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Context Although waterlogging is known to decrease grain yield in wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.), its effect on plant N traits is still unknow. Aims This study evaluated biomass N dynamics and partitioning to grains, in wheat and barley plants subjected to waterlogging. Methods Under contrasting environmental conditions, two pot experiments exposing wheat and barley plants to waterlogging events for 15–20 days at five different developmental stages, from emergence to maturity were performed. Grain N concentration, grain N content, biomass N concentration, N utilisation efficiency (NUE) and N remobilisation were recorded. Key results Both species responded similarly to waterlogging for most N traits. Reductions in grain N content differed according to the moment waterlogging occurred. The greatest reductions (46–77% compared to the control) being for waterlogging from the beginning of stem elongation to anthesis, which also showed the highest reductions in N remobilisation, N uptake at maturity, and N partitioning to the grains, but only a slight decrease in NUE. Grain N concentration raised drastically (up to 45 mg N g DW−1) with minimal grain yields. N concentration of aboveground biomass decreased during waterlogging, recovering control values at maturity. N content at maturity was related to the total biomass. Conclusions Waterlogging differentially reduced N uptake and remobilisation to grains of wheat and barley depending on the developmental stage when water excess occurred. Implications The impact of waterlogging on N economy of wheat and barley appears indirect and predominantly related to carrying effects of the stress on carbon economy due to growth reductions.

Episodes of heat stress constrain crop production and will be aggravated in the near future according to short and medium-term climate scenarios. Global increase in cloudiness has also been observed, decreasing the incident solar radiation. This work was aimed to quantify the probability of occurrence of heat stress and cloudiness, alone or combined, during the typical post-flowering period of wheat and canola in the Southern Cone of South America. Extended climate series (last 3–5 decades with daily register) of 33 conventional weather stations from Argentina, Brazil, Chile and Uruguay (23 to 40°S) were analysed considering the period from September to December. Two different daily events of heat stress were determined: (i) maximum daily temperature above 30 °C (T > 30 °C) and (ii) 5 °C above the historical average maximum temperature of that day (T + 5 °C). A cloudiness event was defined in our work as incident solar radiation 50% lower than the historical average radiation of that day (R50%). The T > 30 °C event increased its probability of occurrence throughout the post-flowering phase, from September to December. By contrast, the risk of T + 5 °C event decreased slightly, just like for R50%, and the higher the latitude, the lower the probability of R50%. The T > 30 °C plus R50% combined stresses reached greater cumulated probabilities during post-flowering, compared to T + 5 °C plus R50%, being 42% vs 15% in northernmost locations, 26% vs. 19% in central (between 31 and 35°S) and 28% vs. 1% in southernmost locations, respectively. A curvilinear relationship emerged between the monthly probability of combined stresses and the number of days with stress per month. In summary, T > 30 °C was the most frequent thermal stress during post-flowering in wheat and canola. Both combined stresses had a noticeable risk of occurrence, but T > 30 °C plus R50% was the highest. Evidence of the recent past and current occurrence of heat stress individually, and its combination with cloudiness events during post-flowering of temperate crops, serves as a baseline for future climate scenarios in main cropped areas in the Southern Cone of South America.

Fil: Cantoro, Renata. Universidad Nacional de Rio Cuarto. Facultad de Ciencias Exactas Fisicoquimicas y Naturales. Instituto de Investigacion en Micologia y Micotoxicologia. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Investigacion en Micologia y Micotoxicologia; Argentina

Most of the required increases in food production over the next decades are expected to be achieved through increases in crop yield. As wheat is essential for food security it is worrying that its yield gains over the last two decades were small. To achieve further yield increases it is critical to continue increasing number of grains per unit area (GN m(-2)), the trait best related to yield. In this context, it is relevant to identify the main determinants of GN m(-2) in response to genetic and environmental factors as well as the trade-offs between them. In the present study we compiled a large database across the literature to analyse the relative importance of components when affected by genetic or environmental factors, producing small or large changes in GN m(-2) and its components, either numerical (the number of spikes per m(2), SN m(-2); and the number of grains per spike, GN spike(-1)) or physiological (spike dry weight at anthesis, SDWa; and fruiting efficiency, FE) determinants. The database included 367 papers published in: (i) Field Crop Research (FCR), (ii) European Journal of Agronomy (EJA), (iii) Crop Science (CS) and (iv) Crop and Pasture Science (CPS, formerly Australian Journal of Agricultural Research) between 1990 and 2020. The complete dataset was split into classes, depending on the source of experimental variation, environment or genotype and was normalised to remove the differences between experiments and determine the environmental and genotypic effects within each experiment. Normalised data showed that the responsiveness of GN m(-2)was similarly explained by changes in both SN m(-2) and GN spike(-1), but in terms of physiological components SDWa was more relevant than FE for explaining the variations in GN m(-2). Considering the numerical components of GN m(-2) genotypic and environmental factors modified more GN spike(-1) than in SN m(-2). On the other hand, physiological components were differently modified by genotype and environment: for genotypic effects FE was more critical than SDWa and the other way around for environmental factors. A tradeoff between numerical and physiological components was observed although was greater between physiological than between numerical components. Research of the authors on wheat yield physiology has been funded along years by many different grants from different funding bodies; most recently mainly from (i) the International Wheat Yield Partnership (IWYP25FP) , (ii) , the Spanish State Agency for Research (latest project was RTI2018-096213-B-100) , and (iii) Argentine Fund for Scientific and Technological Research (latest project PICT RAICES 2019-04333) .

