Sea Beet Research Articles

Salt and Drought Stress Responses in Cultivated Beets (Beta vulgaris L.) and Wild Beet (Beta maritima L.).

Cultivated beets, including leaf beets, garden beets, fodder beets, and sugar beets, which belong to the species Beta vulgaris L., are economically important edible crops that have been originated from a halophytic wild ancestor, Beta maritima L. (sea beet or wild beet). Salt and drought are major abiotic stresses, which limit crop growth and production and have been most studied in beets compared to other environmental stresses. Characteristically, beets are salt- and drought-tolerant crops; however, prolonged and persistent exposure to salt and drought stress results in a significant drop in beet productivity and yield. Hence, to harness the best benefits of beet cultivation, knowledge of stress-coping strategies, and stress-tolerant beet varieties, are prerequisites. In the current review, we have summarized morpho-physiological, biochemical, and molecular responses of sugar beet, fodder beet, red beet, chard (B. vulgaris L.), and their ancestor, wild beet (B. maritima L.) under salt and drought stresses. We have also described the beet genes and noncoding RNAs previously reported for their roles in salt and drought response/tolerance. The plant biologists and breeders can potentiate the utilization of these resources as prospective targets for developing crops with abiotic stress tolerance.

Evolution of Root Morphology in Table Beet: Historical and Iconographic.

The Beta vulgaris complex includes sugar beet, mangel wurzel, Swiss chard, fodder beet, and table beet. Mangel wurzel and fodder beet are considered to be the same general crop type, with the former possessing lower dry matter content (<13%) than the latter. Mangel is likely derived from crosses between table beet and chard, while fodder beet may have a more recent origin, arising from crosses between mangel and sugarbeet. The table beet was derived from the wild sea beet, B. vulgaris (L.) subsp. maritima (L.) Arcang, with small non-spherical roots. Table beet is presently a popular vegetable cultivated for its pigmented roots, typically red but also yellow and other colors. Wild forms were consumed in antiquity mainly for their leaves with roots used medicinally. Beet is referred to in the Septuagint, a Greek translation of the first five books of the Hebrew bible, made in Ptolomeic Egypt in the third century BCE. A beet identified as Beta maritima is included in De Material Medicus of Pedanius Dioscorides written in the first century CE, and the first illustrated version of 512, known as the Juliana Anicia Codex, includes an image with non-spherical root. Beet is mentioned in several tractates of the Talmud, a sixth century collection of history and civil law written in Babylonia. Beta maritima possesses supernumerary root cambia, which facilitated selection of swollen rooted forms. The first colored illustration of swollen rooted table beet, B. vulgaris, can be found in the 1515–1517 frescos of Raphael Sanzio and Giovanni Martina da Udine in the Villa Farnesina in Rome. Swollen roots in Roman beet are illustrated and described in the 1587 French herbal Historia Generalis Plantarum of Jacques Dalechamps. Conically shaped beet roots are found in the market painting of Franz Snijders in the 17th century. Various spherical forms of beet root are found in the work of American painter James Peale in 1826. A complete array of beet root types is found in the Benary catalog of 1876. Modern, spherical beet roots were depicted in 1936 by the Russian painter Zinaida Serebriankov, 1936. Artistic and historical representations of table beet suggest that swollen rooted forms have existed during the past five centuries, but conically shaped roots were gradually replaced by spherically shaped roots during this period.

