Relative bioavailability of selenium in rice using a rat model and its application to human health risk assessment.

Deficiencies of selenium (Se), a necessary microelement for humans, can be remedied by appropriately supplying Se-enriched rice. However, overconsumption of Se-enriched rice poses a potential risk. To accurately assess Se human health risks associated with Se-enriched rice consumption, we developed a rat in vivo model to systematically explore the relative bioavailability of Se (Se-RBA) from Se-enriched rice from a wide geographic range. Se concentrations were in the range of 0.06 ± 0.05 to 0.15 ± 0.15 mg kg-1, averaging 0.12 ± 0.11 mg kg-1, in 196 rice samples from 21 Chinese provinces, and selenomethionine (SeMet) was the dominant Se fraction (58.0-96.5%). The Se-RBA of Se-enriched rice calculated from urine ranged from 34.86% to 102.29%, averaging 62.27% (n = 12), and was positively correlated with the proportion of SeMet in rice (p < 0.05, R2 = 0.51). Furthermore, the Se intake calculated based on the Se-RBA indicated that the Se intake of consumers of Se-enriched rice was far less than the tolerable upper intake level. Thus, the limits established by law assume overestimates of the actual nutritional value of the Se content in Se-enriched rice, and it is important to consider Se bioavailability. The current study offers suggestions for future research and provides methods to reduce the uncertainty in estimating the health risks associated with Se intake from rice.

Biochar performance for preventing cadmium and arsenic accumulation, and the health risks associated with mustard (Brassica juncea) grown in co-contaminated soils.

Cadmium (Cd) and arsenic (As) in co-contaminated soil can enter the human body harming health via the food chain, such as vegetables. Biochar derived from waste has been used to reduce heavy metal uptake by plant, but long-term effects of biochar under Cd and As co-contaminated soil needs to be investigated. A following mustard (Brassica juncea) was grown on co-contaminated soil amended with different raw materials of biochar including biochars pyrolyzed by lignite coal (LCB), rice straw (RSB), silkworm excrement (SEB), and sugar refinery sludge (SSB). The results showed that compared to the control, Cd and As contents of mustard shoot in SSB treatment decreased by 45-49% and 19-37% in two growing seasons, respectively, which was the most effective among 4 biochars. This probably due to SSB owns more abundant Fe-O functional groups. Biochar also altered the microbial community composition, specifically SSB increased proteobacteria abundance by 50% and 80% in the first and second growing seasons, thereby promoted the simultaneous immobilization of Cd and As in soils which may reduce the potential risks to humans. In summary, considering the long-term effects and security of SSB application on mustard, not only is it an effective waste recycle option, but it should also be promoted as a promising approach for safe vegetable production in Cd and As co-contaminated soils.

Zinc glycerolate (Glyzinc): A novel foliar fertilizer for zinc biofortification and cadmium reduction in wheat (Triticum aestivum L.).

Sustainable strategies are essential for zinc (Zn) biofortification and cadmium (Cd) reduction in staple food crops. Herein, we evaluated the phytotoxicity of Glyzinc under foliar and root application (FA&RA) in a lab-scale experiment, and then investigated its Zn efficiency and Cd reduction through foliar application on wheat (Triticum aestivum L.) under field conditions. Compared to RA, FA of Glyzinc exhibited no adverse effect on wheat growth and oxidative stresses at all doses. In field conditions, FA of Glyzinc remarkably increased Zn (28.7 %), S (10.4 %), Cu (17.3 %) and crude protein (9.1 %) content in wheat grain at 100 mg/L without damaging wheat yield. Furthermore, FA of Glyzinc significantly reduced the grain phytic acid (PA) (23.7 %) and Cd level (19.5 %), as well as PA to Zn molar ratio (32.3 %). Overall, our results indicate that Glyzinc has great potential as a high-efficiency foliar fertilizer for Zn biofortification and safe crop production in nano-enabled agriculture.

An integrated physiology, cytology, and proteomics analysis reveals a network of sugarcane protoplast responses to enzymolysis.

