Genomic insight into the origin, domestication, dispersal, diversification and human selection of Tartary buckwheat.

BACKGROUND: Tartary buckwheat, Fagopyrum tataricum, is a pseudocereal crop with worldwide distribution and high nutritional value. However, the origin and domestication history of this crop remain to be elucidated. RESULTS: Here, by analyzing the population genomics of 567 accessions collected worldwide and reviewing historical documents, we find that Tartary buckwheat originated in the Himalayan region and then spread southwest possibly along with the migration of the Yi people, a minority in Southwestern China that has a long history of planting Tartary buckwheat. Along with the expansion of the Mongol Empire, Tartary buckwheat dispersed to Europe and ultimately to the rest of the world. The different natural growth environments resulted in adaptation, especially significant differences in salt tolerance between northern and southern Chinese Tartary buckwheat populations. By scanning for selective sweeps and using a genome-wide association study, we identify genes responsible for Tartary buckwheat domestication and differentiation, which we then experimentally validate. Comparative genomics and QTL analysis further shed light on the genetic foundation of the easily dehulled trait in a particular variety that was artificially selected by the Wa people, a minority group in Southwestern China known for cultivating Tartary buckwheat specifically for steaming as a staple food to prevent lysine deficiency. CONCLUSIONS: This study provides both comprehensive insights into the origin and domestication of, and a foundation for molecular breeding for, Tartary buckwheat.

Comparative and population genomics of buckwheat species reveal key determinants of flavor and fertility.

Common buckwheat (Fagopyrum esculentum) is an ancient crop with a world-wide distribution. Due to its excellent nutritional quality and high economic and ecological value, common buckwheat is becoming increasingly important throughout the world. The availability of a high-quality reference genome sequence and population genomic data will accelerate the breeding of common buckwheat, but the high heterozygosity due to the outcrossing nature has greatly hindered the genome assembly. Here we report the assembly of a chromosome-scale high-quality reference genome of F. esculentum var. homotropicum, a homozygous self-pollinating variant of common buckwheat. Comparative genomics revealed that two cultivated buckwheat species, common buckwheat (F. esculentum) and Tartary buckwheat (F. tataricum), underwent metabolomic divergence and ecotype differentiation. The expansion of several gene families in common buckwheat, including FhFAR genes, is associated with its wider distribution than Tartary buckwheat. Copy number variation of genes involved in the metabolism of flavonoids is associated with the difference of rutin content between common and Tartary buckwheat. Furthermore, we present a comprehensive atlas of genomic variation based on whole-genome resequencing of 572 accessions of common buckwheat. Population and evolutionary genomics reveal genetic variation associated with environmental adaptability and floral development between Chinese and non-Chinese cultivated groups. Genome-wide association analyses of multi-year agronomic traits with the content of flavonoids revealed that Fh05G014970 is a potential major regulator of flowering period, a key agronomic trait controlling the yield of outcrossing crops, and that Fh06G015130 is a crucial gene underlying flavor-associated flavonoids. Intriguingly, we found that the gene translocation and sequence variation of FhS-ELF3 contribute to the homomorphic self-compatibility of common buckwheat. Collectively, our results elucidate the genetic basis of speciation, ecological adaptation, fertility, and unique flavor of common buckwheat, and provide new resources for future genomics-assisted breeding of this economically important crop.

Phytochemistry, Bioactivities of Metabolites, and Traditional Uses of Fagopyrum tataricum.

In Tartary buckwheat (Fagopyrum tataricum), the edible parts are mainly grain and sprouts. Tartary buckwheat contains protecting substances, which make it possible for plants to survive on high altitudes and under strong natural ultraviolet radiation. The diversity and high content of phenolic substances are important for Tartary buckwheat to grow and reproduce under unfriendly environmental effects, diseases, and grazing. These substances are mainly flavonoids (rutin, quercetin, quercitrin, vitexin, catechin, epicatechin and epicatechin gallate), phenolic acids, fagopyrins, and emodin. Synthesis of protecting substances depends on genetic layout and on the environmental conditions, mainly UV radiation and temperature. Flavonoids and their glycosides are among Tartary buckwheat plants bioactive metabolites. Flavonoids are compounds of special interest due to their antioxidant properties and potential in preventing tiredness, diabetes mellitus, oxidative stress, and neurodegenerative disorders such as Parkinson's disease. During the processing and production of food items, Tartary buckwheat metabolites are subjected to molecular transformations. The main Tartary buckwheat traditional food products are bread, groats, and sprouts.

