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There is a generalised belief that barley is more resilient to stress than wheat. Consequently, land allocation to wheat and barley is based on a presumed differential sensitivity to stresses between these species. Previous field experiments showed that yield of both crops tended to be similar under both low- and high-productivity conditions under Mediterranean environments, but in some particular studies barley advantages are reported. Therefore, the aim of this study was to determine the comparative performance of wheat and barley across a wide range of conditions through the literature published over the first 20 years of this century considering exclusively studies where both cereals had been grown side-by-side in field experiments. We compiled a rigorous database from papers of high-standard journals reporting actual yield data (we excluded simulated yields) measured in experiments under field conditions where both crops were grown side-by-side in the same experiment (excluding studies analysing wheat and barley grown separately). Yield distribution for both species across studies was symmetrical with an average of c. 440 g m−2 and a range from c. 50-900 g m−2. The yields of the lowest quartile ranged from 58 to 293 g m−2, being the comparison of performance in this quartile suitable for detecting differences in low-yielding conditions. Considering individual papers, it is possible to identify any possible outcome of the differential performance of these cereals. However, considering all papers together it was clear that there was not a consistent advantage of barley over wheat at most stressful conditions. Indeed, at very low yielding conditions wheat tended to outyield barley. The trends described above were not influenced by the data-points based on comparisons of barley with the tetraploid wheats, nor by our own experimental data-points. Thus, we confirm in this review that barley does not consistently outyield wheat under low yielding conditions, despite the generalised belief that it does. We are grateful to Prof Ignacio Romagosa (University of Lleida and AGROTECNIO) for generous advice on statistical procedures. Research of the authors on wheat and barley yield physiology has been funded along years by many different grants from different funding bodies; most recently mainly from the Spanish State Agency for Research (latest projects were RTI2018–096213-B-100 and PID2021–127415OB-I00 on wheat and PCI2019–103536 on barley).

Identifying traits for improving sink-strength is a bottleneck to increasing wheat yield. The interacting processes determining sink-strength and yield potential are reviewed and visualized in a set of 'Wiring Diagrams', covering critical phases of development (and summarizing known underlying genetics). Using this framework, we reviewed and assembled the main traits determining sink-strength and identified research gaps and potential hypotheses to be tested for achieving gains in sink-strength. In pre-anthesis grain number could be increased through: (i) enhanced spike growth associated with optimized floret development and/or a reduction in specific stem-internode lengths and (ii) improved fruiting efficiency through accelerated rate of floret development, improved partitioning between spike or optimized spike cytokinin levels. In post-anthesis grain sink-strength could be augmented through manipulation of grain size potential via ovary size and/or endosperm cell division and expansion. Prospects for improving spike vascular architecture to support all rapidly growing florets, enabling the improved flow of assimilate, are also discussed. Finally, we considered the prospects for enhancing grain weight realization in relation to genetic variation in stay-green traits as well as stem carbohydrate remobilization. The Wiring Diagrams provide a potential workspace for breeders and crop scientists to achieve yield gains in wheat and other field crops. Research of the authors on physiology and genetics of wheat yield potential has been funded by many different sources over the years. Most recent grants include the International Wheat Yield Partnership (IWYP) projects funded by the Biotechnology and Biological Research Council of the UK (e.g., IWYP48 BB/N021061/1, IWYP64 BB/ N020871/2, IWYP163 BB/S005072/1, and IWYP25FP), as well as projects funded by other donors (State Research Agency of Spain: AGL2015-69595-R and RTI2018-096213-B-100).

Source traits are currently of great interest for the enhancement of yield potential; for example, much effort is being expended to find ways of modifying photosynthesis. However, photosynthesis is but one component of crop regulation, so sink activities and the coordination of diverse processes throughout the crop must be considered in an integrated, systems approach. A set of ‘wiring diagrams’ has been devised as a visual tool to integrate the interactions of component processes at different stages of wheat development. They enable the roles of chloroplast, leaf, and whole-canopy processes to be seen in the context of sink development and crop growth as a whole. In this review, we dissect source traits both anatomically (foliar and non-foliar) and temporally (pre- and post-anthesis), and consider the evidence for their regulation at local and whole-plant/crop levels. We consider how the formation of a canopy creates challenges (self-occlusion) and opportunities (dynamic photosynthesis) for components of photosynthesis. Lastly, we discuss the regulation of source activity by feedback regulation. The review is written in the framework of the wiring diagrams which, as integrated descriptors of traits underpinning grain yield, are designed to provide a potential workspace for breeders and other crop scientists that, along with high-throughput and precision phenotyping data, genetics, and bioinformatics, will help build future dynamic models of trait and gene interactions to achieve yield gains in wheat and other field crops. Research of the authors on physiology and genetics of wheat yield potential has been funded by many different sources over the years. Recent grants include the International Wheat Yield Partnership (IWYP) projects funded by the Biotechnology and Biological Research Council of the UK [BB/N021061/1, BB/ N020871/2, BB/S005072/1] (IWYP48, IWYP64, IWYP163 and IWYP25FP, respectively), as well as projects funded by other donors (State Research Agency of Spain: AGL2015-69595-R and RTI2018-096213-B-100).

