Natural Plant Populations Research Articles

Plant invasion alters latitudinal pattern of plant-defense syndromes.

The relationship between herbivory and latitude may differ between native and introduced populations of invasive plants, which can generate latitudinal heterogeneity in the strength of enemy release. However, still little is known about how latitudinal heterogeneity in herbivore pressure influences latitudinal variation in defense phenotypes of invasive plants. We tested how latitudinal patterns in multi-variate defense syndromes differed between native (Argentinian) and introduced (Chinese) populations of the invasive herb Alternanthera philoxeroides. In addition, to better understand the drivers underlying latitudinal patterns, we also tested whether associations of defense syndromes with climate and herbivory differed between native and introduced ranges. We found that native plant populations clustered into three main defense syndromes associated with latitude. In contrast, we only found two defense syndromes in the introduced range. One matched the high-latitude syndrome from the native range, but was distributed at both the northern and southern range limits in the introduced range. The other was unique to the introduced range and occurred at mid-latitudes. Climatic conditions were associated with variation in syndromes in the native range, and climatic conditions and herbivory were associated with variation in syndromes in the introduced range. Together, our results demonstrate that plants may under the new environmental conditions in the introduced range show latitudinal patterns of defense syndromes that are different from those in their native range. This emphasizes that geographical dependence of population differentiation should be explicitly considered in studies on the evolution of defense in invasive plants.

Increased CG, CHG and CHH methylation at the cycloidea gene in the “Peloria” mutant of Linaria vulgaris

Heritable DNA methylation variation is frequently observed in natural populations of plants, but is thought mostly to be functionally inconsequential. An exception to this is the “Peloria” mutant of Linaria vulgaris, which was originally described by Carl von Linné in 1744. A study in 1999 found that the Peloria phenotype is caused by an epiallele of the L. vulgaris cycloidea homolog Lcyc that showed increased levels of DNA methylation compared to wild-type. The DNA methylation results in silencing of Lcyc, which causes radial flower symmetry in the peloric mutant, whereas wild-type plants have flowers with bilateral symmetry. However, a detailed view of DNA methylation at Lcyc at the single-nucleotide level has not been available.In this study, we investigated DNA methylation at Lcyc and, as a control, at the LvHIRZ gene in wild-type and peloric plants of L. vulgaris using DNA bisulfite treatment coupled to next-generation sequencing. We found strong increases in CHG and CHH methylation at Lcyc, but not LvHIRZ, in Peloria. CG methylation was also increased, but wild-type Lcyc also showed moderate levels of CG methylation. Our results suggest that DNA methylation in all three sequence contexts has been maintained, and potentially transgenerationally inherited, in the peloric L. vulgaris population over decades or even centuries.

Flower Color Evolution and the Evidence of Pollinator-Mediated Selection.

The evolution of floral traits in animal-pollinated plants involves the interaction between flowers as signal senders and pollinators as signal receivers. Flower colors are very diverse, effect pollinator attraction and flower foraging behavior, and are hypothesized to be shaped through pollinator-mediated selection. However, most of our current understanding of flower color evolution arises from variation between discrete color morphs and completed color shifts accompanying pollinator shifts, while evidence for pollinator-mediated selection on continuous variation in flower colors within populations is still scarce. In this review, we summarize experiments quantifying selection on continuous flower color variation in natural plant populations in the context of pollinator interactions. We found that evidence for significant pollinator-mediated selection is surprisingly limited among existing studies. We propose several possible explanations related to the complexity in the interaction between the colors of flowers and the sensory and cognitive abilities of pollinators as well as pollinator behavioral responses, on the one hand, and the distribution of variation in color phenotypes and fitness, on the other hand. We emphasize currently persisting weaknesses in experimental procedures, and provide some suggestions for how to improve methodology. In conclusion, we encourage future research to bring together plant and animal scientists to jointly forward our understanding of the mechanisms and circumstances of pollinator-mediated selection on flower color.

