Dietary Zn deficiency, the current situation and potential solutions.

Zinc (Zn) deficiency is a worldwide problem, and this review presents an overview of the magnitude of Zn deficiency with a particular emphasis on present global challenges, current recommendations for Zn intake, and factors that affect dietary requirements. The challenges of monitoring Zn status are clarified together with the discussion of relevant Zn bioaccessibility and bioavailability issues. Modern lifestyle factors that may exacerbate Zn deficiency and new strategies of reducing its effects are presented. Biofortification, as a potentially useful strategy for improving Zn status in sensitive populations, is discussed. The review proposes potential actions that could deliver promising results both in terms of monitoring dietary and physiological Zn status as well as in alleviating dietary Zn deficiency in affected populations.

Genomic prediction of zinc-biofortification potential in rice gene bank accessions.

KEY MESSAGE: A genomic prediction model successfully predicted grain Zn concentrations in 3000 gene bank accessions and this was verified experimentally with selected potential donors having high on-farm grain-Zn in Madagascar. Increasing zinc (Zn) concentrations in edible parts of food crops, an approach termed Zn-biofortification, is a global breeding objective to alleviate micro-nutrient malnutrition. In particular, infants in countries like Madagascar are at risk of Zn deficiency because their dominant food source, rice, contains insufficient Zn. Biofortified rice varieties with increased grain Zn concentrations would offer a solution and our objective is to explore the genotypic variation present among rice gene bank accessions and to possibly identify underlying genetic factors through genomic prediction and genome-wide association studies (GWAS). A training set of 253 rice accessions was grown at two field sites in Madagascar to determine grain Zn concentrations and grain yield. A multi-locus GWAS analysis identified eight loci. Among these, QTN_11.3 had the largest effect and a rare allele increased grain Zn concentrations by 15%. A genomic prediction model was developed from the above training set to predict Zn concentrations of 3000 sequenced rice accessions. Predicted concentrations ranged from 17.1 to 40.2 ppm with a prediction accuracy of 0.51. An independent confirmation with 61 gene bank seed samples provided high correlations (r = 0.74) between measured and predicted values. Accessions from the aus sub-species had the highest predicted grain Zn concentrations and these were confirmed in additional field experiments, with one potential donor having more than twice the grain Zn compared to a local check variety. We conclude utilizing donors from the aus sub-species and employing genomic selection during the breeding process is the most promising approach to raise grain Zn concentrations in rice.

Identification of genomic regions conferring rust resistance and enhanced mineral accumulation in a HarvestPlus Association Mapping Panel of wheat.

KEY MESSAGE: New genomic regions for high accumulation of 10 minerals were identified. The 1B:1R and 2NS translocations enhanced concentrations of four and two minerals, respectively, in addition to disease resistance. Puccinia species, the causal agents of rust diseases of wheat, have the potential to cause total crop failures due their high evolutionary ability to acquire virulence for resistance genes deployed in commercial cultivars. Hence, the discovery of genetically diverse sources of rust resistance is essential. On the other hand, biofortification of wheat for essential nutrients, such as zinc (Zn) and iron (Fe), is also an objective in wheat improvement programs to tackle micronutrient deficiency. The development of rust-resistant and nutrient-concentrated wheat cultivars would be important for sustainable production and the fight against malnutrition. The HarvestPlus association mapping panel (HPAMP) that included nutrient-dense sources from diverse genetic backgrounds was genotyped using a 90 K Infinium SNP array and 13 markers linked with rust resistance genes. The HPAMP was used for genome-wide association mapping to identify genomic regions underpinning rust resistance and mineral accumulation. Twelve QTL for rust resistance and 53 for concentrations of 10 minerals were identified. Comparison of results from this study with the published QTL information revealed the detection of already known and some putatively new genes/QTL underpinning stripe rust and leaf rust resistance in this panel. Thirty-six new QTL for mineral concentration were identified on 17 chromosomes. Accessions carrying the 1B:1R translocation accumulated higher concentrations of Zn, Fe, Copper (Cu) and sulphur (S). The 2NS segment showed enhanced accumulation of grain Fe and Cu. Fifteen rust-resistant and biofortified accessions were identified for use as donor sources in breeding programs.

Genomic selection can accelerate the biofortification of spring wheat.