Future grain yield (GY) improvements require the identification of beneficial traits within the context of high yield potential and not just based on the pleiotropic effect of traits such as crop height and heading date. We evaluated 1937 lines from Nested Association Mapping (NAM) population derived from 13 bi-parental varietal crosses under field conditions. We selected 493 lines with similar time to anthesis to that of the two checks used in the study (across and within each family) which reduced the range of plant height in the selected lines. Yield components were measured in these 493 lines from which 231 lines were selected by excluding lines with lowest number of grains so excluded low yielding lines. Later the subset of 231 lines were evaluated in two field experiments (2016−17, CS1 and 2017−18, CS2). Numerical and physiological components of grain yield were measured. The two-step selection maximised GY within an acceptable range of variation for height and anthesis. GY in 231 lines showed very high G × E interaction. Taking both seasons together, we selected lines from upper and lower quartile GY groups to identify stable beneficial trait combinations for improved GY. Differences in GY were explained by grain number driven by increased spike dry weight at anthesis (SDWa) and fruiting efficiency (FE). Increased GY was accompanied by sink limitation. The data points towards increases in grain number as the route towards future GY increases in wheat breeding. Funding for the experimental work was partly provided by projects AGL2015-69595-R, from the Spanish Research Agency (AEI), and IWYP25FP, from the International Wheat Yield Partnership (IWYP). PB held a pre-doctoral research contract from the agency for Management of University and Research (AGAUR) from the Generalitat de Catalunya.

Carolight® is a transgenic maize variety that accumulates extraordinary levels of carotenoids, including those with vitamin A activity. The development of Carolight® maize involved the technical implementation of a novel combinatorial transformation method, followed by rigorous testing for transgene expression and the accumulation of different carotenoid molecules. Carolight® was envisaged as a way to improve the nutritional health of human populations that cannot access a diverse diet, but this ultimate humanitarian application can only be achieved after extensive testing for safety, agronomic performance and nutritional sufficiency. In this article, we chart the history of Carolight® maize focusing on its development, extensive field testing for agronomic performance and resistance to pests and pathogens, and feeding trials to analyze its impact on farm animals (and their meat/dairy products) as well as animal models of human diseases. We also describe more advanced versions of Carolight® endowed with pest-resistance traits, and other carotenoid-enhanced maize varieties originating from the same series of initial transformation experiments. Finally we discuss the further steps required before Carolight® can fulfil its humanitarian objectives, including the intellectual property and regulatory constraints that lie in its path. European Research Council Advanced Grant (BIOFORCE) and Proof of Concept Grant (Multinutrient Maize) to PC; Spanish Ministry of Economy and Competitiveness (AGL2014-53970-C2-1-R, AGL2015-65846-R, BIO2014-54426-P and BIO2014-54441-P); RecerCaixa project PC084082; Catalan Autonomous Community 2014 SGR 1296 Agricultural Biotechnology Research Group and Agrotecnio Research Center. JDG thanks the UdL for a Ph.D. fellowship.