New insights for the production of medicinal plant materials: Ex vitro and in vitro propagation of valuable Lamiaceae species from northern Africa

The overuse of natural medicinal plants forces the search for alternative production techniques to meet the growing needs, compensate for habitat degradation and conserve natural populations of plants. This study investigated the macropropagation and micropropagation of four medicinal plants from the Lamiaceae family growing in Algeria: Thymus algeriensis Boiss & Reut., Rosmarinus officinalis L., Marrubium vulgare L. and Salvia officinalis L. This baseline study aimed to describe biotechnology techniques that will help in restoring these important species and the developed callus culture can be a source of pharmaceutically important metabolites. It included two experiments: In Experiment 1, macrocuttings of 10−15 cm were cultivated in plastic pots containing soil and submitted in open greenhouse conditions. The rates of developed cuttings into whole plants were estimated. Experiment 2: segments of 5 mm taken from young stems were washed, sterilized using 0.1 % HgCl2 and then cultured on semi-solid Murashige and Skoog (MS) medium supplemented with various combined concentrations of plant growth regulators (PGRs): indole-3-acetic acid (IAA) and Kinetin or N-6-furfuryladenine (Kin). The explants were incubated in a photoperiod (16 h light/25 °C, 8 h dark/15 °C) in a phytotron. The rates of callogenesis and caulogenesis were evaluated for different IAA/Kin combinations. The obtained results from macropropagation experiment showed significant differences (P < 0.001) in regeneration rates between the plant species. Salvia officinalis presented the highest success rate of regeneration (100 %) compared to other plants that showed low success rates. The combinations between IAA and Kin exhibited significant effects (P < 0.05 and P < 0.001) on callogenesis and caulogenesis. The best results of callus formation in T. algeriensis were observed at the combination of (5 mg/L IAA, 5 mg/L Kin) and (5 mg/L IAA, 10 mg/L Kin) where regeneration rates reached 23.3 % and 20 % respectively. In R. officinalis, the greatest callus production was obtained at (2.5 mg/L IAA, 5 mg/L Kin) with a rate of 56.7 %. In M. vulgare, the highest callus formation was marked at (2.5 mg/L IAA, 2.5 mg/L Kin), (2.5 mg/L IAA, 5 mg/L Kin) and (5 mg/L IAA, 5 mg/L Kin) with success rates varied between 33.3 % and 36.7 %. While S. officinalis can be significantly regenerated through macrocutting, the application of IAA and Kin combinations influenced greatly callus and shoots proliferation in T. algeriensis, R. officinalis and M. vulgare in in vitro micropropagation. The caulogenesis scores were low in the three above plants. Whereas, S. officinalis did not show any organogenic changes with all PGR combinations.

Species diversity and biological trait function: Effectiveness of ant–plant mutualism decreases as ant species diversity increases

Abstract One of the major concerns of ecological and evolutionary research is the prediction of community function in relation to the degree of biodiversity. To clarify the relationship between biodiversity and the expression of plant defence traits, we investigated ant–plant defensive mutualism in the pioneer plant Mallotus japonicus at several sites across Japan. The plant bears ant‐attracting extrafloral nectar (EFN) and food bodies (FBs) as indirect defence traits. To reveal variations in ant–plant interactions in the field, we measured species richness of nectar‐feeding ants and interaction strength between each ant species and the plant (visiting frequency of each ant species to the plant). We also investigated the expression of EFNs and FBs in natural plant populations at the study sites. To assess the defensive quality of each ant species, we then experimentally estimated the aggressiveness of the dominant ant species. To examine the link between ant species richness and the defensive function of ants, we conducted an ant‐exclusion experiment and a common garden experiment to clarify whether the defence efficacy of ants varied in relation to ant species richness. Ant species richness differed among the study sites. We found negative relationships between ant species richness and the mean interaction strength of ant species, the interaction strength of aggressive ant species and the number of EFNs per leaf. The effectiveness of indirect defence by ants was poor at sites where ant species richness was high. When cultivated in the same environment, plants from sites with low ant species richness developed a larger number of EFNs per leaf than those from sites with high ant species richness. Our results suggest that facultative ant–plant defensive mutualism is weakened at sites where ant species richness is high, resulting in a decrease in the number of EFNs per leaf. Such a link between species richness and an indirect trait function may help us to understand the evolutionary patterns of various species traits in complex biological communities. A free Plain Language Summary can be found within the Supporting Information of this article.