KEY MESSAGE: Genomic selection enabled accurate prediction for the concentration of 13 nutritional element traits in wheat. Wheat biofortification is one of the most sustainable strategies to alleviate mineral deficiency in human diets. Here, we investigated the potential of genomic selection using BayesR and Bayesian ridge regression (BRR) models to predict grain yield (YLD) and the concentration of 13 nutritional elements in grains (B, Ca, Co, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P and Zn) using a population of 1470 spring wheat lines. The lines were grown in replicated field trials with two times of sowing (TOS) at 3 locations (Narrabri-NSW, all lines; Merredin-WA and Horsham-VIC, 200 core lines). Narrow-sense heritability across environments (locations/TOS) ranged from 0.09 to 0.45. Co, K, Na and Ca showed low to negative genetic correlations with other traits including YLD, while the remaining traits were negatively correlated with YLD. When all environments were included in the reference population, medium to high prediction accuracy was observed for the different traits across environments. BayesR had higher average prediction accuracy for mineral concentrations (r = 0.55) compared to BRR (r = 0.48) across all traits and environments but both methods had comparable accuracies for YLD. We also investigated the utility of one or two locations (reference locations) to predict the remaining location(s), as well as the ability of one TOS to predict the other. Under these scenarios, BayesR and BRR showed comparable performance but with lower prediction accuracy compared to the scenario of predicting reference environments for new lines. Our study demonstrates the potential of genomic selection for enriching wheat grain with nutritional elements in biofortification breeding.

Effects of Dietary Fibre from the Traditional Indonesian Food, Green Cincau (Premna oblongifolia Merr.) on Preneoplastic Lesions and Short Chain Fatty Acid Production in an Azoxymethane Rat Model of Colon Cancer.

Green cincau (Premna oblongifolia Merr.) is a traditional food of Indonesia and provides a natural source of dietary fibre and antioxidants. This study evaluated the ability of green cincau, and other dietary fibres with or without the addition of anti-oxidant, epigallocatechin-3-gallate (EGCG), to prevent colorectal cancer in a 12 week azoxymethane (AOM) rat model. While all dietary treatments stimulated short chain fatty acid production (SCFA) in the digesta and faeces, no one treatment was able to significantly protect against aberrant crypt formation (ACF), when compared to the control diet. However, feeding green cincau leaves or extracts did not result in an increase in ACF compared to the control diet. Unexpectedly, when the dietary fibre source was pectin, 0.1% EGCG increased proliferative activity and liver lipid peroxidation when compared to the control diet containing cellulose. Examination of faecal microbial communities identified the presence of short chain acid producing bacteria, but a distinct community profile was not observed from any individual diet group. Overall, this research implies that combining dietary fibre with an antioxidant does not automatically equate to a beneficial response. Further work is required to investigate the health-promoting properties of green cincau.

New perspectives on the regulation of iron absorption via cellular zinc concentrations in humans.

Iron deficiency is the most prevalent nutritional deficiency, affecting more than 30% of the total world's population. It is a major public health problem in many countries around the world. Over the years various methods have been used with an effort to try and control iron-deficiency anemia. However, there has only been a marginal reduction in the global prevalence of anemia. Why is this so? Iron and zinc are essential trace elements for humans. These metals influence the transport and absorption of one another across the enterocytes and hepatocytes, due to similar ionic properties. This paper describes the structure and roles of major iron and zinc transport proteins, clarifies iron-zinc interactions at these sites, and provides a model for the mechanism of these interactions both at the local and systemic level. This review provides evidence that much of the massive extent of iron deficiency anemia in the world may be due to an underlying deficiency of zinc. It explains the reasons for predominance of cellular zinc status in determination of iron/zinc interactions and for the first time thoroughly explains mechanisms by which zinc brings about these changes.

The influence of food consumption and socio-economic factors on the relationship between zinc and iron intake and status in a healthy population.