The frequency and intensity of extreme high temperature events are expected to increase with climate change. Higher temperatures near anthesis have a large negative effect on maize (Zea mays, L.) grain yield. While crop growth models are commonly used to assess climate change impacts on maize and other crops, it is only recently that they have accounted for such heat stress effects, despite limited field data availability for model evaluation. There is also increasing awareness but limited testing of the importance of canopy temperature as compared to air temperature for heat stress impact simulations. In this study, four independent irrigated field trials with controlled heating imposed using polyethylene shelters were used to develop and evaluate a heat stress response function in the crop modeling framework SIMPLACE, in which the Lintul5 crop model was combined with a canopy temperature model. A dataset from Argentina with the temperate hybrid Nidera AX 842 MG (RM 119) was used to develop a yield reduction function based on accumulated hourly stress thermal time above a critical temperature of 34 °C. A second dataset from Spain with a FAO 700 cultivar was used to evaluate the model with daily weather inputs in two sets of simulations. The first was used to calibrate SIMPLACE for conditions with no heat stress, and the second was used to evaluate SIMPLACE under conditions of heat stress using the reduction factor obtained with the Argentine dataset. Both sets of simulations were conducted twice; with the heat stress function alternatively driven with air and simulated canopy temperature. Grain yield simulated under heat stress conditions improved when canopy temperature was used instead of air temperature (RMSE equal to 175 and 309 g m−2, respectively). For the irrigated and high radiative conditions, raising the critical threshold temperature for heat stress to 39 °C improved yield simulation using air temperature (RMSE: 221 g m−2) without the need to simulate canopy temperature (RMSE: 175 g m−2). However, this approach of adjusting thresholds is only likely to work in environments where climatic variables and the level of soil water deficit are constant, such as irrigated conditions and are not appropriate for rainfed production conditions. Fil: Gabaldón Leal, C.. Centro Alameda del Obispo; España Fil: Webber, H.. Universitat Bonn; Alemania Fil: Otegui, Maria Elena. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Producción Vegetal; Argentina Fil: Slafer, Gustavo Ariel. Universidad de Lleida; España. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Institució Catalana de Recerca i Estudis Avancats; España Fil: Ordóñez, R. A.. Universidad de Lleida; España Fil: Gaiser, T.. Universitat Bonn; Alemania Fil: Lorite, I. J.. Centro Alameda del Obispo; España Fil: Ruiz Ramos, M.. Universidad Politécnica de Madrid; España Fil: Ewert, F.. Universitat Bonn; Alemania

Highlight Outcomes of floret initiation, mortality/survival, grain set/abortion, and fruiting efficiency have been quantified in 30 cultivars and connected to the processes determining the fate of floret primordia using ovary size., Spike fertility traits are critical attributes for grain yield in wheat (Triticum aestivum L.). Here, we examine the genotypic variation in three important traits: maximum number of floret primordia, number of fertile florets, and number of grains. We determine their relationship in determining spike fertility in 30 genotypes grown under two contrasting conditions: field and greenhouse. The maximum number of floret primordia per spikelet (MFS), fertile florets per spikelet (FFS), and number of grains per spikelet (GS) not only exhibited large genotypic variation in both growth conditions and across all spikelet positions studied, but also displayed moderate levels of heritability. FFS was closely associated with floret survival and only weakly related to MFS. We also found that the post-anthesis process of grain set/abortion was important in determining genotypic variation in GS; an increase in GS was mainly associated with improved grain survival. Ovary size at anthesis was associated with both floret survival (pre-anthesis) and grain survival (post-anthesis), and was thus believed to ‘connect’ the two traits. In this work, proximal florets (i.e. the first three florets from the base of a spikelet: F1, F2, and F3) produced fertile florets and set grains in most cases. The ovary size of more distal florets (F4 and beyond) seemed to act as a decisive factor for grain setting and effectively reflected pre-anthesis floret development. In both growth conditions, GS positively correlated with ovary size of florets in the distal position (F4), suggesting that assimilates allocated to distal florets may play a critical role in regulating grain set.

Highlights • Time to terminal spikelet and from then to anthesis were largely independent. • The length of the stem elongation phase was slightly but positively related to grains per m2. • Fruiting efficiency was critical for determining grain number, but it was also negatively related to grain weight. • The length of the stem elongation phase seems to have imposed an upper threshold for fruiting efficiency., Developmental patterns strongly influence spike fertility and grain number, which are primarily determined during the stem elongation period (i.e. time between terminal spikelet phase and anthesis). It has been proposed that the length of the stem elongation phase may, to an extent, affect grain number; thus it would be beneficial to identify genetic variation for the duration of this phase in elite germplasm. Variation in these developmental patterns was studied using 27 elite wheat lines in four experiments across three growing seasons. The results showed that the length of the stem elongation phase was (i) only slightly related to the period from seedling emergence to terminal spikelet, and (ii) more relevant than it for determining time to anthesis. Thus, phenological phases were largely independent and any particular time to anthesis may be reached with different combinations of component phases. Yield components were largely explained by fruiting efficiency of the elite lines used: the relationships were strongly positive and strongly negative with grain number and with grain weight, respectively. Although fruiting efficiency showed a positive trend with the duration of stem elongation that was not significant, a boundary function (which was highly significant) suggests that the length of this phase may impose an upper threshold for fruiting efficiency and grain number, and that maximum values of fruiting efficiency may require a relatively long stem elongation phase.