The protoplast experimental system eis an effective tool for functional genomics and cell fusion breeding. However, the physiological and molecular mechanisms of protoplast response to enzymolysis are not clear, which has become a major obstacle to protoplast regeneration. Here, we used physiological, cytological, proteomics and gene expression analysis to compare the young leaves of sugarcane and enzymolized protoplasts. After enzymatic digestion, we obtained protoplasts with viability of > 90%. Meanwhile, the content of malondialdehyde, an oxidation product, increased in the protoplasts following enzymolysis, and the activity of antioxidant enzymes, such as peroxidase (POD), catalase (CAT), acid peroxidase (APX), and O2-, significantly decreased. Cytologic analysis results showed that, post enzymolysis, the cell membranes were perforated to different degrees, the nuclear activity was weakened, the nucleolus structure was not obvious, and the microtubules depolymerized and formed several short rod-like structures in protoplasts. In this study, a proteomics approaches was used to identify proteins of protoplasts in response to the enzymatic digestion process. GO, KEGG, and KOG enrichment analyses revealed that the abundant proteins were mainly involved in bioenergetic metabolism, cellular processes, osmotic stress, and redox homeostasis of protoplasts, which allow for protein biosynthesis or degradation. RT-qPCR analysis revealed that the expression of osmotic stress resistance genes, such as DREB, WRKY, MAPK4, and NAC, was upregulated, while that of key regeneration genes, such as CyclinD3, CyclinA, CyclinB, Cdc2, PSK, CESA, and GAUT, was significantly downregulated in the protoplasts. Hierarchical clustering and identification of redox proteins and oxidation products showed that these proteins were involved in dynamic networks in response to oxidative stress after enzymolysis. Our findings can facilitate the development of a standard system to produce regenerated protoplasts using molecular markers and antibody detection of enzymolysis.

Comparative evaluation of in vivo relative bioavailability and in vitro bioaccessibility of arsenic in leafy vegetables and its implication in human exposure assessment.

Arsenic (As) contamination in vegetables is a severe threat to human health. However, the evaluation of As relative bioavailability (As-RBA) or bioaccessibility in vegetables is still unexplored. The study sought to evaluate the As-RBA in commonly consumed ten leaf vegetables collected from As-polluted farmlands. Additionally, the As-RBA was determined using rat bioassay and compared with As bioaccessibility through five commonly used in vitro methods, including UBM (Unified BARGE Method), SBRC (Solubility Bioavailability Research Consortium), DIN (Deutsches Institut für Normung e.V.), IVG (In Vitro Gastrointestinal), and PBET (Physiologically Based Extraction Test). Results showed that the As-RBA values were 14.3-54.0% among different vegetables. Notably, significant in vivo-in vitro correlations (IVIVC) were observed between the As-RBA and the As bioaccessibility determined by the PBET assay (r2 = 0.763-0.847). However, the other assays (r2 = 0.417-0.788) showed a comparatively weaker relationship. The estimation of As-RBA using derived IVIVC to assess As exposure risk via vegetable consumption confirmed that As exposure risk based on As-RBA was lower than that the total As concentrations. Therefore, it was concluded that PBET could better predict the As-RBA in vegetables than other in vitro assays. Furthermore, As-RBA values should be considered for accurate health risk assessment of As in vegetables.

In Vivo-In Vitro Correlations for the Assessment of Cadmium Bioavailability in Vegetables.

The correlation of in vitro and in vivo assays for determining bioavailable Cd amounts in vegetables is limited. Herein, the correlations between Cd relative bioavailability (Cd-RBA) in rat models and Cd bioaccessibility in four in vitro assays were examined in vegetables. Results showed that the combined liver plus kidney data provided the appropriate endpoint and was used as a biomarker to estimate Cd-RBA. The Cd-RBA was negatively correlated with the mole ratio of Ca/Cd and Fe/Cd in vegetables. Strong in vivo-in vitro correlations were found from physiologically based extraction test (PBET) and in vitro gastrointestinal (IVG) (R2 = 0.66-0.69). We concluded that PBET and IVG were optimal models for Cd-RBA determination in vegetables. The nutritional elements in the vegetables could affect Cd absorption. Furthermore, the Cd bioavailability in vegetables should be considered because risk estimates solely based on the total Cd concentration in vegetables would overestimate Cd intake.

Effect of Different Forms of Selenium on the Physiological Response and the Cadmium Uptake by Rice under Cadmium Stress.

