The effect of humic acid and Na2EDDHA on the uptake of Cu,Fe, and Zn by barley in sand culture

Summary Humic acid affected nutrient uptake differently in sand culture. It generally increased Cu uptake, slightly, though insignificantly, increased Fe uptake and practically had no effect on Zn uptake. Such results agree fairly well with the relative stability of humic acid with these metals.When humic acid was added to sand culture at increasing concentration of the metal, it considerably increased dry weight, Cu uptake and Cu concentration through decreasing its toxicity to plant. With Fe, however, humic acid and Na₂EDDHA slightly increased Fe uptake at lower Fe concentration (30 ppm) but significantly reduced both Fe uptake and Fe concentration in plant at higher concentration of Fe compared to the control treatment. Humic acid reduced Zn uptake and Zn concentration in plant at concentrations of 0.5–1.5 ppm Zn, and guarded against Zn toxicity which developed at higher concentration of Zn when no humic acid was added.     

Response of flooded rice grown on a vertisol from northern nigeria to zinc sources and methods of application

Summary Greenhouse and laboratory studies were conducted to study the effect of zinc sources and methods of application on correcting zinc deficiency in flooded rice grown on Vertisol from Ngala, northern Nigeria, using the variety IR-20.Plant dry matter yield was similar for ZnSO₄, ZnEDTA, metallic Zn and fritted Zn with mixed soil application. Zinc uptake was affected in the following order; ZnSO₄ > ZnEDTA > metallic Zn > fritted Zn. Comparable dry matter yield and zinc uptake were obtained with mixing, surface broadcasting and banding of ZnEDTA. Mixing the fritted Zn gave higher dry matter yield and zinc uptake than broadcasting or banding.Seed soaking with a suspension of fritted Zn resulted in higher dry matter yield and zinc uptake than with ZnEDTA solution. Seed soaking for 24 hours with fritted Zn suspension at a concentration of about 0.5 per cent Zn appeared to be a suitable method for applying zinc with direct seeded rice.     

Interaction of phosphorus and molybdenum in relation to uptake and utilization of molybdenum,phosphorus, zinc,copper and manganese by rice

Summary The effect of phosphorus and molybdenum alone and combined, on the uptake and utilization of Mo, Mn, Zn, Cu and P by rice (Var. IR-579) was studied in the greenhouse at varying levels of Mo (0, 2.5 and 5.0 ppm) and (0,100 and 200 ppm). Application of P increased the dry matter yield of shoot and root. Combined application of P and Mo increased the dry matter yield of shoot. Application of Mo increased the concentration of Mo and P in shoot. Applied P caused an increase in the concentration of Mo, Zn and P in shoot. Combined application of P and Mo resulted in an increase in concentration and uptake of Mo in shoot.     

栽培模式对旱地小麦产量和籽粒养分含量的影响

通过田间试验,研究地膜覆盖、秸秆还田和种植绿肥对冬小麦籽粒产量和籽粒养分含量的影响.结果表明:与传统模式相比,地膜覆盖并不总能提高旱地小麦产量,3年平均产量无显著变化,但籽粒磷吸收量却增加8.4%,磷含量平均提高13.0%;籽粒氮、硫和铁吸收量分别降低12.6%、15.0%和11.1%,含量分别降低12.1%、12.9%和10.1%,锌含量无显著变化.秸秆还田使小麦籽粒产量下降12.1%,籽粒氮、硫和铁吸收量分别降低22.5%、21.0%和19.8%,含量分别降低10.1%、9.4%和3.8%;磷吸收量降低9.8%,含量却增加5.0%,锌含量亦无显著变化.种植绿肥的小麦籽粒产量降低12.1%,籽粒氮和锌吸收量无显著变化,含量分别增加12.1%和12.6%,对磷、硫和铁含量无显著影响.可见,旱地条件下,不同栽培模式引起的籽粒产量增减与其养分吸收量变化不一致是养分含量变化的主要原因.在旱地小麦生产中,需注意地膜覆盖和秸秆还田的减产风险及对籽粒养分的不利影响,适当调控氮肥用量,保证小麦产量形成的养分需求,协调氮、硫、铁养分的吸收利用.种植绿肥能培肥土壤,提高籽粒氮和锌含量,但也应注意其减产问题.     

