Lower Cd Uptake Research Articles

Effects of root morphology and anatomy on cadmium uptake and translocation in rice (Oryza sativa L.)

A clear description of the certain mechanisms of cadmium (Cd) uptake and translocation in rice (Oryza sativa L.) may help to reduce Cd accumulation in rice grain. Hydroponic experiments were carried out to determine the effects of cultivation conditions (aerated and stagnant) on the uptake, translocation and subcellular distribution of Cd in relation to the morphology and anatomy of roots in two rice genotypes with different Cd accumulations in grains. Marked differences in morphology and anatomy were observed between these two genotypes under different cultivation conditions. Genotypes with low Cd accumulation in grains tended to develop fewer root tips per root surface area, larger root porosity and more mature apoplastic barriers. The stagnant cultivation condition decreased the number of root tips per root surface area but increased root porosity and accelerated apoplastic barrier formation in root tissues. Correlative Cd uptake studies revealed that rice plants with fewer number of root tips per root surface area reduced root Cd uptake ability, while mature apoplastic barriers increased root Cd retention in cell walls and the symplast. Thus, the fewer number of root tips per root surface area and the earlier formation of mature apoplastic barriers led to lower Cd uptake and translocation. The results indicated that the morphology and anatomy of roots could play important roles in Cd uptake and translocation in rice, and could be influenced by both genotype and cultivation conditions. The present results would be useful in screening and planting rice plants with low Cd accumulation.

Effects of different humic substances concentrations on root anatomy and Cd accumulation in seedlings of Avicennia germinans (black mangrove)

Mangrove areas are among most threatened tropical ecosystems worldwide. Among polluting agents Cadmium is often found in high concentrations in mangrove sediments. Humic substances, complex biomolecules formed in soil and sediments during animal and plant residuals decomposition, have a known biostimulant activity and can be adopted to counteract various plant stresses. This study explores, in controlled conditions, the effect of humic substances on Avicennia germinans seedlings, with or without cadmium contamination. Humic compounds significantly changed plant root architecture, and, when coupled with cadmium, root anatomy and Cortex to Vascular Cylinder diameter ratio. These modifications led to lower Cd uptake by humic substances-treated plants. Humic substances amendment could be effective, depending on their concentrations, on improving plant health in mangrove areas, for forest recuperation and/or dredged sediments phytoremediation purposes.

Identification and Validation of a New Source of Low Grain Cadmium Accumulation in Durum Wheat.

Cadmium (Cd) is a heavy metal that has no known biological function and is toxic for many living organisms. The maximum level of Cd concentration allowed in the international market for wheat grain is 0.2 mg kg−1. Because phenotyping for Cd uptake is expensive and time consuming, molecular markers associated with genes conferring low Cd uptake would expedite selection and lead to the development of durum cultivars with reduced Cd concentrations. Here, we identified single nucleotide polymorphisms (SNPs) associated with a novel low Cd uptake locus in the durum experimental line D041735, which has hexaploid common wheat in its pedigree. Genetic analysis revealed a single major QTL for Cd uptake on chromosome arm 5BL within a 0.3 cM interval flanked by SNP markers. Analysis of the intervening sequence revealed a gene with homology to an aluminum-induced protein as a candidate gene. Validation and allelism tests revealed that the low Cd uptake gene identified in this study is different from the closely linked Cdu1-B gene, which also resides on 5BL. This study therefore showed that the durum experimental line D041735 contains a novel low Cd uptake gene that was likely acquired from hexaploid wheat.

Use of low-calcium cultivars to reduce cadmium uptake and accumulation in edible amaranth (Amaranthus mangostanus L.)

