Identification of wheat (Triticum aestivum L.) genotypes for food safety on two different cadmium contaminated soils.

Over the last decade, human population has been facing great challenges in ensuring appropriate supply of food free from cadmium (Cd) contamination. Selection of genetically low-Cd wheat (Triticum aestivum L.) genotypes, with a large biomass and high accumulation of Cd in straw but low-Cd concentration in grains, is an inventive approach of phytoremediation while keeping agricultural production in moderately contaminated soils. In this study, variations in Cd uptake and translocation among the 30 wheat genotypes in two different sites were investigated in field experiments. Significant differences in grain Cd concentration were observed between the two sites, with averaged values of 0.048 and 0.053 mg kg-1 DW, respectively. Based on straw Cd accumulation, grain Cd concentration, and TFrs, Bainong207 and Aikang58 for site A and Huaimai23 and Yannong21 for site B are promising candidates of low-Cd genotypes, which have considerable potential in achieving phytoremediation while keeping agricultural production on moderately or slightly Cd-polluted soil. The results indicate that it is possible to select the optimal low-Cd genotypes of wheat for different soil types by taking consideration of the effect of soil-wheat genotype interaction on grain Cd concentration.

Efficiency of lime, biochar, Fe containing biochar and composite amendments for Cd and Pb immobilization in a co-contaminated alluvial soil.

Present study reports the laboratory and field scale application of different organic and inorganic amendments to immobilize cadmium (Cd) and lead (Pb) in a co-contaminated alluvial paddy soil. For that purpose, lime, biochar, Fe-biochar and two composite amendments (CA) composed of biochar, lime, sepiolite and zeolite (CA1: composite amendment 1) and manure, lime and sepiolite (CA2: composite amendment 2) were firstly tested in an incubation experiment to ameliorate Cd and Pb co-contaminated alluvial soil. It was observed that liming and CA2 elevated the soil pH and reduced DTPA extractable Cd and Pb in the incubated soil leading to higher metal immobilization. Therefore, efficiency of lime and CA2 was further investigated in field conditions with mid rice as the test crop to evaluate field scale immobilization and precise application rate for the tested soil type. DTPA and CaCl2 extractable Cd (46 and 51%) and Pb (68 and 70%) in field soil were decreased with applied treatments. Speciation of Cd and Pb also promoted conversion of metal exchangeable contents to less-available forms. Activated functional groups on amendments' surface (_OH bonding, C_O and CO, -O-H, Si-O-Si, carboxylic and ester groups) sequestered metals by precipitation, adsorption, ion exchange or electro static attributes. Application of lime at 2400 kg/acre (T4) and CA2 at 1200 kg/acre was more effective in reducing rice shoot and grains metal contents. Moreover, obtained results in terms of pH, extractable content, speciation and yield, and microanalysis of amendments highlights the remarkable efficiency of lime and composite amendment to sorb Cd and Pb providing the key evidence of these amendments for metals immobilization and environmental remediation. Considering these results, lime and CA2 are potential amendments for co-contaminated rice field especially in context of alluvial soil.

Accumulation and distribution of cadmium and lead in 28 oilseed rape cultivars grown in a contaminated field.

Heavy metal pollution in soils has become an important concern for human health. Therefore, it is vital to develop suitable remediation strategies for contaminated soils. Oilseed rape tolerates high concentrations of heavy metals and is a promising candidate for the phytoextraction of cadmium (Cd) and lead (Pb) from metal-contaminated soils. A field experiment was conducted to evaluate 28 oilseed rape cultivars including Brassica napus L. and Brassica juncea L. for their ability to accumulate Cd and Pb. These cultivars were grown in a field co-contaminated with Cd (0.78 mg kg-1) and Pb (330 mg kg-1). The results showed that concentrations in shoots ranged from 1.22 to 3.01 mg kg-1 for Cd and from 10.8 to 29.5 mg kg-1 for Pb. Cadmium and Pb accumulations in shoots could reach 83.4 and 799 µg plant-1, respectively. The majority of translocation factors (TFs) for Cd (> 1.0) were higher than for Pb (≤ 1.0). However, concentrations of Cd and Pb in seeds were much lower, in the range of 0.04 to 0.21 mg kg-1 and 0.04 to 0.51 mg kg-1, respectively. The seed yields of oilseed rape varied from 1238 to 2904 kg ha-1, with a mean value of 2289 kg ha-1. Among the cultivars, three (OS-9, OS-12, and OS-15) were selected as Cd and Pb potential accumulators, with Cd accumulation in shoots being 2.74-3.70 times higher and Pb accumulation in shoots being 3.37-5.23 times higher as compared with the lowest accumulating cultivar. These selected cultivars (B. napus) have application potential for phytoextraction of Cd and Pb from polluted soils without stopping agricultural activities and accompanying food safety issues.

Comparative assessment of Indian mustard (Brassica juncea L.) genotypes for phytoremediation of Cd and Pb contaminated soils.