Cadmium (Cd) is a pollutant toxic to plants and a potential threat to human health. Selenium (Se), though not essential for plants, has beneficial effects on plants under abiotic stress. A hydroponic experiment was conducted to investigate the impact of different forms of Se (Nano-Se, selenite, selenate, and SeMet) on accumulation, subcellular distribution, and chemical forms of Cd, as well as oxidative stress in rice seedlings. Cd (20 µmol·L-1) treatment significantly decreased biomass accumulation and chlorophyll content. The application of all Se forms, except selenate, mitigated the adverse effects of Cd on growth and chlorophyll content. The application of selenite, Nano-Se, and SeMet decreased root and shoot Cd concentrations as well as root-to-shoot Cd translocation in rice seedlings. Selenate application decreased shoot Cd concentration and root-to-shoot Cd translocation with no effect on root Cd concentration. Accordingly, Se increased the sequestration of Cd in the cell wall and vacuoles and decreased the active chemical form of Cd in rice seedlings. SeMet was the most effective supplement that decreased Cd concentration and enhanced Se concentration in the roots and shoots of rice seedlings. All forms of Se further enhanced catalase (CAT) and glutathione peroxidase (GSH-Px) activities and inhibited MDA accumulation. To conclude, Se influenced Cd accumulation and translocation in rice seedlings by altering the subcellular distribution, chemical forms, and antioxidant defense system under Cd stress. These effects were highly significant with SeMet treatment, probably due to better absorption and utilization by the plant.

Combined use of arbuscular mycorrhizal fungus and selenium fertilizer shapes microbial community structure and enhances organic selenium accumulation in rice grain.

Selenium (Se) deficiency is a public health concern that is mainly caused by inadequate intake of Se from staple crops. The purpose of this study is to investigate the effects of inoculation with different arbuscular mycorrhizal fungus (AMF) strains, including Funneliformis mosseae (Fm) and Glomus versiforme (Gv), and fertilization with selenite or selenate on the accumulation and speciation of Se in rice. The results showed that using both AMF inoculation and Se fertilization could promote organic Se accumulation in rice grain than using only Se fertilization. Moreover, grain of rice inoculated with Fm and grown in soil fertilized with selenate had the highest accumulation of Se, of which selenomethionine was the dominant Se species. The AMF inoculation also led to high content of available Se and high relative abundance of Firmicutes in soil. The high concentration of available Se in soil suggests that the AMF inoculation may modify the microbial community, which then causes the Se uptake of rice to increase, in turn causing the amount of organic Se accumulated in rice to increase. Based on these results, using AMF inoculation combined with Se fertilization can be a promising strategy for Se biofortification in rice.

Genetic and physiological regulation of folate in pak choi (Brassica rapa subsp. Chinensis) germplasm.

Folates are one of the essential micronutrients for all living organisms. Due to inadequate dietary intake, folate deficiency remains prevalent in humans. Genetically diverse germplasms can potentially be used as parents in breeding programs and also for understanding the folate regulatory network. Therefore, we investigated the natural genetic diversity of folates and their physiological regulation in pak choi (Brassica rapa subsp. Chinensis) germplasm. The total folate concentration ranged from 52.7 µg 100 gFW-1 to 166.9 µg 100 gFW-1, with 3.2-fold variation. The main folate vitamer was represented by 5-CH3-H4folate, with 4.5-fold variation. The activities of GTP cyclohydrolase I and aminodeoxy chorismate synthase, the first step of folate synthesis, were high in high folate accessions and low in low folate accessions. Analysis of the transcription levels of 11 genes associated with folate metabolism demonstrated that the difference in folate concentrations may be primarily controlled at the post-transcriptional level. A general correlation between total folate and their precursors was observed. Folate diversity and chlorophyll content were tightly regulated through the methyl cycle. The diverse genetic variation in pak choi germplasm indicated the great genetic potential to integrate breeding programs for folate biofortification and unravel the physiological basis of folate homeostasis in planta.

Evaluation of selenium bioavailability to Brassica juncea in representative Chinese soils based on diffusive gradients in thin-films (DGT) and chemical extraction methods.