Molecular Shield for Protection of Buckwheat Plants from UV-B Radiation.

Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) and common buckwheat (Fagopyrum esculentum Moench) are adapted to growing in harsh conditions of high altitudes. Ultraviolet radiation at high altitudes strongly impacts plant growth and development. Under the influence of ultraviolet radiation, protecting substances are synthesized in plants. The synthesis of UV-B defense metabolites is genetically conditioned, and their quantity depends on the intensity of the ultraviolet radiation to which the plants and plant parts are exposed. These substances include flavonoids, and especially rutin. Other substances with aromatic rings of six carbon atoms have a similar function, including fagopyrin, the metabolite specific for buckwheat. Defensive substances are formed in the leaves and flowers of common and Tartary buckwheat, up to about the same concentration in both species. In comparison, the concentration of rutin in the grain of Tartary buckwheat is much higher than in common buckwheat. Flavonoids also have other functions in plants so that they can protect them from pests and diseases. After crushing the grains, rutin is exposed to contact with the molecules of rutin-degrading enzymes. In an environment with the necessary humidity, rutin is turned into bitter quercetin under the action of rutin-degrading enzymes. This bitterness has a deterrent effect against pests. Moreover, flavonoids have important functions in human nutrition to prevent several chronic diseases, including obesity, cardiovascular diseases, gallstone formation, and hypertension.

Impact of Rutin and Other Phenolic Substances on the Digestibility of Buckwheat Grain Metabolites.

Tartary buckwheat (Fagopyrum tataricum Gaertn.) is grown in eastern and central Asia (the Himalayan regions of China, Nepal, Bhutan and India) and in central and eastern Europe (Luxemburg, Germany, Slovenia and Bosnia and Herzegovina). It is known for its high concentration of rutin and other phenolic metabolites. Besides the grain, the other aboveground parts of Tartary buckwheat contain rutin as well. After the mixing of the milled buckwheat products with water, the flavonoid quercetin is obtained in the flour-water mixture, a result of rutin degradation by rutinosidase. Heating by hot water or steam inactivates the rutin-degrading enzymes in buckwheat flour and dough. The low buckwheat protein digestibility is due to the high content of phenolic substances. Phenolic compounds have low absorption after food intake, so, after ingestion, they remain for some time in the gastrointestinal tract. They can act in an inhibitory manner on enzymes, degrading proteins and other food constituents. In common and Tartary buckwheat, the rutin and quercetin complexation with protein and starch molecules has an impact on the in vitro digestibility and the appearance of resistant starch and slowly digestible proteins. Slowly digestible starch and proteins are important for the functional and health-promoting properties of buckwheat products.

Resequencing of global Tartary buckwheat accessions reveals multiple domestication events and key loci associated with agronomic traits.

BACKGROUND: Tartary buckwheat (Fagopyrum tataricum) is a nutritionally balanced and flavonoid-rich crop plant that has been in cultivation for 4000 years and is now grown globally. Despite its nutraceutical and agricultural value, the characterization of its genetics and its domestication history is limited. RESULTS: Here, we report a comprehensive database of Tartary buckwheat genomic variation based on whole-genome resequencing of 510 germplasms. Our analysis suggests that two independent domestication events occurred in southwestern and northern China, resulting in diverse characteristics of modern Tartary buckwheat varieties. Genome-wide association studies for important agricultural traits identify several candidate genes, including FtUFGT3 and FtAP2YT1 that significantly correlate with flavonoid accumulation and grain weight, respectively. CONCLUSIONS: We describe the domestication history of Tartary buckwheat and provide a detailed resource of genomic variation to allow for genomic-assisted breeding in the improvement of elite cultivars.