High-carotenoid corn (Carolight®) has been developed as a vehicle to deliver pro-vitamin A in the diet and thus address vitamin A deficiency in at-risk populations in developing countries. Like any other novel crop, the performance of Carolight® must be tested in different environments to ensure that optimal yields and productivity are maintained, particularly in this case to ensure that the engineered metabolic pathway does not attract a yield penalty. Here we compared the performance of Carolight® with its near isogenic white corn inbred parental line under greenhouse and field conditions, and monitored the stability of the introduced trait. We found that Carolight® was indistinguishable from its near isogenic line in terms of agronomic performance, particularly grain yield and its main components. We also established experimentally that the functionality of the introduced trait was indistinguishable when plants were grown in a controlled environment or in the field. Such thorough characterization under different agronomic conditions is rarely performed even for first-generation traits such as herbicide tolerance and pest resistance, and certainly not for complex second-generation traits such as the metabolic remodeling in the Carolight® variety. Our results therefore indicate that Carolight® can now be incorporated into breeding lines to generate hybrids with locally adapted varieties for further product development and assessment. This work was supported by Agrotecnio (Fundació Centre de Recerca en Agrotecnologia, VitaMaize 01 project) and Fundació la Caixa (Grant P13005).

Further improvements in wheat yields are critical, for which increases in grain number would be required. In the recent past, higher grain number was achieved through increased growth of the juvenile spikes before anthesis, due to the reduction in stem growth. As current cultivars have already an optimum height, alternatives must be identifi ed for further increasing grain number. One of them is increasing fruiting effi ciency (grains set per unit of spike dry weight at anthesis). Fruiting effi ciency is the fi nal outcome of the fate of fl oret development and differences in this trait within modern cultivars would be related to higher survival of fl oret primordia. Then there are two alternative physiological pathways to improve fruiting effi ciency by allowing a normal development of most vulnerable fl oret primordia: an increased allocation of assimilates for the developing fl orets before anthesis, or reduced demand of the fl orets for maintaining their normal development. Both alternatives may be possible, and it might be critical to recognize which of them is the actual cause of differences in fruiting effi ciency. When considering this trait in breeding we must be aware of potential trade- offs and therefore it must be avoided that increases in fruiting effi ciency be constitutively related to decreases in either spike dry weight at anthesis or grain weight. In this review we described fruiting effi ciency and its physiological bases, analyzing genetic variation and considering potential drawbacks that must be taken into account to avoid increases in fruiting effi ciency being compensated by other traits Fil: Gustavo A. Slafer. AGROTECNIO; España. Universidad de Lleida. Departamento de Producción Vegetal y Ciencia Forestal; España. Institució Catalana de Recerca i Estudis Avançats; España Fil: Elia, Mónica. Universidad de Lleida. Departamento de Producción Vegetal y Ciencia Forestal; España. AGROTECNIO; España Fil: Savin, Roxana. Universidad de Lleida. Departamento de Producción Vegetal y Ciencia Forestal; España. AGROTECNIO; España Fil: García, Guillermo Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; Argentina Fil: Terrile, Ignacio Ismael. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Norte. Estación Experimental Agropecuaria Pergamino; Argentina Fil: Ferrante, Ariel. The University of Queensland. Queensland Alliance for Agriculture and Food Innovation; Australia Fil: Miralles, Daniel Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; Argentina Fil: González, Fernanda Gabriela. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Norte. Estación Experimental Agropecuaria Pergamino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

A detailed and accurate phenotyping of mapping populations is an important “bottleneck” for the understanding of the phenotype–genotype relationships. Grain number per unit area (GN), the main wheat yield component, can be analyzed through physiological components as spike dry weight at flowering, determined by crop growth rate and biomass partitioning to spike during stem elongation phase, and fruiting efficiency. The phenotypic variability of these physiological traits responsible for variation in GN and the relationships among them was analyzed in an elite wheat doubled-haploid (DH) population grown in two different environments. Positive transgressive segregation (i.e. DH lines that exceed parental phenotypic values) was observed for all GN determining traits, suggesting that increases in GN could be achieved through their improvement. However, focusing on top DH lines, which represent a feasible genetic improvement, fruiting efficiency was the most relevant physiological trait for consistently improving GN, and thereby grain yield, in both environments. Fil: García, Guillermo Ariel. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Serrago, Roman Augusto. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: González, Fernanda Gabriela. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Norte. Estación Experimental Agropecuaria Pergamino; Argentina Fil: Slafer, Gustavo Ariel. Institució Catalana de Recerca i Estudis Avancats; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Reynolds, Matthew P.. Centro Internacional de Mejoramiento de Maíz y Trigo; México Fil: Miralles, Daniel Julio. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