Inheritance of DNA methylation differences in the mangrove Rhizophora mangle.

The capacity to respond to environmental challenges ultimately relies on phenotypic variation which manifests from complex interactions of genetic and nongenetic mechanisms through development. While we know something about genetic variation and structure of many species of conservation importance, we know very little about the nongenetic contributions to variation. Rhizophora mangle is a foundation species that occurs in coastal estuarine habitats throughout the neotropics where it provides critical ecosystem functions and is potentially threatened by anthropogenic environmental changes. Several studies have documented landscape-level patterns of genetic variation in this species, but we know virtually nothing about the inheritance of nongenetic variation. To assess one type of nongenetic variation, we examined the patterns of DNA sequence and DNA methylation in maternal plants and offspring from natural populations of R. mangle from the Gulf Coast of Florida. We used a reduced representation bisulfite sequencing approach (epi-genotyping by sequencing; epiGBS) to address the following questions: (a) What are the levels of genetic and epigenetic diversity in natural populations of R. mangle? (b) How are genetic and epigenetic variation structured within and among populations? (c) How faithfully is epigenetic variation inherited? We found low genetic diversity but high epigenetic diversity from natural populations of maternal plants in the field. In addition, a large portion (up to ~25%) of epigenetic differences among offspring grown in common garden was explained by maternal family. Therefore, epigenetic variation could be an important source of response to challenging environments in the genetically depauperate populations of this foundation species.

Producers, production, marketing, and sales of non-timber forest products in the United States: a review and synthesis

Non-timber forest products (NTFPs) are derived from natural populations of plants or fungi, or farmed in forests. Harvesters and producers often benefit from NTFPs by selling them to generate income. This article explores research on the producers, production, marketing, and sales of NTFPs in the United States, including the continuum of production from wild-harvesting to forest farming of NTFPs, and their costs and benefits. Specific examples are presented, but the concepts and generalizations are broadly applicable to many NTFPs throughout the U.S. and other parts of the world. Integrating NTFPs into forest management can enhance economic opportunities but also will increase complexity, and will entail balancing multiple and potentially conflicting objectives among a diverse community of stakeholders. We identify information gaps including the need for inventories and yield models of NTFPs, understanding the effect of silvicultural activities on NTFP survival and yield, time series and trends in collection of NTFPs by U.S. households, identification of vulnerable and marginalized communities associated with NTFP harvest, and harvesters’ motivations and drivers.

Intensity of grass invasion negatively correlated with population density and age structure of an endangered dune plant across its range

Invasive species are a global threat to ecosystem biodiversity and function; non-native grass invasion has been particularly problematic in sparsely vegetated ecosystems such as open dunes. Native plant population responses to invasion, however, are infrequently translated to landscape scales, limiting the effectiveness of these data for addressing conservation issues. We quantified population density, total population size, and age class distribution of the federally-endangered plant species Antioch Dunes evening primrose (Oenothera deltoides subsp. howellii), at sites along a non-native grass invasion gradient in California, USA. We then scaled relationships between invasion and plant density across the species’ range using spatial models and remote sensing data. Adult and juvenile O. deltoides subsp. howellii densities were more than 10 times higher in non-invaded areas (grids with 10% total plant cover) when compared to highly-invaded areas (grids with 80% total plant cover). The ratio of O. deltoides subsp. howellii juveniles to adults decreased to less than 1 at 54% total cover, highlighting sensitivity of the regeneration niche to invasion. Spatial models mapped hotspots of O. deltoides subsp. howellii abundance and population structure across the landscape at sub-meter scales. Scaling the impacts of increasing invasion on plant species of conservation concern holds promise when coupled with remote sensing approaches, especially in naturally low-cover ecosystems where readily available metrics (e.g., Normalized Difference Vegetation Index) can be used to quantify invasion. These spatial models inform how future invasive species management may influence population size and spatial distribution of species of conservation concern.

Inter-annual and spatial climatic variability have led to a balance between local fluctuating selection and wide-range directional selection in a perennial grass species.