This study aimed to investigate the mechanism of low Cd accumulation in crops using edible amaranth (Amaranthus mangostanus L.) as a model. Fifteen amaranth cultivars were grown in long-term contaminated soil, and the differences in soil Cd mobilization, root uptake, and root-shoot translocation between low- and high-Cd accumulating cultivars were examined. The transport pathways of Cd across the root were further identified in Hoagland nutrient solution using the Ca channel blocker La3+, the ATP inhibitor 2, 4-dinitrophenol (DNP), and a nutrition-deficient culture. Cd concentrations in amaranth cultivars varied about six-fold and showed an elevated trend as the concentration of Ca and Zn increased (p < 0.01), but did not exhibit any correlation with Mg and Fe. The concentrations of essential metals (Ca, Mg, Zn, and Fe) in the rhizosphere of low-Cd cultivars were significantly lower than those of high-Cd cultivars, and decreased with decreasing levels of soluble rhizosphere exudates. These findings indicated that low co-mobilization of Cd with essential metals mediated by root-induced exudates of low-Cd cultivars contributed to its low accumulation in amaranth. Uptake of Cd was inhibited along with Ca by La3+ and DNP, but was promoted by Ca or Fe deficiency treatment. Therefore, the Ca pathway is likely the mode of Cd entry into amaranth roots, although Zn and Fe transporters may also be involved. Low-Ca cultivars exhibited lower Cd uptake capability than high-Ca cultivars. The low translocation efficiency of Cd from root to shoot also contributed to its low content accumulation in edible parts of amaranth.

Identification and validation of a major cadmium accumulation locus and closely associated SNP markers in North Dakota durum wheat cultivars

Durum wheat has the tendency of accumulating more cadmium (Cd), a biotoxic heavy metal, in seeds than other commonly grown cereals, thus posing a serious food safety/public health concern. This could have serious negative impact on the national pasta industry and the international export market of durum wheat. The phenotyping for selecting low Cd lines is expensive and time consuming. The use of markers could be a more sustainable approach for selecting lines with low Cd levels. Here, a RIL population developed from a cross between Grenora (high Cd) × Haurani (low Cd) and two association mapping panels consisting of advanced breeding lines from the North Dakota durum wheat breeding program were used to identify QTL and associated markers for Cd. A major QTL, with Haurani contributing low Cd uptake allele and explaining 54.3 % phenotypic variation, was detected on chromosome 5BL. Association mapping using 2010 collection validated the results of linkage mapping and identified major QTL on 5BL. The 2009 collection, showed the presence of a major QTL on chromosome 2B. The SNP marker associated with major QTL on 5BL was converted to user friendly KASPar assay. The major QTL and associated KASPar marker were further validated using another RIL population developed from a cross of Strongfield (low Cd) and Alkabo (high Cd). The development of suitable marker assay, associated with major Cd uptake QTL, would help the selection for low Cd accumulating lines, minimizing the costly phenotypic evaluation for this important trait.

Effect of liming using a partial mixing technique on reductions in the seed cadmium levels for soybeans (Glycine max (L.) Merr.) under field conditions

ABSTRACTTo reduce the availability of soil cadmium (Cd) to soybeans (Glycine max (L.) Merr.), we employed a liming by partial mixing (PM) technique in two drained paddy fields on Gray Lowland soils, which had 0.1 mol L–1 hydrochloric acid-extractable Cd concentrations as high as 1.08 and 1.40 mg kg–1. Among the different application methods tested, PM application (PM2) using a width of 20 cm and a depth of 20 cm was found to be most appropriate for reducing the seed Cd concentration and to obtain the optimum yield at Site A. Under PM2, a liming rate of 38% of that for broadcast incorporated into the surface 15 cm layer (Bc) was suitable to reduce the seed Cd concentration at Site A, whereas the lime rate with PM2 was set at 50% of that for Bc (PM2-50) at Site B due to the higher availability of soil Cd. The root system was limited within the range of lime and fertilizer application for PM2 as well as PM2-50; thus, the lime and fertilizer were supplied successfully to the rooting zone. The soil pH value was lower under PM2 at Site A and PM2-50 at Site B compared with Bc, whereas the seed Cd concentration was lower for PM2 and PM2-50. This may be explained by the intensive uptake of calcium and magnesium with PM2 as well as PM2-50. The seed Cd concentration in the cultivar “Ryuhou” at the target pH of 6.5 was approximately 30% lower with PM2-50 than Bc at Site B. In addition, the average seed Cd concentrations in one cultivar and two lines, characterized by the lower Cd uptake with higher retention in roots and higher accumulation in leaves, were approximately 40% lower compared with “Ryuhou.” Thus, the combination of liming with PM2-50 at the target pH of 6.5 and a low-Cd cultivar (or lines) minimized the seed Cd concentration. The highest seed Cd concentration was found in the first year of soybean cultivation, which was considered to be caused by the release of Cd from organic nitrogen compounds during the nitrogen mineralization process.