Wheat is the only temperate cereal for which yield trends have been exhaustively analysed on both global and national bases. This paper aims (i) to compare global yield trends of wheat, barley, oat and rye for the last five decades, (ii) to analyse their yield trends in Canada, Denmark, Norway, Sweden and Finland, the northernmost limits for extensive agriculture, and (iii) using case studies, to assess the relative contribution to yield gains made by cereal breeding. Average global yield data from FAO were regressed against years using linear or bilinear regressions. Yield gains in absolute and relative terms were calculated for comparison among countries and cereals. Data from the literature were used to assess the estimated contributions made by breeding to yield gains. Global yield trends were not standard throughout the 1950-1998 period: rye exhibited a constant yield gain (c. 28 kg ha-1 y-1), while barley and oat showed marked increases until around 1970 (c. 38 and 32 kg ha-1 y-1, respectively) but quite modest increases (c.19 and 5 kg ha-1 y-1, respectively) over the last 30 years. Wheat also showed a bilinear trend with only limited yield gains until the 1960s, followed by a more than 3-fold increase in rate of yield gain from then on (16 and 40 kg ha-1 y-1, respectively). However, during the 1990s wheat yield gains have been less than previously. Hence, global yields of barley, oat and wheat have increased very slowly lately. Trends for each combination of cereals and countries indicated consistently higher yields during the 1990s than at mid-century. In general, wheat yield tended to increase at a faster rate than yield of the other cereals. There was a trend in the last decade of low rates of yield increase compared with those of previous decades. This was clear for oat and barley, and a similar trend is emerging for wheat. This suggests that genetic and/or management improvements have had less effect in recent times. Furthermore, we found preliminary evidence to suggest that with the exception of wheat in Canada, genetic contributions in northern areas were smaller than those reported for wheat and barley at lower latitudes. Therefore, alternative approaches must be sought for future breeding work under these high latitude conditions., Buenos Airesin yliopisto, Argentiina ja MTT (Maa- ja elintarviketalouden tutkimuskeskus)Vehnä on ainoa lauhkean vyöhykkeen vilja, jonka satoisuuden kehitystä on aiemmin tarkasteltu kattavasti maailmanlaajuisesti ja viljelyalueittain. Tämän tutkimuksen tarkoituksena oli verrata kauran, ohran, rukiin ja vehnän satoisuuden kehittymistä viimeisen viiden vuosikymmenen ajan erityisesti pohjoisen viljelyn alueilla (Kanada, Norja, Ruotsi, Suomi ja Tanska). Lisäksi arvioitiin kasvinjalostuksen osuutta satoisuuden kehittymisessä. Aineistona käytettiin FAO:n tilastoja. Kun verrattiin eri viljalajien satoisuuden muutoksia tutkitulla ajanjaksolla (1950-1998), havaittiin, että rukiin hehtaarisadot kasvoivat tasaisesti noin 28 kg vuodessa. Sen sijaan ohran (38 kg/ha/vuosi) ja kauran sadot (32 kg/ha/vuosi) kasvoivat ensin huomattavasti 1970-luvun paikkeille saakka, ja kasvu tasaantui voimakkaasti viimeisen 30 vuoden aikana. Myös vehnän satoisuuden kehitystä kuvasi parhaiten bi-lineaarinen malli: vähäistä satoisuuden kasvua 1960-luvulle saakka, satoisuuden kolminkertaistuminen 1990-luvulle mentäessä ja tästä edelleen kasvun tasaantuminen. Tutkittaessa satoisuuskehitystä niin pohjoismaissa kuin Kanadassakin voitiin havaita, että yleisesti ottaen vehnän satoisuus kehittyi muita viljoja nopeammin. Tämä kuvastanee vehnän arvostusta ja kehitystyöhön käytettyjen tutkimusvarojen runsautta. Toisaalta kauran ja ohran, mutta vähissä määrin myös vehnän, osalta voidaan havaita satoisuuskehityksen hidastumista viime vuosikymmenenä. Alustavat tuloksemme antoivat myös viitettä siitä, että kasvinjalostuksen rooli tutkittujen viljalajien satoisuuden parantamisessa oli pohjoisilla viljelyalueilla pienempi (poikkeuksena vehnän tuotanto Kanadassa) kuin mitä on raportoitu viljeltäessä vehnää ja ohraa alhaisemmilla leveysasteilla.

A better understanding of the effects of different source?sink ratio during the grain filling period on grain growth may be relevant in order to further increase cereal grain yield. The main objective of the present work was to determine the effect of different manipulations of the source?sink ratios in wheat and barley grown at four different environmental conditions on responsiveness of sinks (grain growth and yield) and sources (spike photosynthesis and water soluble carbohydrates in the stems). Four treatments were imposed 7 days after anthesis in two contrasting locations with low- and high-inputs conditions in wheat (cv. Soissons) and barley (cv. Sunrise): they were a control, a treatment removing all the spikelets from the upper half of the spikes (TS), and shadings decreasing incident radiation by 75% on the whole canopy (SW) or only on the leaves (having the top area of the meshes individual holes for each spike to be exposed to solar radiation, SL). As expected grain yield was closely related to grain number per m2. Average grain weight was reduced by shading treatments far more markedly in Sw than in SL. Interestingly, significant amounts of water soluble carbohydrates in the stems remained at maturity in SL and Sw treatments and spike photosynthesis in SL was consistently higher than in the unshaded controls in both species. These results may be an indication that wheat and barley are not source-limited during grain filling and that only when subjected to an extremely severe stress, grain size would be reduced due to lack of enough assimilates available to fill them. Fil: Serrago, Roman Augusto. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina Fil: Alzueta, Ignacio. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina Fil: Savin, Roxana. Universitat de Lleida. Departament de Producció Vegetal i Ciència Forestal; España. Universitat de Lleida. Agrotecnio; España Fil: Slafer, Gustavo Ariel. Universitat de Lleida. Departament de Producció Vegetal i Ciència Forestal; España. Institució Catalana de Recerca i Estudis Avancats; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