Genetic diversity is enhanced in Wild × Cultivated hybrids of sugarbeet (Beta vulgaris L.) despite multiple selection cycles for cultivated traits

Genetic diversity is enhanced by introgressing wild germplasm into breeding lines and populations. Such introgression, however, commonly introduces wild traits that must be removed by backcrossing and selection before lines are useful for elite breeding programs. Selection against wild characteristics is expected to reduce genetic diversity in introgressed lines. However, the effect of such selection on genetic diversity has not been evaluated for sugarbeet (Beta vulgaris L.). Therefore, genetic diversity was determined for 24 germplasm releases derived from cultivated sugarbeet × wild sea beet [B. vulgaris subsp. maritima (L.) Arcang.] crosses after multiple selection cycles for cultivated traits and compared to the diversity of their wild parents and cultivated sugarbeet lines using simple sequence repeat (SSR) analysis. Diversity in germplasm derived from wild × cultivated hybrids was intermediate of wild and cultivated lines in observed heterozygosity, inbreeding coefficient, and the number of alleles, private alleles, and low frequency alleles. Principal component and neighbor joining analyses demonstrated that wild × cultivated-derived germplasm shared greater similarity with cultivated germplasm than to their wild parents, while STRUCTURE analysis indicated that wild × cultivated-derived germplasm was an admixture of wild and cultivated-derived germplasm. Diversity, therefore, was enhanced in germplasm derived from wild × cultivated hybrids, although selection for cultivated traits reduced the diversity added by introgression with wild accessions. Nevertheless, the enhanced genetic diversity in germplasm releases derived from wild × cultivated hybrids identify these lines as a resource for unique genes and alleles to improve crop productivity, adaptation, and disease tolerance in sugarbeet.

Choosing source of microorganisms and processing technology for next generation beet bioinoculant

The increase of human population and associated increasing demand for agricultural products lead to soil over-exploitation. Biofertilizers based on lyophilized plant material containing living plant growth-promoting microorganisms (PGPM) could be an alternative to conventional fertilizers that fits into sustainable agricultural technologies ideas. We aimed to: (1) assess the diversity of endophytic bacteria in sugar and sea beet roots and (2) determine the influence of osmoprotectants (trehalose and ectoine) addition during lyophilization on bacterial density, viability and salt tolerance. Microbiome diversity was assessed based on 16S rRNA amplicons sequencing, bacterial density and salt tolerance was evaluated in cultures, while bacterial viability was calculated by using fluorescence microscopy and flow cytometry. Here we show that plant genotype shapes its endophytic microbiome diversity and determines rhizosphere soil properties. Sea beet endophytic microbiome, consisting of genera characteristic for extreme environments, is more diverse and salt resistant than its crop relative. Supplementing osmoprotectants during root tissue lyophilization exerts a positive effect on bacterial community salt stress tolerance, viability and density. Trehalose improves the above-mentioned parameters more effectively than ectoine, moreover its use is economically advantageous, thus it may be used to formulate improved biofertilizers.

A comparative analysis of stomatal traits and photosynthetic responses in closely related halophytic and glycophytic species under saline conditions

To understand the adaptive strategies employed by plants to deal with saline conditions, two halophytic species [Chenopodium quinoa (quinoa) and Beta maritima (sea beet)] and their glycophytic relatives [Chenopodium album and Beta vulgaris (sugar beet)] were grown under 0−500 mM salt concentrations followed by the comprehensive assessment of their agronomical, ionic, gas exchange characteristics. Salinity levels up to 300 mM NaCl had no adverse effect on quinoa biomass and 200 mM NaCl stimulated sea beet growth. Stomatal conductance decreased in a dose-dependent manner in all species with increasing NaCl concentrations. However, CO2 assimilation rates remained constant or displayed higher values at the medium level of salinity (100−200 mM NaCl) in quinoa, sugar beet and sea beet. High maximum carboxylation rate of Rubisco (Vcmax) and higher rate of electron transport through photosystem II (J) were responsible for the high photosynthetic rates and biomass productions under these conditions. Both characteristics were much higher in halophytic species for the given external NaCl level. Stomatal densities were intrinsically lower in halophytic species (14–34%); these increased with increasing salinity levels in the sugar beet and sea beet while C. album and quinoa stomata remained less dense under saline conditions. Stomata responses to environmental stimuli were much faster in halophytes (16.6–49.7%), and substitution of K+ by Na+ resulted in promotion of stomatal opening under 50 mM NaCl and 50 mM KCl in quinoa. It is concluded that superior salinity tolerance in halophytes is achieved by significantly faster stomatal opening and closure, their ability to discriminate K+ over Na+, and uncoupling of CO2 assimilation from changes in stomatal aperture.

