Energy-dispersive X-ray fluorescence spectrometry as a tool for zinc, iron and selenium analysis in whole grain wheat

Background and aims

Crop biofortification programs require fast, accurate and inexpensive methods of identifying nutrient dense genotypes. This study investigated energy-dispersive X-ray fluorescence spectrometry (EDXRF) for the measurement of zinc (Zn), iron (Fe) and selenium (Se) concentrations in whole grain wheat.

Methods

Grain samples were obtained from existing biofortification programs. Reference Zn, Fe and Se concentrations were obtained using inductively coupled plasma optical emission spectrometry (ICP-OES) and/or inductively coupled plasma mass spectrometry (ICP-MS). One set of 25 samples was used to calibrate for Zn (19–60?mg?kg^–1) and Fe (26–41?mg?kg^–1), with 25 further samples used to calibrate for Se (2–31?mg?kg^–1 ). Calibrations were validated using an additional 40–50 wheat samples.

Results

EDXRF limits of quantification (LOQ) were estimated as 7, 3 and 2?mg?kg^–1 for Zn, Fe, and Se, respectively. EDXRF results were highly correlated with ICP-OES or -MS values. Standard errors of EDXRF predictions were ±2.2?mg Zn kg^–1, ±2.6?mg Fe kg^–1, and ±1.5?mg Se kg^–1.

Conclusion

EDXRF offers a fast and economical method for the assessment of Zn, Fe and Se concentration in wheat biofortification programs.     

Characterization of grain protein content gene (<Emphasis Type="Italic">GPC</Emphasis>-<Emphasis Type="Italic">B1</Emphasis>) introgression lines and its potential use in breeding for enhanced grain zinc and iron concentration in spring wheat

At least two billion people around the world suffer from micronutrient deficiency, or hidden hunger, which is characterized by iron-deficiency anemia, vitamin A and zinc deficiency. As a key staple food crop, wheat provides 20% of the world’s dietary energy and protein, therefore wheat is an ideal vehicle for biofortification. Developing biofortified wheat varieties with genetically enhanced levels of grain zinc (Zn) and iron (Fe) concentrations, and protein content provides a cost-effective and sustainable solution to the resource-poor wheat consumers. Large genetic variation for Fe and Zn were found in the primitive and wild relatives of wheat, the potential high Zn and Fe containing genetic resources were used as progenitors to breed high-yielding biofortified wheat varieties with 30–40% higher Zn content. Grain protein content (GPC) determines processing and end-use quality of wheat for making diverse food products. The GPC-B1 allele from Triticum turgidum L. var. dicoccoides have been well characterized for the increase in GPC and the associated pleiotropic effect on grain Zn and Fe concentrations in wheat. In this study effect of GPC-B1 allele on grain Zn and Fe concentrations in wheat were measured in different genetic backgrounds and two different agronomic management practices (with- and without foliar Zn fertilization). Six pairs of near-isogenic lines differing for GPC-B1 gene evaluated at CIMMYT, Mexico showed that GPC-B1 influenced marginal increase for grain Zn, Fe concentrations, grain protein content and slight reduction in kernel weight and grain yield. However, the magnitude of GPC and grain Zn and Fe reductions varied depending on the genetic background. Introgression of GPC-B1 functional allele in combination with normal or delayed maturity alleles in the CIMMYT elite wheat germplasm has the potential to improve GPC and grain Zn and Fe concentrations without the negative effect on grain yield due to early senescence and accelerated maturity.     

Traits associated with improved P-uptake efficiency in CIMMYT's semidwarf spring bread wheat grown on an acid Andisol in Mexico

