Cd Accumulation In Wheat Grain Research Articles

Application of Lanthanum at the Heading Stage Effectively Suppresses Cadmium Accumulation in Wheat Grains by Downregulating the Expression of TaZIP7 to Increase Cadmium Retention in Nodes.

Reducing cadmium (Cd) accumulation in wheat is an effective way to decrease the potential threats of Cd to human health. The application of lanthanum (La) in agricultural fields is eliciting extensive attention due to its beneficial effects on improving yields and inhibiting Cd accumulation in edible parts of crops. However, the potential mechanism of La-restricted Cd accumulation in crop grains is not entirely understood. Here, we investigated the effects of La and Cd accumulation in wheat grains by implementing application at the shooting and heading stages. Some associated mechanisms were explored. Results showed that La application at the shooting and heading stages considerably promoted the thousand-grain weight. La application at the shooting and heading stages increased Cd accumulation in the first node beneath the panicle (N1) but reduced Cd levels in the other tissues. La application at the heading stage exerted greater effects on Cd storage in N1 while reducing Cd concentrations in the other tissues compared with La application at the shooting stage. La addition substantially decreased the translocation of Cd from the lower nodes to the upper internodes, but increased Cd translocation from the lower internodes to the upper nodes. The expression of TaZIP7 in N1 was downregulated by La treatment. These results suggest that the effective reduction in Cd in wheat grains by La application at the heading stage is probably a consequence of the successful promotion of Cd storage in nodes by downregulating the expression of TaZIP7 during the grain-filling stage, thereby hindering the redirection Cd from nodes to grains.

Cadmium immobilization by mercapto-palygorskite in alkaline soil: Impacts on soil microbial communities and wheat rhizosphere metabolism

Weakly alkaline cadmium (Cd) contaminated soil in China has aroused great concern regarding its impact on food security and human health. Mercapto-modified palygorskite (MP) has exhibited good potential to minimize Cd accumulation in wheat, it is imperative to understand the underlying mechanisms within the soil-wheat-microbial system for sustainable development of agrochemicals. This study evaluated the effects of various MP dosages on soil Cd bioavailability, rhizosphere metabolomics, microbial community structure and wheat growth. The results indicated that MP (0.05–0.2 %) application significantly reduced Cd accumulation in wheat grains by 59.0–83.2 % (p < 0.05) and inhibited Cd translocation from root to grain. MP also promoted Mn oxide formation and redistributed the exchangeable Cd to Fe–Mn oxide-bound forms (44.2–109.6 %), thus lowering soil Cd bioavailability by 17.9–32.5 %. Additionally, MP reduced wheat rhizosphere organic acid levels, altered rhizosphere carbon and nitrogen pools, and stimulated the growth of Cd-tolerant Alternaria and Cladosporium, while inhibiting the growth of Fusarium. These findings highlight the potential of MP to modulate soil rhizosphere metabolism and microbial communities, offering a novel perspective on its environmental implications and supporting agrochemical sustainability.

Cadmium Minimization in Grains of Maize and Wheat Grown on Smelting-Impacted Land Ameliorated by Limestone.

Cadmium (Cd) contamination in agricultural soils has emerged as a significant concern, particularly due to its potential impact on plant-based food. Soil pH reductions can exacerbate Cd mobility, leading to excessive accumulation in crops. While liming has been demonstrated as an effective method to mitigate Cd accumulation in rice grains in acid soils of southern China, its efficacy in remediating acid soils in northern China remains unclear. In this study, a multi-year field experiment was conducted on farmland impacted by zinc ore smelting at coordinates of 33.92° N 112.46° E to investigate the use of limestone for controlling Cd accumulation in wheat and maize grains. The results indicated that applying 7.5 t ha-1 of limestone significantly raised the soil pH from 4.5 to 6.8 as anticipated. Different rates of limestone application (2.25, 4.45, and 7.50 t ha-1) reduced Cd bioavailability in the soil by 20-54%, and Cd accumulation in wheat grains by 5-38% and maize grains by 21-63%, without yield penalty. The remediation effects were sustained for at least 27 months, highlighting limestone as a promising ameliorant for smelting-affected farmland in northern China.

Trade-offs of reproductive growth and Cd remobilization regulated Cd accumulation in wheat grains (Triticum aestivum L.)