Late foliar diseases that appear during the grain filling period reduce radiation interception/absorption decreasing assimilation supply, inducing reductions in grain weight and yield. We hypothesize that crops with higher source-sink ratio (established immediately after anthesis) could have more capacity to avoid reductions in terms of yield, at same level of foliar disease. Thus, it is speculated that the yield reduction caused by late foliar diseases is a complex interaction between current photosynthesis availability per grain and the remobilization capacity according to the sink size determined demand. The objective of the present study was to analyze physiological attributes associated with yield reduction caused by late foliar diseases in wheat when source-sink ratio is modified. Experiments were carried out during two consecutive years (2009 and 2010) applying a combination of (i) two disease levels (i.e. healthy and diseased plots), (ii) two different levels of incident radiation applied immediately previous to anthesis, to reduce grain number exclusively (i.e. non-shaded and shaded plots) and (iii) source-sink manipulations during grain filling (i.e. control and trimmed spikes). Shading during pre-anthesis significantly reduced grain number and then, the source-sink ratio was modified between non-shaded and shaded plots, being two fold higher in non-shaded than in shaded plots. In both years and shading treatments, diseases appeared after anthesis, the diseased plots showing higher values of non-green leaf area than healthy plots, in both shaded and non-shaded treatments. Late foliar diseases significantly reduced grain yield in both, 2009 and 2010 mainly due to reductions in grain weight. There was significant interaction in the crop performance to foliar diseases between shading treatments and growing seasons. While the reduction caused by late foliar diseases was similar between shading treatments during 2009, in 2010 significant differences were observed, being reductions lower in shaded than in non-shaded plots. The source-sink manipulation treatment confirmed these responses, as there were no significant differences in grain weight of trimmed spikes between healthy and diseased crops, confirming that the grain weight reduction due to late foliar diseases is driven by the source sink balance.

Promising yield-determining responses to artificial photoperiod manipulation during post-flowering phases have been identified in soybean [Glycine max (L.) Merrill]. These responses enhance resource capture as a result of changes in phase duration, and resource use efficiency as a result of changes in node production and pod development, alleviating intra-node pod interference. This work aims to evaluate the relevance of these responses under natural conditions and discriminate direct from indirect photoperiodic effects, that is, effects caused by changes in the capture of resources. Two field experiments were conducted with a combination of sowing dates, with similar pre- and different post-flowering photoperiod, indeterminate genotypes including near isogenic lines and commercial varieties with different photoperiod sensitivity, and shadings with different incident radiation during post-flowering. Longer post-flowering photoperiod and higher plant photoperiod sensitivity delayed crop development, particularly in lines with alleles E2, E3 or Clark background. This delay resulted in extra radiation capture and node production, which were positively related to yield. Direct photoperiodic effects on nodes per m2 were evidenced in response to changes in post-flowering photoperiod and plant photoperiod sensitivity. The distribution of available resources such as radiation in more nodes per m2 increased use efficiency. Longer post-flowering photoperiod and higher plant photoperiod sensitivity enhanced pod establishment on usually dominated positions such as lateral racemes, affecting pods per m2. Finding these relevant yield-determining effects under natural conditions suggests that processes related to post-flowering photoperiodic responses are a plausible way to enhance resource capture and use efficiency and yield in soybean production systems. In cropping systems in which the whole growing season is used to maximize yield, these post-flowering photoperiodic responses could be adopted at the expense of the pre-flowering phase duration.

Background: The heterologous expression of isopentenyl transferase (IPT) under the transcriptional control of the senescence-associated receptor-like kinase (SARK) promoter delayed cellular senescence and, through it, increased drought tolerance in plants. To evaluate the effect of pSARK::IPT expression in bread wheat, six independent transgenic events were obtained through the biolistic method and evaluated transgene expression, phenology, grain yield and physiological biomass components in plants grown under both drought and well-irrigating conditions. Experiments were performed at different levels: (i) pots and (ii) microplots inside a biosafety greenhouse, as well as under (iii) field conditions. Results: Two transgenic events, called TR1 and TR4, outperformed the wild-type control under drought conditions. Transgenic plants showed higher yield under both greenhouse and field conditions, which was positively correlated to grain number (given by more spikes and grains per spike) than wild type. Interestingly, this yield advantage of the transgenic events was observed under both drought and well-watered conditions. Conclusions: The results obtained allow us to conclude that the SARK promoter-regulated expression of the IPT gene in bread wheat not only reduced the yield penalty produced by water stress but also led to improved productivity under well-watered conditions. EEA Pergamino Fil: Beznec, Ailin. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina Fil: Faccio, Paula Daniela. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina Fil: Miralles, Daniel. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Cerealicultura; Argentina Fil: Miralles, Daniel. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA); Argentina Fil: Abeledo, Leonor G. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Cerealicultura; Argentina Fil: Décima Oneto, Cecilia Andrea. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Laboratorio de Agrobiotecnología; Argentina Fil: Décima Oneto, Cecilia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Garibotto, María De Belén. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina Fil: Garibotto, María De Belén. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gonzalez, Germán Andrés. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bordenave; Argentina Fil: Moreyra, Federico. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bordenave; Argentina Fil: Elizondo, Matias. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Juan; Argentina Fil: Elizondo, Matias. Universidad Nacional de San Juan. Facultad de Ingeniería. Departamento de Agronomía. Unidad Integrada INTA-UNSJ; Argentina Fil: Ruiz, Mónica Beatriz. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Juan; Argentina Fil: Ruiz, Mónica Beatriz. Universidad Nacional de San Juan. Facultad de Ingeniería. Departamento de Agronomía. Unidad Integrada INTA-UNSJ; Argentina Fil: Lewi, Dalia Marcela. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina Fil: Blumwald, Eduardo. University of California. Department of Plant Sciences; Estados Unidos Fil: Llorente, Berta. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina Fil: Diaz Paleo, Antonio Horacio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino. Sección Laboratorio Biotecnología; Argentina Fil: Bossio, Adrian Ezequiel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética; Argentina