The persistence of a plant population under a specific local climatic regime requires phenotypic adaptation with underlying particular combinations of alleles at adaptive loci. The level of allele diversity at adaptive loci within a natural plant population conditions its potential to evolve, notably towards adaptation to a change in climate. Investigating the environmental factors that contribute to the maintenance of adaptive diversity in populations is thus worthwhile. Within-population allele diversity at adaptive loci can be partly driven by the mean climate at the population site but also by its temporal variability. The effects of climate temporal mean and variability on within-population allele diversity at putatively adaptive quantitative trait loci (QTLs) were evaluated using 385 natural populations of Lolium perenne (perennial ryegrass) collected right across Europe. For seven adaptive traits related to reproductive phenology and vegetative potential growth seasonality, the average within-population allele diversity at major QTLs (HeA) was computed. Significant relationships were found between HeA of these traits and the temporal mean and variability of the local climate. These relationships were consistent with functional ecology theory. Results indicated that temporal variability of local climate has likely led to fluctuating directional selection, which has contributed to the maintenance of allele diversity at adaptive loci and thus potential for further adaptation.

Effects of Heterogeneous Environment After Deforestation on Plant Phenotypic Plasticity of Three Shrubs Based on Leaf Traits and Biomass Allocation

Phenotypic plasticity among natural plant populations is a species-specific ecological phenomenon of paramount importance that depends on their life forms, development stages, as well as environmental factors. While this phenomenon is broadly understood, it has hardly been observed in nature. This study aimed at understanding phenotypic plasticity and ecological adaptability in three shrubs (Salix etosia, Rubus setchuenensis, and Hydrangea aspera) affected by potential environmental variables after deforesting in sparse Larix spp. forest and tall shrub mixed secondary forests. Soil organic carbon content, total nitrogen content, and available nitrogen content were greater outside the forests, contrary to other measured factors whose availability was higher in the forest interiors. In case of leaf traits and stoichiometric indicators, there were significant interactions of leaf area (LA), leaf dry matter (DW), specific leaf area (SLA), and leaf phosphorus content (LPC) between shrub species and heterogeneous environments (P &amp;lt; 0.05) but not for leaf C/N, N/P, and C/P. Principal components analysis (PCA) indicated that soil temperature, pH value, soil carbon content, soil nitrogen content, and MBC and MBN mainly constituted the first component. Summarized results indicated that TB and leaf C/P of S. etosia were significantly correlated with three principal components, but only marginal significant correlations existed between R/S and relevant components. SLA and R/S of R. setchuenensis had marginal significant relationships with independent variables. Both SLA and TB of H. aspera were significantly correlated with three principal components. Based on the pooled values of leaf functional traits and leaf stoichiometric indicators, R. setchuenensis (vining type) had better leaf traits plasticity to adapt to a heterogeneous environment. In descending order, the ranks of biomass allocation plasticity index of three shrubs were H. aspera (bunch type), R. setchuenensis (vining type), and S. etosia (erect type). The highest integrated plasticity values of leaf traits and biomass allocation was observed in H. aspera (bunch type), followed by R. setchuenensis, and by S. etosia with less adaptive plasticity in heterogeneous environments.

Impacts of plant invasions in native plant-pollinator networks.

The disruption of mutualisms by invasive species has consequences for biodiversity loss and ecosystem function. Although invasive plant effects on the pollination of individual native species has been the subject of much study, their impacts on entire plant-pollinator communities are less understood. Community-level studies on plant invasion have mainly focused on two fronts: understanding the mechanisms that mediate their integration; and their effects on plant-pollinator network structure. Here we briefly review current knowledge and propose a more unified framework for evaluating invasive species integration and their effects on plant-pollinator communities. We further outline gaps in our understanding and propose ways to advance knowledge in this field. Specifically, modeling approaches have so far yielded important predictions regarding the outcome and drivers of invasive species effects on plant communities. However, experimental studies that test these predictions in the field are lacking. We further emphasize the need to understand the link between invasive plant effects on pollination network structure and their consequences for native plant population dynamics (population growth). Integrating demographic studies with those on pollination networks is thus key in order to achieve a more predictive understanding of pollinator-mediated effects of invasive species on the persistence of native plant biodiversity.