Genomes of the wild beets Beta patula and Beta vulgaris ssp. maritima.

SummaryWe present draft genome assemblies of Beta patula, a critically endangered wild beet endemic to the Madeira archipelago, and of the closely related Beta vulgaris ssp. maritima (sea beet). Evidence‐based reference gene sets for B. patula and sea beet were generated, consisting of 25 127 and 27 662 genes, respectively. The genomes and gene sets of the two wild beets were compared with their cultivated sister taxon B. vulgaris ssp. vulgaris (sugar beet). Large syntenic regions were identified, and a display tool for automatic genome‐wide synteny image generation was developed. Phylogenetic analysis based on 9861 genes showing 1:1:1 orthology supported the close relationship of B. patula to sea beet and sugar beet. A comparative analysis of the Rz2 locus, responsible for rhizomania resistance, suggested that the sequenced B. patula accession was rhizomania susceptible. Reference karyotypes for the two wild beets were established, and genomic rearrangements were detected. We consider our data as highly valuable and comprehensive resources for wild beet studies, B. patula conservation management, and sugar beet breeding research.

Efficacy of Certain Tribenuron-Methyl Formulations for the Control of Broad-Leaved Weeds in Wheat under Field Conditions

Two field experiments were conducted during 2017-2018 and 2018-2019 seasons to evaluate the effect of eight tribenuron-methyl formulations (four as WG 75% and four as DF 75%) beside hand weeding (twice at 21 and 42 DAS) on broad-leaved weeds (BLWs) in wheat under field conditions. All the agricultural practices were carried out uniformly as recommended. All treatments were arranged in randomized complete block design and replicated four times each of 42 m2 (6×7 m). All formulations were applied at the rate of 8.0 gm fed.-1 in 200 L. water fed.-1 by Knapsack sprayer (CP3) at 30 days after sowing (DAS). After two months from sowing (2MAS) (one month after treatment, one MAT), weeds were collected from an area of 2m2 which was randomly selected from each plot (by using a square woody frame, 50 cm×50 cm). The removed annual BLWs were identified and counted for density as number m-2 and biomass [fresh weight gm m-2] in all treatments. In the untreated control, biomass, biomass%, density and density% for each BLW were recorded. The common prevailed annual BLWs in the experimental wheat field during both seasons were annual Sowthistle (Sonchus oleraceus L.), cheese weed, little mallow (Malva parviflora L.), chicory (Cichorium pumpilum Jacq.), dentated dock (Rumex dentatus L.), medic (Medicago intertexta (L.) Mill.), scarlet pimpernel (Anagallis arvensis L.), sea beet, wild beet (Beta vulgaris L.) and sweet clover, Indian melilot (Melilotus indica L.). The results clearly indicated that biomass and density were varied according to the dominant weed species and from season to another. The BLWs were the most dominant and also they were common in wheat fields and the biomass and density of BLWs were varied between years and weeds. The herbicidal treatments gave the minimum weed biomass and density and gave good weed control efficiency (WCE %) than hand weeding treatments. Granstar formulation completely controlled C. pumpilum weed (in the first season), A. arvensis, R. dentatus and S. oleraceus weeds (in the second season). Skylla formulation completely controlled M. parviflora and R. dentatus weeds in the first season. The tested tribenuron-methyl formulations did not cause complete control for B. vulgaris, M. intertexta and M. indica weeds in both seasons. In all cases, the herbicidal treatments increased significantly the biological yield, grain yield, straw yield, harvest index and thousand grain weight in comparison with untreated control. Also, Granstar, Skylla and Cash Cool herbicides were the most effective, while Ownostar was the least effective. We can concluded that, Granstar, Skylla and Cash Cool formulations are the most effective in controlling broad-leaved weeds in wheat field and consequently increased the grain yield.