Iron,zinc and manganese nutrition of wetland rice (Oryza sativa L.) on a gypsum amended sodic soil

A field experiment was conducted to evaluate the effect of three levels of Fe and two levels of Zn, and their combinations, on the growth, yield and Fe, Zn, and Mn nutrition of rice on a zinc deficient sodic soil amended with gypsum. Iron and zinc were supplied as sulphates. Application of Zn significantly enhanced the yield of rice and available soil and plant Zn irrespective of Fe application. Maximum response of rice to Zn was obtained when Fe was applied at the highest rate. While Fe application brought about a significant improvement in available soil and plant Fe and Mn, it decreased significantly Zn content of the crop. After crop harvest, recovery of added Fe was 20% and Zn 12%. Results suggest that benefits of Fe application to rice in sodic soils can only be realised if it is applied along with Zn.     

Effect of phosphorus and zinc on nodulation and nitrogen fixation in chickpea (Cicer arietinum L.)

A green house study was conducted on the effect of P and Zn on nodulation and N fixation in chickpea (Cicer arietinum L.) in a loamy sand (Typic Torripsamments) using treatment combinations of five levels of P (0, 25, 50, 100 and 250 ppm), and six levels of Zn (0, 5, 10, 20, 40 and 100 ppm). The number, dry matter and leghaemoglobin content of nodules, and amount of N fixed generally increased with Zn alone upto 19 ppm and P alone upto 50 ppm, and decreased with their higher levels. Application of 25 to 50 ppm P and 5 to 10 ppm Zn counteracted to a greater extent the adverse effect of 40 and 100 ppm Zn, and 250 ppm P, resp. Maximum nodulation and N fixation (91 to 145% over zero P and Zn, at maturity) was recorded with 25 to 50 ppm P applied along with 5 to 10 ppm Zn. At 64 days, depletion in soil-N was noted, particularly when P was applied, whereas at maturity there was a gain in soil-N, ranging from 10.5 to 44.5 kg/2×10⁶ kg soil depending upon P and Zn treatments. The increase in nodulation and N fixation with balanced P and Zn nutrition might be attributed to an increase in leghaemoglobin, and K and Fe concentration in nodules, and increased plant growth, resulting into enhanced activity of N fixing organisms. The results showed that balanced P and Zn nutrition is essential not only for plant growth but also for maximum activity of Rhizobium for N fixation. Work done at Harvana Agricultural University, Hissar, India.     

The effect of sodium selenite toxicity on tissue distribution of zinc,iron, and copper in rats

Male Sprague-Dawley rats were used to determine the effects of suptoxic and toxic concentrations of selenite in the drinking water on tissue distribution of zinc (Zn), iron (Fe), and copper (Cu). Se (as sodium selenite) was provided in drinking water at concentrations of 0, 2, 4, and 8 ppm. At 19 d, half of the rats in 4 and 8 ppm Sesupplemented groups were kept on drinking water alone for additional 13 d. All rats were sacrificed at the end of 32 d of experiment. Heart, liver, and kidney were analyzed for the concentrations of Fe, Zn, and Cu by atomic absorption spectrophotometry and of Se by a fluorometric method. Results indicated that rats receiving 4 and 8 ppm Se in drinking water showed a marked reduction in food intake and a reduced growth rate. These adverse effects were quickly reversed when high Se intake was discontinued. Se toxicity caused minimal change in zinc status, reduced tissue iron concentrations and caused a marked increase in copper contents in heart, liver, and kidney. The latter findings were only partly reversed after removal of Se in drinking water. The accumulation of Cu in the tissues of Se-toxic rats provides the evidence of some interaction between Se and Cu.     

