Tartary buckwheat is one of the nutritious minor cereals and is grown in high-cold mountainous areas of arid and semi-arid zones where drought is a common phenomenon, potentially reducing the growth and yield. Melatonin, which is an amphiphilic low molecular weight compound, has been proven to exert significant effects in plants, under abiotic stresses, but its role in the Tartary buckwheat under drought stress remains unexplored. We evaluated the influence of melatonin supplementation on plant morphology and different physiological activities, to enhance tolerance to posed drought stress by scavenging reactive oxygen species (ROS) and alleviating lipid peroxidation. Drought stress decreased the plant growth and biomass production compared to the control. Drought also decreased Chl a, b, and the Fv/Fm ratio by 54%, 70%, and 8%, respectively, which was associated with the disorganized stomatal properties. Under drought stress, H₂O₂, O₂^•−, and malondialdehyde (MDA) contents increased by 2.30, 2.43, and 2.22-folds, respectively, which caused oxidative stress. In contrast, proline and soluble sugar content were increased by 84% and 39%, respectively. However, exogenous melatonin (100 µM) could improve plant growth by preventing ROS-induced oxidative damage by increasing photosynthesis, enzymatic antioxidants (superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase), secondary metabolites like phenylalanine ammonialyase, phenolics, and flavonoids, total antioxidant scavenging (free radical DPPH scavenging), and maintaining relative water content and osmoregulation substances under water stress. Therefore, our study suggested that exogenous melatonin could accelerate drought resistance by enhancing photosynthesis and antioxidant defense in Tartary buckwheat plants.

Flavonoids from plants are particularly important in our diet. Buckwheat is a special crop that is rich in flavonoids. In this study, four important buckwheat varieties, including one tartary buckwheat and three common buckwheat varieties, were selected as experimental materials. The total flavonoid content of leaves from red-flowered common buckwheat was the highest, followed by tartary buckwheat leaves. A total of 182 flavonoid metabolites (including 53 flavone, 37 flavonol, 32 flavone C-glycosides, 24 flavanone, 18 anthocyanins, 7 isoflavone, 6 flavonolignan, and 5 proanthocyanidins) were identified based on Ultra Performance Liquid Chromatography–Electrospray Ionization–Tandem Mass Spectrometry (UPLC-ESI-MS/MS) system. Through clustering analysis, principal component analysis (PCA), and orthogonal signal correction and partial least squares-discriminant analysis (OPLS-DA), different samples were clearly separated. Considerable differences were observed in the flavonoid metabolites between tartary buckwheat leaves and common buckwheat leaves, and both displayed unique metabolites with important biological functions. This study provides new insights into the differences of flavonoid metabolites between tartary buckwheat and common buckwheat leaves and provides theoretical basis for the sufficient utilization of buckwheat.

Background: Drought stress is a major abiotic stress that causes huge losses in agricultural production. Proso millet (Panicum miliaceum L.) can efficiently adapt to drought stress and provides important information and gene resources to improve drought tolerance. However, its complex drought-responsive mechanisms remain unclear. Results: Among 37 core Chinese proso millet cultivars, Jinshu 6 (JS6) was selected as the drought-sensitive test material, whereas Neimi 5 (NM5) was selected as the drought-tolerant test material under PEG-induced water stress. After sequencing, 1695 differentially expressed genes (DEGs) were observed in JS6 and NM5 without PEG-induced water stress (JS6CK and NM5CK). A total of 833 and 2166 DEGs were found in the two cultivars under simulated drought by using 20% PEG-6000 for 6 (JS6T6 and NM5T6) and 24 h (JS6T24 and NM5T24), respectively. The DEGs in JS6T6 and JS6T24 treatments were approximately 0.298- and 0.754-fold higher than those in NM5T6 and NM5T24, respectively. Compared with the respective controls, more DEGs were found in T6 treatments than in T24 treatments. A delay in the transcriptional responses of the ROS scavenging system to simulated drought treatment and relatively easy recovery of the expression of photosynthesis-associated genes were observed in NM5. Compared with JS6, different regulation strategies were observed in the jasmonic acid (JA) signal transduction pathway of NM5. Conclusion: Under PEG-induced water stress, NM5 maintained highly stable gene expression levels. Compared with drought-sensitive cultivars, the different regulation strategies in the JA signal transduction pathway in drought-tolerant cultivars may be one of the driving forces underlying drought stress tolerance.