Sustainable Valorization of Halophytes from the Mediterranean Area: A Comprehensive Evaluation of Their Fatty Acid Profile and Implications for Human and Animal Nutrition

Halophytic plants can provide an economical and environmentally sustainable source of products for human and animal feeding, in the context of the increase of worldwide emergent semi-arid landscapes. This work reports a comprehensive evaluation of the qualitative and quantitative composition of fatty acids (FA) of nineteen Mediterranean halophytes collected in southern Portugal, with the purpose of establishing their possible uses as food and feed. For FA determination, lipids and free FA were converted to the corresponding fatty acid methyl esters (FAME) and analyzed by GC-MS. Beta maritima had the highest FAME levels (7.3 mg/g DW) while Suaeda vera had the lowest content (1.0 mg/g DW). The most common saturated fatty acid (SFA) across all studied species was palmitic acid. The most prevalent monounsaturated fatty acid (MUFA) was oleic acid. Polyunsaturated fatty acids (PUFA) levels were led by linoleic acid. Less common FAMEs were also detected, namely eicosadienoic and hexadecatrienoic acids. Cotula coronopifolia, Phragmites australis and Suaeda vera displayed the best FA nutritional profiles. These species also showed bioactivities relevant for both human and animal health according to the literature and thus, collectively with this study, they could be further explored as food and feed.

Beta vulgaris mitovirus 1 in diverse cultivars of beet and chard

Recent results indicate that mitoviruses, which replicate persistently in host mitochondria, are not restricted to fungi, but instead are found also in plants. Beta vulgaris mitovirus 1 (BevuMV1) is an example first discovered in sugar beet cultivars. For the current study, complete coding sequences of 42 BevuMV1 strains were newly determined, derived from not only sugar beet but also fodder beet, table beet, and Swiss chard cultivars of Beta vulgaris, as well as wild sea beet. BevuMV1 is thus a common phytobiome component of this valuable crop species. Most of the new BevuMV1 sequences originated from RNA extracted from B. vulgaris seed clusters, consistent with vertical transmission of this virus. Results suggest that BevuMV1 entered the B. vulgaris lineage prior to human cultivation and also provides a marker for tracing the maternal ancestry of B. vulgaris cultivars. Especially notable is the monophyletic relationship and limited sequence divergence among BevuMV1 strains from cultivars that are thought or shown to share the “Owen” trait for cytoplasmic male sterility, which is transmitted by maternal mitochondria and has been broadly established in commercial breeding lines of B. vulgaris since the mid-20th century.

Salt stress vs. salt shock - the case of sugar beet and its halophytic ancestor

BackgroundSugar beet is a highly salt-tolerant crop. However, its ability to withstand high salinity is reduced compared to sea beet, a wild ancestor of all beet crops. The aim of this study was to investigate transcriptional patterns associated with physiological, cytological and biochemical mechanisms involved in salt response in these closely related subspecies. Salt acclimation strategies were assessed in plants subjected to either gradually increasing salt levels (salt-stress) or in excised leaves, exposed instantly to salinity (salt-shock).ResultThe majority of DEGs was down-regulated under stress, which may lead to certain aspects of metabolism being reduced in this treatment, as exemplified by lowered transpiration and photosynthesis. This effect was more pronounced in sugar beet. Additionally, sugar beet, but not sea beet, growth was restricted. Silencing of genes encoding numerous transcription factors and signaling proteins was observed, concomitantly with the up-regulation of lipid transfer protein-encoding genes and those coding for NRTs. Bark storage protein genes were up-regulated in sugar beet to the level observed in unstressed sea beet. Osmotic adjustment, manifested by increased water and proline content, occurred in salt-shocked leaves of both genotypes, due to the concerted activation of genes encoding aquaporins, ion channels and osmoprotectants synthesizing enzymes. bHLH137 was the only TF-encoding gene induced by salt in a dose-dependent manner irrespective of the mode of salt treatment. Moreover, the incidence of bHLH-binding motives in promoter regions of salinity-regulated genes was significantly greater than in non-regulated ones.ConclusionsMaintaining homeostasis under salt stress requires deeper transcriptomic changes in the sugar beet than in the sea beet. In both genotypes salt shock elicits greater transcriptomic changes than stress and it results in greater number of up-regulated genes compared to the latter. NRTs and bark storage protein may play a yet undefined role in salt stress-acclimation in beet. bHLH is a putative regulator of salt response in beet leaves and a promising candidate for further studies.