Effect of salinity,alkalinity and iron application on the availability of iron,manganese, phosphorus and sodium in pea (Pisum sativum L.) crop

Summary The effect of the salinity, alkalinity and Fe application on the dry matter yield and availability of Fe, Mn, P and Na were studied in the greenhouse on pea (Pisum sativum L.) crop. The highest dry matter yield was recorded in normal soil which decreased with the increase in the salinity and alkalinity, minimum being at 40 ESP. Alkalinity was more harmful to pea crop than salinity.Fe at 10 ppm increased the dry matter yield significantly. Highest Fe concentration (408.12 ppm) was recorded in 40 ESP soil followed by 20 ESP (395.2 ppm). Salinity alongwith marginal or higher alkalinity reduced harmful effect of alkalinity. The uptake of Fe was the highest in normal soil due to the high dry matter yield. All the three sources increased the concentration of Fe and its uptake than the control in all the soils but did not show much distinction among themselves.The concentration of Mn decreased more with the increase in alkalinity than salinity but salinity with alkalinity improved Mn concentration. Similarly uptake of Mn also decreased sharply with the increase in salinity and alkalinity. The application of Fe sources decreased Mn concentration but increased the uptake. The highest decrease was caused with FeSO₄ and lowest with Fe rayplex.Like Mn the concentration and uptake of P decreased with the increased levels of salinity and alkalinity. The addition of Fe decreased the concentration of P, highest depression being with Fe KE-MIN.Increase in ESP increased the concentration and the uptake of Na greatly. Addition of Fe through all the sources increased Na concentration and uptake significantly but sources did not differ much in their effect on Na.     

Relative effectiveness of various types and methods of zinc application on rice and maize crops grown in calcareous soil

Summary Application of zinc sulphate mixed with compost/poultry manure proved to be equivalent to the effect of dipping the seedling roots in 4% ZnO suspension with respect to rice yields but Zn-amended organic manures were superior to other treatments with regards to total Zn uptake. A marked residual effect of soil applied treatments was recorded on the succeeding maize crop. Application of poultry manure alone was about one and a half times more effective than compost alone in increasing the rice and maize grain yields. Poultry manure surpassed compost in increasing zinc uptake by the crops and at the same time it built up more available Zn in soil than compost for the following crop. The magnitude of yields and Zn uptake response were magnified when zinc sulphate was applied along with organic manures. Application of 25 kg zinc sulphate/ha alone had the same effect as 50 quintals poultry manure alone or 12.5 kg zinc sulphate applied with 50 quintals compost/ha with respect to crop yields. A significant positive correlation was, recorded in both the crops between Zn concentration in grain or straw and their respective yields.     

Effect of farm yard manure and iron on dry matter yield and nutrients uptake by oats (Avena sativa)

A pot culture experiment was conducted on a loamy sand soil to study the effect of FYM and Fe on dry matter yield and uptake of nutrients by oats (Avena sativa) crop in green-house. Application of Fe @ 5 and 20 ppm increased dry matter yield by 5.11 and 11.55 per cent, respectively. The per cent increase in dry matter yield over control with the application of 0.5 and 1.0 percent FYM was 19.06 and 30.07, respectively. Application of FYM increased concentration and uptake of P significantly. Phosphorus uptake increased by 23.60, 54.38, 91.01 and 134.61 per cent over control with 0.5, 1.0, 2.0 and 4.0 per cent FYM, respectively. Phosphorus concentration decreased at 20 ppm Fe but uptake increased significantly at 5 ppm Fe. Concentration and uptake of Ca increased with increasing amounts of Fe and application of FYM decreased concentration of Ca but uptake increased upto 1.0 per cent FYM over control. The Mg concentration and uptake decreased significantly with increased amount of Fe. Application of FYM also decreased Mg concentration but its uptake increased upto 1.0 per cent FYM and then decreased.Iron concentration and uptake increased upto 2 per cent FYM and then decreased. Whereas concentration of Fe decreased with increased amount of applied Fe but its uptake increased nonsignificantly with increased amount of added Fe.Managenese concentration and uptake decreased significantly with increased amount of applied Fe. Managenese concentration increased upto 0.5 per cent FYM but its uptake continued increasing with increasing amounts of applied FYM.     