OBJECTIVE: To examine Zn and Fe nutritional status of a healthy population by means of anthropometric, dietary and biochemical measurements and to investigate the relationship of usual Zn and Fe dietary intakes to Zn and Fe status. In addition, to examine the impact of food choices and socio-economic factors on Fe and Zn dietary intakes and status with the aim to identify groups at risk of dietary deficiency and suggest factors that may influence the status of these nutrients. DESIGN: Food consumption was assessed by 24 h recall questionnaires. Twenty biochemical parameters were measured, of which Hb, haematocrit, erythrocyte count and plasma concentrations of Fe and Zn were directly related to Fe and Zn nutrition. The prevalence of study participants with inadequate micronutrient intakes was calculated using the Estimated Average Requirement cut-point method. SETTING: Serbia, Europe. SUBJECTS: Apparently healthy adults (25-65 years of age). RESULTS: Mean daily Zn and Fe intakes were 9·1 mg and 11·6 mg for males and 7·3 mg and 9·4 mg for females, respectively. Five per cent of the study population had inadequate dietary Fe intake and 15-25 % had inadequate Zn intake. Lower Hb concentrations were measured in women with lower Zn intakes. No differences in Fe and Zn intakes and status among various socio-economic groups were observed, except for Fe intake between the low-income and affluent groups. CONCLUSIONS: Regular follow-ups are needed to ensure that potential deficiencies of Zn and Fe do get recognized and addressed in a timely manner.

Nutrient variability in phloem: examining changes in K, Mg, Zn and Fe concentration during grain loading in common wheat (Triticum aestivum).

In wheat, nutrients are transported to seeds via the phloem yet access to this vascular tissue for exudate collection and quantitative analysis of elemental composition is difficult. The purest phloem is collected through the use of aphid stylectomy with volumes of exudate collected normally in the range of 20-500 nl. In this work a new method using inductively coupled plasma mass spectroscopy (ICP-MS) was developed to measure the concentration of K, Mg, Zn and Fe in volumes of wheat (Triticum aestivum, genotype Samnyt 16) phloem as small as 15.5 nl. This improved method was used to observe changes in phloem nutrient concentration during the grain loading period. There were statistically significant increases in phloem Mg and Zn concentration and a significant decrease in K over the period from 1-2 days after anthesis (DAA) to 9-12 DAA. During this period, there was no statistically significant change in phloem Fe concentration.

The effect of wheat prebiotics on the gut bacterial population and iron status of iron deficient broiler chickens.

BACKGROUND: Currently, there is a lot of interest in improving gut health, and consequently increasing Fe absorption, by managing the colonic microbial population. This is traditionally done by the consumption of probiotics, live microbial food supplements. However, an alternative, and often very effective approach, is the consumption of food ingredients known as prebiotics. Fructans and arabinoxylans are naturally occurring non-digestible oligosaccharides in wheat that exhibit prebiotic properties and may enhance intestinal iron (Fe) absorption. The aim of this study was to assess the effect of prebiotics from wheat on Fe bioavailability in vitro (Caco-2 cells) and in vivo (broiler chickens, Gallus gallus). METHODS: In the current study, the effect of intra-amniotic administration of wheat samples extracts at 17 d of embryonic incubation on the Fe status and possible changes in the bacterial population in intestinal content of broiler hatchlings were investigated. A group of 144 eggs were injected with the specified solution (1 ml per egg) into the amniotic fluid. Immediately after hatch (21 d) and from each treatment group, 10 chicks were euthanized and their small intestine, liver and cecum were removed for relative mRNA abundance of intestinal Fe related transporters, relative liver ferritin amounts and bacterial analysis of cecal content, respectively. RESULTS: The in vivo results are in agreement with the in vitro observations, showing no differences in the hatchling Fe status between the treatment groups, as Fe bioavailability was not increased in vitro and no significant differences were measured in the intestinal expression of DMT1, Ferroportin and DcytB in vivo. However, there was significant variation in relative amounts of bifidobacteria and lactobacilli in the intestinal content between the treatments groups, with generally more bifidobacteria being produced with increased prebiotic content. CONCLUSIONS: In this study we showed that prebiotics naturally found in wheat grains/bread products significantly increased intestinal beneficial bacterial population in Fe deficient broiler chickens. With this short-term feeding trial we were not able to show differences in the Fe-status of broilers. Nevertheless, the increase in relative amounts of bifidobacteria and lactobacilli in the presence of wheat prebiotics is an important finding as these bacterial populations may affect Fe bioavailability in long-term studies.

Stability of grain zinc concentrations across lowland rice environments favors zinc biofortification breeding.