Effect of in vitro gastrointestinal digestion on the total phenolic contents and antioxidant activity of wild Mediterranean edible plant extracts

The recent interest in wild edible plants is associated with their health benefits, which are mainly due to their richness in antioxidant compounds, particularly phenolics. Nevertheless, some of these compounds are metabolized after ingestion, being transformed into metabolites frequently with lower antioxidant activity. The aim of the present study was to evaluate the influence of the digestive process on the total phenolic contents and antioxidant activity of extracts from four wild edible plants used in the Mediterranean diet (Beta maritima L., Plantago major L., Oxalis pes-caprae L. and Scolymus hispanicus L.). HPLC-DAD analysis revealed that S. hispanicus is characterized by the presence of caffeoylquinic acids, dicaffeoylquinic acids and flavonol derivatives, P. major by high amounts of verbascoside, B. maritima possesses 2,4-dihydroxybenzoic acid, 5-O-caffeoylquinic acid, quercetin derivatives and kaempferol-3-O-rutinoside, and O. pes-caprae extract contains hydroxycinnamic acids and flavone derivatives. Total phenolic contents were determined by Folin–Ciocalteu assay, and antioxidant activity by the ABTS, DPPH, ORAC and FRAP assays. Phenolic contents of P. major and S. hispanicus extracts were not affected by digestion, but they significantly decreased in B. maritima after both phases of digestion process and in O. pes-caprae after the gastric phase. The antioxidant activity results varied with the extract and the method used to evaluate the activity. Results showed that P. major extract has the highest total phenolic contents and antioxidant activity, with considerable values even after digestion, reinforcing the health benefits of this species.

Management of beet rust in accordance with IPM principles

High disease pressure from beet rust (Uromyces beticola) has been registered in Denmark in recent years, increasing the need to manage this pathogen in accordance with principles of Integrated Pest Management (IPM). A revised disease cycle with all major steps has been proposed including spread of the disease by sea beets (Beta vulgaris subsp. maritima) acting as a green bridge. Locations with early onset of beet rust were investigated and indicated a connection between early rust occurrence and the presence of local wild sea beets. The impact of the disease was investigated through data from 15 years of testing. In field trials with significant infection, yield reductions up to 11% have been measured and two treatments with reduced doses of epoxiconazole + pyraclostrobin resulted in the highest economic returns on average. Fungicide efficacy and susceptibility of sugar beet cultivars were tested in greenhouse and under field conditions. Results indicated high sensitivity of the pathogen to major fungicides. In greenhouse trials high efficacy was obtained by all conventional fungicides (epoxiconazole, pyraclostrobin, epoxiconazole + pyraclostrobin, difenoconazole + propiconazole) both as preventive and curative treatments. Hydrogen peroxide was tested as control agent, but was not significantly different from the untreated control. The biological control agent Bacillus subtilis QST 713 provided 76% control of beet rust when used preventively (not significant). A ranking of relevant cultivars showed variation across years and differences in susceptibility where the least susceptible cultivar on average reduced disease severity to 66% of the most susceptible cultivar. Based on the relevant literature and the findings in this study an IPM management strategy for beet rust should include less susceptible cultivars, fungicides with different modes of action, appropriate doses and application should be carried out according to monitoring and predictions.