Efforts to anticipate how climate change and variability will affect future crop production can benefit from understanding the impacts of current and historic changes. This study aimed to quantify and compare the impact of increased night temperature on potential yield and phenology of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) crops modelled using APSIM with historical climate series (1961–2014) in sites representative of the Argentinean Pampas. For each site, the sowing date was adjusted to avoid frost and heat events at flowering, based on historical probability. The critical period was the more sensitive crop phase (shortened by 0.6 d decade−1) for the observed asymmetric warming; regional minimum temperature trend of ca. 0.14 and 0.16 °C decade−1 in wheat and barley, respectively. Wheat and barley yields declined across the region between ca. 2% and 9% per °C increase in the minimum temperature during the critical period, linked to lower cumulative radiation capture as a result of a shorter crop phase and lower incident radiation due to displacement towards winter. Regional variability in the simulated yield response to the observed night warming was mainly explained by differences the response of incident solar radiation during the critical period to the minimum temperature increase. 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. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; 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 Fil: Serrago, Roman Augusto. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Alzueta, Ignacio. 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: Huth, Neil. CSIRO Agriculture and Food; Australia Fil: Dreccer, Maria Fernanda. CSIRO Agriculture and Food; Australia

Warmer nights, caused by climate change, are one of the factors with greatest impact on wheat performance. Limited studies have evaluated the effects of higher night temperature on wheat quality. In the present study, the effects of warmer nights on milling and breadmaking quality of wheat are analysed. Field experiments were carried out in 2013, 2016 and 2017 under three-night temperature conditions: control unheated, night temperature increase during the critical period (i.e., from third visible node to 10 days after anthesis), and during the grain filling period (i.e., from 10 days after anthesis to physiological maturity). Warmer nights during the critical period shortened the time to anthesis (ca. 5 days), while during grain filling the duration was shortened ca. 2 days. Warmer nights during the critical period and during grain filling reduced grain yield ca. 23% and ca. 20%, respectively. However, warmer nights increased wheat quality attributes as gluten content. Crops under higher night temperatures during the critical period presented the highest values of grain protein concentration, gluten content and dough baking strength (AlvW). Variations in AlvW were related to changes in the dough extensibility. The main effect of warmer nights on breadmaking quality was indirect because of yield penalization, especially during the critical period.

Malt extract is the most relevant parameter describing malting quality in barley. The observed differences in malt extract from crops grown in different environments are complex to explain, and their interpretation might represent an opportunity to improve malting quality for barley crops grown under field conditions. Although the effect of some grain attributes on malt extract are overall known (e.g. protein content and grain size) other are less understood and are complex to replicate across experiments, with few evidence of how they are controlled by the environment during grain filling (e.g. hordeins and pasting properties). Four commercial malting barley cultivars were sown on eleven sowing dates across four years to explore a wide range of thermal conditions during grain filling. Contrasting nitrogen availabilities were included to promote variability in the protein content. Grain plumpness, protein content, pasting temperature, and the amount of d - and γ-hordeins showed a significant effect on malt extract. Protein content showed a negative effect on malt extract only when it was above a threshold value of ca. 10 %, although that threshold varied between cultivars. Pasting temperature presented a significant interaction with protein content. d -hordein showed a negative effect on malt extract only when the protein content was below the threshold, explaining some of the contradictory results reported in the literature. Evidence of a negative effect of γ-hordeins on malt extract was found as well. The period between pollination and physiological maturity was arbitrarily divided into thermal-time intervals, and correlation analyses were performed between mean temperature during each period and the grain attributes affecting malt extract. For all the cultivars, only two attributes were found to be modulated by the thermal environment explored by the crop during grain filling: pasting temperature was positively correlated to the mean temperature explored by the crop during the middle of grain filling, whereas grain plumpness was negatively correlated with the mean temperature during the second half of grain filling. Quantitative models reported in the present study in addition to offering an explanation of how malting quality is shaped in the field, constitute a useful tool for agro-climatic zoning for the suitability of high-quality malting barley production.

