Increased grain yield and micronutrient concentration in transgenic winter wheat by ectopic expression of a barley sucrose transporter Isolde Saalbach a , Isabel Mora-Ramírez a , Nicola Weichert a , Franka Andersch a , Georgia Guild b , Herbert Wieser c , Peter Koehler c , James Stangoulis b , Jochen Kumlehn a , Winfriede Weschke a , Hans Weber a, * a Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung (IPK), D-06466 Gatersleben, Germany b School of Biological Sciences, Flinders University, Bedford Park, SA 5042, Australia c German Research Centre for Food Chemistry/Leibniz Institute, Lise-Meitner-Straße 34, D-85353 Freising, Germany article info Article history: Received 26 July 2013 Received in revised form 22 January 2014 Accepted 26 January 2014 Keywords: Micronutrients Seed protein Seed size Sucrose transporter wheat grain yield abstract Optimising assimilate partitioning to spikes is important to increase wheat yield potential. Novel winter wheat lines (HOSUT), ectopically expressing barley sucrose transporter HvSUT1 controlled by the barley Hordein B1 promoter were used to evaluate the potential of improved sucrose uptake capacity on grain yield and quality under field-like conditions. Three independent HOSUT lines were grown over three years in micro-plots. Grain yield per plot was significantly increased by 28%, together with higher protein yield per plot and higher iron and zinc concentration when compared to the non-transformed control wheat Certo. Thousand grain weight was enhanced, indicating that expression of HvSUT1 increases in- dividual grain sink strength. HOSUT grains are larger, display increased grain width and to a lesser extent grain length, indicating transgene effects at a stage when grains grow under filial control. Grain number per spike was decreased by 15% and protein contents by 5%, on average, especially that of glutenins. Overall, despite some compensating effects on grain number per spike and protein contents, HOSUT lines generate a significant yield advantage. The findings can contribute to understanding determinants of grain size and number and its relationship to grain sink strength and might identify limitations of wheat yield potential. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Wheat is a major crop plant, accounting for about 30% of global grain production and for 45% of the cereals used as food (Shewry, 2009; Charmet, 2011). Between 1997 and 2007 the actual rate of wheat production increased by only 0.5% per year, which is much less than the required 1.4% that would be necessary to cope with growing human populations (Reynolds et al., 2009). In addition, the agricultural area worldwide cannot be increased significantly and will become further limited due to climatic changes. Therefore, improved wheat production must be achieved by further increasing the yield per area. Wheat yield potential in the past has been improved by increasing the harvest index and much less by higher biomass gain (Reynolds et al., 2009). However, the current increase of wheat yield decelerates and the harvest index approaches a theoretical limit (Reynolds et al., 2011). The available genetic pool seems to be widely exhausted and domestication and modern breeding has further led to reduced genetic variability (Charmet, 2011). Novel strategies are therefore required to further boost wheat yield potential. Optimising photosynthetic performance and assimilating partitioning to grains are major topics put forward by The International Wheat Yield Consortium for the next years (Reynolds et al., 2011) and an important approach is to improve grain size and grain filling. Both grain size and grain number determine yield, although there is often a negative correlation between the two traits (Gupta et al., 2006). Seed filling is largely dependent on assimilate supply and metabolic regulation. Increased assimilate partitioning to the developing spike and grain historically had the greatest impact on improving yield potential in wheat (Calderini et al., 1999). * Corresponding author. Tel.: þ49 (0)39482 5208; fax: þ49 (0)39482 5758. E-mail addresses: saalbach@ipk-gatersleben.de (I. Saalbach), moram@ipk- gatersleben.de (I. Mora-Ramírez), andersch@ipk-gatersleben.de (F. Andersch), georgia.guild@flinders.edu.au (G. Guild), H.Wieser@lrz.tum.de (H. Wieser), Peter. Koehler@tum.de (P. Koehler), james.stangoulis@flinders.edu.au (J. Stangoulis), Kumlehn@ipk-gatersleben.de (J. Kumlehn), weschke@ipk-gatersleben.de (W. Weschke), weber@ipk-gatersleben.de (H. Weber). Contents lists available at ScienceDirect Journal of Cereal Science journal homepage: www.elsevier.com/locate/jcs http://dx.doi.org/10.1016/j.jcs.2014.01.017 0733-5210/Ó 2014 Elsevier Ltd. All rights reserved. Journal of Cereal Science xxx (2014) 1e7 Please cite this article in press as: Saalbach, I., et al., Increased grain yield and micronutrient concentration in transgenic winter wheat by ectopic expression of a barley sucrose transporter, Journal of Cereal Science (2014), http://dx.doi.org/10.1016/j.jcs.2014.01.017