Zinc deficiency is a well-documented problem in food crops, causing decreased crop yields and nutritional quality. Generally, the regions in the world with Zn-deficient soils are also characterized by widespread Zn deficiency in humans. Recent estimates indicate that nearly half of world population suffers from Zn deficiency. Cereal crops play an important role in satisfying daily calorie intake in developing world, but they are inherently very low in Zn concentrations in grain, particularly when grown on Zn-deficient soils. The reliance on cereal-based diets may induce Zn deficiency-related health problems in humans, such as impairments in physical development, immune system and brain function. Among the strategies being discussed as major solution to Zn deficiency, plant breeding strategy (e.g., genetic biofortification) appears to be a most sustainable and cost-effective approach useful in improving Zn concentrations in grain. The breeding approach is, however, a long-term process requiring a substantial effort and resources. A successful breeding program for biofortifying food crops with Zn is very much dependent on the size of plant-available Zn pools in soil. In most parts of the cereal-growing areas, soils have, however, a variety of chemical and physical problems that significantly reduce availability of Zn to plant roots. Hence, the genetic capacity of the newly developed (biofortified) cultivars to absorb sufficient amount of Zn from soil and accumulate it in the grain may not be expressed to the full extent. It is, therefore, essential to have a short-term approach to improve Zn concentration in cereal grains. Application of Zn fertilizers or Zn-enriched NPK fertilizers (e.g., agronomic biofortification) offers a rapid solution to the problem, and represents useful complementary approach to on-going breeding programs. There is increasing evidence showing that foliar or combined soil+foliar application of Zn fertilizers under field conditions are highly effective and very practical way to maximize uptake and accumulation of Zn in whole wheat grain, raising concentration up to 60 mg Zn kg−1. Zinc-enriched grains are also of great importance for crop productivity resulting in better seedling vigor, denser stands and higher stress tolerance on potentially Zn-deficient soils. Agronomic biofortification strategy appears to be essential in keeping sufficient amount of available Zn in soil solution and maintaining adequate Zn transport to the seeds during reproductive growth stage. Finally, agronomic biofortification is required for optimizing and ensuring the success of genetic biofortification of cereal grains with Zn. In case of greater bioavailability of the grain Zn derived from foliar applications than from soil, agronomic biofortification would be a very attractive and useful strategy in solving Zn deficiency-related health problems globally and effectively.

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Enrichment of cereal grains with zinc: Agronomic or genetic biofortification?

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.

Lipoxygenases: Occurrence, Functions, Catalysis, and Acquisition of Substrate

A number of molecular genetic maps of the soybean [Glycine max (L.) Merr.] have been developed over the past 10 yr. These maps are primarily based on restriction fragment length polymorphism (RFLP) markers. Parental surveys have shown that most RFLP loci have only two known alleles. However, because the soybean is an ancient polyploid, RFLP probes typically hybridize and map to more than one position in the genome. Thus, the polymorphic potential of an RFLP probe is primarily a function of the frequency of the two alleles at each locus the probe detects. In contrast, simple sequence repeat (SSR) markers are single locus markers with multiple alleles. The polymorphic potential of an SSR marker is dependent on the number of alleles and their frequencies. Single locus markers provide an unambiguous means of defining linkage group homology across mapping populations. The objective of the work reported here was to develop and map a large set of SSR markers. A total of 606 SSR loci were mapped in one or more of three populations: the USDA/Iowa State G. max × G. soja F 2 population, the Univ. of Utah Minsoy × Noir 1 recombinant inbred population, and the Univ. of Nebraska Clark × Harosoy F 2 population. Each SSR mapped to a single locus in the genome, with a map order that was essentially identical in all three populations. Many SSR loci were segregating in two or all three populations. Thus, it was relatively simple to align the 20+ linkage groups derived from each of the three populations into a consensus set of 20 homologous linkage groups presumed to correspond to the 20 pairs of soybean chromosomes. On the basis of in situ segregation or linkage reports in the literature all but one of the classical linkage groups can now be assigned to a corresponding molecular linkage group.