Introduction: One-third of the human population consumes insufficient zinc (Zn) to sustain a healthy life. Zn deficiency can be relieved by increasing the Zn concentration ([Zn]) in staple food crops through biofortification breeding. Rice is a poor source of Zn, and in countries predominantly relying on rice without sufficient dietary diversification, such as Madagascar, Zn biofortification is a priority. Methods: Multi-environmental trials were performed in Madagascar over two years, 2019 and 2020, to screen a total of 28 genotypes including local and imported germplasm. The trials were conducted in the highlands of Ankazomiriotra, Anjiro, and Behenji and in Morovoay, a location representative of the coastal ecosystem. Contributions of genotype (G), environment (E), and G by E interactions (GEIs) were investigated. Result: The grain [Zn] of local Malagasy rice varieties was similar to the internationally established grain [Zn] baseline of 18-20 µg/g for brown rice. While several imported breeding lines reached 50% of our breeding target set at +12 µg/g, only few met farmers' appreciation criteria. Levels of grain [Zn] were stable across E. The G effects accounted for a main fraction of the variation, 76% to 83% of the variation for year 1 and year 2 trials, respectively, while GEI effects were comparatively small, contributing 23% to 9%. This contrasted with dominant E and GEI effects for grain yield. Our results indicate that local varieties tested contained insufficient Zn to alleviate Zn malnutrition, and developing new Zn-biofortified varieties should therefore be a priority. GGE analysis did not distinguish mega-environments for grain [Zn], whereas at least three mega-environments existed for grain yield, differentiated by the presence of limiting environmental conditions and responsiveness to improved soil fertility. Discussion: Our main conclusion reveals that grain [Zn] seems to be under strong genetic control in the agro-climatic conditions of Madagascar. We could identify several interesting genotypes as potential donors for the breeding program, among those BF156, with a relatively stable grain [Zn] (AMMI stability value (ASV) = 0.89) reaching our target (>26 µg/g). While selection for grain yield, general adaptation, and farmers' appreciation would have to rely on multi-environment testing, selection for grain [Zn] could be centralized in earlier generations.

Quantitative trait loci and genomic prediction for grain sugar and mineral concentrations of cowpea [Vigna unguiculata (L.) Walp.].

Development of high yielding cowpea varieties coupled with good taste and rich in essential minerals can promote consumption and thus nutrition and profitability. The sweet taste of cowpea grain is determined by its sugar content, which comprises mainly sucrose and galacto-oligosaccharides (GOS) including raffinose and stachyose. However, GOS are indigestible and their fermentation in the colon can produce excess intestinal gas, causing undesirable bloating and flatulence. In this study, we aimed to examine variation in grain sugar and mineral concentrations, then map quantitative trait loci (QTLs) and estimate genomic-prediction (GP) accuracies for possible application in breeding. Grain samples were collected from a multi-parent advanced generation intercross (MAGIC) population grown in California during 2016-2017. Grain sugars were assayed using high-performance liquid chromatography. Grain minerals were determined by inductively coupled plasma-optical emission spectrometry and combustion. Considerable variation was observed for sucrose (0.6-6.9%) and stachyose (2.3-8.4%). Major QTLs for sucrose (QSuc.vu-1.1), stachyose (QSta.vu-7.1), copper (QCu.vu-1.1) and manganese (QMn.vu-5.1) were identified. Allelic effects of major sugar QTLs were validated using the MAGIC grain samples grown in West Africa in 2017. GP accuracies for minerals were moderate (0.4-0.58). These findings help guide future breeding efforts to develop mineral-rich cowpea varieties with desirable sugar content.

Characterisation of ethylene pathway components in non-climacteric capsicum.