Evaluation of the effectiveness of sepiolite, bentonite, and phosphate amendments on the stabilization remediation of cadmium-contaminated soils

A pot trial was conducted to assess the effectiveness of sepiolite, bentonite, and phosphate on the immobilization remediation of cadmium (Cd)-contaminated soils using a set of variables, namely, physiological traits, sequential extraction procedure, plant growth and Cd concentration, and soil enzymatic activities and microbial population. Results showed that superoxide dismutase and peroxidase activities in the leaves of Oryza sativa L. and catalase activities in soils were stimulated after applying the amendments. However, soluble protein contents in leaves and urease and invertase activities in soils were reduced from 7.1% to 31.7%, 1.0%–23.3%, and 21.1%–62.5%, respectively, compared with the control. Results of the sequence extraction procedures revealed that the exchangeable fraction of Cd in soils was mostly converted into carbonated-associated forms. The water soluble plus exchangeable fraction (SE) of Cd in soil decreased when treated with single and compound materials of sepiolite, bentonite and phosphate, which resulted in 13.2%–69.2% reduction compared with that of CK (control test). The amendments led to decreased Cd concentrations in roots, stems, leaves, brown rice, and rice hull by 16.2%–54.5%, 16.6%–42.8%, 19.6%–59.6%, 5.0%–68.2%, and 6.2%–20.4%, respectively. Higher bacterial and actinomycete amount indicated that remediation measures improved soil environmental quality. Composite amendments could be more efficiently used for the stabilization remediation of Cd contaminated soils with low Cd uptake and translocation in the plants and available contents of Cd in soil.

The long-term variation of Cd and Zn hyperaccumulation by Noccaea spp and Arabidopsis halleri plants in both pot and field conditions

ABSTRACTThree Cd and Zn hyperaccumulating plant species Noccaea caerulescens Noccaea praecox and Arabidopsis halleri (Brassicacceae) were cultivated in seven subsequent vegetation seasons in both pot and field conditions in soil highly contaminated with Cd, Pb, and Zn. The results confirmed the hyperaccumulation ability of both plant species, although A. halleri showed lower Cd uptake compared to N. caerulescens. Conversely, Pb phytoextraction was negligible for both species in this case. Because of the high variability in plant yield and element contents in the aboveground biomass of plants, great variation in Cd and Zn accumulation was observed during the experiment. The extraction ability in field conditions varied in the case of Cd from 0.2 to 2.9 kg ha−1 (N. caerulescens) and up to 0.15 kg ha−1 (A. halleri), and in the case of Zn from 0.2 to 6.4 kg ha−1 (N. caerulescens) and up to 13.8 kg.ha−1 (A. halleri). Taking into account the 20 cm root zone of the soil, the plants were able to extract up to 4.1% Cd and 0.2% Zn in one season. However, cropping measures should be optimized to improve and stabilize the long-term phytoextraction potential of these plants.

Effects of cultivars and water management on cadmium accumulation in water spinach (Ipomoea aquatica Forsk.)

