical growth-limiting factor in a changing climate. Drought tolerance is one of the decisive factors for the survival, productivity, and appearance of perennial ornamental plants. Understanding and elucidating the molecular mechanisms that determine plant response to abiotic stress is essential. De novo transcriptome assembly of diploid and autotetraploid Hemerocallis spp. cv. Trahlyta was performed under artificially induced stress to elucidate the molecular mechanisms related to plant response to drought. In daylily mRNA, 237,886 transcripts were detected, and 42.4% of them were identified as annotated unigenes. In the experiment, diploid plants were more stressed, with 2871 upregulated or downregulated DEGs (differentially expressed genes) responding to drought, while tetraploid plants had 1599 DEGs. The proportion of upregulated DEGs differed by 1.3 times between diploid and autotetraploid genotypes, whereas the proportion of downregulated DEGs was 1.8 times greater in diploid plants. Signaling pathways related to the drought response were activated in daylilies, and key candidate genes were identified in both ploidy genotypes. In autotetraploid plants, more drought-related pathways were activated than in diploids—43 and 19, respectively. The most abundant DEGs in both cases were KEGG (Kyoto Encyclopedia of Genes and Genomes), metabolic (ko01100), and biosynthesis of secondary metabolites (ko01110) pathways. Summarizing the data, it was found that autotetraploid plants of the daylily have a wider potential for adaptation to drought stress. Therefore, they adapt faster and better to adverse drought conditions by activating alternative signaling pathways. The comparative transcriptome analysis of diploid and autotetraploid plants allows us to understand the molecular mechanisms of drought resistance and it is also essential for daylily breeding programs to develop drought-resistant genotypes in the future.

This study’s aim was to evaluate the genetic diversity of European plum (Prunus domestica) cultivars and hybrids in Lithuania using SSR markers. In total, 107 plum genotypes (including 68 European plum cultivars and 39 hybrids) from the genetic resources collection of the Institute of Horticulture of the Lithuanian Research Centre for Agriculture and Forestry (LRCAF IH) were evaluated using nine microsatellite markers (SSRs) previously published and suggested by the European Cooperative Programme for Plant Genetic Resources (ECPGR). Up to six alleles per locus with each primer pair were generated for some genotypes due to the hexaploidy of plums. The number of alleles in each primer ranged from 18 to 30, with an average of 24.33. The highest number of alleles was generated with the PacA33 primer pair (30). The most informative primer, according to the PIC value, was BPPCT007. Sixty-two unique alleles (representing 39.5% of all polymorphic alleles) have been detected in the plum germplasm developed in Lithuania. According to UPGMA cluster analysis, 58 European plum genotypes were separated into eight groups without any relation to fruit color or shape. By genetic diversity (UPGMA) and structure (Bayesian) analysis, European plum hybrids were grouped into clusters according to their pedigree.

ABSTRACT The goal of this research was to evaluate the effect of light, temperature, sucrose and PEG on the growth of Fragaria vesca in vitro and the expression of regulatory Myb10, WD40 and enzyme-coding genes CHI, CHS, DFR, EGL, F3H and UFGT , which are essential for anthocyanin biosynthesis. We observed plants’ response to osmotic stress, the decrease in growth and microshoot weight. A change in the expression of the investigated genes was evident under the suboptimal concentration of sucrose. The addition of PEG to the medium caused a decrease in microshoot weight and gene expression. Blue + red lights of the LED lighting system significantly affected microshoot growth in vitro . Red and blue + red + UV lights slightly reduced microshoot weight and caused a reddish colour of petioles, which indicate increased anthocyanin synthesis. Moreover, most of the studied genes’ expression tended to increase when shoots were exposed to blue, blue + red and blue + red + UV lights. A temperature of 15°C (vs 22°C) significantly reduced the mean fresh weight of microshoots while increasing CHI and CHS gene expression and decreasing WD40 gene expression. Exposure to a higher temperature (30°C) induced the vitrification of microshoots, although the fresh weight did not differ from that of the control. Gene expression also depended on the duration of exposure. In the case of CHS , gene expression remained the same or increased after exposure for 1 week and then decreased after exposure for 4 weeks.

In response to pathogen attacks, plants activate a complex of defense mechanisms including an accumulation of the endogenous signaling compounds salicylic acid and jasmonic acid. The activity of pathogenesis-related genes (PRs) and coronatine-insensitive 1 (COI1) in defense-response pathways are established in plants. The aim of this study was to identify homologs of the PRs and COI1 in blackcurrants. Primers with degenerate nucleotides were designed based on the most conservative parts of PR1 and COI1 genes from other plants and applied for amplification of specific fragments of PRs and COI1 in Ribes spp. Seven heterogeneous sequences of PR with a diversity of 66.0–98.3% at nucleic acid level were found. The phylogenetic analysis revealed the dependence of R. nigrum PR homologs on the PR1 and PR6 families. Four heterogeneous sequences of R. nigrum COI1 with an identity of 95.9–98.8% at nucleic acid level were isolated. Specific primers for newly detected genes’ homologs were designed in this study and could be useful for evaluating the defense response to pathogen attacks in blackcurrants.