Heavy metal removal by phytoremediation bears a great potential to decontaminate soils and Brassica juncea L. (Indian mustard) seems to be a possible candidate species for this purpose. A field experiment was conducted to compare the efficiency of eighty Indian mustard cultivars for phytoextraction of cadmium (Cd) and lead (Pb) from bimetal contaminated soil. Our results indicated that total Cd and Pb concentrations in the shoots and roots were in the range of 2.43 ±â€¯0.00 to 0.31 ±â€¯0.02 mg/kg and 2.94 ±â€¯0.05 to 0.44 ±â€¯0.03 mg/kg and 5.33 ±â€¯0.76 to 0.47 ±â€¯0.20 mg/kg and 3.78 ±â€¯0.06 to 0.16 ±â€¯0.08 mg/kg. Significant differences based on the translocation factors indicated that root-to-shoot transfer is higher for Pb (3.87 ±â€¯0.12 to 0.48 ±â€¯0.03) than Cd (3.38 ±â€¯0.05 to 0.22 ±â€¯0.01). Furthermore, significant correlations between dry weights, Cd and Pb concentrations and uptake in both shoots and roots were observed, but translocation factor showed a negative correlation with roots, but not in shoots. Among 80 genotypes of Indian mustard IM-25, IM-13 and IM-65 for Cd and IM-79, IM-24 and IM-32 for Pb seems to perform well for phytoextraction. The results of the field experiment suggest that certain Brassica juncea L. cultivars are suitable for removal of Cd and Pb in low to moderately contaminated soils.

Distribution, availability and translocation of heavy metals in soil-oilseed rape (Brassica napus L.) system related to soil properties.

Heavy metals contamination in agricultural soil has become a worldwide problem, and soil characteristics modulate metal availability in soils. Four field experiments were conducted simultaneously to evaluate concentration and distribution of cadmium (Cd) and lead (Pb) in 39 oilseed rape cultivars at four agricultural locations with different contamination levels of Cd and Pb, as well as the influence of soil characteristics together with soil total and bioavailable Cd and Pb concentration on metal transfer from soil to oilseed rape. Shoot concentrations of Cd and Pb in oilseed rape cultivars ranged from 0.09 to 3.18 and from 0.01 to 10.5 mg kg-1 across four sites. For most cultivars, Cd concentration in root or shoot were higher than pod and lowest in seed, while the highest Pb concentration was observed in root followed by shoot and seed. Stepwise multiple linear regression analysis allows for a better estimation of Cd and Pb concentration in oilseed rape while taking soil properties into consideration. The results demonstrated that Cd and Pb concentration in oilseed rape were correlated with soil organic matter (OM), cation exchange capacity (CEC), available phosphorus (AP), available potassium (AK), sand, soil total and available Cd and Pb concentration, and R2 varied from 0.993 to 0.999 (P < 0.05). The Cd and Pb levels found in oilseed rape indicated its phytoextraction potential for Cd and Pb co-contaminated agricultural soils in winter without stopping agricultural activities.

Effects of CO2 application coupled with endophyte inoculation on rhizosphere characteristics and cadmium uptake by Sedum alfredii Hance in response to cadmium stress.

Comparative impact of CO2 application and endophyte inoculation was investigated on the growth, rhizosphere characteristics, and cadmium (Cd) absorption of two ecotypes of Sedum alfredii Hance in response to Cd stress under hydroponic or rhizo-box culture conditions. The results showed that both CO2 application and endophyte inoculation significantly (P < 0.05) promoted plant growth (fresh weight and dry weight), improved root morphological properties (SRL, SRA, SRV, ARD and RTN) and exudation (pH, TOC, TN, soluble sugar and organic acids), changed Cd uptake and distribution of both ecotypes of S. alfredii. Meanwhile soil total and DTPA extractable Cd in rhizo-box decreased by biofortification treatments. Superposition biofortification exhibits utmost improvement for the above mentioned parameters, and has potential for enhancing phytoremediation efficiency of hyperaccumulator and sustaining regular growth of non-hyperaccumulator in Cd contaminated soils.

Characterization of fava bean (Vicia faba L.) genotypes for phytoremediation of cadmium and lead co-contaminated soils coupled with agro-production.

The identification of high yield genotypes that are capable of accumulating multiple heavy metals in the non-edible parts (roots and shoots), but not in the edible parts (seeds) and have desired nutritional value is necessary for accomplishing phytoremediation coupled with agro-production. In this study, 17 fava bean genotypes were screened in two different field conditions to examine their phytoremediation potential in terms of uptake and translocation of Cd and Pb. Ten genotypes, LBAO, JNJX, DCAN, QXCJ, QIKM, LXYC, YDL6, RBCD, QPID and ZHW6 were found as the best accumulators for Cd and Pb with permissible limit of metals in seeds. The concentration of plant nutrients were genotype and soil type dependent and there was a significant correlation between these two factors. Furthermore, the three genotypes DCAN, LBAO and LXYC showed best performance in alluvial soil type while QPID, RBCD and LXYC were the best in red soil type. Genotype LXYC was similar for both soil types and appeared to be the best fit for phytoremediation coupled with agro-production for slightly or moderately Cd and Pb co-contaminated soil. Therefore, fava bean LXYC genotype is suggested as a potential candidate for phytoremediation of Cd/Pb co-contaminated soils coupled with agro-production.