Effects of prescribed fire timing on grazing performance of yearling beef cattle, forage biomass accumulation, and plant community characteristics on native tallgrass prairie in the Kansas Flint Hills.

Recent research demonstrated that mid- or late-summer prescribed fires can be employed to manage sericea lespedeza (Lespedeza cuneata) infestations in the Kansas Flint Hills. The effects of prescribed fire applied during the growing season (i.e., August to October) on grazing performance of yearling cattle have not been evaluated. Native pastures (n = 18; 22 ± 4.0 ha) were grouped by watershed and assigned randomly to one of three prescribed-fire treatments: spring (7 April ± 2.1 d), summer (21 August ± 5.7 d), or autumn (2 October ± 9.9 d). Yearling beef cattle were grazed from May to August at a targeted stocking density of 280 kg live-weight/ha following prescribed-fire application. Forage biomass accumulations, soil cover, plant species composition, and root carbohydrate concentrations in four native plant species were evaluated. Total body weight (BW) gains and average daily gain were greater (P = 0.01) for cattle that grazed the spring and summer prescribed-fire treatments compared with those that grazed the autumn prescribed-fire treatment. As a result, final BW were greater (P = 0.04) in the spring and summer treatments than the autumn treatment. Conversely, forage biomass accumulations did not differ (P = 0.91) between fire regimes. Proportions of bare soil were greater (P < 0.01) in the spring treatment compared with the summer and autumn treatments, whereas proportions of litter on the soil surface were greater (P < 0.01) in summer- and autumn-burned pastures compared with spring-burned pastures. Total basal cover of graminoids and forbs did not differ (P ≤ 0.15) between prescribed fire treatments. Likewise, total basal cover of C3 or C4 perennial grasses did not differ (P ≥ 0.23) between prescribed-fire treatments. No treatment differences (P = 0.24) in root starch or root water-soluble carbohydrate concentrations in big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), Indiangrass (Sorghastrum nutans), or purple prairieclover (Dalea purpurea) were detected. These data were interpreted to suggest that summer or autumn prescribed fire can be applied without reducing forage biomass accumulations, root carbohydrate concentrations in key native plant species, or considerably altering native plant populations compared with conventional spring-season prescribed fire; however, summer prescribed fire could be favored over spring or autumn prescribed fire both to maintain stocker cattle growth performance and to achieve control over sericea lespedeza.

Opposing health effects of hybridization for conservation

AbstractThe continuing decline of many natural plant and animal populations emphasizes the importance of conservation strategies. Hybridization as a management tool has proven successful in introducing gene flow to small, inbred populations, but can be also associated with health risks. For example, hybridization can change susceptibility to infection in either direction due to heterosis (hybrid vigor) and outbreeding depression, but such health effects have rarely been considered in the genetic management of populations. Here, we investigated the effects of experimental outcrossing between the critically endangered Saimaa landlocked salmon (Salmo salar m. sebago) and the genetically more diverse Atlantic salmon (S. salar) on infection susceptibility. We exposed the parent populations and their hybrids to two parasites that commonly infect these species, the bacterium Flavobacterium columnare and the macroparasitic fluke Diplostomum pseudospathaceum. We found that landlocked salmon had lower survival during the bacterial epidemic, but higher resistance against the fluke, compared with Atlantic salmon. Hybrids showed intermediate survival and resistance, suggesting that hybridization decreased susceptibility to one parasite, but concurrently increased it to another. Our results emphasize the importance of considering health effects of different types of infections when employing hybridization for conservation.

The spread of infectious asexuality through haploid pollen.