Selenium (Se) is an essential micronutrient for humans but is toxic when consumed in excess through the food chain, such as vegetables. Therefore, it is imperative to understand the relationship between the bioavailability of Se in soil and its uptake in edible parts of vegetables. This study investigated Se bioavailability of Brassica juncea in six representative Chinese soils treated with different concentrations of exogenous selenate fertilizer (0-2 mg·kg-1) by comparing diffusive gradients in thin-films (DGT) and chemical extraction methods. The correlation coefficients between the Se uptake by Brassica juncea and soil available Se determined by different extraction methods was as follows: DGT > KCl > Water > EDTA > KH2PO4 > NaHCO3 extractions. In addition, soil properties were correlated between Brassica juncea and soil Se concentrations determined by chemical extraction methods, while the DGT method was independent of soil properties. DGT was more suitable for the measurement of Se thresholds for Udic Ferrisols, Mollisols, Stagnic Anthrosols, Fluviogenic Loamy Paddy soil, Silty Loam soil, and Calcaric Regosols with values of 373.34, 648.68, 436.29, 589.84, 295.35, and 464.95 µg·L-1, respectively. Thus, DGT may be an effective method for the prediction and evaluation of Se bioavailability to Brassica juncea in different soil types.

Transcriptome Comparison Reveals the Adaptive Evolution of Two Contrasting Ecotypes of Zn/Cd Hyperaccumulator Sedum alfredii Hance.

Hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) of Sedum alfredii Hance belong to the same species but exhibit contrasting characteristics regarding hyperaccumulation and hypertolerance to cadmium and zinc. The Illumina Hiseq 2500 platform was employed to sequence HE and NHE to study the genetic evolution of this contrasting trait. Greater than 90 million clean reads were obtained and 118,479/228,051 unigenes of HE/NHE were annotated based on seven existing databases. We identified 149,668/319,830 single nucleotide polymorphisms (SNPs) and 12,691/14,428 simple sequence repeats (SSRs) of HE/NHE. We used a branch-site model to identify 18 divergent orthologous genes and 57 conserved orthologous genes of S. alfredii Hance. The divergent orthologous genes were mainly involved in the transcription and translation processes, protein metabolism process, calcium (Ca2+) pathway, stress response process and signal transduction process. To the best of our knowledge, this is the first study to use RNA-seq to compare the genetic evolution of hyperaccumulating and non-hyperaccumulating plants from the same species. In addition, this study made the sole concrete for further studies on molecular markers and divergent orthologous genes to depict the evolution process and formation of the hyperaccumulation and hypertolerance traits in S. alfredii Hance.

A rapid method for sensitive profiling of folates from plant leaf by ultra-performance liquid chromatography coupled to tandem quadrupole mass spectrometer.

Previous published methods for the analysis of folates are time consuming because of lengthy sample extraction, clean-up and total running time. This study details the development and validation of a rapid, sensitive and robust method that combines a simple extraction step with ultra-performance liquid chromatography coupled to tandem quadrupole mass spectrometry. Here, we reported application of a tandem quadrupole mass spectrometer to analyze maximum seven vitamers of folate from plant origin. The analytical performance was evaluated by linearity, sensitivity, precision, recovery test and analysis of certified reference materials. The limit of detection and limit of quantification ranged between 0.003 and 0.021µg/100g FW and between 0.011 and 0.041µg/100g FW, respectively; the recovery and precession ranged from 71.27 to 99. 01% and from 1.7 to 7.8% RSD, respectively, depending upon folate vitamers. This newly developed and validated method is rapid (a chromatographic run time of 5min), easy to be performed (no laborious and time consuming clean-up) and can be used to simultaneously analyze seven vitamers of folate from plant sources.

Sorption of sulphamethoxazole by the biochars derived from rice straw and alligator flag.

The sorption ability of sulphamethoxazole (SMX) by biochar derived from rice straw (RS) and alligator flag (AF) at 600°C was studied to assess the ability of biochar as adsorbent to remove SMX from aqueous solution. The results indicated that sorption of SMX by biochars was well described using the Langmuir equation (R2>0.94), and the maximum sorption parameter (Q) of RS (3650 mg kg(-1)) was much higher than that of AF (1963 mg kg(-1)). Temperature had no effect on SMX sorption by biochars, while thermodynamics analysis indicated that the sorption of SMX on both biochars was a spontaneous physical process. The d 250 RS (diameter of RS sieved through 250 µm) and d 150 AF (diameter of AF sieved through 150 µm) showed excellent sorption ability for SMX. The sorption amount of RS was larger than that of AF when pH<7, whereas, the sorption amount of AF surpassed RS when pH≥7. The presence of Cu2+ and/or Cd2+ ion at low concentrations (20 mg L(-1)) significantly (P<0.05) increased the sorption of SMX on both RS and AF. Our study confirms that biochar derived from the wetland plants could be used as effective adsorbents to remove SMX from aqueous solution.

Metallothionein 2 (SaMT2) from Sedum alfredii Hance confers increased Cd tolerance and accumulation in yeast and tobacco.

