Relationship of Cultivated Grain Amaranth Species and Wild Relative Accessions

Amaranthus is a genus of C4 dicotyledonous herbaceous plants, and three New World species have been domesticated to produce grain crops with light colored seed which are classified as pseudo-cereals rich in protein and minerals. A core collection of grain amaranths and immediate precursor species has been established, representing the closest related species. The goal of this study was to evaluate the genetic diversity in that collection of cultivated and wild species, using competitive allele single nucleotide polymorphism markers. A secondary objective was to determine the relationships among the three cultivated species and non-domesticated Amaranthus, while a third objective was to evaluate the utility of the markers in detecting diversity in the 276 genotypes. The markers were found to be highly variable with an average polymorphism information content of 0.365. All markers were bi-allelic; and the major allele frequency ranged from 0.388 to 0.871. Population structure analysis of the cultigens revealed the presence of two sub populations. Phylogeny confirmed that the two Mesoamerican species, Amaranthus cruentus and Amaranthus hypochondriacus, were related and distant from the South American species Amaranthus caudatus, which in turn was very closely clustered with Amaranthus quitensis, even though this is considered a weedy relative. The first pair of species were likely to have inter-crossed, while the latter two likely exist in a wild-cultivated hybrid state. In conclusion, the results of this SNP study provided insights on amaranth cultivars and their relationship to wild species, the probable domestication events leading to the cultivars, and possible crop breeding or germplasm conservation strategies.

Photosynthetic pigments content and parameters of oxidative stress in the amaranth species with increasing water deficiency

The dynamics of the photosynthetic pigments content and parameters of oxidative stress with an increasing water deficit in the leaves of 40-days-old plants of two amaranth species - Amaranthus paniculatus L. (cv. Rubin) and Amaranthus caudatus L. (cv. Chyrvony aksamit), grown in a pot culture, was studied. Specific features of the development of water deficiency in amaranth leaves were revealed: amaranth plants Amaranthus paniculatus L. showed a stronger development of water deficit in leaves than Amaranthus caudatus L. after 4-days soil drought, which after 8 days increased in two species to 73.7 and 55.7 %, respectively. Under moderate drought, the amount of photosynthetic pigments (chlorophyll (Chl) and carotenoids) based on dry leaf weight increased in two amaranth species, but after 8 days of soil drought, the content of Chl (a + b) was reduced by 2.0-2.1 times, and carotenoids - 1.8-1.9 times relative to the physiological level. As a result of a 4-days soil drought in the leaves of Amaranthus paniculatus L., there was a significant decrease in the content of reactive oxygen species (ROS) and the activity of lipid peroxidation (LPO), while in Amaranthus caudatus L. an increase in the levels of ROS and LPO was observed. With an increase in the pressure of the stress factor in the leaves of amaranth of the two studied species, a decrease in the ROS content and LPO activity relative to physiological values was revealed. A conclusion was made about the different mechanisms of ROS generation and the flow of LPO processes at different stages of soil drought in the leaves of different amaranth species.

PopAmaranth: A population genetic genome browser for grain amaranths and their wild relatives

The combination of genomic, physiological, and population genetic research has accelerated the understanding and improvement of numerous crops. For non-model crops the lack of interdisciplinary research hinders their improvement. Grain amaranth is an ancient nutritious pseudocereal that has been domesticated three times in different regions of the Americas. We present and employ PopAmaranth, a population genetic genome browser, which provides an accessible representation of the genetic variation of the three grain amaranth species (A. hypochondriacus, A. cruentus, and A. caudatus) and two wild relatives (A. hybridus and A. quitensis) along the A. hypochondriacus reference sequence. We performed population-scale diversity and selection analysis from whole-genome sequencing data of 88 curated genetically and taxonomically unambiguously classified accessions. We employ the platform to show that genetic diversity in the water stress-related MIF1 gene declined during amaranth domestication and provide evidence for convergent saponin reduction between amaranth and quinoa. PopAmaranth is available through amaranthGDB at amaranthgdb.org/popamaranth.html.

