Contents lists available at ScienceDirect Journal of Cereal Science journal homepage: www.elsevier.com/locate/jcs Does Fe accumulation in durum wheat seeds benefit from improved whole- plant sulfur nutrition? Stefania Astolfi a,* , Youry Pii b , Roberto Terzano c , Tanja Mimmo b , Silvia Celletti a,b , Ignazio Allegretta c , Domenico Lafiandra a , Stefano Cesco b a DAFNE, Università Degli Studi Della Tuscia, Viterbo, Italy b Faculty of Science and Technology, Free University of Bozen-Bolzano, I-39100, Bolzano, Italy c Di.S.S.P.A, Università Degli Studi di Bari, Bari, Italy ARTICLE INFO Keywords: Biofortification Iron Sulfur Triticum durum μ-XRF ABSTRACT Sulfur and iron balanced supply is of paramount importance for plants, since Fe homoeostasis in plants has been shown to be strongly dependent on sulfate availability; vice versa the adaptation to Fe deficiency requires the adjustment of S uptake and assimilation rate. Interestingly, it has been demonstrated that providing S above adequate concentrations may enhance Fe use efficiency in wheat and this effect seems to be especially ad- vantageous for plants grown under severe Fe shortage. Therefore, the investigation of sulfate effect on Fe uptake and allocation in crop could be of great significance. Aim of this study was to clarify in wheat at both leaf and seed level whether and to what extent the changes in S and Fe supply affect concentration and distribution of sulfate and also how different availability of S changes the mineral concentration and distribution in wheat adequately or poorly fed with Fe. Obtained results showed how plants recovered from Fe deficiency stress by means of a tuned S fertilization, without additional input of Fe fertilizers. Also, with decreasing Fe availability the Zn concentration of grains significantly increased, suggesting that a balanced crop Fe nutrition could allow a successful biofortification of wheat grains with Zn. 1. Introduction Iron (Fe) is one of the most critical nutrients, being not only one of the main causes of yield limitation of crops in the World but also one of the most widespread human nutritional disorders affecting over 30% of the World's population (Hind and Guerinot, 2012). Cereals are the primary food source for humans, particularly in developing countries; thus, the nutritional level of the grain (as well as the nutritional state of plants) is of central importance to human health (Grusak and Dellapenna, 1999). Both plants and humans need an adequate supply of minerals for their nutrition; in this regard, the acquisition of Fe from soil can be often problematic for plants. Iron is sparingly soluble under aerobic conditions, especially in high pH and calcareous soils, representing a serious problem for more that 30% of the World's cultivated soils (Guerinot and Yi, 1994). To cope with this nutritional disorder and to favour the micronutrient acquisi- tion, higher plants have developed specific strategies (Marschner et al., 1986). In particular, graminaceous species cope with Fe deficiency stress by enhancing the exudation of phytosiderophores (PS) into the rhizosphere. These non-proteinogenic amino acids belonging to the mugineic acid family, form stable complexes with Fe 3+ and are taken up by roots as intact Fe 3+ –PS complexes via the Yellow Stripe 1 (YS1) transporter (Murata et al., 2006). Iron metabolism in plants is closely linked to sulfur (S) since the sulfur-containing amino acid methionine (Met) is the sole precursor of the mugineic acid family of PS (Mori and Nishizawa, 1987). In fact, it has been clearly demonstrated that plant capability to take up and accumulate Fe is strongly dependent on S availability in the growth medium in cereal plants (Bouranis et al., 2003; Astolfi et al., 2006; Zuchi et al., 2012). On the other hand, the modulation of S uptake and assimilation rate play a significant role in the plant adaptation to the changes of Fe availability (Ciaffi et al., 2013; Celletti et al., 2016a). For instance, it has been shown that a super- optimal S feeding (2.4 mM vs 1.2 mM which is considered as optimal) favours an accumulation of Fe in shoots of durum wheat (Zuchi et al., 2012). Recently, it has been observed a positive correlation between changes in S accumulation and plant capability to release PS (and correspondingly to accumulate Fe), indicating that a super-optimal S fertilization of plants can increase the Fe use efficiency of roots. Since https://doi.org/10.1016/j.jcs.2018.07.010 Received 19 June 2018; Received in revised form 19 July 2018; Accepted 21 July 2018 * Corresponding author. Universita degli Studi della Tuscia – DAFNE, Via San Camillo de Lellis, 01100, Viterbo, Italy. E-mail address: sastolfi@unitus.it (S. Astolfi). Journal of Cereal Science 83 (2018) 74–82 Available online 23 July 2018 0733-5210/ © 2018 Elsevier Ltd. All rights reserved. T