Foliar diseases limit yield and modify the quality of the bread wheat. Due to genetic improvement reduced source:sink ratio, it is possible to speculate that the diseases infections penalize yield more in modern than in old cultivars, affecting differentially quality commercial and milling properties. The objective of this work was to analyze the changes in yield and quality of bread wheat due to the presence of foliar diseases in old and modern bread wheat cultivars artificially inoculated with Puccinia triticina, compared to a control plots protected with fungicide. Foliar diseases penalized yield due to reductions in the number of grains in all cultivars. Protein in grain-flour, wet-dry gluten and sedimentation were reduced when Pyrenophora tritici-repentis was the main pathogen, while Puccinia triticina only reduced the protein content in grain. Modern cultivars shower greater decreased proteins in grain-flour and gluten than old cultivars, probably associated with higher yield and lower source:sink ratio respect to the old cultivars. The changes in dough rheology and breadmaking quality, as a consequence of foliar diseases, were not as marked or as consistent as observed on milling quality, and the magnitude and direction of those effects were not as clear as those observed in milling quality.

Sunlight is a crucial environmental factor for photosynthesis. Plant density affects both quality and quantity at light penetration into the canopy. The effects of plant density on the expression of photomorphogenic traits in cultivated spring rapeseed (Brassica napus L.), and their consequences on seed production per unit area are unknown. The aims of this work were to: i) analyze the magnitude of shade avoidance responses to plant densities in five spring rapeseed genotypes, ii) describe the dynamics of floral branching in response to genotype and plant density, and iii) study yield and its components and seed quality in field-cultivated plants with contrasting plant densities (15 and 240 pl m−2). Rosette diameter was the main attribute of vegetative plasticity modified by plant density, without significant changes in petiole length. Plant density changed the relationship between intercepted solar radiation (ISR) and red/far red ratio (R/FR) during crop development, but at flowering all densities reached ISR = 95% and R/FR ratio

tThe use of physiological traits for indirect selection may help to increase wheat yield potential. Fruitingefficiency (FE, grain number per unit of spike dry weight at anthesis −SDWa-) may be an alternativeto increase grain number per unit area (GN), but the possible cross-over genotype (G) × environment(E) interaction and trade-off with SDWa and grain weight (GW) may limit its usefulness. The presentpaper aimed to determine (i) the degree of G × E interaction of FE at plot, main stem and tiller levels,(ii) the relationship between GN and FE, and (iii) the possible trade-off between FE and (a) SDWa, and(b) GW. Three FE contrasting genotypes (B11 and B19 ? high FE, and B2002 ? low FE) were grown underdifferent Nitrogen (N) availability at sowing [(i) low ? Ni: ca. 50 kg N ha−1; (ii) middle −130 kg N ha−1and (iii) high −200 kg N ha−1). Two other treatments were applied within the 200N: (iv) late sowing, i.e.delaying sowing 30 days in relation to optimum date (200N + LS) and (v) shading the canopy during stemelongation (200N + SH). The FE showed G × E interaction (year × genotype and genotype × treatment) butit only explained 13.4% of its variation. The environment (year) had similar impact than the genotype,explaining both ca. 38% of FE variation (19% each). The FE of tiller spikes was higher than that of mainstem spikes, but the difference among cultivars was maintained. Thus, canopies of the same genotypewith different proportion of main stem and tiller spikes may present different FE value at plot level.Nevertheless, a high correlation (r = 0.82, p < 0.0001) and a close 1:1 relationship was observed between FEat plot level and FE in main stems, for all treatments and cultivars, suggesting that sampling the main stemspikes represents the FE at plot level in dense canopies. A G × E cross-over interaction was observed whenthe sowing was delayed one month (200N + LS) from the optimum date because B19 reached anthesislater than B2002, exploring higher heat stress index (◦Ch > 27◦C) around anthesis, which reduced FE.The correlation of GN with FE was high and significant (r = 0.74, p < 0.00001) for all treatments and fora wide range of SDWa values (from 90 to 188 g m−2). The B19, selected as a high FE genotype, showedhigher GN than B2002 (selected as a low FE genotype) under all treatments, while B11 (also of high FE)showed similar or higher GN than B2002, depending on treatment. Thus, despite the G × E interaction, thegenotypes with higher FE had more GN under a wide range of environments. Nevertheless, the SDWa andGW were negatively correlated with FE (for SDWa r = −0.73 p < 0.005, without considering 200N + SH; andfor GW r = −0.48 p < 0.01 for all treatments or r = −0.75 p < 0.08 for genotypes only). Then, special attentionshould be given to SDWa and GW when selecting for higher FE in a breeding program. Fil: Terrile, Ignacio Ismael. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Norte. Estación Experimental Agropecuaria Pergamino; 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; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina Fil: González, Fernanda Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia del Noroeste de la Provincia de Buenos Aires. Universidad Nacional del Noroeste de la Provincia de Buenos Aires. Centro de Investigaciones y Transferencia del Noroeste de la Provincia de Buenos Aires; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Norte. Estación Experimental Agropecuaria Pergamino; Argentina