Water spinach is a common leafy vegetable in Asia, with a strong ability to accumulate cadmium (Cd) in its edible parts. The aims of this study were to investigate the effects of cultivar variation and water management on Cd accumulation in this plant. Three experiments were conducted: a soil pot trial with 32 cultivars, a rhizobox trial with 4 cultivars under flooded and non-flooded conditions and an uptake kinetics trial with 2 cultivars. There were significant differences in Cd accumulation between the different cultivars, and Cd concentrations in shoots were significantly lower in the flooded (0.25–1.4, mean 0.90 mg kg−1 DW) than in the non-flooded (1.9–4.7, 3.2 mg kg−1) treatments. Cultivars with a low Cd accumulation had a lower Cd bioavailability and mobility in the rhizosphere soil, higher Cd combined with Fe plaque on roots, lower Cd uptake capacity by roots, and lower Cd transfer factors than those with a high Cd accumulation. Water spinach grown under anaerobic conditions effectively reduces Cd accumulation in edible parts. Low Cd-accumulating cultivars tend to possess a high ability to reduce Cd bioavailability in rhizosphere soil, as well as decrease Cd uptake, and translocation from root to shoot.

Xylem transport and gene expression play decisive roles in cadmium accumulation in shoots of two oilseed rape cultivars (Brassica napus)

Cadmium (Cd) is a toxic metal which harms human health through food chains. The mechanisms underlying Cd accumulation in oilseed rape are still poorly understood. Here, we investigated the physiological and genetic processes involved in Cd uptake and transport of two oilseed rape cultivars (Brassica napus). L351 accumulates more Cd in shoots but less in roots than L338. A scanning ion-selective electrode technique (SIET) and uptake kinetics of Cd showed that roots were not responsible for the different Cd accumulation in shoots since L351 showed a lower Cd uptake ability. However, concentration-dependent and time-dependent dynamics of Cd transport by xylem showed L351 exhibited a superordinate capacity of Cd translocation to shoots. Additionally, the Cd concentrations of shoots and xylem sap showed a great correlation in both cultivars. Furthermore, gene expression levels related to Cd uptake by roots (IRT1) and Cd transport by xylem (HMA2 and HMA4) were consistent with the tendencies of Cd absorption and transport at the physiological level respectively. In other words, L351 had stronger gene expression for Cd transport but lower for Cd uptake. Overall, results revealed that the process of Cd translocation to shoots is a determinative factor for Cd accumulation in shoots, both at physiological and genetic levels.

The significant contribution of mycorrhizal fungi and earthworms to maize protection and phytoremediation in Cd-polluted soils

Abstract Mycorrhizal fungi and earthworms can individually or interactively influence plant growth and heavy metal uptake. The influence of earthworms and arbuscular mycorrhizal (AM) fungi either alone or in combination on maize (Zea mays L.) growth and cadmium (Cd) uptake was investigated in a calcareous soil artificially spiked with Cd. Soils were contaminated with Cd (10 and 20 mg Cd kg−1), inoculated or un-inoculated with the epigeic earthworm Lumbricus rubellus and two AM fungal species (Rhizophagus irregularis and Funneliformis mosseae) for two months of growth under greenhouse conditions. Generally, earthworms alone increased both shoot P uptake and biomass but decreased shoot Cd concentration and root Cd uptake. AM fungi individually often increased total maize P uptake, declined shoot Cd concentration, and consequently produced higher total biomass. However, R. irregularis enhanced shoot Cd uptake at low Cd level and root Cd uptake at high Cd level. In plants inoculated with F. mosseae species, earthworms increased shoot biomass and Cd uptake, decreased root biomass and Cd uptake at all Cd levels, and increased shoot Cd concentration at low Cd level. In plants colonized by R. irregularis species, however, earthworm addition decreased maize biomass only at high Cd level and root Cd concentration and total maize Cd uptake at both Cd levels. Earthworm activity decreased Cd transfer from the soil to maize roots at low Cd level, but this was counterbalanced in the presence of F. mosseae. Mycorrhizal symbiosis significantly reduced the transfer of Cd from roots to shoots, independence of earthworm effect. Overall, it is concluded that L. rubellus and AM fungi, in particular F. mosseae isolate, improved maize tolerance to Cd toxicity both individually and interactively by increasing plant growth and P nutrition, and restricting Cd transfer to the aboveground biomass. Consequently, the single and interactive effects of the two soil organisms might potentially be important not only in protecting maize plants against Cd toxicity, but also in Cd phytostabilization in soils polluted by this highly toxic metal.