Unraveling the Strategies Used by the Underexploited Amaranth Species to Confront Salt Stress: Similarities and Differences With Quinoa Species

Yield losses due to cultivation in saline soils is a common problem all over the world as most crop plants are glycophytes and, hence, susceptible to salt stress. The use of halophytic crops could be an interesting alternative to cope with this issue. The Amaranthaceae family comprises by far the highest proportion of salt-tolerant halophytic species. Amaranth and quinoa belong to this family, and their seeds used as pseudo-cereal grains have received much attention in recent years because of their exceptional nutritional value. While advances in the knowledge of salt tolerance mechanisms of quinoa have been remarkable in recent years, much less attention was received by amaranth, despite evidences pointing to amaranth as a promising species to be grown under salinity. In order to advance in the understanding of strategies used by amaranth to confront salt stress, we studied the comparative responses of amaranth and quinoa to salinity (100 mM NaCl) at the physiological, anatomical, and molecular levels. Amaranth was able to exhibit salt tolerance throughout its life cycle, since grain production was not affected by the saline conditions applied. The high salt tolerance of amaranth is associated with a low basal stomatal conductance due to a low number of stomata (stomatal density) and degree of stomata aperture (in adaxial surface) of leaves, which contributes to avoid leaf water loss under salt stress in a more efficient way than in quinoa. With respect to Na+ homeostasis, amaranth showed a pattern of Na+ distribution throughout the plant similar to glycophytes, with the highest accumulation found in the roots, followed by the stem and the lowest one detected in the leaves. Contrarily, quinoa exhibited a Na+ includer character with the highest accumulation detected in the shoots. Expression levels of main genes involved in Na+ homeostasis (SOS1, HKT1s, and NHX1) showed different patterns between amaranth and quinoa, with a marked higher basal expression in amaranth roots. These results highlight the important differences in the physiological and molecular responses of amaranth and quinoa when confronted with salinity.

Photosynthetic Phenomics of Field- and Greenhouse-Grown Amaranths vs. Sensory and Species Delimits

Consumers hesitate to purchase field-grown shoot-tops of amaranths in Sri Lanka, citing the low-cleanliness making growers focus on greenhouse farming. However, the photosynthetic and growth variations in relation to the organoleptic preference of the greenhouse-grown amaranths in comparison to field-grown counterparts have not been studied. Also, the species delimits of the amaranths in Sri Lanka have not been identified, limiting our ability to interpret species-specific production characteristics. Thus, we assessed the common types of amaranths under greenhouse and field conditions. The photosynthesis was measured using a MultispeQ device of the PhotosynQ phenomic platform, which records chlorophyll fluorescence-based parameters. The shoot-tops were harvested and prepared as dishes according to the typical recipe for amaranths in Sri Lanka. The dishes were subjected to an organoleptic assessment for the parameters color, aroma, bitterness, texture, and overall taste. The differences in plant and the shoot-top biomass were also assessed. The markers atpB-rbcL, matk-trnT, and ITS were used to define the species delimits. The field-grown and greenhouse-grown amaranths exhibited species/cultivar-specific photosynthetic variations. The texture and overall taste of the dishes were different among greenhouse and field-grown material. The tasters preferred the texture and the overall taste of the greenhouse-grown shoot-tops. The greenhouse-grown plants also yielded higher shoot-top harvests compared to field-grown counterparts. Out of the tested markers, ITS defines the delimits of amaranth species. The higher organoleptic preference, the appreciable yield levels, unique photosynthetic patterns of the greenhouse-grown amaranths, and species definitions provide the much-needed platform for clean shoot-top production guaranteeing the highest end-user trust.

PopAmaranth: A population genetic genome browser for grain amaranths and their wild relatives

