Quantitative trait loci conferring grain mineral nutrient concentrations in durum wheat 3 wild emmer wheat RIL population

Mineral nutrient malnutrition, and particularly deficiency in zinc and iron, afflicts over 3 billion people worldwide. Wild emmer wheat, Triticum turgidum ssp. dicoccoides, genepool harbors a rich allelic repertoire for mineral nutrients in the grain. The genetic and physiological basis of grain protein, micronutrients (zinc, iron, copper and manganese) and macronutrients (calcium, magnesium, potassium, phosphorus and sulfur) concentration was studied in tetraploid wheat population of 152 recombinant inbred lines (RILs), derived from a cross between durum wheat (cv. Langdon) and wild emmer (accession G18-16). Wide genetic variation was found among the RILs for all grain minerals, with considerable transgressive effect. A total of 82 QTLs were mapped for 10 minerals with LOD score range of 3.2–16.7. Most QTLs were in favor of the wild allele (50 QTLs). Fourteen pairs of QTLs for the same trait were mapped to seemingly homoeologous positions, reflecting synteny between the A and B genomes. Significant positive correlation was found between grain protein concentration (GPC), Zn, Fe and Cu, which was supported by significant overlap between the respective QTLs, suggesting common physiological and/or genetic factors controlling the concentrations of these mineral nutrients. Few genomic regions (chromosomes 2A, 5A, 6B and 7A) were found to harbor clusters of QTLs for GPC and other nutrients. These identified QTLs may facilitate the use of wild alleles for improving grain nutritional quality of elite wheat cultivars, especially in terms of protein, Zn and Fe

Genome wide association mapping of grain arsenic, copper, molybdenum and zinc in rice (Oryza sativa L.) grown at four international field sites

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Metabolomics of capsicum ripening reveals modification of the ethylene related-pathway and carbon metabolism

Capsicum (Capsicum annuum L. cv. Aries) is a non-climacteric bell-pepper fruit, exhibiting limited ethylene and respiration levels during ripening. In contrast to climacteric fruit, such as tomato which is largely dependent upon ethylene to ripen, the regulation of non-climacteric ripening is still inadequately understood. A metabolomics approach was used to identify differentially abundant compounds between ripening stages with the aim of elucidating metabolic pathways involved in the regulation of non-climacteric ripening. Metabolite profiling using gas chromatography-mass spectrometry (GC-MS) was initially employed to screen potential metabolite differences among three ripening stages (Green, Breaker Red 1 and Light Red). Targeted analyses using liquid chromatography-mass spectrometry (LC-MS) or enzymatic assays were subsequently employed to characterise selected metabolites in more ripening stages. Starch, sugars and their derivatives were significantly modified during ripening which may affect the abundance of some glycolysis intermediates and consequently other metabolic pathways involving amino acids, colour and pungency precursors, and tricarboxylic acid (TCA) cycle intermediates. Furthermore, metabolites closely related to ethylene production such as cysteine and methionine gradually increased between the ripening stages, whereas putrescine significantly decreased during ripening, suggesting that some parts of the ethylene pathway may still be functional in this non-climacteric fruit. Thus, this study which utilised both profiling and targeted metabolomics, has identified a wide range of metabolites which are involved in various biochemical pathways and highlights the overall metabolic shifts during non-climacteric capsicum ripening. © 2013 Elsevier B.V

Metabolite profiling of wheat (Triticum aestivum L.) phloem exudate

Background: Biofortification of staple crops with essential micronutrients relies on the efficient, long distance transport of nutrients to the developing seed. The main route of this transport in common wheat (Triticum aestivum) is via the phloem, but due to the reactive nature of some essential micronutrients (specifically Fe and Zn), they need to form ligands with metabolites for transport within the phloem. Current methods available in collecting phloem exudate allows for small volumes (μL or nL) to be collected which limits the breadth of metabolite analysis. We present a technical advance in the measurement of 79 metabolites in as little as 19.5 nL of phloem exudate. This was achieved by using mass spectrometry based, metabolomic techniques.Results: Using gas chromatography-mass spectrometry (GC-MS), 79 metabolites were detected in wheat phloem. Of these, 53 were identified with respect to their chemistry and 26 were classified as unknowns. Using the ratio of ion area for each metabolite to the total ion area for all metabolites, 39 showed significant changes in metabolite profile with a change in wheat reproductive maturity, from 8-12 to 17-21 days after anthesis. Of these, 21 were shown to increase and 18 decreased as the plant matured. An amine group derivitisation method coupled with liquid chromatography MS (LC-MS) based metabolomics was able to quantify 26 metabolites and semi-quantitative data was available for a further 3 metabolites.Conclusions: This study demonstrates that it is possible to determine metabolite profiles from extremely small volumes of phloem exudate and that this method can be used to determine variability within the metabolite profile of phloem that has occurred with changes in maturity. This is also believed to be the first report of the presence of the important metal complexing metabolite, nicotianamine in the phloem of wheat