Minimization of cadmium (Cd) accumulation in wheat grain (Triticum aestivum L.) is an important way to prevent Cd hazards to humans. However, little is known about the mechanisms of varietal variation of Cd accumulation in wheat grain. This study explores the physiological mechanisms of Cd bioaccumulation through field and hydroponic experiments on two wheat varieties of low-Cd-accumulating variety (L-6331) and high-Cd-accumulating variety (H-6049). Field study showed that average Cd accumulative rates in spikes of H-6049 were 1.57-fold of L-6331 after flowering, ultimately grain-Cd of H-6049 was 1.70-fold of L-6331 in Cd-contaminated farmland. The hydroponic experiment further confirmed that more vegetative tissues of L-6331 were involved in the remobilization of Cd, which jointly mitigated the process of Cd loaded to grains when leaf-cutting conducted after Cd stress. Additionally, the L1 and N1 of L-6331 play an especially important role in regulating Cd remobilization, and the larger EVB areas in N1 have the morphological feature that facilitates the transfer of Cd to L1. Overall results implied that low-Cd-accumulating variety initiated more trade-offs of reproductive growth and Cd remobilizatoin under Cd-stress after flowering compared with high-Cd-accumulating variety, and provided new insights into the processes of Cd loaded into wheat grains among different varieties.

Comparison of soil addition, foliar spraying, seed soaking, and seed dressing of selenium and silicon nanoparticles effects on cadmium reduction in wheat (Triticum turgidum L.)

Wheat cadmium (Cd) contamination is a critical food security issue worldwide, and selenium (Se) and silicon (Si) are widely reported to reduce Cd accumulation in cereal crops. However, few studies have compared the most effective pathway to reduce Cd accumulation in crops using Se nanoparticles (nano-Se), Si nanoparticles (nano-Si), and their mixtures. Here, we investigated the concentrations of Cd in wheat using four application modes: soil addition, foliar spraying, seed soaking, and seed dressing combined with three different materials. The concentration of Cd in wheat grains can be significantly reduced by 31.30–62.99% and 36.96–51.04% through four applications of nano-Se and soil application and seed soaking of nano-Si, respectively. However, all treatments involving mixtures of nano-Si and nano-Se did not show a reduction in Cd concentration. The applications of both nano-Se and nano-Si can enhance antioxidant enzyme systems and regulate Cd-related gene expression to safeguard wheat tissues from Cd stress. Downregulation of the influx transporter from soil to root (TaNramp5) and from root to shoot (TaLCT1), along with the upregulation of the efflux transporter from cytoplasm to vacuole (TaHMA3), contributed to the nano-Si/nano-Se dependent Cd transport and reduced Cd accumulation in wheat grains. Overall, the application of nano-Se instead of nano-Si, and soil addition rather than foliar spraying, seed soaking, and seed dressing, can be efficiently utilized to reduce grain Cd accumulation from Cd-contaminated soils.

Foliar Application of Nanoparticles Reduced Cadmium Content in Wheat (Triticum aestivum L.) Grains via Long-Distance "Leaf-Root-Microorganism" Regulation.

Foliar application of beneficial nanoparticles (NPs) exhibits potential in reducing cadmium (Cd) uptake in crops, necessitating a systematic understanding of their leaf-root-microorganism process for sustainable development of efficient nano-enabled agrochemicals. Herein, wheat grown in Cd-contaminated soil (5.23 mg/kg) was sprayed with different rates of four commonly used NPs, including nano selenium (SeNPs)/silica (SiO2NPs)/zinc oxide/manganese dioxide. SeNPs and SiO2NPs most effectively reduced the Cd concentration in wheat grains. Compared to the control, Cd concentration in grains was significantly decreased by 35.0 and 33.3% by applying 0.96 mg/plant SeNPs and 2.4 mg/plant SiO2NPs, and the grain yield was significantly increased by 33.9% with SeNPs application. Down-regulated gene expression of Cd transport proteins (TaNramp5 and TaLCT1) and up-regulated gene expression of vacuolar Cd fixation proteins (TaHMA3 and TaTM20) were observed with foliar SeNPs and SiO2NPs use. SeNPs increased the levels of leaf antioxidant metabolites. Additionally, foliar spray of SeNPs resulted in lower abundances of rhizosphere organic acids and reduced Cd bioavailability in rhizosphere soil, and soil microorganisms related to carbon and nitrogen (Solirubrobacter and Pedomicrobium) were promoted. Our findings underscore the potential of the foliar application of SeNPs and SiO2NPs as a plant and rhizosphere soil metabolism-regulating approach to reduce Cd accumulation in wheat grains.