Tan spot [Pyrenophora tritici-repentis (Died.) Drechs., anamorph Drechslera tritici-repentis) (Died.) Shoem.] and leaf rust (Puccinia triticina Eriks) are major diseases worldwide and some of the main biotic causes of yield and quality reduction in wheat (Triticum aestivum L.). Although wheat crop losses due to foliar diseases have already been studied based on an ecophysiological approach, none of these studies analyzed the independent effects of foliar pathogens with different nutritional habits. The aim of the present study was to determine the independent effects of (i) Py. tritici-repentis (necrothroph) and (ii) Puccinia triticina (biotroph) on the physiological components of biomass production: accumulated intercepted by green tissue photosynthetic active radiation (IGPAR), radiation use efficiency calculated by intercepted radiation (RUEint) as well as by intercepted by green tissue (RUEgt) in a wide range of Argentine commercial bread wheat cultivars growing in two field environments. Field experiments were carried out during two consecutive years combining a large range of wheat bread commercial cultivars and two levels of inoculation to promote infection of Tan spot and Leaf rust diseases, including a control without inoculation. Treatments were arranged in an experimental split-split plot design with three replications, where the main plots were both diseases, subplots corresponded to inoculation treatments 1- without inoculation (WI), 2- low concentration of inoculum of each disease (LC), 3- high concentration of inoculum of each disease (HC) and ten Argentine bread wheat commercial cultivars were the sub-subplots. Area under disease progress (AUDPC), area under percentage of non-green leaf area (AU %NGLA), crop growth rate (CGR) and healthy area duration (HAD) were calculated. Green leaf area index (GLAI), aboveground biomass (AGB), IGPAR and RUE were measured at three different crop stages (GS39, GS61 and GS82). Increases of inoculum concentration decreased AGB between 8 and 20% mainly explained by reductions in HAD and decreases on IGPAR by 14–18% with higher reductions when the crop was inoculated with Py. tritici-repentis than with P. triticina. Although both diseases reduced the physiological components of accumulated biomass related to radiation interception (IGPAR), RUEint (−23%), RUEgt (−11%) and CGR (−29%) were more reduced, respect to WI, when plants were inoculated with P. triticina compared to Pyrenophora tritici-repentis. The differential responses in RUE could be associated with the nutritional habit of P. triticina that reduces leaf nitrogen concentration, enhance assimilates consume by leaf respiration, reducing radiation use efficiency. Fil: Schierenbeck, Matías. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Fleitas, María Constanza. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; 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 Fil: Simon, Maria Rosa. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Identification of secondary traits in mapping populations is usually hindered by the strong effect of anthesis time. Thus, considering the variability in time to anthesis in combination with an accurate phenotyping of mapping populations and available molecular tools is a possible way for recognising secondary traits to improve yield potential. The aim of this work was to identify secondary traits to perform indirect selection for grain yield (GY) in a bread wheat mapping population consisting of 124 doubled haploid lines, derived from the cross between two soft red winter wheat genotypes with contrasting photoperiod response. Genomic regions linked to different traits were analysed under two environments. The population showed a strong effect of time to anthesis over GY, as expected. A large variability in GY was observed but only two QTLs were detected on chromosome 5A for this trait, which co-localized with QTLs of time to anthesis. GY variation was partially associated with above-ground dry matter at maturity (AGDM) and to a lesser extent with harvest index (HI). Detected QTLs for grains per m2 (GN), grain weight, AGDM and HI explained between 25 and 61% of the GY additive genetic variance. GN, defined as the product between spike dry weight at anthesis (SDW) and fruiting efficiency (FE), was the main numerical component that explained most of the variation in GY. Five QTLs were detected for SDW, which did not co-localize with QTLs of time to anthesis and captured ca. 50% of the additive genetic variance, while there was a weak relationship between NG and FE. When genotypes were filtered by similar anthesis time and plant height, SDW was identified as a promising secondary trait to be targeted for indirect selection of GY.