Proso and foxtail millets are widely cultivated due to their excellent resistance to biotic and abiotic stresses and high nutritional value. Starch is the most important component of millet kernels. Starches with different amylose contents have different physicochemical properties. In this study, starches in proso (non-waxy and waxy) and foxtail millets (non-waxy and waxy) were isolated and investigated. All the starch granules had regular polygonal round shapes and exhibited typical “Maltese crosses”. These four starches all showed bimodal size distribution. The waxy proso and foxtail millets had higher weight-average molar mass and branching degree and lower average chain length of amylopectin. These four starches all presented A-type crystallinity; however, the relative crystallinity of waxy proso and foxtail millets was higher. The two waxy millets had higher onset temperature, peak temperature, conclusion temperature, and gelatinization enthalpy. However, the two non-waxy millets had higher setback viscosity, peak time, and pasting temperature. The significantly different physicochemical properties of waxy and non-waxy millet starches resulted in their different functional properties.

DNA binding with one finger (Dof) proteins have been proven to be involved in multiple biological processes. However, genome-wide identification of the Dof gene family has not been reported for Tartary buckwheat (Fagopyrum tataricum). In this study, 35 FtDof proteins were identified, and they could be divided into nine phylogenetic subgroups. Proteins within the same subgroup had similar gene structure and motif composition. Moreover, abundant cis-acting elements were present in the promoter regions of FtDof genes. Segmental duplication was the primary driving force for the evolution of the FtDof gene family. Synteny analysis indicated that Tartary buckwheat was closer to dicotyledons, and more orthologous Dof genes existed among them. The expression pattern of FtDofs in different tissues and at different fruit developmental stages varied. Different tissues contained several genes that were specifically expressed. FtDof expression was mainly upregulated under methyl jasmonate treatment and downregulated under other hormone treatments. Taken together, FtDofs may play important roles in the growth and development of Tartary buckwheat and in response to abiotic and biotic stresses. Therefore, the genome-wide identification and expression pattern analysis of the Tartary buckwheat Dof gene family lays a foundation for further exploration of the functional characteristics of FtDofs in the future.

Drought stress is one of the key factors impeding agricultural productivity worldwide. This experiment aimed at investigating the polyethylene glycol (PEG)-induced drought stress effects on seed germination, physiology, and biochemical mechanisms in Tartary buckwheat genotypes. Four PEG-induced stress conditions (0%, 10%, 20%, and 30%) were applied to 14 selected genotypes at the germination stage to evaluate their stress tolerance capacity. Significant differences were obtained in germination percentage, relative water content (RWC), and all growth parameters among the studied 14 genotypes. Based on the stress tolerance index (STI), XiNong 9943, XiNong 9940, and QianKu-5 were found to be tolerant, and QuanKu-4 was susceptible. These cultivars were selected for further physiological and biochemical characterization. The results demonstrated that the activity of enzymes was significantly increased with the increase in PEG dose. SOD (superoxide dismutase), POD (peroxidase), CAT (catalase), and APX (ascorbate peroxidase) levels obtained at 30% PEG in the XiNong 9943 genotype were 2.01, 2.19, 4.92, and 4.46 times higher, respectively, than the normal growth condition (T₀). Moreover, the secondary metabolite content also increased with the increase in PEG dose. At 30% PEG, the genotype XiNong 9943 yielded phenols, flavonoids, polyphenol oxidase (PPO), and phenylalanine ammonia lyase (PAL) levels that were higher by 131%, 95%, 154%, and 164%, respectively, than T₀ condition. From both the findings of the activity of enzymes and the secondary metabolite content, the genotypic response to drought was ranked in the following order: XiNong 9943 > XiNong 9940 > QianKu-5 > QianKu-4, which supported the STI selection system. Assessing the overall performance, the genotype XiNong 9943 shows drought tolerance, which can be useful material for future buckwheat breeding programs.