Biofortification of common buckwheat microgreens and seeds with different forms of selenium and iodine.

BACKGROUND: The biofortification of crops can counteract human diseases, including selenium (Se) and iodine (I) deficiencies in the diet. Little is known about the effects of combinations of Se and I on microgreens and seeds, or on their accumulation in these tissues. The present study aimed to evaluate Se (SeO3 2- , SeO4 2- ) and I (I- , IO3 - ) biofortification of common buckwheat microgreens and seeds with respect to the effects of the addition of Se, I and Se + I on yield and on physiological and biochemical characteristics. RESULTS: In combination treatments, microgreens yield (600-800 g m-2 ) was 50-70% higher than for Se and I alone. The respiratory potential also increased by 60-120%. Fv /Fm was close to 0.8 in all samples. Se content [0.24 µg g-1 dry weight (DW)] was 50% higher for combination treatments than for Se and I alone. I content was highest for IO3 - treatment (216 µg g-1 DW) and decreased in combination treatments with Se by 50%. CONCLUSION: Biofortification of buckwheat microgreens with Se and I should be performed with care because there are synergistic and antagonistic effects of these elements with respect to their accumulation. IO3 - for the biofortification of microgreens should be kept low to prevent exceeding the recommended daily intake of I. © 2019 Society of Chemical Industry.

The temperature threshold for the transformation of rutin to quercetin in Tartary buckwheat dough.

The aim was to determine conditions under which rutin can be retained during production of Tartary buckwheat (Fagopyrum tataricum) dough. Tartary buckwheat flour was hydrothermally treated by mixing with water at 25, 40, 60, 80 and 95 °C, with unprocessed Tartary buckwheat flour as control. With hydrothermal treatments at 25, 40 and 60 °C, most of the rutin was transformed to quercetin. However, for hydrothermal treatments at 80 and 95 °C, rutin was retained due to denaturation of the rutin-degrading enzymes during hydrothermal treatment. This is the first report to describe a temperature threshold for denaturation of rutin-degrading enzymes in any buckwheat material. Tartary buckwheat dough produced at 95 °C contained 12 mg rutin/g dry matter. Based on these characteristics, dough from hydrothermally treated Tartary buckwheat is a promising, rutin-rich functional food material.

Is foliar enrichment of pea plants with iodine and selenium appropriate for production of functional food?

Pea (Pisum sativum L.) plants were sown in a field and foliar sprayed at blooming stage with solutions of different forms of iodine (I) - I- and IO3- and selenium (Se) - SeO32- and SeO42-. The possibility of enrichment of pea seeds to nutritionally important levels of both elements and their distribution through the plant parts were studied. To evaluate stress caused by application of I and Se, some morphological, physiological and biochemical characteristics were determined. The results showed elevated concentrations of both elements in all parts of pea plants. In seeds, I content was more than 6-fold higher, while Se content was up to 12-fold higher than in control plants. Although the plants were in good condition, some differences in pod characteristics and electron transport system activity were observed. Glutathione content was not affected by any treatment and only the I- + SeO42- combination decreased the amount of anthocyanins in plants.

Calcium oxalate druses affect leaf optical properties in selenium-treated Fagopyrum tataricum.