Haplotype Variation of Flowering Time Genes of Sugar Beet and Its Wild Relatives and the Impact on Life Cycle Regimes.

The species Beta vulgaris encompasses wild and cultivated members with a broad range of phenological development. The annual life cycle is commonly found in sea beets (ssp. maritima) from Mediterranean environments which germinate, bolt, and flower within one season under long day conditions. Biennials such as the cultivated sugar beet (B. vulgaris ssp. vulgaris) as well as sea beets from northern latitudes require prolonged exposure to cold temperature over winter to acquire floral competence. Sugar beet is mainly cultivated for sugar production in Europe and is likely to have originated from sea beet. Flowering time strongly affects seed yield and yield potential and is thus a trait of high agronomic relevance. Besides environmental cues, there are complex genetic networks known to impact life cycle switch in flowering plants. In sugar beet, BTC1, BvBBX19, BvFT1, and BvFT2 are major flowering time regulators. In this study, we phenotyped plants from a diversity Beta panel encompassing cultivated and wild species from different geographical origin. Plants were grown under different day length regimes with and without vernalization. Haplotype analysis of BTC1, BvBBX19, BvFT1, and BvFT2 was performed to identify natural diversity of these genes and their impact on flowering. We found that accessions from northern latitudes flowered significantly later than those from southern latitudes. Some plants did not flower at all, indicating a strong impact of latitude of origin on life cycle. Haplotype analysis revealed a high conservation of the CCT-, REC-, BBX-, and PEBP-domains with regard to SNP occurrence. We identified sequence variation which may impact life cycle adaptation in beet. Our data endorse the importance of BTC1 in the domestication process of cultivated beets and contribute to the understanding of distribution and adaption of Beta species to different life cycle regimes in response to different environments. Moreover, our data provide a resource for haplotypes identified for the major floral regulators in beet.

Targeted Next-Generation Sequencing Identification of Mutations in Disease Resistance Gene Analogs (RGAs) in Wild and Cultivated Beets

Resistance gene analogs (RGAs) were searched bioinformatically in the sugar beet (Beta vulgaris L.) genome as potential candidates for improving resistance against different diseases. In the present study, Ion Torrent sequencing technology was used to identify mutations in 21 RGAs. The DNA samples of ninety-six individuals from six sea beets (Beta vulgaris L. subsp. maritima) and six sugar beet pollinators (eight individuals each) were used for the discovery of single-nucleotide polymorphisms (SNPs). Target amplicons of about 200 bp in length were designed with the Ion AmpliSeq Designer system in order to cover the DNA sequences of the RGAs. The number of SNPs ranged from 0 in four individuals to 278 in the pollinator R740 (which is resistant to rhizomania infection). Among different groups of beets, cytoplasmic male sterile lines had the highest number of SNPs (132) whereas the lowest number of SNPs belonged to O-types (95). The principal coordinates analysis (PCoA) showed that the polymorphisms inside the gene Bv8_184910_pkon (including the CCCTCC sequence) can effectively differentiate wild from cultivated beets, pointing at a possible mutation associated to rhizomania resistance that originated directly from cultivated beets. This is unlike other resistance sources that are introgressed from wild beets. This gene belongs to the receptor-like kinase (RLK) class of RGAs, and is associated to a hypothetical protein. In conclusion, this first report of using Ion Torrent sequencing technology in beet germplasm suggests that the identified sequence CCCTCC can be used in marker-assisted programs to differentiate wild from domestic beets and to identify other unknown disease resistance genes in beet.