Determining the optimum time for rapeseed harvest is challenging due to non-uniform seed maturity resulting from asynchronous flowering and pod dehiscence from sequential racemes. Identifying physiological maturity (PM) by visual methods is subjective and results can be affected by environmental conditions. PM can be determined using a quantitative model based on seed water concentration (SWC) as previously demonstrated for several other crops, although not yet developed for rapeseed crop. The objective of this work was to study the relationship between the dynamics of seed dry weight and water concentration in seven spring rapeseed cultivars grown at two contrasting densities (15 and 60 pl m−2) in three experiments at one location in Buenos Aires (Argentina). We evaluated the timing of PM on the basis of SWC in seeds located in the main raceme, second and fourth floral branches. The evolution of seed fresh and dry weight was followed bi-weekly from the beginning of flowering to harvest maturity. In Exp. 1, the grain-filling duration ranged from 39 to 57 days (700–1100 °C d) and the growth of seeds from floral branches finished 3–8 days later than those from the main raceme. Seed dry weight at PM ranged from 2.4 to 2.7 and from 3.0 to 3.2 mg for Lynx and Monty cultivars, respectively, without significant effects of floral position or plant density. Bi-linear functions were used to fit the relationship between relative seed dry weight (RSDW) and SWC relationships (R2 from 0.85 to 0.95). Across cultivars and floral positions, PM was attained when seeds exhibited 46.3 ± 0.7% SWC (R2 = 0.90, P < 0.001, n = 441). This model was validated against independent data from Exps. 2 and 3, successfully simulating the dynamics of relative seed dry weight based on fruit WC (r = 0.88; P < 0.001, n = 275). At PM, the water content (WC) of whole pod was about 70% and the pod shattering began after this point, when the WC of the pod dropped drastically. We conclude that under non-stressful conditions, PM in rapeseed occurs at 46% SWC. Swathing can be conducted from SWC < 46%, instead of the currently recommended 35%, advancing the harvest and leaving the land available for sowing the next crop, which would represent an advantage for double cropping in intensified agricultural systems. Fil: Menendez, Yesica Cristina. 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: Botto, Javier Francisco. 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: Gomez, Nora V.. Universidad de Buenos Aires. Facultad de Agronomía; 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 Fil: Rondanini, Deborah Paola. Universidad Nacional de Lomas de Zamora. Facultad de Ciencias Agrarias. Instituto de Investigación en Producción Agropecuaria Ambiente y Salud. - Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Instituto de Investigación en Producción Agropecuaria Ambiente y Salud; Argentina

Fil: Ploschuk, Rocío Antonella. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina. Fil: Miralles, Daniel Julio. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina. Fil: Colmer, Timothy David. University of Western Australia. Faculty of Science. School of Agriculture and Environment. Crawley, Australia. Fil: Ploschuk, Edmundo Leonardo. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cultivos Industriales. Buenos Aires, Argentina. Fil: Striker, Gustavo Gabriel. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina. Waterlogging is expected to increase as a consequence of global climate change, constraining crop production in various parts of the world. This study assessed tolerance to 14-days of early- or late-stage waterlogging of the major winter crops wheat, barley, rapeseed and field pea. Aerenchyma formation in adventitious roots, leaf physiological parameters (net photosynthesis, stomatal and mesophyll conductances, chlorophyll fluorescence), shoot and root growth during and after waterlogging, and seed production were evaluated. Wheat produced adventitious roots with 20– 22% of aerenchyma, photosynthesis was maintained during waterlogging, and seed production was 86 and 71% of controls for early- and late-waterlogging events. In barley and rapeseed, plants were less affected by early- than by late-waterlogging. Barley adventitious roots contained 19% aerenchyma, whereas rapeseed did not form aerenchyma. In barley, photosynthesis was reduced during early-waterlogging mainly by stomatal limitations, and by non-stomatal constraints (lower mesophyll conductance and damage to photosynthetic apparatus as revealed by chlorophyll fluorescence) during late-waterlogging. In rapeseed, photosynthesis was mostly reduced by nonstomatal limitations during early- and late-waterlogging, which also impacted shoot and root growth. Early-waterlogged plants of both barley and rapeseed were able to recover in growth upon drainage, and seed production reached ca. 79–85% of the controls, while late-waterlogged plants only attained 26–32% in seed production. Field pea showed no ability to develop root aerenchyma when waterlogged, and its photosynthesis (and stomatal and mesophyll conductances) was rapidly decreased by the stress. Consequently, waterlogging drastically reduced field pea seed production to 6% of controls both at early- and late-stages with plants being unable to resume growth upon drainage. In conclusion, wheat generates a set of adaptive responses to withstand 14 days of waterlogging, barley and rapeseed can still produce significant yield if transiently waterlogged during early plant stages but are more adversely impacted at the late stage, and field pea is not suitable for areas prone to waterlogging events of 14 days at either growth stage. tbls., grafs., fot.

In wheat, warmer nights during the critical period reduce grain yield due to a diminished grain number per unit area, associated with lower spike number. Previous studies have evaluated the impact of increased night temperatures, but only under potential growing conditions. The aims of this study were to: (i) evaluate the impact of warmer nights during the critical period (i.e. from third detectable node to 10 days after anthesis) on grain yield and its numerical components, under contrasting nitrogen (N) and water levels and (ii) determine whether plant density could be useful as a management strategy to reduce yield losses caused by warmer nights. Two sets of experiments were conducted in Buenos Aires, the first in 2015 and 2016. In both years trials were carried out combining (i) two levels of nitrogen availability (60 and 200 kg N ha−1), (ii) two levels of water availability (rainfed and irrigated) and (iii) two conditions of night temperature (increased night temperature from third visible node to 10 days after anthesis and unheated crops during the whole crop cycle). The second experiment was performed in 2017 and combined: (i) three plant densities (ca. 100, ca. 150 and 300 plants m−2) and (ii) two-night temperature regimes (increased night temperature from third visible node to 10 days after anthesis and unheated crops during the whole crop cycle). Night temperatures were increased by heating systems, during the critical period average night temperatures ranged from 10.7 °C to 15.1 °C. Yield losses occurred when plants were exposed to warmer nights at high nitrogen levels (ca. 7% - i.e. 550 g m−2 - loss per °C of increase) but no effects were apparent under lower nitrogen availability. Warmer nights increased tiller mortality only under high nitrogen availability. No conclusions could be reached concerning water supply management or the convenience of this strategy to reduce the impact of warmer nights due to the lack of response of grain yield or grain number to modifications in water availability. Grain yield was significantly reduced by increases in night temperature only under higher nitrogen supply mostly due to a reduction in grain number per unit area, associated with reductions in spike dry weight; however, crops under high nitrogen levels yielded significantly more than those grown under low nitrogen, even when exposed to warmer nights. For all three densities, warmer nights reduced grain yield similarly (on average ca. 15 %).