Posidonia oceanica (L.) based compost as substrate for potted basil production.

Peat is the main component of growing media but is also a non-renewable resource; therefore European policy strongly encourages the use of peat alternatives such as compost. Posidonia is a Mediterranean seagrass that produces very conspicuous onshore deposits that can be composted. In this study, a commercial green compost and a Posidonia residue-based compost were tested in order to assess their potential use as substitutes or complements to peat. All macro and micro-element concentrations of the substrates were positively and significantly related to the percentage of composts in the growing media. Plant grown on peat showed higher content of P, Ca, K, Na, Cu, Mn, Zn and Fe, and a slightly higher biomass production in comparison to compost-based growing media. In contrast, plants grown on compost-based substrates showed lower uptake of Cd and Cr than peat. The results indicate that both composts can be used as a complement to the peat for substrate preparation, especially at a rate of 30%. The Posidonia-based compost showed better productive results in comparison to the green one. Basil grown on the two compost-based media showed reduced absorption level of potentially toxic metals in comparison to peat.

Cd Accumulation and Quality Characteristics of Chinese Cabbage Growth in Cd-Contaminated Soil

33 species Chinese cabbage sold in local market were seeded and growth on Cd polluted (Cd 0.65-9.0 mg/kg) soil in the old irrigation area, Shenyang, P.R.China. The harvested Chinese cabbages were collected for analysis of Cd content, soluble protein and soluble sugar, respectively. Results showed that the Cd content in edible parts of varieties Chinese cabbage does not exceed, partly exceed and all out of the allowed standard of 0.2 mg/kg fresh weight Cd, as the soil Cd contents were in the range of 0.65-1.8 mg/kg, 1.81-4.17 mg/kg and 4.18 to 5.3 mg/kg. Soil Cd content has a positive correlation with Cd content in the edible part of all varieties of Chinese cabbage. And soluble sugar and soluble protein showed increased trend as soil cd increase. According to above results, we concluded that the products of Chinese cabbage is relatively safety in quality if growth in soil with Cd content from 0.65 to 1.81 mg/kg , and appropriate screening of low Cd uptake species for Chinese cabbage is necessary as soil Cd content was from 1.81-4.17 mg/kg, to insure the safety of agricultural products , and suitable remediation technology should be used as soil Cd content was from 4.18-5.3 an till 9.0 mg/kg, in order to reduce the food-chains transportation risk brought by Cd accumulated in Chinese cabbage.

Cadmium phytoremediation by Arundo donax L. from contaminated soil and water.

The potential of Arundo donax L. for phytoextraction of cadmium (Cd) from contaminated soil and water was probed. The plants were grown under greenhouse conditions in pots containing a nutrient solution or soil with increasing doses of Cd (0, 50, 100, 250, 500, 750, and 1000 μg L−1) for 21 days. The growth and physiology of plants were evaluated at the end of the experiment. The maximum Cd content in root was 300 μg g−1 during hydroponics experiments over 230 μg g−1 in soil experiment. Cd concentration in stem was 262 μg g−1 at 750 μg L−1 supplied Cd in hydroponics over 191.2 μg g−1 at 1000 in soil experiment. The maximum Cd concentration in leaves from hydroponics was 187 μg g−1. Relatively low Cd uptake occurred during soil experiment with low translocation factor (TF) values. Both Bioaccumulation Factor (BF) and TF values for hydroponics were greater than 1. The IC50 values of ABTS and DPPH showed that both time and increasing Cd concentrations affected the production of antioxidants with lower half maximal inhibitory concentration (IC50) value on the 21st days. A. donax showed better potential for Cd remediation of aquatic environments.