Plants of the genus Fagopyrum contain high levels of crystalline calcium oxalate (CaOx) deposits, or druses, that can affect the leaf optical properties. As selenium has been shown to modify the uptake and accumulation of metabolically important elements such as calcium, we hypothesised that the numbers of druses can be altered by selenium treatment, and this would affect the leaf optical properties. Tartary buckwheat (Fagopyrum tataricum Gaertn.) was grown outdoors in an experimental field. At the beginning of flowering, plants were foliarly sprayed with sodium selenate solution at 10 mg selenium L-1 or only with water. Plant morphological, biochemical, physiological and optical properties were examined, along with leaf elemental composition and content. Se spraying did not affect leaf biochemical and functional properties. However, it increased leaf thickness and the contents of Se in the leaves, and decreased the density of calcium oxalate druses in the leaves. Except Se content, Se spraying did not affect contents of other elements in leaves, including total calcium per dry mass of leaf tissue. Redundancy analysis showed that of all parameters tested, only the calcium oxalate druses parameters were significant in explaining the variability of the leaf reflectance and transmittance spectra. The density of CaOx druses positively correlated with the reflectance in the blue, green, yellow and UV-B regions of the spectrum, while the area of CaOx druses per mm2 of leaf transection area positively correlated with the transmittance in the green and yellow regions of the spectrum.

Seed soaking in I and Se solutions increases concentrations of both elements and changes morphological and some physiological parameters of pea sprouts.

Pea (Pisum sativum L., cv. 'Petit Provencal') seeds were soaked in solutions of different iodine (I) and selenium (Se) forms (1000 mg I L-1 and 10 mg Se L-1). Iodine and selenium content in different parts of pea sprouts, as well as morphological, biochemical and physiological characteristics were measured in sprouts. The results showed increased concentrations of both elements in sprouts grown from treated seeds. Soaking influenced the biomass and height of the sprouts. Significant differences between plants grown from treated seeds in comparison with control plants were also observed for electron transport system activity and concentrations of tocopherol and glutathione. On the other hand, the content of photosynthetic pigments and anthocyanins remained similar as in control plants. Potential photochemical efficiency of photosystem II was close to theoretical maximum 0.8 in all samples. From the pattern of changes of stress indicators we suppose that plants adapted to the stress earlier in the experiment, i.e. before they were sampled for physiological measurements.

The effect of selenium and UV radiation on leaf traits and biomass production in Triticum aestivum L.

UV radiation as an evolutionarily important environmental factor, significantly affects plants traits and alters the effects of other environmental factors. Single and combined effects of ambient UV radiation, its exclusion, and Se foliar treatments on Si concentrations and production of Si phytoliths in wheat (Triticum aestivum L.) cv. 'Reska' were studied. The effects of these treatments on growth parameters of the plants, structural and biochemical traits of the leaves, and interactions of the leaves with light, as Si incrustation is the first barrier to light at the leaf surface were also examined. Under ambient UV radiation and foliar treatment with 10mgL-1 sodium selenate solution, there was a trade-off between the plant investment in primary and secondary metabolism, as the production of UV-absorbing compounds was enhanced while photosynthetic pigment levels were reduced. Independent of Se treatment, ambient UV radiation lowered respiratory potential, Ca concentration, and leaf thickness, and increased Si concentration, Si phytoliths formation, and cuticle thickness. The Se treatment has little effect on plant traits and biomass production but it increased Se concentrations in the plants by >100-fold, independent of UV radiation. In combination with UV radiation Se strengthen the protection of plants against stress by increasing the amount of UV absorbing compounds, light reflectance and transmittance.

Sulphur interferes with selenium accumulation in Tartary buckwheat plants.

Tartary buckwheat (Fagopyrum tataricum Gaertn.) and common buckwheat (Fagopyrum esculentum Moench.) plants grown in the field were treated foliarly with 126 µM solutions of selenate and/or sulphate in order to study the effect of sulphur (S) on selenium (Se) concentration in plants. In both species, the concentration of Se in all plant parts was similar in control and S treated plants. In Tartary buckwheat the concentration of Se was higher in S and Se treated plants than in plants treated with Se alone. S was shown to enhance Se accumulation in Tartary buckwheat. It was also shown that it is possible to produce grain and herb of Tartary and common buckwheat containing appropriate amounts of Se for food without affecting the yield of the plants.

Selenium and its compounds in aquatic plant Veronica anagallis-aquatica.