Control location could confuse the evaluation of passivation effect of iron-based biochar and selenium application on wheat grain cadmium accumulation

Inhibiting cadmium (Cd) accumulation in wheat grain could reduce the risk of Cd exposure to human. This study conducted a field experiment and evaluated the effect of iron-based biochar and selenium (Se) application individually or together on Cd accumulation in wheat grains in Cd contaminated soils. Considering the soil Cd heterogeneity in field, we set up 13 replicates of control (CK) and three replicates of each treatment. Results clearly showed that CK location could greatly affect the evaluation whether the difference in the wheat grain Cd concentration between treatments and CK was significant. When we assessed the difference between the treatments (foliar and soil application of Se, iron-based biochar application) and the adjacent CK, there was insignificant difference in the wheat grain Cd concentration between treatment and CK groups. Although soil application of 2 mg kg-1 Se or foliar application of 4 mg L-1 Se significantly increased the grain Se concentration as compared with the adjacent CK, but they still could not reduce the Cd concentrations in wheat grain. However, when we selected the CK that had the highest averaged grain Cd concentration, foliar and soil application of Se could significantly reduce the wheat grain Cd concentration by 47.7% and 41.3-46.1%, respectively. No matter which CK was selected, application of Fe-based biochar had no significant impact on Cd accumulation in wheat grain, and there was insignificant difference in DTPA-Cd concentrations between the iron-based biochar treatment and adjacent control. In conclusion, applying Fe-based biochar and Se in the field could not reduce the Cd accumulation in wheat grain in Cd contaminated weakly alkaline soils.

Selenate reduced wheat grain cadmium accumulation by inhibiting cadmium absorption and increasing root cadmium retention

Selenium (Se) fertilizer has been recently used to reduce cadmium (Cd) accumulation in plant. A pot culture was performed to analyze Cd uptake, translocation, and distribution in wheat plants during the reproductive growth period in a Cd–contaminated soil after selenate was applied to the soil, and a hydroponic culture was carried out to investigate the effects of selenate application on Cd2+ influx, subcellular Cd distribution, and Cd accumulation in wheat seedlings. Results showed that selenate application had no significant effect on DTPA–Cd and Cd fraction in soil. The application of selenate greatly inhibited the whole–plant Cd absorption by 14%–23%. In addition, selenate prompted the retention of Cd in root by increasing the Cd distribution in the vacuole, which reduced the root–to–shoot Cd translocation by 18%–53%. The application of selenate increased the Cd concentration in nodes, inhibited Cd remobilization from nutritive organs to grain, and ultimately reduced Cd accumulation in wheat grain. Further, heading to grain filling was the key growth stage for exogenous selenate to regulate grain Cd accumulation. In summary, soil selenate application is an effective method to reduce grain Cd concentration in wheat, which provided scientific basis for remediation of Cd–contaminated soil.

Effects of Nitrogen and Zinc Fertilization on Alleviating Cadmium Accumulation in Durum Wheat Grains

ABSTRACT Cadmium (Cd) accumulation in durum wheat (Triticum durum L.) is of particular concern compared to the other commonly cultivated cereals. This study was conducted to determine the effects of zinc (Zn) and nitrogen (N) applications on grain Cd concentration of durum wheat grown in a Cd contaminated soil. The experimental design consisted of randomized plots with four replications. The treatments included low and adequate (0.05 and 5 mg kg−1) Zn doses, and inadequate, optimal and high (200, 400 and 600 mg kg−1) N doses. Cadmium application rates were 0 and 5 mg kg−1. The findings demonstrated that Cd application caused a significant increase in grain Cd concentrations, and a decrease in straw and grain yields under low and adequate doses of Zn and all N doses. However, increasing N applications with adequate soil Zn caused an increase in the straw and grain yields and a significant decrease in grain Cd concentration. The grain Cd concentration in low Zn and optimum N treatment under Cd application was 6206 µg kg−1, while the grain Cd concentration decreased by 26.3% (4574 µg kg−1) in the Zn and optimum N treatment. In addition, the grain Zn concentration of durum wheat under low soil Zn conditions was decreased in Cd application, whereas the grain Zn concentration increased in Cd application under adequate soil Zn concentration. The results revealed that combined application of N and Zn in Zn deficient soils is highly effective at decreasing Cd accumulation in wheat grains compared to individual applications.