The food production and processing value chain is under pressure from all sides-increasing demand driven by a growing and more affluent population; dwindling resources caused by urbanization, land erosion, pollution and competing agriculture such as biofuels; and increasing constraints on production methods driven by consumers and regulators demanding higher quality, reduced chemical use, and most of all environmentally beneficial practices 'from farm to fork'. This pressure can only be addressed by developing efficient and sustainable agricultural practices that are harmonized throughout the value chain, so that renewable resources can be exploited without damaging the environment. Bridges must, therefore, be built between the diverse areas within the food production and processing value chain, including bridges between different stages of production, between currently unlinked agronomic practices, and between the different levels and areas of research to achieve joined-up thinking within the industry, so that the wider impact of different technologies, practices and materials on productivity and sustainability is understood at the local, regional, national and global scales. In this article, we consider the challenges at different stages and levels of the value chain and how new technologies and strategies could be used to build bridges and achieve more sustainable food/feed production in the future. Research at the University of Lleida is supported by MINECO, Spain (AGL2009-11006; AGL2009-11475; AGL2009-11964; AGL2009-13517-C03-02; AGL2010-21572; AGL-22050-C03-01; AGL2010-22084-CO2-O1; AGL2010-22182; AGL2011-23996; AGL2011-24862; AGL2011-30529-C02-02; AGL2012-35300; AGL2012-40144-C03-03; BIO2011-22525; BIO2011-23324; BIO2007-61413; CTQ2009-07831; CTM2009-14612 and PIM2010PKB-00746); EU FP7 Integrated Project 222716 SmartCell; EU FP7 European Research Council IDEAS Advanced Grant (to PC) Program-BIOFORCE; EU FP7 Large-scale integrated project KBBE 222738 Selection and improving of fit-for-purpose sampling procedures for specific foods and risks (BASELINE); EU FP7 Program-SICA project KBBE 222690; COST Action FA0804: Molecular farming: plants as a production platform for high value proteins; COST Action FA 1006: Plant Engine; COST Action TD1104: Development of electroporation-based technologies; Centre CONSOLIDER on Agrigenomics funded by MICINN, Spain; the HENUFOOD project (CEN-20101016) as part of the CENIT program and the INCOMES project as part of the INNPRONTA 2011.

A number of evidences have shown that triticale produces more above-ground dry matter (AGDM) than other winter cereals indry environments.AsAGDMaccumulated by crop before anthesishas beenpointed out as an important attribute under rainfed environments, the comparison of its physiological attributes (i.e. accumulated intercepted radiation – IPAR and radiation use efficiency – RUE), comparing among different cultivars and respect to other cereals, could be valuable to identify prospective traits to be used in breeding programs. Three experiments were carried out during the 2004 and 2005 growing seasons to (i) determine the effect of water stress on the yield and the eco-physiological components of biomass (i.e. accumulated intercepted radiation and RUE throughout the crop cycle) in a wide range of triticale cultivars to evaluate the genotypic variability (in interaction with water regime) for those traits and (ii) to analyze the causes for the commonly found differences in yield and AGDM between triticale and wheat under different water and nitrogen conditions. The triticale cultivars showed an important variability in yield and yield components sensitivity to drought. Water restrictions reduced AGDM, more than its partitioning to the reproductive organs, due to reductions in crop growth rate mainly through reduced RUE when different triticale cultivars were analyzed. Triticale outyielded wheat due to an increased biomass at anthesis and at maturity associated with higher RUE, probably due to a better light distribution into the canopy, more than by differences in IPAR. Triticale advantages were especially noticeable in the Mediterranean-type environment where yield and biomass were almosttwice than that of wheat, associated with differences of similar magnitude in RUE. Fil: Estrada Campuzano, Gaspar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Slafer, Gustavo Ariel. Institució Catalana de Recerca i Estudis Avancats; España. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Miralles, Daniel Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