Metallothioneins are cysteine-rich metal-binding proteins. In the present study, SaMT2, a type 2 metallothionein gene, was isolated from Cd/Zn co-hyperaccumulator Sedum alfredii Hance. SaMT2 encodes a putative peptide of 79 amino acid residues including two cysteine-rich domains. The transcript level of SaMT2 was higher in shoots than in roots of S. alfredii, and was significantly induced by Cd and Zn treatments. Yeast expression assay showed SaMT2 significantly enhanced Cd tolerance and accumulation in yeast. Ectopic expression of SaMT2 in tobacco enhanced Cd and Zn tolerance and accumulation in both shoots and roots of the transgenic plants. The transgenic plants had higher antioxidant enzyme activities and accumulated less H2O2 than wild-type plants under Cd and Zn treatment. Thus, SaMT2 could significantly enhance Cd and Zn tolerance and accumulation in transgenic tobacco plants by chelating metals and improving antioxidant system.

Role of sulfur assimilation pathway in cadmium hyperaccumulation by Sedum alfredii Hance.

Sedum alfredii Hance is a promising cadmium (Cd) hyperaccumulating plant recently identified in China. However, the physiological and molecular mechanisms underlying Cd accumulation, which differentiate hyperaccumulating ecotype (HE) from non-hyperaccumulating ecotype (NHE) has not been elucidated yet. A hydroponic experiment was conducted to investigate the role of sulfur assimilation pathway in Cd hyperaccumulation by the S. alfredii Hance, by analyzing gene expression pattern in sulfur assimilation pathway and the concentration of some sulfur containing compounds. The results show that, sulfur assimilation pathway was affected by Cd differently in HE and NHE S. alfredii Hance. The gene expression pattern of sulfur assimilation pathway was regulated differently in HE and NHE plants, especially the nicotianamine synthase (NAS). NAS transcript levels in root of HE was 141-fold higher than NHE, while in shoots of HE only 0.31-fold higher than NHE. In HE roots, NAS expression level was maximum 3171-fold higher than shoots, while in NHE plants roots NAS expression level was maximum 45.3-fold higher than shoots. In HE plant roots, sulfur, cysteine and methionine concentrations increased 30%, 46% and 835% respectively, by Cd treatment, but in NHE plants roots, sulfur concentration increased less than 1%, cysteine and methionine concentrations decreased 78.5% and 13.3% respectively, by Cd. Cd exposure increased glutathione levels by 142% in HE but less than 10% in NHE plant roots.

Iron concentration, bioavailability, and nutritional quality of polished rice affected by different forms of foliar iron fertilizer.

The present study compared the effects of four different forms of foliar iron (Fe) fertilizers on Fe concentration, bioavailability and nutritional quality of polished rice. The results showed that foliar fertilisation at the anthesis stage was an effective way to promote Fe concentration and bioavailability of polished rice, especially in case of DTPA-Fe. Compared to the control, foliar application of DTPA-Fe increased sulphur concentration and the nutrition promoter cysteine content, whereas decreased phosphorus concentration and the antinutrient phytic acid content of polished rice, as a result increased 67.2% ferrtin formation in Caco-2 cell. Moreover, foliar DTPA-Fe application could maintain amylase, protein and minerals quality of polished rice. According to the current study, DTPA-Fe is recommended as an excellent foliar Fe form for Fe biofortification program.

Complexation with dissolved organic matter and mobility control of heavy metals in the rhizosphere of hyperaccumulator Sedum alfredii.

The complexation of Zn, Cd and Pb with dissolved organic matter (DOM) in the rhizosphere of hyperaccumulating ecotype (HE) and a non-hyperaccumulating ecotype (NHE) of Sedum alfredii was measured using resin equilibration method. After the growth of HE S. alfredii, the rhizosphere soil pH was reduced by 0.27-0.33 units, due to enhanced DOM derived from root exudation. For both ecotypes of S. alfredii, the fraction of free metal as a percentage of soluble metal varied from 22.1 to 42.5% for Zn(2+), from 8.1 to 15.5% for Cd(2+), and from 4.5 to 10.4% for Pb(2+). Resin equilibration experiment results indicated that HE-DOM had greater ability to form complexes with Zn, Cd and Pb than NHE-DOM, Visual MINTEQ model gave excellent predictions of the complexation of Zn and Cd by DOM (R(2) > 0.97). DOM in the rhizosphere of HE S. alfredii could significantly increase metal mobility through the formation of soluble DOM-metal complexes.