Role of Soil and Foliar-Applied Carbon Dots in Plant Iron Biofortification and Cadmium Mitigation by Triggering Opposite Iron Signaling in Roots.

In China, iron (Fe) availability is low in most soils but cadmium (Cd) generally exceeds regulatory soil pollution limits. Thus, biofortification of Fe along with mitigation of Cd in edible plant parts is important for human nutrition and health. Carbon dots (CDs) are considered as potential nanomaterials for agricultural applications. Here, Salvia miltiorrhiza-derived CDs are an efficient modulator of Fe, manganese (Mn), zinc (Zn), and Cd accumulation in plants. CDs irrigation (1mgmL-1 , performed every week starting at the jointing stage for 12 weeks) increased Fe content by 18% but mitigated Cd accumulation by 20% in wheat grains. This findingwasassociated with the Fe3+ -mobilizing properties of CDs from the soil and root cell wall, as well as endocytosis-dependent internalization in roots. The resulting excess Fe signaling mitigated Cd uptake via inhibiting TaNRAMP5 expression. Foliar spraying of CDs enhanced Fe (44%), Mn (30%), and Zn (19%) content with an unchanged Cd accumulation in wheat grains. This result is attributed to CDs-enhanced light signaling, which triggered shoot-to-root Fe deficiency response. This study not only reveals the molecular mechanism underlying CDs modulation of Fe signaling in plants but also provides useful strategies for concurrent Fe biofortification and Cd mitigation in plant-based foods.

Distribution and accumulation of cadmium in soil under wheat-cultivation system and human health risk assessment in coal mining area of China

The soil contamination caused by the discharge of cadmium (Cd) from coal mining activities has aroused continuous attention due to the detrimental effects on the human health. This study aimed to investigate the characteristics on distribution of Cd in soils and its accumulation in wheat grains under wheat-cultivation system, and further assess the human health risks to adults and children. 58 soils and wheat samples in pairs from Linhuan coal mining area, Anhui Province were collected and analyzed. Results showed that the concentrations of Cd in 17.24% of soil samples exceeded the limit value established by the Ministry of Ecology and Environment. The ordinary kriging interpolation displayed that the spatial variability of Cd concentrations in soils was mainly influenced by coal mining activities. The transfer capacity of Cd from soils to wheat roots was greater than that from the wheat roots to grains. Multiple linear regression model clarified that soil pH and exchangeable Cd fraction in soils were the critical factors affecting the Cd accumulation in wheat grains. The carcinogenic risk of Cd levels in our studied wheat grains was a concern but still within the acceptable range, while their non-carcinogenic hazard was negligible for adults and children. The calculation results were in accord with the uncertainty analysis conclusion based on Monte Carlo simulation. The study was expected to promote the source management and control strategy of reducing tailing discharge, and providing scientific references for current soil remediation and land degradation prevention.

Effect of Zinc Fertilizer Application on Cadmium Accumulation in Wheat Grain and Its Application Risk

The interaction of zinc (Zn) and cadmium (Cd) is an important research direction in the prevention and control of Cd pollution of wheat in recent years. In this study, a typical wheat field in North China was selected as the object to explore the control effect and application risk of Zn fertilizer on Cd pollution in a soil-wheat system through field experiments. The results showed that under the treatment of a low dosage of Zn, the Cd concentrations in wheat grains in Jiyuan City and Kaifeng City decreased by 33.4% and 25.3% compared with those in the control, respectively. By contrast, Cd concentrations in wheat grains treated with a high dosage of Zn increased by 22.4% and 34.2% compared with that of the low-dosage Zn treatment. After the application of Zn, the total amount and available Zn concentrations increased significantly, and Cd was partially activated in these two locations. Canonical correlation analysis (CCA) showed that when the Zn concentrations in the soils were less than 200 mg·kg-1, soil Zn was the main factor affecting Cd accumulation in the soil-wheat system, whereas when Zn concentrations in soils were greater than 200 mg·kg-1, the activation of soil Cd was the main factor affecting Cd accumulation in wheat grains. Regression analysis showed that when the soil Cd/Zn ratio decreased to 0.0089 (low dosage of Zn), Zn and Cd showed an antagonistic effect, whereas when the soil Cd/Zn ratio decreased to 0.0078 (high dosage of Zn), Zn and Cd showed a synergistic effect. According to the characteristics of regional Cd pollution, adjusting the amount of Zn fertilizer can improve the efficiency of pollution control and avoid aggravating the harm of Cd pollution.