Rhizosphere effects of maize hybrids and N forms on Cd bioavailability in a limed soil

Replacing new corn genotypes in agricultural practices requires adequate information on the reaction of the selected hybrids to Cd uptake in Cd-polluted soil and an understanding of interactions with N fertilizers. A 2 × 2 × 3 factorial pot experiment with limed soil (pH 8), two maize (Zea mays) hybrids (Pioneer cultivar yellow and Pioneer cultivar white), two N fertilization forms (NH4 + and NO3 −) and three Cd exposures (0, 2 and 5 mg kg−1 soil) was conducted under greenhouse conditions. Shoot dry mass increased significantly with NH4 + nutrition compared with NO3 − nutrition in both maize hybrids, with greater negative influence of Cd application combined with NH4 + nutrition. The yellow cultivar had significantly greater shoot dry mass and lower Cd uptake than the white cultivar. Both hybrids exhibited similar N uptake in shoots and roots, with the exception of yellow cultivar with NH4 + nutrition without Cd application. NO3 − nutrition always decreased Cd uptake in both cultivars compared with NH4 + nutrition. The N balance (mean across cultivars and Cd supply) after harvest showed most N uptake with NH4 + nutrition (63.4%) and Nmin remains in the soil with NO3 − nutrition (48.7%). Soil pH decreased more with NH4 + (−0.95 pH units) than NO3 − nutrition (−0.21).

Factors influencing uptake of contaminated particulate matter in leafy vegetables

Abstract The contents of cadmium, iron, lead and zinc in the biomass of two species of leafy vegetables after urban particulate matter (PM) application was investigated in lettuce (Lactuca sativa var. capitata) and chard (Beta vulgaris var. cicla). The experimental design consisted of four variables: i) two different soil types, ii) two vegetables, iii) two size fractions of contaminated particulate matter (PM) (0.063–0.119 mm, and &lt;0.063 mm), and iv) foliar and soil application of the PM. The aliquots of the PM samples were applied to the soil before the experiment and as a foliar suspension during plant growth. The element uptake by plant biomass was significantly higher via foliar application, simulating the atmospheric deposition, than via the roots from the soil application treatment. The content in plants increased rapidly compared to the control treatment for the elements iron, lead and zinc. Gently washing the leaves only slightly reduced the amounts of Fe and Zn. However, the majority of Pb was removed by washing with the concentration dropping from 3000% to 500%. The effect of PM application on Cd contents in plant leaves was negligible, in most cases. Lettuce exhibited higher element uptake compared to chard. No adverse effects of PM application on growth parameters of the vegetables were observed. No significant differences were reported for particle size fractions of PM. Fluvisol soils had a higher element uptake via roots than Chernozem soils. Moreover, the addition of PM into the Fluvisol altered the sorption properties of the soil resulting in a lower Cd uptake by plants growing in PM amended Fluvisols.

Differences in Cadmium Accumulation and Root Morphology in Seedlings of Japanese Wheat Varieties with Distinctive Grain Cadmium Concentration

A low cadmium (Cd) concentration in wheat grain is desirable because of Cd toxicity to humans. Grain Cd concentrations in Japanese wheat differed among the varieties in previous study. In this study, we hypothesized that the varieties with a low concentration of Cd in grain have (1) low Cd uptake from the soil through the roots during early growth and/or (2) low Cd translocation from the roots to shoots, and also, that (3) Cd uptake from soil is affected by root morphology. These hypotheses were verified by investigating the concentration and quantity of Cd in root, shoot and leaf tissues, and examining the root morphology of young seedlings of wheat varieties with high and low grain Cd concentrations. Seedlings of ‘Kitahonami’ and ‘Nanbukomugi’ which had low grain Cd concentration (low Cd/G varieties) had a lower Cd quantity in whole plant tissues than ‘Nishikazekomugi’ and ‘Kitakamikomugi’ which had high grain Cd concentration (high Cd/G varieties) during early growth. Low Cd/G varieties also showed lower root to shoot (aerial parts) translocation of Cd than high Cd/G varieties. Seedlings of low Cd/G varieties showed less root branching than high Cd/G varieties. Root frequency showed a significant positive correlation with Cd quantity in whole plant tissues. These results suggest that low Cd/G varieties used in this study have low Cd uptake and translocation from the roots to shoots during early growth, and furthermore, that low Cd uptake at the seedling stage may relate to slow and/or limited development of branching roots.