Plant in vitro cultures initiated from surface-sterilized explants often harbor complex microbial communities. Antibiotics are commonly used to decontaminate plant tissue culture or during genetic transformation; however, the effect of antibiotic treatment on the diversity of indigenous microbial populations and the consequences on the performance of tissue culture is not completely understood. Therefore, the aim of this study was to assess the effect of antibiotic treatment on the growth and stress level of tobacco ( Nicotiana tabacum L.) shoots in vitro as well as the composition of the plant-associated microbiome. The study revealed that shoot cultivation on a medium supplemented with 250 mg L −1 timentin resulted in 29 ± 4% reduced biomass accumulation and a 1.2–1.6-fold higher level of oxidative stress injury compared to the control samples. Moreover, the growth properties of shoots were only partially restored after transfer to a medium without the antibiotic. Microbiome analysis of the shoot samples using multivariable region-based 16S rRNA gene sequencing revealed a diverse microbial community in the control tobacco shoots, including 59 bacterial families; however, it was largely dominated by Mycobacteriaceae . Antibiotic treatment resulted in a decline in microbial diversity (the number of families was reduced 4.5-fold) and increased domination by the Mycobacteriaceae family. These results imply that the diversity of the plant-associated microbiome might represent a significant factor contributing to the efficient propagation of in vitro tissue culture.

The most damaging pathogen in blackcurrant plantations is mite-transmitted blackcurrant reversion virus (BRV). Some Ribes species have an encoded genetic resistance to BRV. We performed RNA sequencing analysis of BRV-resistant blackcurrant cv. Aldoniai to evaluate the molecular mechanisms related to the BRV infection response. The RNA of virus-inoculated and mock-inoculated microshoots was sequenced, and the transcriptional changes at 2- and 4-days post inoculation (dpi) were analyzed. The accumulation and expression of BRV RNA1 were detected in infected plants. In total, 159,701 transcripts were obtained and 30.7% were unigenes, annotated in 7 databases. More than 25,000 differentially expressed genes (DEGs) according to FPKM were upregulated or downregulated. We observed 221 and 850 DEGs at 2 and 4 dpi, respectively, in BRV-infected microshoots related to the stress response. The proportion of upregulated DEGs at 4 dpi was about 3.5 times higher than at 2 dpi. Pathways of the virus defense response were activated, and key candidate genes were identified. The phenylpropanoid and the cutin, suberine, and wax biosynthesis pathways were activated in infected plants. Our comparative de novo analysis of the R. nigrum transcriptome provides clues not only for understanding the molecular BRV resistance mechanisms but also for breeding BRV-tolerant genotypes.

Blackcurrant reversion virus (BRV) is the most destructive currant-infecting and mite-transmitted pathogen from the genus Nepovirus. In this work, BRV transmission in the system Ribes ex vitro–Ribes in vitro was applied for the first time. Triple infection of BRV identified in blackcurrant cv. Gojai was used for phylogenetic analysis and inoculation assay. Transmission of BRV was successful due to its stability in the inoculum for up to 8 days at 4 °C; all BRV isolates were infectious. Our suggested inoculation method through roots was applied in six Ribes spp. genotypes with 100.0% reliability, and the expression levels of defence-related gene PR1 to biotic stress was observed. The prevalence of the virus in microshoots after 2–14 days post-inoculation (dpi) was established by PCR. In resistant genotypes, the BRV was identified up to 8 dpi; meanwhile, infection remained constant in susceptible genotypes. We established that BRV transmission under controlled conditions depends on the inoculum quality, post-inoculation cultivation temperature, and host-plant susceptibility to pathogen. This in vitro inoculation method opens possibilities to reveal the resistance mechanisms or response pathways to BRV and can be used for the selection of resistant Ribes spp. in breeding programs.

Daylily (Hemerocallis L.) is a popular herbaceous perennial ornamental plant. The American Hemerocallis Society (AHS) currently has over 96,000 cultivars registered. Of these, half are tetraploids (4x), and the other half are diploids (2x). To enrich the breeding lines of tetraploid daylilies, colchicine is the most widely used. During the experiment, oryzalin (ORZ) and colchicine (CLC) were used for the polyploidisation of daylilies. Germinating seeds derived from diploid and tetraploid daylily cultivars as maternal plants were exposed to solutions of ORZ and CLC at different concentrations. Ploidy of seedlings was determined after six months by flow cytometry, and the obtained results were related to the size of the stomata. Chimerism of the young side shoots developing on treated plants was assessed three years after polyploidisation by checking the ploidy using a flow cytometer. It has been found that whole-genome duplication is not common in daylilies during polyploidisation of germinating seeds - triploids (3x), pentaploids (5x), hexaploids (6x), and heptaploids (7x) were obtained. The optimal concentration of CLC for induction higher ploidy was 125-250 mu mol when exposed to seeds of the diploid maternal plant (DMP) and 250-500 mu mol when exposed to the tetraploid maternal plant (TMP) one. In the case of ORZ, optimal treatments were 10 mu mol for germinating DMP seeds and 40 mu mol for TMP seeds, respectively. Stomata size can preliminarily determine daylily ploidy. A flow cytometry should be used for a more accurate determination of ploidy. Individuals treated with antimitotic agents are prone to chimerism. The most extensive ploidy variation observed in individuals with uneven ploidy is usually in the direction of even ploidy. Therefore, the ploidy of clones used for breeding should be checked regularly.

The present study evaluated genetic diversity of Lithuanian populations of Lythrum salicaria in relation to parameters of riparian environment. Growing along Nemunas, Seaside and Lielupė river basins, 15 populations were examined using amplified fragment length polymorphism markers. Molecular data were related to the river basins, type of land use and cover, natural vice versa regulated fragments of the rivers. Population mean genetic diversity parameters were as follows: percentage of polymorphic loci (57.2), expected heterozygosity (0.183), polymorphismc information content (0.218). Mantel test revealed correlation (R2 = 0.0986, p = 0.01) between genetic and geographic distance of populations. Greater genetic diversity within, rather than among populations (ΦPT = 0.213) was observed. According to the Bayesian clustering, studied populations are admixtures of two gene pools. Analysis of molecular variance revealed significant differentiation between populations belonging to distinct river basins, between populations from natural vs. regulated fragments of the rivers.