Effect of iron plaque outside roots on nutrient uptake by rice (Oryza sativa L.). Zinc uptake by Fe-deficient rice

This solution culture study examined the effect of the deposition of iron plaque on zinc uptake by Fe-deficient rice plants. Different amounts of iron plaque were induced by adding Fe(OH)₃ at 0, 10, 20, 30, and 50 mg Fe/L in the nutrient solution. After 24 h of growth, the amount of iron plaque was correlated positively with the Fe(OH)₃ addition to the nutrient solution. Increasing iron plaque up to 12.1 g/kg root dry weight increased zinc concentration in shoots by 42% compared to that at 0.16 g/kg root dry weight. Increasing the amount of iron plaque further decreased zinc concentration. When the amounts of iron plaque reached 24.9 g/kg root dry weight, zinc concentration in shoots was lower than that in shoots without iron plaque, implying that the plaque became a barrier for zinc uptake. While rice plants were pre-cultured in –Fe and +Fe nutrient solution in order to produce the Fe-deficient and Fe-sufficient plants and then Fe(OH)₃ was added at 20, 30, and 50 mg Fe/L in nutrient solution, zinc concentrations in shoots of Fe-deficient plants were 54, 48, and 43 mg/kg, respectively, in contrast to 32, 35, and 40 mg/kg zinc in shoots of Fe-sufficient rice plants. Furthermore, Fe(OH)₃ addition at 20 mg Fe/L and increasing zinc concentration from 0.065 to 0.65 mg Zn/L in nutrient solution increased zinc uptake more in Fe-deficient plants than in Fe-sufficient plant. The results suggested that root exudates of Fe-deficient plants, especially phytosiderophores, could enhance zinc uptake by rice plants with iron plaque up to a particular amount of Fe.     

Reversal of Cadmium-Induced Thyroid Dysfunction by Selenium, Zinc, or Their Combination in Rat

The aim of this study was to evaluate the potential benefit of combined treatment with zinc (Zn) and selenium (Se) in reversing cadmium (Cd)-induced thyroid dysfunction compared to Se or Zn treatment alone in rats exposed to Cd. For this purpose, 30 adult male Wistar albino rats were equally divided into control and four treated groups receiving either 200 ppm Cd (as CdCl2), 200 ppm Cd + 500 ppm Zn (as ZnCl2), 200 ppm Cd + 0.1 ppm Se (as Na2SeO3), or 200 ppm Cd + 500 ppm Zn + 0.1 ppm Se in their drinking water for 35 days. The results showed that Cd exposure increased significantly the relative thyroid weight (RTW), the thyroid Cd concentration, and the serum thyroid stimulating hormone (TSH) level, whereas the serum thyroxine (T4) level was decreased compared to control rats. The treatment of Cd-exposed rats with Se alone only partially protected from the Cd-induced decrease in serum T4 level. The treatment of Cd-exposed animals with Zn alone partially protected against Cd-induced thyroid dysfunction by maintaining normal RTW and by decreasing Cd concentration in the thyroid. It also partially prevents Cd-induced decrease in serum T4 level. The combined treatment of Cd-exposed animals with Se and Zn induced a more significant decrease in the thyroid Cd concentration than the Zn supplement and a total correction of the RTW. This treatment was also more effective than that with Se or Zn alone in reversing Cd-induced decrease in serum T4 level and Cd-induced increase in serum TSH level. Se and Zn can have a synergistic role against Cd-induced thyroid dysfunction.     