The mechanisms of initiation and transmission of apomixis (asexual reproduction through seeds) in natural plant populations are important for understanding the evolution of reproductive variation. Here, we used the phylogenetic diversity of the genus Boechera (Brassicaceae), together with natural diversity in pollen types produced by apomictic lines, to test whether hybridization triggers the transition to asexuality, and whether a 'triploid bridge' is required for the formation of polyploid apomicts. We performed crosses between diploid sexual recipient and diploid apomictic donor lines and tested whether the mating system (interspecific hybridization vs intraspecific outcrossing) or pollen type (haploid vs diploid) influenced the transmission of apomixis from diploid apomictic donors into sexual recipients. We used genetic markers and flow cytometric analyses of embryo and endosperm in seeds to infer the reproductive mode. Within a single generation, initiation of both diploid and polyploid apomixis in sexual Boechera can occur. Diploid apomixis is transmitted through haploid pollen (infectious asexuality) and polyploids can form through multiple pathways. The three functional elements of apomixis occasionally segregate. Variation in pollen ploidy and the segregation of apomixis elements drive reproductive diversity of hybrids and outcrosses and can be utilized for apomixis initiation in crop breeding programs.

Vector preference and heterogeneity in host sex ratio can affect pathogen spread in natural plant populations.

Vector-borne diseases threaten human and agricultural health and are a critical component of the ecology of plants and animals. While previous studies have shown that pathogen spread can be affected by vector preferences for host infection status, less attention has been paid to vector preference for host sex, despite abundant evidence of sex-specific variation in disease burden. We investigated vector preference for host infection status and sex in the sterilizing "anther-smut" pathogen (Microbotryum) of the alpine carnation, Dianthus pavonius. The pathogen is transferred among hosts by pollinators that visit infected flowers and become contaminated with spores produced by infected anthers. The host plant has a mixed breeding system with hermaphrodites and females. In experimental floral arrays, pollinators strongly preferred healthy hermaphrodites over both females and diseased plants, consistently across different guilds of pollinators and over multiple years. Using an agent-based model, we showed that pollinator preferences for sex can affect pathogen spread in populations with variable sex ratios, even if there is no preference for infection status. Our results demonstrate that vector preferences for host traits other than infection status can play a critical role in pathogen transmission dynamics when there is heterogeneity for those traits in the host population.

Network analysis highlights increased generalisation and evenness of plant-pollinator interactions after conservation measures

The decline of pollinators may alter the complex system of interactions that they establish with flowering plants, with potential negative consequences on both partners. Within this context, network analysis may be a useful tool to study ecological properties of plant-pollinator interactions and to evaluate the outcomes of conservation actions. Three conservation measures were implemented within the European LIFE + PP-ICON project to support the local pollinator community of a population of the rare plant Dictamnus albus in a protected area near Bologna, Italy. Artificial nesting sites were installed to support solitary bees, populations of native plants were reinforced to increase foraging resources for pollinators, and colonies of bumblebees reared from wild queens were released in the study area. In this work we evaluate the effects of these conservation actions on plant-pollinator networks over a period of four years, comparing a pre- (2011–2012) and a post-conservation (2013–2014) action period. The overall network generalisation increased after the implementation of conservation measures and interactions were more evenly distributed. Module composition significantly changed between the two periods, showing a marked rewiring of interactions. D. albus was a module hub both before and after conservation actions, thus emerging as an important node within its own module. In addition, some plant and pollinator species directly targeted by conservation measures became module connectors, highlighting their increased importance in linking different modules. Finally, the reinforcement of plant and pollinator populations led to increased flower visitation. These results indicate that conservation actions affected species both directly and indirectly and that the network of interactions has potentially increased its robustness and resilience towards possible species loss. This study highlights ways in which network analysis can be used to measure changes in plant-pollinator interactions in response to conservation actions.

Early Warning Systems as a Component of Integrated Pest Management to Prevent the Introduction of Exotic Pests

Abstract When introduced to novel habitats, invasive alien plant pests have the potential to reduce fitness or cause aesthetic damage to naïve plant hosts, or to cause widespread mortality in both native and cultivated plant populations. Once established, the cost of mitigation, eradication, and damage and losses from invasive alien plant pests often exceeds the cost of preventing introductions from occurring. National plant protection organizations (NPPOs) have therefore implemented trade restrictions and regulations to minimize the introduction of alien plant pest species. To be effective, NPPOs must stay informed about pest species that may pose a threat to natural or agricultural systems. Early warning systems such as PestLens, the European and Mediterranean Plant Protection Organization Reporting Service, and others collect relevant and current plant pest information and disseminate it to NPPOs, thereby facilitating informed regulatory decision-making. Herein, we describe the processes and goals of some of the existing plant pest early warning systems and how these systems may be used.

