Main conclusion: Wheat and its related genotypes show distinct distribution patterns for mineral nutrients in maternal and filial tissues in grains. X-ray-based imaging techniques are very informative to identify genotypes with contrasting tissue-specific localization of different elements. This can help in the selection of suitable genotypes for nutritional improvement of food grain crops. Understanding mineral localization in cereal grains is important for their nutritional improvement. Spatial distribution of mineral nutrients (Mg, P, S, K, Ca, Fe, Zn, Mn and Cu) was investigated between and within the maternal and filial tissues in grains of two wheat cultivars (Triticum aestivum Cv. WH291 and WL711), a landrace (T. aestivum L. IITR26) and a related wild species Aegilops kotschyi, using micro-proton-induced X-ray emission (μ-PIXE) and micro-X-ray fluorescence (μ-XRF). Aleurone and scutellum were major storage tissues for macro (P, K, Ca and Mg) as well as micro (Fe, Zn, Cu and Mn) nutrients. Distinct elemental distribution patterns were observed in each of the four genotypes. A. kotschyi, the wild relative of wheat and the landrace, T. aestivum L. IITR26, accumulated more Zn and Fe in scutellum and aleurone than the cultivated wheat varieties, WH291 and WL711. The landrace IITR26, accumulated far more S in grains, Mn in scutellum, aleurone and embryo region, Ca and Cu in aleurone and scutellum, and Mg, K and P in scutellum than the other genotypes. Unlike wheat, lower Mn and higher Fe, Cu and Zn concentrations were noticed in the pigment strand of A. kotschyi. Multivariate statistical analysis, performed on mineral distribution in major grain tissues (aleurone, scutellum, endosperm and embryo region) resolved the four genotypes into distinct clusters.
Bibliographical noteFunding Information:
Acknowledgments this work was supported by the Department of Biotechnology (DBt, government of India), and Slovenian research agency research Programmes P1-0112 and P-0212. Micro-PIXe at JSI was upgraded in the project 7FP eU no. 227012 “SPIrIt”. access to synchrotron radiation facilities of clS (project 14-3657) and Iaea framework of coordinated research project 16796 “applications of synchrotron radiation for environmental sciences and materials research for development of environmentally friendly resources” (cSI, KV) are acknowledged. Dr. renfei Feng of clS is acknowledged for expert advice on beamline operation, and Prof. Harcharan S. Dhaliwal of eternal University for providing the grains. SPS acknowledges DBt for supporting the visit to clS, canada. rt thanks Department of Science and technology, government of India, for J. c. Bose fellowship.