Intercropping with herbs minimizes cadmium availability through altering physicochemical dynamics and metabolite profiles in wheat rhizosphere

AbstractFor the past few years, the production of safe crops in Cd‐contaminated soil has attracted more and more attention, and the intercropping of wheat and herbaceous plants has gradually become an effective way. However, how the physicochemical and metabolic processes because of the intercropping change Cd availability are still unclear. In this study, we studied the influence of changes in soil physicochemical properties induced by intercropping of wheat with different herbs on soil Cd availability of Cd. Meanwhile, we innovatively studied the effect of intercropping on rhizosphere metabolites and evaluated the impact on Cd transfer. Results showed that the highest wheat biomass was presented in the intercropping system with the Cichorium intybus L. (W4) and Aus hypochondriacus L. (W5) increasing by 57.66% and 54.05% individually, compared with monocropping, while W1, W2, and W3 increasing slightly. Further, the Cd accumulation in wheat grains under W4 and W5 treatment decreased by 44.95% and 43.12%, respectively. Structural equation model confirmed that the increased pH, CEC contributed to the decreased Cd availability in soil, as well the changed metabolic profiles in wheat rhizosphere after intercropping. Specially, up‐regulation of fatty acid metabolism allowed wheat plants to maintain a normal intracellular environment under stress conditions. Similarly, up‐regulation of saccharide and amino acid metabolism induced the accumulation of sugars and proteins, which positively increased wheat biomass and Cd‐binding proteins, thus inhibiting the migration of soil Cd into wheat tissue. Collectively, this study provided reasonable insights towards understanding the metabolic mechanisms how intercropping altered Cd availability.

A novel wheat β-amylase gene TaBMY1 reduces Cd accumulation in common wheat grains

Cadmium (Cd) is one of the most environmentally hazardous heavy metals, posing a significant threat to food safety. In the present study, we identified a novel cytoplasmic amylase gene, TaBMY1 , involved in Cd transport in wheat ( Triticum aestivum ) plants. Cysteine residues in the core domain of BMY1 formed disulfide bridges. Yeast expressing TaBMY1 exhibited poor Cd tolerance. These findings suggested that BMY1 might participate in metal tolerance and translocation. Subsequently, RNA interference (RNAi) and overexpression (OE) transgenic wheat were obtained. Compared to wild-type (WT), RNAi lines exhibited shoot or root elongation and increased dry mass and chlorophyll content, whereas TaBMY1 overexpression showed a sensitive growth phenotype. RNAi lines accumulated less Cd and reduced Cd translocation from root to shoot by approximately 38%, as well as Cd accumulation in grains by 71–74%, whereas the OE lines had increased Cd accumulation. Our results suggest that silencing the TaBMY1 gene may affect Cd allocation and distribution. This work provides a novel approach to decreasing Cd accumulation in wheat crops and reducing environmental risks to human health through food chains. • A novel wheat β-amylase gene, TaBMY1 , was investigated. • TaBMY1 was first reported to reside in the cytoplasm. • Heterologous expression of TaBMY1 gene in yeast showed no transport activities for Cd. • Silencing of TaBMY1 decreased root-to-shoot Cd translocation and Cd accumulation in wheat grains. • This study offers a highly effective solution for breeding lower Cd-accumulating wheat crop.

Comparison of Pb and Cd in wheat grains under air-soil-wheat system near lead-zinc smelters and total suspended particulate introduced modeling attempt