Correlation of Aflatoxin Contamination With Zinc Content of Chicken Feed

Feed samples from chicken houses in five commercial chicken operations were analyzed for Zn, Mn, Fe, Cu, Cd, and aflatoxin content. Mean aflatoxin content of these samples was 14 ppb (14 ng/g) as opposed to 1.2 ppb in samples taken when the feed was made. Aflatoxin content of the feed samples correlated (r = 0.325) significantly (P < 0.05) with Zn content but not with Mn, Fe, or Cu, all of which correlated significantly with Zn. Zn content of unamended feed (<20 ppm [20 μg/g]) is normally supplemented with a mineral premix containing Zn, Mn, Fe, and Cu to meet the nutrient requirements of chickens (40 ppm of Zn). The mean zinc concentration of the feed samples (117 ppm) was about threefold greater than the nutrient requirement and ranged from 58 to 162 ppm in individual samples. These field survey results parallel earlier reports of augmented production of aflatoxin in monocultures of aflatoxigenic fungi in corn and other ingredients supplemented with Zn. These results suggest that stricter control of Zn levels during manufacture could reduce aflatoxin contamination of feed consumed by chickens.     

From Flooded to Aerobic Conditions in Rice Cultivation: Consequences for Zinc Uptake

Scarcity of water causes a shift from flooded to aerobic conditions for rice production in zinc deficient areas in Northern China. This shift alters soil conditions that affect zinc availability to the crop. This paper concerns the effect of aerobic compared to flooded conditions on crop biomass production, grain yield and zinc content. A field experiment was done with six rice genotypes (Oryza sativa L.) grown on a calcareous soil, both with (23 kg Zn ha⁻¹) and without Zn fertilization. Sampling was conducted at tillering and physiological mature stage. Zn concentration in the shoots was significantly lower at both stages in plants grown in the aerobic field. At maturity, Zn uptake, biomass production, grain yield and Zn-harvest index [grain Zn/(shoot + grain Zn)] were lower under aerobic cultivation. Rice genotypes including aerobic rice and lowland rice differ in degree of response to low Zn supply. A twofold difference was found among aerobic genotypes in grain yield and Zn uptake. Also Zn-harvest index varied significantly. Zn application affected neither grain yield nor grain Zn content, although it significantly improved biomass production in both systems in most genotypes. These results demonstrate that introduction of aerobic rice systems on calcareous soils may increase Zn deficiency problems.     

‘On-farm’ seed priming with zinc in chickpea and wheat in Pakistan

A series of on-station trials was implemented between 2002 and 2006 to assess the response of wheat (Triticum aestivum L.) and chickpea (Cicer arietinum) to zinc (Zn) added by soaking seeds (priming) in solutions of ZnSO₄ before sowing. Wheat seed was primed for 10 h in 0.3% Zn and chickpea for 6 h in 0.05% Zn. Seed treatments increased the seed concentration in wheat from 27 to 470 mg/kg and in chickpea from 49 to 780 mg/kg. Priming wheat seeds with 0.3% Zn significantly increased the mean shoot dry mass, Zn concentration and Zn uptake of 15-day-old seedlings relative to non-primed controls and seeds primed with water alone. Using 0.4% Zn further increased shoot Zn concentration but depressed shoot dry mass to the level of the non-primed control. In seven trials, mean grain yield of wheat was significantly increased from 2.28 to 2.42 t/ha (6%) by priming with water alone and to 2.61 t/ha (14%) by priming with 0.3% Zn. Mean grain yield of chickpea in seven trials was increased significantly from 1.39 to 1.65 t/ha (19%) by priming seeds with 0.05% Zn. The effect of priming chickpea seeds with water was intermediate (1.49 t/ha) and not statistically separable from the non-primed and zinc-primed treatments. Increased grain yield due to priming in both crops was associated with increases in total biomass but there was no significant effect of priming on harvest index. In addition to increasing yield, priming seeds with Zn also significantly increased grain zinc concentration, by 12% in wheat (mean of three trials) and by 29% in chickpea (one trial) and the total amount of Zn taken up by the grain (by 27% in wheat and by 130% in chickpea). Using ZnSO₄ to prime seeds was very cost-effective, with net benefit-to-cost ratios of 75 for wheat and 780 for chickpea. An erratum to this article can be found at     