Effects of CO2 application and endophytic bacterial inoculation on morphological properties, photosynthetic characteristics and cadmium uptake of two ecotypes of Sedum alfredii Hance.

Plant uptake of cadmium (Cd) is affected by soil and environmental conditions. In this study, hydroponic experiments were conducted to investigate the effects of elevated CO2 coupled with inoculated endophytic bacteria M002 on morphological properties, gas exchange, photosynthetic pigments, chlorophyll fluorescence, and Cd uptake of S. alfredii. The results showed that bio-fortification processes (elevated CO2 and/or inoculated with endophytic bacteria) significantly (p < 0.05) promoted growth patterns, improved photosynthetic characteristics and increased Cd tolerance of both ecotypes of S. alfredii, as compared to normal conditions. Net photosynthetic rate (Pn) in intact leaves of hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) were increased by 73.93 and 32.90%, respectively at the low Cd (2 µM), 84.41 and 57.65%, respectively at the high Cd level (10 µM). Superposition treatment increased Cd concentration in shoots and roots of HE, by 50.87 and 82.12%, respectively at the low Cd and 46.75 and 88.92%, respectively at the high Cd level. Besides, superposition treatment declined Cd transfer factor of NHE, by 0.85% at non-Cd rate, 17.22% at the low Cd and 22.26% at the high Cd level. These results indicate that elevated CO2 coupled with endophytic bacterial inoculation may effectively improve phytoremediation efficiency of Cd-contaminated soils by hyperaccumulator, and alleviate Cd toxicity to non-hyperaccumulator ecotype of Sedum alfredii.

Hyperaccumulator Plants from China: A Synthesis of the Current State of Knowledge.

Hyperaccumulator plants are the material basis for phytoextraction research and for practical applications in decontaminating polluted soils and industrial wastes. China's high biodiversity and substantial mineral resources make it a global hotspot for hyperaccumulator plant species. Intensive screening efforts over the past 20 years by researchers working in China have led to the discovery of many different hyperaccumulators for a range of elements. In this review, we present the state of knowledge on all currently reported hyperaccumulator species from China, including Cardamine hupingshanensis (selenium, Se), Dicranopteris dichotoma (rare earth elements, REEs), Elsholtzia splendens (copper, Cu), Phytolacca americana (manganese, Mn), Pteris vittata (arsenic, As), Sedum alfredii, and Sedum plumbizincicola (cadmium/zinc, Cd/Zn). This review covers aspects of the ecophysiology and molecular biology of tolerance and hyperaccumulation for each element. The major scientific advances resulting from the study of hyperaccumulator plants in China are summarized and synthesized.

Variations in cadmium and nitrate co-accumulation among water spinach genotypes and implications for screening safe genotypes for human consumption.

Vegetables are important constituents of the human diet. Heavy metals and nitrate are among the major contaminants of vegetables. Consumption of vegetables and fruits with accumulated heavy metals and nitrate has the potential to damage different body organs leading to unwanted effects. Breeding vegetables with low heavy metal and nitrate contaminants is a cost-effective approach. We investigated 38 water spinach genotypes for low Cd and nitrate co-accumulation. Four genotypes, i.e. JXDY, GZQL, XGDB, and B888, were found to have low co-accumulation of Cd (<0.71 mg/kg dry weight) and nitrate (<3100 mg/kg fresh weight) in the edible parts when grown in soils with moderate contamination of both Cd (1.10 mg/kg) and nitrate (235.2 mg/kg). These genotypes should be appropriate with minimized risk to humans who consume them. The Cd levels in the edible parts of water spinach were positively correlated with the concentration of Pb or Zn, but Cd, Pb, or Zn was negatively correlated with P concentration. These results indicate that these three heavy metals may be absorbed into the plant in similar proportions or in combination, minimizing the influx to aerial parts. Increasing P fertilizer application rates appears to prevent heavy metal and nitrate translocation to shoot tissues and the edible parts of water spinach on co-contaminated soils.

Field crops (Ipomoea aquatica Forsk. and Brassica chinensis L.) for phytoremediation of cadmium and nitrate co-contaminated soils via rotation with Sedum alfredii Hance.

Phytoremediation coupled with crop rotation (PCC) is a feasible strategy for remediation of contaminated soil without interrupting crop production. The objective of this study was to develop a PCC technology system for greenhouse fields co-contaminated with Cd and nitrate using hyperaccumulator Sedum alfredii. In this system, endophytic bacterium M002 inoculation, CO2 fertilization, and fermentation residue were continuously applied to improve the growth of S. alfredii, and low-accumulator Ipomoea aquatica and low-accumulator Brassica chinensis were rotated under reasonable water management. These comprehensive management practices were shown to increase S. alfredii biomass and Cd uptake and reduce Cd and nitrate concentration in I. aquatica and B. chinensis. This crop rotating system could remove 56.5% total Cd, 62.3% DTPA extractable Cd, and 65.4% nitrate, respectively, from the co-contaminated soil in 2 years of phytoremediation, and is an effective way of remediating moderately co-contaminated soil by Cd and nitrate.