The excessive accumulation of wheat grain metals and metalloids caused by ambient air contamination has drawn an increasing concern. However, at present, the differences in the pathways of cadmium and lead accumulation in wheat grains in an air-soil-wheat system are not clear. In this study, wheat was grown around a lead‑zinc smelting area and exposed to different soil Pb and Cd levels and different ambient air Pb and Cd levels. Lead and Cd accumulation in wheat grains was examined in this study. Two models of wheat grain Pb and Cd concentrations were established based on the 3 variables including soil Pb and Cd concentration, ambient air Pb and Cd concentration, and soil pH. The results showed that total suspended particulate (TSP), soil, and wheat grains exhibited different degrees of Pb and Cd contamination in the study area, and the contamination of Cd is more serious than Pb contamination. The Pb in wheat grains was more likely to derive from ambient air than from soil, whereas the impact of ambient air on the accumulation of Cd in wheat grains might be very limited. This speculation was confirmed by the results of the predictor variable relative weight method based on the multiple regression analysis. Introduction of ambient air factor (TSP Pb and Cd) greatly improved the modeling effect of wheat grains Pb, while the modeling of grain Cd was more dependent on soil pH and total soil Cd. This research suggests that the reduction in wheat grain Pb is likely to be achieved by the control over ambient air Pb, whereas the reduction in the wheat grain Cd by the remediation of soil pollutants.

New SFT2-like Vesicle Transport Protein (SFT2L) Enhances Cadmium Tolerance and Reduces Cadmium Accumulation in Common Wheat Grains.

Cadmium (Cd) is one of the most toxic heavy metal elements to the environment, which seriously threatens the safe production of food crops. In this study, we identified a novel function of the cytomembrane TaSFT2L protein in wheat (Triticum aestivum). Expression of the TaSFT2L gene in yeast showed no transport activities for Cd, which could explain the role of TaSFT2L in metal tolerance. It was observed that increased autophagic activity in roots caused by silencing of TaSFT2L enhanced Cd tolerance. Transgenic wheat revealed that RNA interference (RNAi) lines enhanced the wheat growth concerning the increased shoot or root elongation, dry weight, and chlorophyll accumulation. Furthermore, RNAi lines decreased root-to-grain Cd translocation in wheat by nearly 68% and Cd accumulation in wheat grains by 53%. Meanwhile, the overexpression lines displayed a compromised growth response and increased Cd accumulation in wheat tissues, compared to wild type. These findings show that TaSFT2L is a key gene involved in regulation of Cd translocation in wheat, and its silencing to form transgenic wheat can inhibit Cd accumulation. This has the ability to alleviate the food chain-associated impact of environmental pollution on human health.

Evaluating the contributions of leaf organ to wheat grain cadmium at the filling stage

Cadmium (Cd) is an element of global concern in agricultural fields owing to its high bioavailability and its risk to human health via the consumption of wheat products. However, whether wheat leaves can directly absorb atmospheric Cd and transport them to the grains along with the contribution of leaves to Cd accumulation in the grains is not clear. We evaluated this mechanism through three comparative treatments: 1) exposure to atmospheric deposition (CK), 2) no exposure to atmospheric deposition (T1), and 3) exposure to atmospheric deposition with leaf cutting (T2). The Cd accumulation rate of grains in the CK, T1, and T2 groups all showed an increasing trend, followed by a decreasing trend, which was consistent with the trend of filling rate. Moreover, the critical period for leaf Cd accumulation in the grains was the early filling period, and its contribution decreased gradually as filling progressed. The contribution of the leaves to grain Cd reached 31.73% at maturity, with the reactivation of stored Cd in leaves pre-flowering and the newly absorbed atmospheric Cd by leaves post-flowering contributing 19.76% and 11.97% to Cd accumulation in grains, respectively, at maturity. Sub-microstructure analysis of the leaves further confirmed that the direct Cd absorption by leaves from atmospheric deposition through stomata contributed to Cd accumulation in wheat grains. Therefore, controlling the sources of atmospheric Cd pollution and reducing Cd absorption by leaves during grain filling can effectively control Cd pollution of wheat grains. This study provides significant insights on how to more effectively control the Cd content of edible part of wheat and ensure food security.

Variations in Cadmium Accumulation and Transport and Ionomic Traits Among Different Winter Wheat Varieties