The last decades of genomic, physiological, and population genetic research have accelerated the understanding and improvement of a numerous crops. The transfer of methods to minor crops could accelerate their improvement if knowledge is effectively shared between disciplines. Grain amaranth is an ancient nutritious pseudocereal from the Americas that is regaining importance due to its high protein content and favorable amino acid and micronutrient composition. To effectively combine genomic and population genetic information with molecular genetics, plant physiology, and use it for interdisciplinary research and crop improvement, an intuitive interaction for scientists across disciplines is essential. Here, we present PopAmaranth, a population genetic genome browser, which provides an accessible representation of the genetic variation of the three grain amaranth species (A. hypochondriacus, A. cruentus, and A. caudatus) and two wild relatives (A. hybridus and A. quitensis) along the A. hypochondriacus reference sequence. We performed population-scale diversity and selection analysis from whole-genome sequencing data of 88 curated genetically and taxonomically unambiguously classified accessions. We incorporate the domestication history of the three grain amaranths to make an evolutionary perspective for candidate genes and regions available. We employ the platform to show that genetic diversity in the water stress-related MIF1 gene declined during amaranth domestication and provide evidence for convergent saponin reduction between amaranth and quinoa. These examples show that our tool enables the detailed study of individual genes, provides target regions for breeding efforts and can enhance the interdisciplinary integration of population genomic findings across species. PopAmaranth is available through amaranthGDB at amaranthgdb.org/popamaranth.htmlSignificanceSharing population genetic results between disciplines can facilitate interdisciplinary research and accelerate the improvement of crops. Since the onset of genome sequencing online genome browser platforms have provide access to features of an organisms genetic information. Rarely this has been extended to population-wide summary statistics for evolutionary hypothesis testing. We implemented a population genetic genome browser PopAmaranth for three grain amaranth species and their two wild relatives. The intuitive and user-friendly interface of PopA-maranth makes the genetic diversity of the species complex available to broad audience of biologists across disciplines. We show how our tool can be used to study convergence across distant genera and find signals of past selection in domestication and stress related genes. Community platforms and genome browsers are an integrative element of numerous study systems. PopAmaranth can serve as template for other research communities to integrate and share their results.

A Review of Recent Studies on the Antioxidant Activities of a Third-Millennium Food: Amaranthus spp.

Amaranth (Amaranthus spp.) plant commonly refers to the sustainable food crop for the 21st century. The crop has witnessed significant attention in recent years due to its high nutritional value and agronomic advantages. It is a relatively well-balanced cosmopolitan food that is a protector against chronic diseases. Usually, the antioxidant activities of amaranth are held responsible for its defensive behavior. Antioxidant activity of plants, generally, is attributed to their phytochemical compounds. The current interest, however, lies in hydrolysates and bioactive peptides because of their numerous biological functions, including antioxidant effect. While the importance of bioactive peptides has been progressively recognized, an integrated review of recent studies on the antioxidant ability of amaranth species, especially their hydrolysates and peptides has not been generated. Hence, in this review, we summarize studies focused on the antioxidant capacity of amaranth renewal over the period 2015–2020. It starts with a background and overall image of the amaranth-related published reviews. The current research focusing on in vitro, in vivo, and chemical assays-based antioxidant activity of different amaranth species are addressed. Finally, the last segment includes the latest studies concerning free radical scavenging activity and metal chelation capacity of amaranth protein hydrolysates and bioactive peptides.

PECULIARITIES OF THE PROCESS OF PURIFICATION OF AMRANT GRAIN FROM IMPURITIES

Proper and balanced nutrition is the key to a person's physical health, especially in the face of deteriorating environmental conditions and the effects of daily stress caused by the accelerated pace of life in recent years. In this regard, the attention of many researchers and entrepreneurs is focused on the development and implementation in mass production of foods that would fully meet human needs for protein, vitamins, micro-and micronutrients, etc. Recently, ingredients made from non-traditional vegetable raw materials have been used for the production of functional foods. Amaranth belongs to such vegetable raw materials. Amaranth culture has been known since ancient times, used by the ancient Aztecs. The main feature of this culture is the unique chemical composition, which causes an extremely wide range of its use, which is not limited to the food industry. In terms of amino acid composition, amaranth grain protein is close to the composition of an ideal protein. The presence of squalene in amaranth oil makes it possible to use it for the manufacture of medicines and cosmetics. However, despite the prospects for the use of amaranth, producers face difficulties with the characteristics of the grain of this crop. Small grain sizes require careful selection of mode parameters of technological equipment for post-harvest processing. To substantiate the cleaning regimes, a study of the particle size distribution, physical-mechanical and aerodynamic properties of amaranth grain mass has been carried out. Based on the research, it is established that despite the fact that some amaranth species like shchyrytsya” have almost the same grain size and shape, the transgression coefficients calculated according to certain divisibility values can predict the possibility of separating a mixture of freshly harvested amaranth grain and its impurities, in particular from difficult to separate . It is proposed to use a set of sieves with round holes of the following sizes (mm) to separate this mixture: B1 – 1.0…1.1; B2 – 1.0…1.1; B2 – 1.0…1.2; G1 – 0.7…0.9; and elongated holes with dimensions (mm): B1 – (0.8…1.0)×20, B2 – (0.5…0.7)×20, B1 – (0.4…0.6)×20 .