Effect of nitrogen on uptake, remobilization and partitioning of zinc and iron throughout the development of durum wheat

Deficiencies of zinc (Zn) and iron (Fe) are global nutritional problems and caused most often by their limited dietary intake. Increasing Zn and Fe concentrations of staple food crops such as wheat is therefore an important global challenge. This study investigated the effects of varied nitrogen (N) and Zn supply on the total uptake, remobilization and partitioning of Zn, Fe and N in durum wheat throughout its ontogenesis. Plants were grown under greenhouse conditions with high or low supply of N and Zn, and harvested at 8 different developmental stages for analysis of Zn, Fe and N in leaves, stems, husks and grains. The results obtained showed that the Zn and Fe uptake per plant was enhanced up to 4-fold by high N supply while the increases in plant growth by high N supply were much less. When both the Zn and N supplies were high, approximately 50% of grain Zn and 80% of grain Fe were provided by post-anthesis shoot uptake, indicating that the contribution of remobilization to grain accumulation was higher for Zn than for Fe. At the high N and Zn application, about 60% of Zn, but only 40% of Fe initially stored in vegetative parts were retranslocated to grains, and nearly 80% of total shoot Zn and 60% of total shoot Fe were harvested with grains. All these values were significantly lower at the low N treatment. Results indicate that N nutrition is a critical factor in both the acquisition and grain allocation of Zn and Fe in wheat.     

Influence of phosphorus and zinc fertilizers on the uptake of P and Zn by corn plants grown in highly calcareous soils

Summary The influence of heavy applications of P (100, 200 and 400 ppm P) and Zn (12.5 and 25 ppm) fertilizers on their extractabilities, availabilities and uptake by corn grown in highly calcareous soil was investigated.A significant increase was found in the levels of (NH₄)₂CO₃-EDTA-extractable Zn either by Zn-applications alone or together with P. The amounts of NaHCO₃-extractable P were also increased with P additions and the influence of Zn applications was not clear.Phosphorus application generally increased the plant dry weight. In the soils treated with P and Zn fertilizers, that increase was mostly related to P rather to Zn.In the soils not treated with Zn, P additions increased Zn uptake by the plants. On the other side, in the soils treated with Zn, P additions decreased Zn uptake.Phosphorus concentration in the whole plant and/or in the different plant parts was increased by P application without being significantly affected by Zn addition. The plants showed greater response to 12.5 ppm Zn application than to 25 ppm.Plants grown for 4 weeks contained lower amounts of Zn relative to those grown for 8 weeks. The influence of plant age on P content was not as clear as occurred with Zn.     

Yield of submerged paddy and uptake of Zn,P and N as affected by liming and Zn fertilizers

The effects of CaCO₃, Zn sources and levels on the yield of submerged paddy and uptake of Zn, P and N to paddy were studied in green-house at Haryana Agricultural University, Hissar. Powdered CaCO₃ was mixed at 0,4 and 8 per cent and Zn was added at 0,5 and 10 ppm through ZnSO₄.7H₂O, ZnO and Zn EDTA separately. Dry weight at tillering and heading and grain and straw at maturity decreased significantly with 4 and 8 per cent CaCO₃ in comparison to the control. Increasing Zn application increased the dry weight and grain yield. Zn EDTA gave highest yield of paddy followed by ZnSO₄.7H₂O and ZnO.Increasing the application of CaCO₃ from 0–8 per cent decreased the concentration and uptake of Zn and increasing Zn application from 0–10 ppm increased concentration and uptake of Zn in paddy at tillering, heading and maturity. Zn EDTA gave the highest concentration and uptake of Zn followed by ZnSO₄.7H₂O and ZnO. There was interaction between Zn sources and CaCO₃.The concentration and uptake of N and P in paddy dry matter at tillering and heading and straw and grain at maturity decreased as compared to control with increasing CaCO₃ addition. The concentration and uptake of N increased and that of P decreased in paddy dry matter straw and grain with increasing Zn application. The highest concentration of N was observed with ZnO, followed by ZnSO₄.7H₂O and Zn EDTA. But highest uptake of N was observed with Zn EDTA followed by ZnSO₄.7H₂O and ZnO. As regards concentration and uptake of P, it was highest with ZnO followed by ZnSO₄.7H₂O and Zn EDTA.     

