In this paper the presence of selected prenylated and unprenylated phenylpropanoids of nutraceutical value, namely umbelliferone, apigenin, 4'-geranyloxyferulic acid, 7-isopentenyloxycoumarin, auraptene, and umbelliprenin have been determined in all parts of the edible herb Amaranthus retroflexus extracted with different methodologies. Roots were seen to contain the widest variety of unprenylated and prenylated phenylpropanoids both in terms of number of secondary metabolites and their quantitites. Findings described in the present study underline how A. retroflexus can be considered as a potential nutraceutical for human welfare.
The widespread occurrence of ALS inhibitor- and glyphosate-resistant Amaranthus palmeri has led to increasing use of protoporphyrinogen oxidase (PPO)-inhibiting herbicides in cotton and soybean. Studies were conducted to confirm resistance to fomesafen (a PPO inhibitor), determine the resistance frequency, examine the resistance profile to other foliar-applied herbicides, and investigate the resistance mechanism of resistant plants in a population collected in 2011 (AR11-LAW B), and its progenies from two cycles of fomesafen selection (C1 and C2).
The amaranth genus contains many important grain and weedy species. We further our understanding of the genus through the development of a complete reference chloroplast genome.
Herbicide efficacy is known to be influenced by temperature, however, underlying mechanism(s) are poorly understood. A marked alteration in mesotrione [a 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor] efficacy on Palmer amaranth (Amaranthus palmeri S. Watson) was observed when grown under low- (LT, 25/15°C, day/night temperatures) and high (HT, 40/30°C) temperature compared to optimum (OT, 32.5/22.5°C) temperature. Based on plant height, injury, and mortality, Palmer amaranth was more sensitive to mesotrione at LT and less sensitive at HT compared to OT (ED50 for mortality; 18.5, 52.3, and 63.7 g ai ha-1, respectively). Similar responses were observed for leaf chlorophyll index and photochemical efficiency of PSII (Fv/Fm). Furthermore, mesotrione translocation and metabolism, and HPPD expression data strongly supported such variation. Relatively more mesotrione was translocated to meristematic regions at LT or OT than at HT. Based on T50 values (time required to metabolize 50% of the 14C mesotrione), plants at HT metabolized mesotrione faster than those at LT or OT (T50; 13, 21, and 16.5 h, respectively). The relative HPPD:CPS (carbamoyl phosphate synthetase) or HPPD:β-tubulin expression in mesotrione-treated plants increased over time in all temperature regimes; however, at 48 HAT, the HPPD:β-tubulin expression was exceedingly higher at HT compared to LT or OT (18.4-, 3.1-, and 3.5-fold relative to untreated plants, respectively). These findings together with an integrated understanding of other interacting key environmental factors will have important implications for a predictable approach for effective weed management.
The sugarbeet root maggot, Tetanops myopaeformis Röder (Diptera: Ulidiidae), is native to North America. However, its primary crop host, sugarbeet, Beta vulgaris L., was introduced to the continent from Europe in the late 19th century. This field and greenhouse research was conducted to compare the relative attractiveness of eight cultivated and wild plant species for oviposition by T. myopaeformis, and the suitability of these potential host plants for larval development to elucidate the potential native and current host range of this pest. Results indicated that females preferred ovipositing in soil immediately adjacent to or on the following plant species: sugarbeet; spinach, Spinacia olerocea L.; common lambsquarters, Chenopodium album L.; redroot pigweed, Amaranthus retroflexus L.; Palmer amaranth, Amaranthus palmeri S. Wats.; and to a lesser extent, spear saltbush, Atriplex patula L. Larval survival was greatest on spinach, sugarbeet, and spear saltbush, which all belong to the family Chenopodiaceae. Larval survival on these plants suggests that T. myopaeformis could have exploited wild chenopodiaceous plants or others within the order Caryophyllales before sugarbeet was introduced to North America. Low larval survival on common lambsquarters, redroot pigweed, and Palmer amaranth suggests that these species are suboptimal hosts, despite demonstrated attractiveness for oviposition. A general lack of oviposition preference by T. myopaeformis females was observed for sunflower, Helianthus annuus L., and common ragweed, Ambrosia artemisiifolia L. These results provide insights regarding the successful and somewhat rapid host preference shift by this insect to sugarbeet after cultivation of the crop began in the continent.