The uptake, distribution and determination of Se and its compounds in macrophyte Veronica anagallis-aquatica were investigated. V. anagallis-aquatica and sediments were sampled in years 2009-2011 and in 2013 in three Slovenian watercourses flowing through an agricultural area, where addition of Se in feedstuffs has been performed for about 25 years. Se content in sediments were up to 0.86 µg g(-1) and in whole plant varied from 0.186 to 1.535 µg g(-1), all on dry weight basis. Se content were measured also in different plant parts; highest content were found in roots and lowest in stems. Separation of extractable Se compounds was performed by ion exchange chromatography and for on-line detection inductively coupled plasma-mass spectrometry was used. The results showed that only approximately 24% of Se in the macrophyte was extracted using enzyme Protease XIV. Extractable Se in plant parts varied from 10.5% in roots to 29.6% in leaves. Identification of Se(IV) and Se(VI) was achieved but no Se-amino acids were detected even at highest Se content. According to our results, we assume that 25 years of Se addition in feedstuff shows minimal impact on Se content in the selected agricultural area.

Monitoring of selenium in macrophytes - the case of Slovenia.

This paper examines macrophytes from various locations in Slovenian streams for selenium (Se) content in an attempt to discover if Se contamination is present and if Se uptake varies between sampling sites. For this purpose, macrophytes and water from ten locations in the Notranjska and Central regions (Slovenia) with different land use in the catchment were sampled. To assess the environmental conditions of the streams the Riparian, Channel, and Environment (RCE) inventory was applied, which revealed that investigated stretches of streams fall into RCE classes III, IV and V. The concentration of Se in water at all locations was less than 1µgSeL(-1). The Se content in macrophytes differed between sampling sites, with the highest content of Se in samples from Zerovniscica stream and the lowest in samples from Lipsenjscica stream. The content of Se was the highest in moss samples (3038ngSeg(-1) DM) and in the amphibious species Veronica anagallis-aquatica (1507ngSeg(-1) DM).

Impact of selenium on mitochondrial activity in young Tartary buckwheat plants.

To investigate the impact of Se on Tartary buckwheat (Fagopyrum tataricum Gaertn.) plants, the plant foliage was sprayed with 10 mg Se(VI) L(-1) at the beginning of flowering. The Se was effectively assimilated by the plants and taken into the seeds, where its concentration was more than double that in untreated plants. The seeds were collected and sown to obtain the progeny of these Se-treated plants. To assess the physiological characteristics of control plants and these Se-treated progeny plants, the estimated respiratory potential via electron transport system (ETS) activity and the photochemical efficiency of photosystem II were measured. Three weeks after germination, the Se-treated progeny plants showed higher ETS activity compared to the controls. Through weeks 4 and 5, this high ETS activity approximately halved, and the difference in ETS activity seen at 3 weeks was lost. On the other hand, at week 4, the potential photochemical efficiency was higher in the Se-treated progeny plants than the controls. In adult plants, the leaves dry mass was significantly greater in the Se-treated progeny plants than the controls. This study demonstrates an impact of Se in Tartary buckwheat on the progeny plants of Se sprayed plants, as shown previously in pea plants.

The uptake and distribution of selenium in three aquatic plants grown in Se(IV) solution.

The uptake of Se(IV) by Myriophyllum spicatum, Ceratophyllum demersum and Potamogeton perfoliatus, and the effects of Se(IV) on their physiological and biochemical characteristics were studied. Plants were cultivated outdoors under semi-controlled conditions in water solution containing Na selenite (20 µg Se L(-1) and 10 mg Se L(-1)). The higher concentration of Se lowered the photochemical efficiency of PSII in all species studied, while the lower concentration had no effect on any species. The higher concentration of Se lowered respiratory potential in M. spicatum. The response of M. spicatum and C. demersum to Se(IV) regarding chlorophylls was variable, however in the majority of cases, there was a trend of increasing the amount of chlorophylls, while in P. perfoliatus the amount of chlorophyll a decreased. The concentration of Se in plants cultured in 10 mg Se(IV) L(-1) ranged from 436 to 839 µg Se g(-1) DM in M. spicatum, 319 to 988 µg Se g(-1) DM in C. demersum and 310 to 661 µg Se g(-1) DM in P. perfoliatus. The amount of soluble Se compounds in enzyme extracts of high Se treatment was 27% in M. spicatum, 41% in C. demersum and 35% in P. perfoliatus. Se compounds were determined using HPLC-ICP-MS. It was observed that the applied Se(IV) was mainly transformed to insoluble Se.