BACKGROUND: Climacteric fruit exhibit high ethylene and respiration levels during ripening but these levels are limited in non-climacteric fruit. Even though capsicum is in the same family as the well-characterised climacteric tomato (Solanaceae), it is non-climacteric and does not ripen normally in response to ethylene or if harvested when mature green. However, ripening progresses normally in capsicum fruit when they are harvested during or after what is called the 'Breaker stage'. Whether ethylene, and components of the ethylene pathway such as 1-aminocyclopropane 1-carboxylate (ACC) oxidase (ACO), ACC synthase (ACS) and the ethylene receptor (ETR), contribute to non-climacteric ripening in capsicum has not been studied in detail. To elucidate the behaviour of ethylene pathway components in capsicum during ripening, further analysis is therefore needed. The effects of ethylene or inhibitors of ethylene perception, such as 1-methylcyclopropene, on capsicum fruit ripening and the ethylene pathway components may also shed some light on the role of ethylene in non-climacteric ripening. RESULTS: The expression of several isoforms of ACO, ACS and ETR were limited during capsicum ripening except one ACO isoform (CaACO4). ACS activity and ACC content were also low in capsicum despite the increase in ACO activity during the onset of ripening. Ethylene did not stimulate capsicum ripening but 1-methylcyclopropene treatment delayed the ripening of Breaker-harvested fruit. Some of the ACO, ACS and ETR isoforms were also differentially expressed upon treatment with ethylene or 1-methylcyclopropene. CONCLUSIONS: ACS activity may be the rate limiting step in the ethylene pathway of capsicum which restricts ACC content. The differential expression of several ethylene pathway components during ripening and upon ethylene or 1-methylclopropene treatment suggests that the ethylene pathway may be regulated differently in non-climacteric capsicum compared to the climacteric tomato. Ethylene independent pathways may also exist in non-climacteric ripening as evidenced by the up-regulation of CaACO4 during ripening onset despite being negatively regulated by ethylene exposure. However, some level of ethylene perception may still be needed to induce ripening especially during the Breaker stage. A model of capsicum ripening is also presented to illustrate the probable role of ethylene in this non-climacteric fruit.

Mechanisms associated with Fe-deficiency tolerance and signaling in shoots of Pisum sativum.

Mechanisms of Fe-deficiency tolerance and signaling were investigated in shoots of Santi (deficiency tolerant) and Parafield (deficiency intolerant) pea genotypes using metabolomic and physiological approaches. From metabolomic studies, Fe deficiency induced significant increases in N-, S- and tricarboxylic acid cycle metabolites in Santi but not in Parafield. Elevated N metabolites reflect an increase in N-recycling processes. Increased glutathione and S-metabolites suggest better protection of pea plants from Fe-deficiency-induced oxidative stress. Furthermore, Fe-deficiency induced increases in citrate and malate in leaves of Santi suggests long-distance transport of Fe is promoted by better xylem unloading. Supporting a role of citrate in the deficiency tolerance mechanism, physiological experiments showed higher Fe and citrate in the xylem of Santi. Reciprocal-grafting experiments confirm that the Fe-deficiency signal driving root Fe reductase and proton extrusion activity is generated in the shoot. Finally, our studies show that auxin can induce increased Fe-reductase activity and proton extrusion in roots. This article identifies several mechanisms in shoots associated with the differential Fe-deficiency tolerance of genotypes within a species, and provides essential background for future efforts to improve the Fe content and deficiency tolerance in peas.

An accurate, reliable, and universal qPCR method to identify homozygous single insert T-DNA with the example of transgenic rice.

Early determination of transgenic plants that are homozygous for a single locus T-DNA insert is highly desirable in most fundamental and applied transgenic research. This study aimed to build on an accurate, rapid, and reliable quantitative real-time PCR (qPCR) method to fast-track the development of multiple homozygous transgenic rice lines in the T1 generation, with low copy number to single T-DNA insert for further analyses. Here, a well-established qPCR protocol, based on the OsSBE4 reference gene and the nos terminator, was optimized in the transgenic Japonica rice cultivar Nipponbare, to distinguish homozygous single-insert plants with 100% accuracy. This method was successfully adapted to transgenic Indica rice plants carrying three different T-DNAs, without any modifications to quickly develop homozygous rice plants in the T1 generation. The accuracy of this qPCR method when applied to transgenic Indica rice approached 100% in 12 putative transgenic lines. Moreover, this protocol also successfully detected homozygous single-locus T-DNA transgenic rice plants with two-transgene T-DNAs, a feature likely to become more popular in future transgenic research. The assay was developed utilizing universal primers targeting common sequence elements of gene cassettes (the nos terminator). This assay could therefore be applied to other transgenic plants carrying the nos terminator. All procedures described here use standardized qPCR reaction conditions and relatively inexpensive dyes, such as SYBR Green, thus the qPCR method could be cost-effective and suitable for lower budget laboratories that are involved in rice transgenic research.