Amaranthus species are an emerging and promising nutritious traditional vegetable food source. Morphological plasticity and poorly resolved dendrograms have led to the need for well resolved species phylogenies. We hypothesized that whole chloroplast phylogenomics would result in more reliable differentiation between closely related amaranth species. The aims of the study were therefore: to construct a fully assembled, annotated chloroplast genome sequence of Amaranthus tricolor; to characterize Amaranthus accessions phylogenetically by comparing barcoding genes (matK, rbcL, ITS) with whole chloroplast sequencing; and to use whole chloroplast phylogenomics to resolve deeper phylogenetic relationships. We generated a complete A. tricolor chloroplast sequence of 150,027 bp. The three barcoding genes revealed poor inter- and intra-species resolution with low bootstrap support. Whole chloroplast phylogenomics of 59 Amaranthus accessions increased the number of parsimoniously informative sites from 92 to 481 compared to the barcoding genes, allowing improved separation of amaranth species. Our results support previous findings that two geographically independent domestication events of Amaranthus hybridus likely gave rise to several species within the Hybridus complex, namely Amaranthus dubius, Amaranthus quitensis, Amaranthus caudatus, Amaranthus cruentus and Amaranthus hypochondriacus. Poor resolution of species within the Hybridus complex supports the recent and ongoing domestication within the complex, and highlights the limitation of chloroplast data for resolving recent evolution. The weedy Amaranthus retroflexus and Amaranthus powellii was found to share a common ancestor with the Hybridus complex. Leafy amaranth, Amaranthus tricolor, Amaranthus blitum, Amaranthus viridis and Amaranthus graecizans formed a stable sister lineage to the aforementioned species across the phylogenetic trees. This study demonstrates the power of next-generation sequencing data and reference-based assemblies to resolve phylogenies, and also facilitated the identification of unknown Amaranthus accessions from a local genebank. The informative phylogeny of the Amaranthus genus will aid in selecting accessions for breeding advanced genotypes to satisfy global food demand.
Palmer amaranth (Amaranthus palmeri S. Wats.), common waterhemp (Amaranthus tuberculatus var. rudis), and redroot pigweed (Amaranthus retroflexus L.) are major weeds occurring in fields throughout Nebraska with recurrent grower complaints regarding control with glyphosate. The objective of this study was to investigate the frequency and distribution of glyphosate-resistant Palmer amaranth, common waterhemp, and redroot pigweed populations in Nebraska. The study also aimed to investigate how agronomic practices influence the occurrence of glyphosate resistance in the three Amaranthus species.
Resistance to the 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide tembotrione in an Amaranthus palmeri population from Nebraska (NER) has previously been confirmed to be due to enhanced metabolism. The objective of this study was to identify and quantify the metabolites formed in susceptible (NES) and NER biotypes.
Imbibed cress ( Lepidium sativum L.) seeds exude ‘allelochemicals’ that promote excessive hypocotyl elongation and inhibit root growth in neighbouring competitors, e.g. amaranth ( Amaranthus caudatus L.) seedlings. The major hypocotyl promoter has recently been shown not to be the previously suggested acidic disaccharide, lepidimoic acid (LMA), a fragment of the pectic polysaccharide domain rhamnogalacturonan-I. The nature of the hypocotyl promoter has now been re-assessed.
Industrial slag from steelwork activities is considered a by-product by the EU legislation and it can be used for civil construction. In this work, an experiment in a greenhouse was conducted over a 6-week period to investigate the effect of soil enrichment with ladle furnace slag on morpho-physiological parameters of Amaranthus paniculatus L. plants. Results showed that the addition of 5% (w/w) slag to soil did not alter the plant growth, highlighting a high tolerance to this slag concentration. Contrarily, plants cultivated in a soil with 10% (w/w) slag showed a marked reduction both in growth and biometric parameters. Moreover, plants grown on a slag-rich soil (20% w/w) highlighted a very low survival rate. This behaviour was confirmed by the biochemical and physiological investigations on chlorophyll a and b content, gas exchange and chlorophyll fluorescence analyses. Metal(loid)s determination showed the accumulation of Ni, Se, Sn, As, Sb and Cd in 10% slag-treated plants, while revealed an increase in Ni, Cd, As and Pb in 5% slag-treated plants. Results are discussed highlighting the profitability of the cultivation of Amaranthus plants on slag enriched soil, as this plant species is largely used both as feedstock for energy production and for environmental restoration.