Further improvements to wheat yield potential will be essential to meet future food demand. As yield is related to the number of fertile florets and grains, an understanding of the basis of their generation is instrumental to raising yield. Based on (i) a strong positive association between the number of fertile florets or grains and spike dry weight at anthesis; and (ii) the finding that floret death occurs when spikes grow at maximum rate, it was always assumed that floret survival depends on the growth of the spike. However, this assumption was recently questioned, suggesting that assimilates diverted to the spike do not determine the number of florets and grains and that the onset of floret death may instead be a developmental process that is not associated with spike growth. In this study, the relationships between the fate of floret primordia and spike growth from six independent experiments that included different growing conditions (greenhouse/field experiments, growing seasons, photoperiod/shading treatments during the floret primordia phase) and diverse cultivar types (winter/spring, semi-dwarf/standard-height, photoperiod sensitive/insensitive) were re-analysed together. Onset of floret death was associated with the beginning of spike growth at the maximum rate in c. 80% of the cases analysed; and the rate of floret death (the main determinant of floret survival) showed a negative quantitative relationship with spike weight at anthesis. As floret death and survival were shown to be linked to pre-anthesis spike growth, the strategy of focusing on traits associated with pre-anthesis spike growth when breeding to increase wheat yield potential further is valuable. Fil: González, Fernanda Gabriela. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Norte. Estación Experimental Agropecuaria Pergamino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Miralles, Daniel Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Norte. Estación Experimental Agropecuaria Pergamino; Argentina Fil: Slafer, Gustavo Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Institució Catalana de Recerca i Estudis Avancats; España. Universidad de Lleida; España

The importance of yield improvement at farm conditions is highly dependent on the interaction between genotype and environment. The aim of the present work was to assess the attainable yield of a traditional and a modern malting barley cultivar growing under a wide range of soil nitrogen (N) availabilities and different water scenarios (low, intermediate and high rainfall conditions during the fallow period and throughout the crop cycle) considering a 25-year climate dataset for two sites (a shallow and a deep soil) in the Pampas, Argentina. For that purpose, a barley model was first calibrated and validated and then used to expand field research information to a range of conditions that are not only much wider but also more realistic than experiments on experimental farms. Yield of the modern cultivar was at least equal to (under the lowest yielding conditions) or significantly higher (under most growing conditions) than that of the traditional cultivar. Averaged across all the scenarios, yield was ~20% higher in the modern than in the traditional cultivar. The average attainable yield represented 42% of the yield potential in the shallow and 79% in the deep soil profiles. Yield advantage of the high yielding cultivar was based on using N more efficiently, which not only determined higher attainable yields but also reduced the requirements of soil N to achieve a particular yield level. Farmers would face little risk in adopting higher yielding cultivars in both high and low yielding environments and even in the latter ones N fertilisation could be beneficial in most years. Fil: Abeledo, Leonor Gabriela. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentina Fil: Calderini, Daniel F.. Universidad Austral de Chile; Chile Fil: Slafer, Gustavo A.. Universitat de Leida; España

A substantial increase in grain yield potential is required, along with better use of water and fertilizer, to ensure food security and environmental protection in future decades. For improvements in photosynthetic capacity to result in additional wheat yield, extra assimilates must be partitioned to developing spikes and grains and/or potential grain weight increased to accommodate the extra assimilates. At the same time, improvement in dry matter partitioning to spikes should ensure that it does not increase stem or root lodging. It is therefore crucial that improvements in structural and reproductive aspects of growth accompany increases in photosynthesis to enhance the net agronomic benefits of genetic modifications. In this article, six complementary approaches are proposed, namely: (i) optimizing developmental pattern to maximize spike fertility and grain number, (ii) optimizing spike growth to maximize grain number and dry matter harvest index, (iii) improving spike fertility through desensitizing floret abortion to environmental cues, (iv) improving potential grain size and grain filling, and (v) improving lodging resistance. Since many of the traits tackled in these approaches interact strongly, an integrative modelling approach is also proposed, to (vi) identify any trade-offs between key traits, hence to define target ideotypes in quantitative terms. The potential for genetic dissection of key traits via quantitative trait loci analysis is discussed for the efficient deployment of existing variation in breeding programmes. These proposals should maximize returns in food production from investments in increased crop biomass by increasing spike fertility, grain number per unit area and harvest index whilst optimizing the trade-offs with potential grain weight and lodging resistance.