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An Integrated Genetic Linkage Map of the Soybean Genome

https://www.cell.com/trends/plant-science/pdf/S1360-1385(05)00250-5.pdf

Biofortifying crops with essential mineral elements

Stages of soybean development

Principles of cultivar development , Principles of cultivar development , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Principles of cultivar development

The objectives of this study were to present an expanded soybean RFLP map and to identify quantitative trait loci (QTL) in soybean [Glycine max (L.) Merr.] for seed protein and oil content. The study population was formed from a cross between a G. max experimental line (A81-356022) and a G. soja Sieb. and Zucc. plant introduction (PI 468916). A total of 252 markers was mapped in the population, forming 31 linkage groups. Protein and oil content were measured on seed harvested from a replicated trial of 60 F2-derived lines in the F3 generation (F2∶3 lines). Each F2∶3 line was genotyped with 243 RFLP, five isozyme, one storage protein, and three morphological markers. Significant (P<0.01) associations were found between the segregation of markers and seed protein and oil content. Segregation of individual markers explained up to 43% of the total variation for specific traits. All G. max alleles at significant loci for oil content were associated with greater oil content than G. soja alleles. All G. soja alleles at significant loci for protein content were associated with greater protein content than G. max alleles.

RFLP analysis of soybean seed protein and oil content

Isoflavones in soybean [Glycine max (L.) Merr.] may have positive impacts on human health. The objective of this study was to determine the role of the genotype, environment, and genotype × environment interactions on isoflavone contents of soybean. Nine isoflavones were measured in six cultivars grown at eight locations during 2 yr. The mean contents of total isoflavones and six of nine individual isoflavones were significantly higher in 1996 than 1995. There were significant differences among locations in one or more years for total and individual isoflavone contents. The year × location interactions were significant due to changes in rank and magnitude among the locations during the 2 yr. The genotype, genotype × year, genotype × location, and genotype × year × location interactions were significant for total and individual isoflavone contents. Despite the significant genotype × environment interactions, the differences between the cultivars with the highest and lowest total and individual isoflavone contents were relatively consistent among the 16 environments. It should be possible to breed for isoflavone content as a quantitative trait in a cultivar development program.

Influence of genotype and environment on isoflavone contents of soybean.

Improving seed yield of soybean [Glycine max (L.) Merr.] is an important breeding goal. The objective of this study was to evaluate two soybean PIs as sources of alleles for the enhancement of seed yield in North American cultivars. A population of 167 F 5 -derived lines was developed from a cross between 'BSR 101' and the experimental line LG82-8379. BSR 101 has nine of 10 major ancestral lines contributing to the commercial gene pool of North America, while LG82-8379 was selected from a cross between PI 68508 and FC 04007B. The F 5 -derived lines, divided into three sets based on maturity, were evaluated for 145 polymorphic simple sequence repeat (SSR) marker loci and for seed yield and other agronomic traits in 12 environments. Fifteen quantitative trait loci (QTL) were significantly [P 2.5] associated with seed yield in at least one set with two significant across all sets. For nine of the yield QTL, the LG82-8379 alleles were associated with yield increases of 1.7 to 5.4% while the BSR 101 alleles increased yield 2.4 to 4.4% at six yield QTL. Four yield QTL were associated with significant changes in R8, eight with plant height, and three with seed protein concentration. Additional QTL were identified for R8, plant height, lodging, and seed protein and oil concentration. These results indicate that soybean PIs have the genetic potential for improving seed yield of U.S. soybean cultivars.

Walter R. Fehr

Papers

Stages of soybean development

Principles of cultivar development

RFLP analysis of soybean seed protein and oil content

Influence of genotype and environment on isoflavone contents of soybean.

Putative Alleles for Increased Yield from Soybean Plant Introductions