Characterization of the BETA1 gene, which might play a role inBeta vulgaris subsp. maritima salt tolerance

Salinity stress has a negative impact on plant growth, which affects homeostasis and productivity. The uptake of nonessential salt ions changes the osmotic balance of the cell and causes dehydration. Higher plants develop salt tolerance mechanisms to avoid dehydration. Sea beet (Beta vulgaris subsp. maritima) is a halophytic ancestor of cultivated sugar beet that displays salt stress tolerance. In this study, we screened a B. vulgaris subsp. maritima cDNA library in Saccharomyces cerevisiae strain Ab11c (ena1Δ, nha1/4Δ, nhx1Δ), which is deficient in sodium transport, to find sodium-detoxifying genes. We identified a cDNA construct, named BETA1, providing salt tolerance to yeast cells. This gene had no previously described function. Intracellular sodium measurements demonstrated no significant differences between yeast cells expressing BETA1 or a sham vector, suggesting that sodium was not effluxed in BETA1-expressing cells. Transcriptionally, BETA1 mRNA levels were induced immediately in leaves and later in the root system in response to the salt stress. Our results suggest that the BETA1 gene is part of the salt tolerance network in B. vulgaris subsp. maritima.

Genetic Diversity and Physiological Performance of Portuguese Wild Beet (Beta vulgaris spp. maritima) from Three Contrasting Habitats.

The establishment of stress resilient sugar beets (Beta vulgaris spp. vulgaris) is an important breeding goal since this cash crop is susceptible to drought and salinity. The genetic diversity in cultivated sugar beets is low and the beet wild relatives are useful genetic resources for tolerance traits. Three wild beet populations (Beta vulgaris spp. maritima) from contrasting environments, Vaiamonte (VMT, dry inland hill), Comporta (CMP, marsh) and Oeiras (OEI, coastland), and one commercial sugar beet (Isella variety, SB), are compared. At the genetic level, the use of six microsatellite allowed to detect a total of seventy six alleles. It was observed that CMP population has the highest value concerning the effective number of alleles and of expected heterozygosity. By contrast, sugar beet has the lowest values for all the parameters considered. Loci analysis with STRUCTURE allows defining three genetic clusters, the sea beet (OEI and CMP), the inland ruderal beet (VMT) and the sugar beet (SB). A screening test for progressive drought and salinity effects demonstrated that: all populations were able to recover from severe stress; drought impact was higher than that from salinity; the impact on biomass (total, shoot, root) was population specific. The distinct strategies were also visible at physiological level. We evaluated the physiological responses of the populations under drought and salt stress, namely at initial stress stages, late stress stages, and early stress recovery. Multivariate analysis showed that the physiological performance can be used to discriminate between genotypes, with a strong contribution of leaf temperature and leaf osmotic adjustment. However, the separation achieved and the groups formed are dependent on the stress type, stress intensity and duration. Each of the wild beet populations evaluated is very rich in genetic terms (allelic richness) and exhibited physiological plasticity, i.e., the capacity to physiologically adjust to changing environments. These characteristics emphasize the importance of the wild beet ecotypes for beet improvement programs. Two striking ecotypes are VMT, which is the best to cope with drought and salinity, and CMP which has the highest root to shoot ratio. These genotypes can supply breeding programs with distinct goals.

Temporal sampling helps unravel the genetic structure of naturally occurring populations of a phytoparasitic nematode. 2. Separating the relative effects of gene flow and genetic drift.

Studying wild pathogen populations in natural ecosystems offers the opportunity to better understand the evolutionary dynamics of biotic diseases in crops and to enhance pest control strategies. We used simulations and genetic markers to investigate the spatial and temporal population genetic structure of wild populations of the beet cyst nematode Heterodera schachtii on a wild host plant species, the sea beet (Beta vulgaris spp. maritima), the wild ancestor of cultivated beets. Our analysis of the variation of eight microsatellite loci across four study sites showed that (i) wild H. schachtii populations displayed fine‐scaled genetic structure with no evidence of substantial levels of gene flow beyond the scale of the host plant, and comparisons with simulations indicated that (ii) genetic drift substantially affected the residual signals of isolation‐by‐distance processes, leading to departures from migration–drift equilibrium. In contrast to what can be suspected for (crop) field populations, this showed that wild cyst nematodes have very low dispersal capabilities and are strongly disconnected from each other. Our results provide some key elements for designing pest control strategies, such as decreasing passive dispersal events to limit the spread of virulence among field nematode populations.