ЭЛЕМЕНТЫ АГРОТЕХНИКИ ЗВЕРОБОЯ ПРОДЫРЯВЛЕННОГО (HYPERICUM PERFORATUM) В УСЛОВИЯХ СВЕТОКУЛЬТУРЫ

This paper discusses the productivity evaluation results (shoot length, shoot number, leaf size, and yields) of hy-droponically grown perforate St. John’s wort (Hypericum perforatum L.). Hydroponic technique enables year-round growing of this medicinal plant preserving natural plant population in the Khanty-Mansiysk Autonomous District -Yugra; perforate St. John’s wortis listed in the District’s Red Book as the species that should be closely monitored in its natural habitat. A vertical ebb-and-flow hydroponic unit was used for growing. The research target was the Optimist variety of perforate St. John’s wort. Generally ac-cepted research methods were applied. Phytopathological evaluation of the perforate St. John’s wort plantation re-vealed low level of infestation with fusarium disease (less than 5%). The experiment showed that the plants reached the best values of all growth indices when grown under white lights of luminous flux of 8000 lm, color temperature of 4000 K, and РРF of 165 μmol s m2. Moreover, lighting with white LEDs stimulates transition of growing plants to flowering stage on the 97th day after planting and increas-es yield to 3.12 kg m2. The variety Optimist variety of perfo-rate St. John’s wort in hydroponic environment forms creeping, aggressively branching shoots that should be considered during growing.

Population studies of the wild tomato species Solanum chilense reveal geographically structured major gene-mediated pathogen resistance.

Natural plant populations encounter strong pathogen pressure and defence-associated genes are known to be under selection dependent on the pressure by the pathogens. Here, we use populations of the wild tomato Solanum chilense to investigate natural resistance against Cladosporium fulvum, a well-known ascomycete pathogen of domesticated tomatoes. Host populations used are from distinct geographical origins and share a defined evolutionary history. We show that distinct populations of S. chilense differ in resistance against the pathogen. Screening for major resistance gene-mediated pathogen recognition throughout the whole species showed clear geographical differences between populations and complete loss of pathogen recognition in the south of the species range. In addition, we observed high complexity in a homologues of Cladosporium resistance (Hcr) locus, underlying the recognition of C. fulvum, in central and northern populations. Our findings show that major gene-mediated recognition specificity is diverse in a natural plant-pathosystem. We place major gene resistance in a geographical context that also defined the evolutionary history of that species. Data suggest that the underlying loci are more complex than previously anticipated, with small-scale gene recombination being possibly responsible for maintaining balanced polymorphisms in the populations that experience pathogen pressure.

Fine-Scale Patterns of Genetic Structure in the Host Plant Chamaecrista fasciculata (Fabaceae) and Its Nodulating Rhizobia Symbionts.

In natural plant populations, a fine-scale spatial genetic structure (SGS) can result from limited gene flow, selection pressures or spatial autocorrelation. However, limited gene flow is considered the predominant determinant in the establishment of SGS. With limited dispersal ability of bacterial cells in soil and host influence on their variety and abundance, spatial autocorrelation of bacterial communities associated with plants is expected. For this study, we collected genetic data from legume host plants, Chamaecrista fasciculata, their Bradyrhizobium symbionts and rhizosphere free-living bacteria at a small spatial scale to evaluate the extent to which symbiotic partners will have similar SGS and to understand how plant hosts choose among nodulating symbionts. We found SGS across all sampled plants for both the host plants and nodulating rhizobia, suggesting that both organisms are influenced by similar mechanisms structuring genetic diversity or shared habitat preferences by both plants and microbes. We also found that plant genetic identity and geographic distance might serve as predictors of nodulating rhizobia genetic identity. Bradyrhizobium elkanii was the only type of rhizobia found in nodules, which suggests some level of selection by the host plant.