Precise phenology modelling of grain filling is essential to understand how the environment explored by barley crops in the field affects malting quality. Grain-filling duration is controlled by temperature; hence thermal time models are widely used for describing grain development. Although a precise base temperature is essential for the accuracy of thermal time models, estimations of this parameter for barley grain filling are scarce in the literature; moreover, the methods employed for its determination seldom establish clearly whether grain filling is being treated as a development or as a growth phenomenon. Even worse, the base temperature during grain filling is usually arbitrarily set to zero. In this work we tested five different methods to estimate the thermal time requirement for completing grain filling in four commercial barley cultivars and the base temperature above which temperature must be accumulated for its calculation, using field-collected data. The crops were sown in a wide range of different dates during three consecutive years and grown under two contrasting nitrogen availabilities. All the estimation methods performed relatively well. Developmental base temperature was close to 8 °C for all cultivars, although genotypic differences were noted. Optimum temperatures for grain filling are reported for three of the four cultivars; however, including this parameter in the models only slightly improved the predictions in one out of three cultivars. The effect of nitrogen availability was negligible and inconsistent across cultivars and environments thus indicating that the models developed can be applied in a wide range of nutritional situations. A broad application model, with a base temperature of 8.4 °C and a thermal time requirement for completing grain filling of 352 °Cd, is reported for barley grain development. All the models were validated against independent data. These models can be used by researchers aiming to unscramble the effects of environment explored by the mother plant on grain malting quality. Further applications include predicting the timing of physiological maturity, and with it, harvest time.

Wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) crops are exposed to warm nights during their growing seasons and this trend is unlikely to change. The aim of this work was to evaluate the effect of higher post-anthesis night temperatures on field-grown crop yield, focusing on final grain weight determination. Experiments combined: (i) two well-adapted crops with similar phenology: bread wheat and two-row malting barley, under (ii) two temperature regimes: ambient and high night temperatures from 10 days after anthesis to physiological maturity during (iii) two contrasting growing seasons in terms of radiation and temperature: late sowing in 2011 and early sowing in 2013. The night temperature increase (ca. 4.1 °C) was achieved using purpose-built heating chambers placed on the crop at 7 pm and removed at 7 am every day during the heating period. Across growing seasons and crops, the average minimum temperature during that period ranged from 14.3 °C to 21.9 °C. Thousand grain weight was reduced by ca. 3% per °C of night temperature increase, similarly for wheat and barley, causing a grain yield reduction of ca. 4% per °C. An accelerated development under high night temperatures led to a shorter effective grain filling period, reducing the final grain weight. The lack of consistent impact on source availability between crops and seasons, measured as senescence and stem water soluble carbohydrates, as well as a similar impact in magnitude and direction on individual grain weight for different grain positions along wheat or barley spikes, suggest that the negative effects of warm nights on grain weight were directly related to processes within the grain itself. 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. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Serrago, Roman Augusto. 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: Dreccer, M. Fernanda. The University Of Queensland; 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. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

The aim of this study was to analyse (i) the crop attributes that determine flowering time (i.e. final leaf number, FLN; and phyllochron, Phy), (ii) the dynamics of tiller appearance and (iii) the synchrony between leaf and tiller appearance in wheat and barley plants exposed to waterlogging. Two experiments were carried out in pots, in which wheat and barley cultivars were exposed to five waterlogging treatments, during different periods throughout the crop cycle, from emergence to maturity. The appearance of leaves and tillers on the main stem was measured twice a week in labelled plants. Waterlogging from emergence to flag leaf appearance significantly delayed time to flowering. The delay was greater when waterlogging occurred at the beginning of tillering, lengthening the period from emergence to flowering 24 % (13–15 days) in barley and 10–15 % (6–10 days) in wheat, as compared to control. Phy was the main attribute explaining the delay in flowering, as FLN was not altered. Waterlogging during the early stages of development reduced tiller appearance rate (TAR) in both species, but this effect was partially counterbalanced by a lengthening of the tillering phase, so the effect on final tiller number at maturity was limited. In conclusion, the exposure of wheat and barley to waterlogging during early stages of development delayed time to flowering and reduce TAR in both species. Waterlogging during more advanced crop stages produced slight effects on tillering dynamics, which would indicate that waterlogging affected structure generation more than mortality.

