Preface.- Contributors.- List of Abbreviations.- Section 1: Basic Principles: Introduction.-Sources of Heavy Metals and Metalloids in Soils.- Chemistry of Heavy Metals and Metalloids in Soils.- Methods for the Determination of Heavy Metals and Metalloids in Soils.- Effects of Heavy Metals and Metalloids on Soil Organisms.- Soil-Plant Relationships of Heavy Metals and Metalloids.- Heavy Metals and Metalloids as Micronutrients for Plants and Animals.-Critical Loads of Heavy Metals for Soils.- Section 2: Key Heavy Metals And Metalloids: Arsenic.- Cadmium.- Chromium and Nickel.- Cobalt and Manganese.- Copper.-Lead.- Mercury.- Selenium.- Zinc.- Section 3: Other Heavy Metals And Metalloids Of Potential Environmental Significance: Antimony.- Barium.- Gold.- Molybdenum.- Silver.- Thallium.- Tin.- Tungsten.- Uranium.- Vanadium.- Glossary of Specialized Terms.- Index.

Heavy metals in soils : trace metals and metalloids in soils and their bioavailability

Summary
The diets of over two-thirds of the world's population lack one or more essential mineral elements. This can be remedied through dietary diversification, mineral supplementation, food fortification, or increasing the concentrations and/or bioavailability of mineral elements in produce (biofortification). This article reviews aspects of soil science, plant physiology and genetics underpinning crop biofortification strategies, as well as agronomic and genetic approaches currently taken to biofortify food crops with the mineral elements most commonly lacking in human diets: iron (Fe), zinc (Zn), copper (Cu), calcium (Ca), magnesium (Mg), iodine (I) and selenium (Se). Two complementary approaches have been successfully adopted to increase the concentrations of bioavailable mineral elements in food crops. First, agronomic approaches optimizing the application of mineral fertilizers and/or improving the solubilization and mobilization of mineral elements in the soil have been implemented. Secondly, crops have been developed with: increased abilities to acquire mineral elements and accumulate them in edible tissues; increased concentrations of ‘promoter’ substances, such as ascorbate, β-carotene and cysteine-rich polypeptides which stimulate the absorption of essential mineral elements by the gut; and reduced concentrations of ‘antinutrients’, such as oxalate, polyphenolics or phytate, which interfere with their absorption. These approaches are addressing mineral malnutrition in humans globally.

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Biofortification of crops with seven mineral elements often lacking in human diets--iron, zinc, copper, calcium, magnesium, selenium and iodine.

Zinc in Soils and Crop Nutrition

Heavy metals in agricultural soils of the European Union with implications for food safety

Mineral Nutrition of Higher Plants, 2nd edition, H. Marschner. Academic Press, London (1995), 889, (ISBN 0-12-473543-6). Price: 29.95 Pound Sterling

Plants require the proper balance of zinc (Zn) for normal growth and optimum yield. Interest in Zn has risen in the last decade because Zn deficiency stress is extensive in many areas, causing decreases in crop yields. Zn deficiency also decreases the amount of Zn in cereal grain and diminishes its nutritional quality. Hence, increasing the Zn content of the edible portions of crops should be considered in plant breeding. Available data indicate that Zn enrichment traits are present within the genomes of crops that could allow for substantial increases in the Zn concentration of edible parts without negatively impacting yield. Increasing the amount of Zn in food crops can improve the Zn status of people. Furthermore, the use of Zn-dense seeds results in greater seedling vigor and increased crop yields when the seeds are sown in Zn-poor soils. Progress toward developing mineral-dense seed has mainly relied upon conventional plant breeding approaches, a process that is labor-intensive and time-consuming. Hence, the identification of DNA markers that are diagnostic of Zn efficiency can accelerate the development of cultivars that can remain productive even in Zn-deficient soils. Additionally, these markers may be used to begin identifying the specific genes responsible for differences in the response of genotypes to Zn deficiency.

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A review of zinc nutrition and plant breeding.