A field trial was conducted to identify the key factors affecting intraspecific variation in the cadmium (Cd) content in the grain of winter wheat. Three wheat cultivars with low Cd accumulation and two wheat cultivars with high Cd accumulation were planted. The Cd accumulation and transport and ionomic traits were examined in different organs of the tested wheat cultivars. Additionally, correlation analysis and principal component analysis were used to identify the key plant organs, translocation pathways, and elements that determine the intraspecific variation in the Cd content in wheat grain. The results showed that the bioaccumulation factors of Cd in glume, rachis, internode 1, and node 1, as well as the transport factors of Cd from rachis to grain, from rachis to glume, from internode 1 to rachis, and from node 1 to internode 1, were significantly correlated with Cd bioaccumulation factors in grain. The above-mentioned bioaccumulation factors and transport factors of Cd made a great contribution to the principal components that could discriminate between the wheat cultivars with low and high Cd accumulation and were significantly different among cultivars. Therefore, glume, rachis, internode 1, and node 1 were the key organs affecting the genotype differences in Cd content in wheat grain, and Cd translocation from rachis to grain, from rachis to glume, from internode 1 to rachis, and from node 1 to internode 1 were the key pathways controlling the variety differences in Cd accumulation in wheat grain. The analysis of wheat ionome showed that the bioaccumulation factors of Mg and Mn in the key organs and the transport factors of Mo, Cr, and Pb in the key transport pathways were significantly correlated with the bioaccumulation factor of Cd in wheat grain and contributed greatly to the differentiation between the wheat cultivars with low and high Cd accumulation in the principal component analyses. Thus, in the above-mentioned key organs and transport pathways, Mg, Mn, Mo, Cr, and Pb were the key elements affecting the genotype differences in Cd content in wheat grain.

Foliar application of several reagents reduces Cd concentration in wheat grains.

Cadmium (Cd) in agricultural soils can be absorbed by wheat and transferred into the grains, risking human health. In order to find the optimal foliar treatment method to reduce Cd accumulation in wheat grain, nineteen single-factor foliar treatments and multi-factor combination treatments were used to study the effects of different foliar sprays on Cd accumulation of wheat grain. The results showed that the foliar application of ethylenediaminetetraacetate (EDTA), selenium (Se), and sodium nitroprusside (SNP) can significantly reduce Cd concentration in wheat grains by 49.2%, 29.6%, and 28.8%, respectively, in the field. Foliar application of EDTA, Se, zinc (Zn), ascorbic acid (ASC), silicon (Si), and molybdenum (Mo) can significantly reduce Cd concentration of wheat grains by 32.3%, 32.0%, 27.7%, 27.7%, 26.3%, and 25.9%, respectively, in pot experiment. Foliar application of 2 mM EDTA and 2 mM Se exerted excellent effects on controlling the Cd accumulation of wheat grains both in pot and field experiment. Foliar application with 0.1 mM Se or 2 mM EDTA significantly reduced Cd concentrations in grains both in grain filling stage and heading + grain filling stage. Spraying at the filling stage has a better effect on reducing Cd concentration in grains than spraying at the heading stage. In addition, the relationship between Cd concentration in grains and husks was significantly positive, while the Cd concentration in grains and flag leaves was significantly negative. Our research proves that foliar spraying of Se and EDTA is feasible to reduce the Cd concentration in wheat grains, which provides technical guidance for the safe production of wheat in low-Cd-contaminated soils.

Phytoavailability, translocation and soil thresholds derivation of cadmium for food safety through soil-wheat (Triticum aestivum L.) system.

Cadmium (Cd) pollution in cultivated soils has posed a great risk to human health through the soil-plant-human pathway. Therefore, it is important to derive soil thresholds for the low-Cd accumulating genotype of wheat (Triticum aestivum L.) to promote its application in agricultural production on Cd-contaminated sites. Here, a pot experiment was performed to explore the transfer characteristics of Cd in two contrasting wheat genotypes at three different soils and the effect of soil parameters together with soil safety Cd thresholds derivation. Generally, grain Cd highly accumulating wheat genotype (Zhenmai10, HT) showed higher Cd accumulation in grains than grain Cd weakly accumulating wheat genotype (Aikang58, LT). Stepwise multiple linear regression (SMLR) analysis (log-transformed Freundlich-type) indicated that Cd accumulation in wheat grains was strongly related to soil total Cd concentration and pH for both genotypes (R2 = 0.907*** for HT; R2 = 0.910*** for LT). Combining the simple regression model of soil-plant transfer system with the risk assessment method based on human health, soil total Cd thresholds for three soils were calculated with the values of 0.62, 0.82, and 0.62 mg kg-1 in LT genotype and 0.31, 0.77, and 0.49 mg kg-1 in HT genotype. Therefore, we suggested that when deducing soil thresholds, the ability of wheat genotypes to accumulate Cd and soil properties should be considered because of the large differences in soil thresholds between different genotypes and types of soils. We believe our results will promote the application of low-Cd wheat genotypes to agricultural production, thereby ensuring the safety of their products.