Selenium and its species in the aquatic moss Fontinalis antipyretica.

The ability of the widely distributed aquatic moss Fontinalis antipyretica to take up Se from water was studied. Nine locations in the Notranjska region (Slovenia) with different land use in the catchment were sampled for water and moss in the year 2010 in spring, summer and autumn. The concentrations of Se in water at all locations did not exceed 0.2 ng mL(-1). F. antipyretica took up Se in the range between 345 and 2250 ng g(-1). All results for Se are expressed on dry matter basis. The Se content varied depending on the location and season. The highest concentration (2250 ± 170 ng g(-1)) of Se was found in the Zerovniscica stream that flows through an agricultural area with dairy farming. The fraction of insoluble Se compounds in the residue after enzymatic hydrolysis using protease (XIV) was around 75%. Soluble Se compounds in the enzymatic extract of F. antipyretica were separated and measured using HPLC coupled to ICP-MS. Se(IV) and Se(VI) were found but no organic Se compounds were detected, even at the highest concentration.

Selenium species in selenium-enriched and drought-exposed potatoes.

The aim of this work was to study selenium (Se) speciation in the potato ( Solanum tuberosum L.) cultivar Desiree, enriched in Se by foliar spraying with a water solution containing 10 mg of Se/L in the form of sodium selenate. Four combinations of treatments were used: well-watered plants with and without Se foliar spraying and drought-exposed plants with and without Se foliar spraying. Water-soluble Se compounds were extracted from potato tubers by water or enzymatic hydrolysis with the enzyme protease XIV, amylase, or a combination of protease XIV and amylase. Extraction was performed using incubation at a constant temperature and stirring (37 degrees C at 200 rpm) or by ultrasound-assisted extraction (300 W), using different extraction times. Separation of soluble Se species (SeCys2, SeMet, SeMeSeCys, selenite, and selenate) was achieved by ion-exchange chromatography, and detection was performed by inductively coupled plasma-mass spectrometry (ICP-MS). Results showed that the concentration of selenate extracted was independent of the enzymatic extraction technique (approximately 98 ng/g for drought-exposed and 308 ng/g for well-watered potato tubers), whereas the extraction yield of SeMet changed with the protocol used (10-36%). Selenate and SeMet were the main soluble Se species (representing 51-68% of total Se) in potato tubers, regardless of the growth conditions.

Combined effects of selenium and drought on photosynthesis and mitochondrial respiration in potato.

The possible effects of selenium (Se) foliar spraying and drought were studied for 3 months in potato (Solanum tuberosum L.) cultivar Desiree in Ljubljana, Slovenia. Four combinations of treatments were conducted: well-watered plants with and without Se foliar spraying, and drought exposed plants with and without Se foliar spraying. The following parameters were monitored 2 and 4 weeks after treatments: net photosynthesis, transpiration rate, quantum yield of photosystem II (PSII), and respiratory potential measured by electron transport system activity. After 3 months of treatments, leaf water potential and tuber yield were determined. The content of Se in tubers was measured after harvesting time. Several effects of drought and Se foliar spraying and their combinations were found. Net photosynthesis and respiratory potential were lower in drought exposed plants 4 weeks after treatments. Se induced higher respiratory potential in the leaves 4 weeks after treatments. Higher efficiency of energy conversion in PSII, expressed by a higher effective quantum yield, was observed in Se treated plants 2 weeks after treatments. Foliarly applied Se was efficiently absorbed by plant leaves and transported to the tubers.