Temporal sampling helps unravel the genetic structure of naturally occurring populations of a phytoparasitic nematode. 1. Insights from the estimation of effective population sizes.

The sustainability of modern agriculture relies on strategies that can control the ability of pathogens to overcome chemicals or genetic resistances through natural selection. This evolutionary potential, which depends partly on effective population size (N e ), is greatly influenced by human activities. In this context, wild pathogen populations can provide valuable information for assessing the long-term risk associated with crop pests. In this study, we estimated the effective population size of the beet cyst nematode, Heterodera schachtii, by sampling 34 populations infecting the sea beet Beta vulgaris spp. maritima twice within a one-year period. Only 20 populations produced enough generations to analyze the variation in allele frequencies, with the remaining populations showing a high mortality rate of the host plant after only 1year. The 20 analyzed populations showed surprisingly low effective population sizes, with most having N e close to 85 individuals. We attribute these low values to the variation in population size through time, systematic inbreeding, and unbalanced sex-ratios. Our results suggest that H.schachtii has low evolutionary potential in natural environments. Pest control strategies in which populations on crops mimic wild populations may help prevent parasite adaptation to host resistance.

Histone acetylation influences the transcriptional activation of POX in Beta vulgaris L. and Beta maritima L. under salt stress

Acetylation of histone proteins is a type of chromatin modification which facilitates the activation of genes. Recent studies brought up the importance of this reversible and rapid process for the regulation of gene expression especially in plant defense against a variety of environmental stresses. Deciphering the exact mechanisms of chromatin modifications under abiotic stress conditions is important for improving crop plants’ performance and yield. In a previous study we compared the salt stress responses of Beta vulgaris (sugar beet) and Beta maritima (wild beet). In accordance with those results we suggested that chromatin remodeling can be an active process in the regulation of genes related to salt stress tolerance of these plants. Therefore we performed ChIP assay in control and salt stressed (250 and 500 mM NaCl) plants and compared the enrichment of acetylation in the associated chromatin sites. We found that the transcriptional activation of one peroxidase (POX) encoding gene was associated with the elevated levels of acetylation in H3K9 and H3K27 sites. The acetylation patterns were remarkably different between two species in which the highest acetylation levels were found at H3K9 and H3K27 in wild beet and sugar beet respectively.

Transcriptomic profiling of the salt stress response in excised leaves of the halophyte Beta vulgaris ssp. maritima

Beta vulgaris ssp. maritima is a halophytic relative of cultivated beets. In the present work a transcriptome response to acute salt stress imposed to excised leaves of sea beet was investigated. Salt treatments consisted of adding NaCl directly to the transpiration stream by immersing the petioles of excised leaves into the salt solutions. Sequencing libraries were generated from leaves subjected to either moderate or strong salt stress. Control libraries were constructed from untreated leaves. Sequencing was performed using the Illumina MiSeq platform. We obtained 32970 unigenes by assembling the pooled reads from all the libraries with Trinity software. Screening the nr database returned 18 362 sequences with functional annotation. Using the reference transcriptome we identified 1 246 genes that were differentially expressed after 48h of NaCl stress. Genes related to several cellular functions such as membrane transport, osmoprotection, molecular chaperoning, redox metabolism or protein synthesis were differentially expressed in response to salt stress. The response of sea beet leaves to salt treatments was marked out by transcriptomic up-regulation of genes related to photosynthetic carbon fixation, ribosome biogenesis, cell wall-building and cell wall expansion. Furthermore, several novel and undescribed transcripts were responsive to salinity in leaves of sea beet.