Proof of concept and early development stage of market-oriented high iron and zinc rice expressing dicot ferritin and rice nicotianamine synthase genes.

Micronutrient deficiencies such as iron (Fe), zinc (Zn), and vitamin A, constitute a severe global public health phenomenon. Over half of preschool children and two-thirds of nonpregnant women of reproductive age worldwide have micronutrient deficiencies. Biofortification is a cost-effective strategy that comprises a meaningful and sustainable means of addressing this issue by delivering micronutrients through staple foods to populations with limited access to diverse diets and other nutritional interventions. Here, we report on the proof-of-concept and early development stage of a collection of biofortified rice events with a high density of Fe and Zn in polished grains that have been pursued further to advance development for product release. In total, eight constructs were developed specifically expressing dicot ferritins and the rice nicotianamine synthase 2 (OsNAS2) gene under different combinations of promoters. A large-scale transformation of these constructs to Bangladesh and Philippines commercial indica cultivars and subsequent molecular screening and confined field evaluations resulted in the identification of a pool of ten events with Fe and Zn concentrations in polished grains of up to 11 µg g-1 and up to 37 µg g-1, respectively. The latter has the potential to reduce the prevalence of inadequate Zn intake for women of childbearing age in Bangladesh and in the Philippines by 30% and 50%, respectively, compared to the current prevalence. To our knowledge, this is the first potential biotechnology public-sector product that adopts the product cycle phase-gated approach, routinely applied in the private sector.

Clusters of genes encoding fructan biosynthesizing enzymes in wheat and barley.

Fructans are soluble carbohydrates with health benefits and possible roles in plant adaptation. Fructan biosynthetic genes were isolated using comparative genomics and physical mapping followed by BAC sequencing in barley. Genes encoding sucrose:sucrose 1-fructosyltransferase (1-SST), fructan:fructan 1-fructosyltransferase (1-FFT) and sucrose:fructan 6-fructosyltransferase (6-SFT) were clustered together with multiple copies of vacuolar invertase genes and a transposable element on two barley BAC. Intron-exon structures of the genes were similar. Phylogenetic analysis of the fructosyltransferases and invertases in the Poaceae showed that the fructan biosynthetic genes may have evolved from vacuolar invertases. Quantitative real-time PCR was performed using leaf RNA extracted from three wheat cultivars grown under different conditions. The 1-SST, 1-FFT and 6-SFT genes had correlated expression patterns in our wheat experiment and in existing barley transcriptome database. Single nucleotide polymorphism (SNP) markers were developed and successfully mapped to a major QTL region affecting wheat grain fructan accumulation in two independent wheat populations. The alleles controlling high- and low- fructan in parental lines were also found to be associated in fructan production in a diverse set of 128 wheat lines. To the authors' knowledge, this is the first report on the mapping and sequencing of a fructan biosynthetic gene cluster and in particular, the isolation of a novel 1-FFT gene from barley.

Natural variation for Fe-efficiency is associated with upregulation of Strategy I mechanisms and enhanced citrate and ethylene synthesis in Pisum sativum L.

Iron (Fe)-deficiency is a common abiotic stress in Pisum sativum L. grown in many parts of the world. The aim of the study was to investigate variation in tolerance to Fe deficiency in two pea genotypes, Santi (Fe-efficient) and Parafield (Fe-inefficient). Fe deficiency caused greater declines in chlorophyll score, leaf Fe concentration and root-shoot development in Parafield compared to Santi, suggesting greater Fe-efficiency in Santi. Fe chelate reductase activity and ethylene production were increased in the roots of Santi and to a lesser extent in Parafield under Fe deficiency, while proton extrusion was only occurred in Santi. Moreover, expression of the Fe chelate reductase gene, FRO1, and Fe transporter, RIT1 were upregulated in Fe-deficient roots of Santi. Expression of HA1 (proton extrusion) was also significantly higher in Santi when compared to Parafield grown in Fe-deficient conditions. Furthermore, the application of the ethylene biosynthesis inhibitor, 1-aminoisobutyric acid reduced the Fe chelate reductase activity, supporting a direct role for ethylene in its induction. A significant increase in root citrate was only observed in Santi under Fe deficiency indicating a role for citrate in the Fe-efficiency mechanism. Taken together, our physiological and molecular data indicate that genotypic variation in tolerance to Fe deficiency in Santi and Parafield plants is a result of variation in a number of Strategy I mechanisms and also suggest a direct role for ethylene in Fe reductase activity. The pea cultivar, Santi provides a new source of Fe-efficiency that can be exploited to breed more Fe-efficient peas.