Effect of ferrous sulfate fortification in germinated brown rice on seed iron concentration and bioavailability.

The present study evaluated the effectiveness of germination and iron fortification on iron concentration and bioavailability of brown rice. Iron fortification during germination process with 0.05-2 g/L ferrous sulfate increased the iron concentration in germinated brown rice from 1.1 to 15.6 times than those in raw brown rice. Based on the recommended dietary allowance of iron, maximum germination rate and γ-aminobutyric acid, we recommend the brown rice fortified with 0.25 g/L FeSO(4) as a suitable fortification level to use in germination process. Iron fortification during the germination process has a positive effect on iron concentration and bioavailability. A significant difference was observed among the cultivars in respect to the capacity for iron accumulation and bioavailability. Germination alone could improve in vitro iron solubility, but had no effect on iron bioavailability in Caco-2 cell, the additional fortification process should be combined to get high amount of bioavailable iron from the brown rice.

Folate content and composition of vegetables commonly consumed in China.

UNLABELLED: Folate deficiency increases the risk of chronic diseases, including neural tube defects (NTDs) in infants, megaloblastic anemia, cardiovascular disease, and some cancers in adults. China is the most NTDs prevalent area in the world. Folate deficiency in China can be reduced by proper supply of fresh leafy green vegetables but little is known about the folate content and vitamers in the vegetables commonly consumed by Chinese population. The purposes of this study were first to analyze most commonly consumed important vegetables that contribute to folate intake in the Chinese population and second to estimate the significance of selected vegetables as a source of dietary folate intake. Folate content and vitamers forms in vegetables were analyzed using a valid liquid chromatography method. Monoenzyme treatment was used for leafy green and some fruit vegetables, and dienzyme treatment for some root vegetables. Total folate content in commonly consumed vegetables ranged from 14.78 to 145.54 µg/100 g in edible portion with an average of 61.99 µg/100 g. The highest folate content (>140 µg/100 g) was found in pak choi and spinach. Total folate contents in leafy vegetables, fruit vegetables, and root vegetables were in the range of 17.22 to 145.54 µg/100g, 18.14 to 86.04 µg/100g, and 14.78 to 75.81 µg/100g, respectively. The considerable variations in folate content were found in different types of vegetables commonly consumed by Chinese population. Leafy vegetables are a better source of folate than fruit and root vegetables commonly consumed by Chinese population. PRACTICAL APPLICATION: Data from this research would facilitate to accurately establish the actual folate intake by Chinese population. Our folate composition data on vegetables can be incorporated into the national food databases. Availability of such data is essential for estimating folate intake and defining an optimal level for fortification program in China.

Biofortification and bioavailability of rice grain zinc as affected by different forms of foliar zinc fertilization.

BACKGROUND: Zinc (Zn) biofortification through foliar Zn application is an attractive strategy to reduce human Zn deficiency. However, little is known about the biofortification efficiency and bioavailability of rice grain from different forms of foliar Zn fertilizers. METHODOLOGY/PRINCIPAL FINDINGS: Four different Zn forms were applied as a foliar treatment among three rice cultivars under field trial. Zinc bioavailability was assessed by in vitro digestion/Caco-2 cell model. Foliar Zn fertilization was an effective agronomic practice to promote grain Zn concentration and Zn bioavailability among three rice cultivars, especially, in case of Zn-amino acid and ZnSO(4). On average, Zn-amino acid and ZnSO(4) increased Zn concentration in polished rice up to 24.04% and 22.47%, respectively. On average, Zn-amino acid and ZnSO(4) increased Zn bioavailability in polished rice up to 68.37% and 64.43%, respectively. The effectiveness of foliar applied Zn-amino acid and ZnSO(4) were higher than Zn-EDTA and Zn-Citrate on improvement of Zn concentration, and reduction of phytic acid, as a results higher accumulation of bioavailable Zn in polished rice. Moreover, foliar Zn application could maintain grain yield, the protein and minerals (Fe and Ca) quality of the polished rice. CONCLUSIONS: Foliar application of Zn in rice offers a practical and useful approach to improve bioavailable Zn in polished rice. According to current study, Zn-amino acid and ZnSO(4) are recommended as excellent foliar Zn forms to ongoing agronomic biofortification.