Forest leaf litter decomposition in the vicinity of a zinc smelter

Summary Concentrations of about 26,000 ppm Zn, 10,000 ppm Fe, 2,300 ppm Pb, 900 ppm Cd, 340 ppm Cu, and 0.40% S were measured in the O₂ litter horizon about 1 km from a zinc smelter at Palmerton, Pennsylvania. Samples taken about 6 km east of the smelter had concentrations of about 15,000 ppm Zn, 6,500 ppm Fe, 970 ppm Pb, 250 ppm Cd, 170 ppm Cu, and 0.26% S. Samples from a control area about 40 km east of the smelter had concentrations of 2,800 ppm Fe, 650 ppm Zn, 260 ppm Pb, 50 ppm Cu, 9 ppm Cd, and 0.13% S.Litter bags were used to estimate first-year weight loss in sassafras leaves and a mixture of chestnut oak/red oak leaves in the three sites. At the end of one year, average weight loss for sassafras was 39.3% in the control site, 21.8% at 6 km, and 17.5% at the 1 km site. For the chestnut oak/red oak mixture, average weight loss was 36.8% (40 km), 25.7% (6 km), and 19.1% (1 km). Numbers and diversity of soil microarthropods inhabiting the litter bags showed a corresponding decline at sites near the smelter. Concentrations of Ca, Cd, Cr, Cu, Fe, Mg, Mn, N, Na, Ni, P, Pb, S and Zn in the decomposing litter were also measured.The average amount of organic matter on the forest floor was estimated to be 3.8 kg/m² in the control site, about 3.8 kg/m² at 6 km, and about 8.1 kg/m² 1 km from the smelter. Average thickness of the litter horizons in these three sites was 6.0 cm (40 km), 7.0 cm (6 km), and 12.4 cm (1 km), suggesting a long-term depression of decomposition and mineral cycling near the smelter.     

Mapping QTLs and candidate genes for iron and zinc concentrations in unpolished rice of Madhukar×Swarna RILs

Identifying QTLs/genes for iron and zinc in rice grains can help in biofortification programs. 168 F(7) RILs derived from Madhukar×Swarna were used to map QTLs for iron and zinc concentrations in unpolished rice grains. Iron ranged from 0.2 to 224ppm and zinc ranged from 0.4 to 104ppm. Genome wide mapping using 101 SSRs and 9 gene specific markers showed 5 QTLs on chromosomes 1, 3, 5, 7 and 12 significantly linked to iron, zinc or both. In all, 14 QTLs were identified for these two traits. QTLs for iron were co-located with QTLs for zinc on chromosomes 7 and 12. In all, ten candidate genes known for iron and zinc homeostasis underlie 12 of the 14 QTLs. Another 6 candidate genes were close to QTLs on chromosomes 3, 5 and 7. Thus the high priority candidate genes for high Fe and Zn in seeds are OsYSL1 and OsMTP1 for iron, OsARD2, OsIRT1, OsNAS1, OsNAS2 for zinc and OsNAS3, OsNRAMP1, Heavy metal ion transport and APRT for both iron and zinc together based on our genetic mapping studies as these genes strictly underlie QTLs. Several elite lines with high Fe, high Zn and both were identified.