Phosphorus deficiency is a major yield limiting constraint in wheat cultivation on acid soils. The plant factors that influence P uptake efficiency (PUPE) are mainly associated with root characteristics. This study was conducted to analyze the genotypic differences and relationships between PUPE, root length density (RLD), colonization by vesicular arbuscular and arbuscular mycorrhizal (V)AM fungi and root excretion of phosphatases in a P-deficient Andisol in the Central Mexican Highlands. Forty-two semidwarf spring-bread-wheat (Triticum aestivumL.) genotypes from CIMMYT were grown without (−P) and with P fertilization (+P), and subsequently in subsets of 30 and 22 genotypes in replicated field trials over 2 and 3 years, respectively. Acid phosphatase activity at the root surface (APASE) was analyzed in accompanying greenhouse experiments in nutrient solution. In this environment, PUPE contributed more than P utilization efficiency, in one experiment almost completely, to the variation of grain yield among genotypes. Late-flowering genotypes were higher yielding, because the postanthesis period of wheat was extended due to the cold weather at the end of the crop cycles, and postanthesis P uptake accounted for 40–45% of total P uptake. PUPE was positively correlated with the numbers of days to anthesis (at −P r=0.57 and at +P r=0.73). The RLD in the upper soil layer (0–20 cm) of the wheat germplasm tested ranged from 0.5 to 2.4 cm cm^-3 at –P and 0.7 to 7.7 at +P. RLD was the most important root trait for improved P absorption, and it was positively genetically correlated with PUPE (at –P r=0.42 and at +P r=0.63) and the number of spikes m^-2 (at –P r=0.58 and at +P r=0.36). RLD in the upper soil layer was more important with P fertilizer application. Without P fertilization, root proliferation in the deeper soil profile secured access to residual, native P in the deeper soil layer. (V)AM-colonisation and APASE were to a lesser degree correlated with PUPE. Among genoptypes, the level of (V)AM-colonisation ranged from 14 to 32% of the RLD in the upper soil layer, and APASE from 0.5 to 1.1 nmol s^-1 plant^-1 10^-2. This revised version was published online in June 2006 with corrections to the Cover Date.     

Combined report of problems and complications in 793 craniofacial operations.

We report the experiences in 6 major craniofacial centers, with similar teams but in different parts of the world, in a total of 793 craniofacial operations. The mortality rate was 1.6%. Complications developed in 16.5% of the cases (including infections in 4.4%). This surgery has many potential advantages, not least of which is its psychosocial effects on previously disfigured patients. Certain problems seem inherent, however, for there are not yet any satisfactory solutions to them. Some of the factors that reduce morbidity and improve results include the use of hypotensive anesthesia, a reduction in operating time, rigid stabilization of the mobilized bones at the end of the operation, a diminution in the number of incisions, and extensive antibiotic therapy.     

Keloid skin scars: the influence of hyperbaric oxygenation on fibroblast growth and on the expression of messenger RNA for insulin like growth factor and for transforming growth factor

Wound healing can result in the development of keloid scars that contain atypical fibroblasts and an overabundance of extracellular matrix components. Hyperbaric oxygenation (HBO) refers to exposure to pure oxygen under increased atmospheric pressure and is recognized as a valuable supplementary method of treatment for problematic wounds. The effect of HBO in the expression of insulin-like growth factor type 1 (ILGF-1) and transforming growth factor β (TGF-β) messenger RNAs was determined by semiquantitative RT-PCR in fibroblasts obtained from keloid scars and nonwound involved skin fibroblast from the same patient. ILGF-1 and TGF-β are the principal mitogens during wound regeneration. We found a decrease in the growth of fibroblasts and in the expression of ILGF-1 and TGF-β messengers in keloid and nonkeloid fibroblast after chronic exposition to hyperbaric oxygenation compared with normal oxygen partial pressure.     

Selenium in Australia: selenium status and biofortification of wheat for better health.

Selenium (Se) is an essential micronutrient for humans and animals, but is deficient in at least a billion people worldwide. Wheat (Triticum aestivum L.) is a major dietary source of Se. The largest survey to date of Se status of Australians found a mean plasma Se concentration of 103 microg/l in 288 Adelaide residents, just above the nutritional adequacy level. In the total sample analysed (six surveys from 1977 to 2002; n = 834), plasma Se was higher in males and increased with age. This study showed that many South Australians consume inadequate Se to maximise selenoenzyme expression and cancer protection, and indicated that levels had declined around 20% from the 1970s. No significant genotypic variability for grain Se concentration was observed in modern wheat cultivars, but the diploid wheat Aegilops tauschii L. and rye (Secale cereale L.) were higher. Grain Se concentrations ranged 5-720 microg/kg and it was apparent that this variation was determined mostly by available soil Se level. Field trials, along with glasshouse and growth chamber studies, were used to investigate agronomic biofortification of wheat. Se applied as sodium selenate at rates of 4-120 g Se/ha increased grain Se concentration progressively up to 133-fold when sprayed on soil at seeding and up to 20-fold when applied as a foliar spray after flowering. A threshold of toxicity of around 325 mg Se/kg in leaves of young wheat plants was observed, a level that would not normally be reached with Se fertilisation. On the other hand sulphur (S) applied at the low rate of 30 kg/ha at seeding reduced grain Se concentration by 16%. Agronomic biofortification could be used by food companies as a cost-effective method to produce high-Se wheat products that contain most Se in the desirable selenomethionine form. Further studies are needed to assess the functionality of high-Se wheat, for example short-term clinical trials that measure changes in genome stability, lipid peroxidation and immunocompetence. Increasing the Se content of wheat is a food systems strategy that could increase the Se intake of whole populations.