The mechanism of boron mobility in wheat and canola phloem.

Low-molecular-weight borate complexes were isolated from canola (Brassica napus) and wheat (Triticum aestivum) phloem exudates, as well as the cytoplasm of the fresh-water alga Chara corallina, and identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Phloem exudate was collected from field-grown canola inflorescence stalks by shallow incision, while wheat phloem exudate was collected by aphid stylectomy. Chara cytoplasm was collected by careful manual separation of the cell wall, vacuole, and cytosolic compartments. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry showed the presence of isotopic borate complexes, at mass-to-charge ratio of 690.22/691.22 in the canola and wheat phloem and at 300.11/301.11 in canola phloem and Chara cytoplasm. Using reference compounds, the borate complexes with mass-to-charge ratio 690.22/691.22 was identified as a bis-sucrose (Suc) borate complex in which the 4,6-hydroxyl pairs from the two alpha-glucopyranoside moieties formed an [L(2)B](-1) complex. Further investigation using liquid chromatography electrospray ionization triple quadrupole mass spectrometry analysis confirmed the presence of the bis-Suc borate complex in wheat phloem with a concentration up to 220 microm. The 300.11/301.11 complex was putatively identified as a bis-N-acetyl-serine borate complex but its concentration was below the detection limits of the liquid chromatography electrospray ionization triple quadrupole mass spectrometer so could not be quantified. The presence of borate complexes in the phloem provides a mechanistic explanation for the observed phloem boron mobility in canola and wheat and other species that transport Suc as their primary photoassimilate.

Calcium Biofortification of Crops-Challenges and Projected Benefits.

Despite Calcium (Ca) being an essential nutrient for humans, deficiency of Ca is becoming an ensuing public health problem worldwide. Breeding staple crops with higher Ca concentrations is a sustainable long-term strategy for alleviating Ca deficiency, and particular criteria for a successful breeding initiative need to be in place. This paper discusses current challenges and projected benefits of Ca-biofortified crops. The most important features of Ca nutrition in plants are presented along with explicit recommendations for additional exploration of this important issue. In order for Ca-biofortified crops to be successfully developed, tested, and effectively implemented in most vulnerable populations, further research is required.

Higher Photochemical Quenching and Better Maintenance of Carbon Dioxide Fixation Are Key Traits for Phosphorus Use Efficiency in the Wheat Breeding Line, RAC875.

Maintaining carbohydrate biosynthesis and C assimilation is critical under phosphorus (P) deficiency as inorganic P (Pi) is essential for ATP synthesis. Low available P in agricultural soils occurs worldwide and fertilizer P sources are being depleted. Thus, identifying biosynthetic traits that are favorable for P use efficiency (PUE) in crops is crucial. This study characterized agronomic traits, gas exchange, and chlorophyll traits of two wheat genotypes that differ in PUE. RAC875 was a P efficient genotype and Wyalkatchem was a P inefficient genotype. The plants were grown in pots under growth room conditions at two P levels; 10 mg P kg-1 soil (low P) and 30 mg P kg-1 soil (adequate P) and gas exchange and chlorophyll fluorescence were measured at the vegetative and booting stages using a portable photosynthesis system (LI-6800, LI-COR, United States). Results showed significant differences in some agronomic traits between the two wheat genotypes, i.e., greater leaf size and area, and a higher ratio of productive tillers to total tillers in RC875 when compared with Wyalkatchem. The CO2 response curve showed Wyalkatchem was more severely affected by low P than RAC875 at the booting stage. The relative ratio of the photosynthetic rate at low P to adequate P was also higher in RAC875 at the booting stage. Photochemical quenching (qP) in RAC875 was significantly higher when compared with Wyalkatchem at the booting stage. Maintaining CO2 fixation capacity under low P and higher qP would be associated with P efficiency in RAC875 and measuring qP could be a potential method to screen for P efficient wheat.