Interaction and accumulation of manganese and cadmium in the manganese accumulator Lupinus albus

The effects of the interaction between Mn and Cd on the growth of the white lupin ( Lupinus albus), uptake of these metals, their accumulation, and effects on heavy metal stress indicators were studied under glasshouse conditions. Plants were grown with and without Mn and/or Cd for 4 weeks. The absence of Mn and Cd led to lipid peroxidation-induced loss of flavonoids and anthocyanins in the roots, reduced the size of the plant canopy, and led to the appearance of proteoid roots. Sensitivity to Cd in white lupin was enhanced by a low Mn supply, despite lower Cd uptake and accumulation (leaf Mn:Cd concentration ratio <3), as evidenced by increased lipid peroxidation in the leaves and strong inhibition of growth. However, when the Mn supply was adequate, the plants showed few symptoms of Cd toxicity, even though Cd uptake and accumulation increased. A Mn:Cd ratio of up to 20 was enough to minimize Cd stress in the leaf, reflecting the plants’ relative tolerance to Cd under such conditions. Irrespective of the Mn supply, the increase in antioxidant compounds observed in the roots of Cd-treated plants might act as a protective mechanism by minimizing the oxidative stress caused by Cd exposure. In summary, high leaf Mn concentrations seem to render white lupins more tolerant to Cd stress.

Chromosomal location of the cadmium uptake gene (Cdu1) in durum wheat

Levels of the heavy metal cadmium (Cd) in food products are a food safety concern. Grain Cd is higher in durum (Triticum turgidum L. var. durum) than in common wheat, so reduction of Cd in durum grain is a priority of breeding programs. Previous research demonstrated that a single dominant gene, Cdu1, confers the low grain Cd phenotype, but the map location of the gene is not known. A doubled haploid population segregating for Cd concentration, developed from the cross of W9262-260D3 (a Kyle*2/Biodur inbred selection with low Cd uptake) and Kofa (high Cd uptake) and mapped with microsatellite markers, was used to locate Cdu1. Grain Cd concentration was determined by standard laboratory methods on field grain samples in 2000 and 2001. The Cd concentration segregated bimodally, allowing Cdu1 to be mapped qualitatively as well as quantitatively with quantitative trait locus analysis. The Cdu1 gene mapped to the long arm of chromosome 5B.

Effect of Lherzolite on Chemical Fractions of Cd and Zn and their Uptake by Plants in Contaminated Soil

Immobilizing materials such as lherzolite could reduce metal bioavailability but the effectiveness of lherzolite on the extractability and bioavailability of cadmium (Cd) and zinc (Zn) is rarely investigated. We conducted a greenhouse experiment to investigate the effect of 5% application of lherzolite to a contaminated soil on the chemical fractionation of Cd and Zn and their uptake by radish (Raphanus sativus L.) and Japanese mustard spinach (Brassica rapa L. var. perviridis). Both plants were grown in a highly contaminated (with Cd and Zn) sandy loam soil. Plants were cultivated consecutively three times in the same pots. After the third cultivation, soil samples were collected and analyzed by sequential extraction procedure into five operationally defined fractions (F1—exchangeable, F2—carbonate-bound, F3—oxides-bound, F4—bound with organic matter, and F5—residual). Addition of lherzolite to soil decreased 50% of exchangeable (F1) Cd but it increased the carbonate (F2), oxide (F3), and organic (F4) fraction Cd. For Zn, application of lherzolite resulted into the reduction of both F1 (87%) and F2 (33%) fractions but it increased the F3, F4, and F5 fractions. The reduction in exchangeable fraction of Cd and Zn in the soil resulted in higher plant growth and lower concentrations of both Cd (64% to 92%) and Zn (78% to 99%) in plant tissues of both plant species grown. We may thus conclude that application of lherzolite resulted into lower availability of these metals in the soil leading to lower uptake of Cd and Zn by plant roots, lower toxicity, and ultimately higher plant growth.