SUMMARYWheat yield and grain nitrogen concentration (GNC; mg N/g grain) are frequently negatively correlated. In most growing conditions, this is mainly due to a feedback process between GNC and the number of grains/m2. In Mediterranean conditions, breeders may have produced cultivars with conservative grain set. The present study aimed at clarifying the main physiological determinants of grain nitrogen accumulation (GNA) in Mediterranean wheat and to analyse how breeding has affected them. Five field experiments were carried out in north-eastern Spain in the 2005/06 and 2006/07 growing seasons with three cultivars released at different times and an advanced line. Depending on the experiment, source-sink ratios during grain filling were altered by reducing grain number/m2 either through pre-anthesis shading (unshaded control or 0·75 shading only between jointing and anthesis) or by directly trimming the spikes after anthesis and before the onset of the effective grain filling period (un-trimmed control or spikes halved 7–10 days after anthesis). Grain nitrogen content (GN content; mg N/grain) decreased with the year of release of the genotypes. As the number of grains/m2 was also increased by breeding there was a clear dilution effect on the amount of nitrogen allocated to each grain. However, the increase in GN content in old genotypes did not compensate for the loss in grain nitrogen yield (GNY) due to the lower number of grains/m2. GN content of all genotypes increased (increases ranged from 0·13 to 0·40 mg N/grain, depending on experiment and genotype) in response to the post-anthesis spike trimming or pre-anthesis shading. The degree of source-limitation for GNA increased with the year of release of the genotypes (and thus with increases in grain number/m2) from 0·22 (mean of the four manipulative experiments) in the oldest cultivar to 0·51 (mean of the four manipulative experiments) in the most modern line. It was found that final GN content depended strongly on the source-sink ratio established at anthesis between the number of grains set and the amount of nitrogen absorbed at this stage. Thus, Mediterranean wheat breeding that improved yield through increases in grain number/m2 reduced the GN content by diluting a rather limited source of nitrogen into more grains. This dilution effect produced by breeding was further confirmed by the reversal effect produced by grain number/m2 reductions due to either pre-anthesis shading or post-anthesis spike trimming.

� Background and Aims The use of perennial crops could contribute to increase agricultural sustainability. However, almost all of the major grain crops are herbaceous annuals and opportunities to replace them with more long-lived perennials have been poorly explored. This follows the presumption that the perennial life cycle is associated with a lower potential yield, due to a reduced allocation of biomass to grains. The hypothesis was tested that allocation to perpetuation organs in the perennial L. mendocina would not be directly related to a lower allocation to seeds. � Methods Two field experiments were carried on with the annual Lesquerella fendleri and the iteroparous perennial L. mendocina, two promising oil-seed crops for low-productivity environments, subjected to different water and nitrogen availability. � Key Results Seed biomass allocation was similar for both species, and unresponsive to water and nitrogen availability. Greater root and vegetative shoot allocation in the perennial was counterbalanced by a lower allocation to other reproductive structures compared with the annual Lesquerella. Allometric relationships revealed that allocation differences between the annual and the perennial increased linearly with plant size. The general allocation patterns for nitrogen did not differ from those of biomass. However, nitrogen concentrations were higher in the vegetative shoot and root of L. mendocina than of L. fendleri but remained stable in seeds of both species. � Conclusions It is concluded that vegetative organs are more hierarchically important sinks in L. mendocina than in the annual L. fendleri, but without disadvantages in seed hierarchy.

Further increases in wheat yield potential could be achieved through a better understanding of the dynamics of floret primordia generation/degeneration, a process which has received little attention. We quantified genotypic variation among elite genotypes of the CIMCOG panel assembled by CIMMYT for its usefulness for wheat breeding. Ten genotypes, representing the range of variation for yield and its components of the whole panel, were grown under high-yielding conditions in NW Mexico for two growing seasons. The stage of development of floret primordia was determined 2–3 times weekly during stem elongation for apical, central and basal spikelets within the spike. The dynamics of floret initiation/death, and the resulting number of fertile florets, were determined for each spikelet position. We found that the variation in number of fertile florets within this elite germplasm was much more related to the survival of floret primordia than to the maximum number of florets initiated. As the two floret primordia most proximal to the rachis were almost always fertile and most distal florets (florets 6–8) were never fertile, the differences in number of fertile florets were clearly attributed to the differential developmental patterns of intermediate florets (floret primordia 3, 4 and 5, counted from the rachis, depending on the spikelet position). We found significant differences among elite germplasm in dynamics of floret development. Differences in floret survival seemed positively related to those in the length of the period of floret development: the longer the duration of floret development the higher the likelihood of that floret becoming fertile. It is proposed that this type of study may be instrumental for identifying prospective parents for further raising yield potential wheat breeding programmes. This work was supported by the Sustainable Modernization of Traditional Agriculture (MasAgro) initiative from the Secretariat of Agriculture, Livestock, Rural Development, Fisheries and Food (SAGARPA) and by the National Council on Science and Technology (CONACYT) scholarship 310626 to O.E.G.N.