Economically important crop chickpea (Cicer arietinum L.) is sensitive to chilling stress, and breeding for chilling tolerance is the economic option even in countries with a high risk for drought and heat stresses. In this study, we have analyzed chilling-induced responses of ten chickpea accessions under field and growth-chamber conditions in order to screen, using phenotypic and physiological methods, for chilling tolerance. The field data analysis revealed that there were significant differences between accessions in their cold tolerance. The percent survival and cold-tolerance scores were the most important indices describing genotype tolerance to low temperature under field conditions; they can be used to assess chickpea cold tolerance. During environmentally controlled testing, the effects of low temperature regimes (−10°C for 15 and 30 min) were studied and cold tolerance was measured by electrolyte leakage from damaged leaves. The analysis of field data and cold treatments showed that two accessions, Sel 95Th1716 and Sel 96Th11439, grouped in one cluster, are good cold-tolerant genotypes (showing low scores for cold tolerance and electrolyte leakage). In comparison with ILC 8262, released as cold-tolerant accession, these genotypes showed more tolerance. Flip 00-6C, ILC 533, and Jam were less tolerant to cold stress. Thus, we have shown that as well as field studies, short-term cold treatment and electrolyte leakage assay can be used to evaluate low temperature tolerance of chickpea profitably in a short time.

Physiological and morphological characteristics of chickpea accessions under low temperature stress

Because of unpredictable conditions in Mediterranean environments, successful crop production requires improved adaptation and yield stability to mitigate major abiotic stresses such as drought and cold. In this study 380 durum wheat (Triticum turgidum L.) landraces with worldwide origins and four checks were evaluated in four rainfed research stations for 3 yr (2008–2011). The main objective was to investigate yield stability and adaptation patterns of the landraces to highland rainfed cold regions of Iran, where drought and cold are limiting factors. The experimental design was an unreplicated trial at each environment. Best linear unbiased predictions (BLUPs) data were used to analyze landrace × environment interactions using multivariate statistical methods. Considerable variability in yield, adaptation, and stability was observed for the landraces, which could be exploited for crop improvement. The landrace and environment groups allowed characterization of origins on the basis of similar performance of landrace within particular environments. Grouping of environments was not repeatable among the years. Many of the durum landraces exhibited a high combination of yield and stability for both drought and cold stresses, comparable to cold- and/or drought-tolerant checks. Most landraces originating from Europe and the United States could be considered as a genetic resource for specific adaptation, while the landraces from Asia may enhance genetic potential of yield stability. In conclusion, current durum wheat selection may lead to yield stability and specific adaptation, which provides opportunities for this collection to be useful for genetic improvement of both drought and cold tolerance in durum wheat

Adaptation Patterns and Yield Stability of Durum Wheat Landraces to Highland Cold Rainfed Areas of Iran

Zinc (Zn) is an important micronutrient for the growth and development of plant and humans, and dietary Zn shortage is a global wide nutritional problem. A field experiment was conducted to investigate the effects of foliar Zn application at different growth stages on grain yield, grain mineral nutrients and its relation to phytic acid content in spring wheat grown on Zn-deficient soil during the 2013–2014 growing season at Maragheh University research field, Iran. Results showed that foliar spray of zinc sulfate at different growth stages, in general, had non-significant effect on thousand grain weight and harvest index, while considerably increased grain yield, number of grains per spike, fertile spikelet per spike and plant height. Zinc and ascorbic acid contents in the grain consistently increased with the timing of the foliar Zn application and were highest at early grain filling stage. However, the timing of the Zn application had no effect on copper and phytic acid contents, but changed grain iron and manganese concentrations, and decreased phytate to Zn molar ratio of wheat grains. Results indicated that foliar Zn application at the booting + milking stages significantly increased agronomic traits, grain Zn content and bioavailability in wheat grown on Zn deficient alkaline soils, thereby improving the wheat grain’s nutritional quality for humans.

Behzad Sadeghzadeh

Papers

Zinc in Soils and Crop Nutrition

A review of zinc nutrition and plant breeding.

Physiological and morphological characteristics of chickpea accessions under low temperature stress

Adaptation Patterns and Yield Stability of Durum Wheat Landraces to Highland Cold Rainfed Areas of Iran

Impact of foliar zinc application on agronomic traits and grain quality parameters of wheat grown in zinc deficient soil