Water shortage, caused by large variations in the amount, frequency and timing of rainfall during the crop cycle, is one of the major abiotic stresses limiting crop production. In this context, environmental variability represents a significant challenge for farmers as optimal management practices vary from season to season. The aim of this study was to optimize wheat (Triticum aestivum L.) management practices considering rainfall variability in the West sandy Pampas of Argentina. This region is characterized by a high annual rainfall variability with predominant summer rainfall and probable deficits during winter and early spring in analogy with many other regions around the world. Two commercial cultivars, commonly used by farmers, with different time to flowering (LF: late flowering; EF: early flowering), under three initial soil water conditions (well-watered, moderately-watered and dry conditions) at three sowing dates were simulated with CERES-WHEAT for a series of 39 years. Wheat yield was higher for the LF than the EF cultivar under average (LF = 5437 vs. EF=5112 kg ha−1) and no-water restriction years (LF = 7915 vs. EF=6956 kg ha−1), while the opposite was observed in dry years (EF = 4128 vs. LF=3255 kg ha−1). Reductions in grain yield were associated with reductions in grain number, mainly explained by a lower partitioning to reproductive organs, principally limited by water shortage. The LF cultivar used more water than the EF cultivar before anthesis depleting soil water reserves (p

Aims Negative effects of waterlogging on wheat and barley yield are expressed mainly through reductions in grain number per plant. Physiological traits associated with reductions in grain number of wheat and barley plants waterlogged at different growth stages during preanthesis were evaluated. Methods Two pot experiments were carried out under contrasting environments, where wheat and barley plants were exposed to waterlogging at four different ontogenic stages, from emergence to anthesis. Physiological traits associated with grain number determination were measured at anthesis and at physiological maturity. Results Waterlogging occurring during the spike growth period significantly reduced grain number per plant up to 70% in wheat and 60% in barley. Reductions in grain number per plant in wheat were mainly related to decreases in grain number per spike, while in barley grain number reductions were related to decreases in the number of spikes. In both species waterlogging produced spike growth reductions that were associated with reductions in the number of fertile florets per spike, without effects on fruiting efficiency. Conclusions The effect of waterlogging on grain number per plant differed between wheat and barley. Waterlogging reduced grain establishment in wheat by affecting the growth capacity of spikes and, consequently, reducing the number of fertile florets per spike. In barley, the main effect of waterlogging was through reductions in the number of spikes per plant, without significant changes in grain number per spike. These differences between species open ways to analyze the impact of different management practices (i.e. nitrogen fertilization, plant population) as alternative to mitigate the negative effect of waterlogging on grain yield. Fil: de San Celedonio, Romina Paola. 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. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Abeledo, Leonor Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina 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. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

The aim of this study was to identify the critical period for yield determination in buckwheat by applying successive shading periods (of 14-days duration) throughout the crop cycle, from nine days after emergence to crop maturity. Experiments were carried out under field conditions during the 2017 and 2018 growing seasons. The critical period was defined as the interval when crop yield was significantly reduced by the shading treatments. This period extended from 74 °C days after the first open flowers to the first brown fruits stage (i.e. 390 °C days duration). Aerial biomass and its partitioning to the achenes (i.e. harvest index) were also reduced by shading. Achene number was reduced in a similar way to that of yield, and crop yield was highly associated with this yield component, while the shading treatments did not affect achene weight. The main cause of achene number reduction was the lower number of achenes per raceme, as the number of racemes was not affected. It is possible to speculate that radiation restriction imposed during the critical period could have increased floret mortality and thereby the number of achenes per raceme. However, further studies are required to determine the causes of reductions in the number of achenes per raceme during the critical period.

Aims: Wheat and barley plants exposed to waterlogging reduced their growth, but the final impact on grain yield depends on the capacity of the plant to recover after stress. The aim of this study was to evaluate shoot and root biomass accumulation in wheat and barley plants during waterlogging events applied at different stages during preflowering and after stress removal. Methods: Wheat and barley plants were waterlogged for 15–20 days at four consecutive periods during phenological cycle from emergence to flowering. Results: Waterlogging produced a delayed effect on shoot biomass, as biomass reductions were detected 20 days after waterlogging was released. The highest relative reductions of shoot biomass (60% in wheat and 68–74% in barley regarding control) occurred when waterlogging was applied early in the cycle (from emergence to tillering). Waterlogged plants showed a remarkable capacity to recover from early waterlogging (reaching similar shoot biomass as control plants at flowering), but recovery capacity decreased when waterlogging occurred later in the phenological cycle. For both species green leaf area and photosynthetic rate were reduced and water soluble carbohydrates increased when waterlogging ended, however the general trend showed values at flowering similar to the control plants. The impact of waterlogging on roots was generally higher than the one on shoots and the effect was detected immediately after treatment. The root system capacity to recover after waterlogging was lower than the one for shoots, and was higher in barley than in wheat. Conclusions: Waterlogging first damaged root biomass while effects on shoots were delayed. Shoot recovery at flowering was possible for waterlogging events previous to stem elongation, but root recovery was lower, especially for wheat. Fil: de San Celedonio, Romina Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina 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; Argentina Fil: Mantese, Anita Ida. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Botánica General; 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. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina

Grain yield variations in bread wheat and two-row barley are better explained by changes in grain number (GN) than mean grain weight. However, the strategies for building GN are different in both species because in two-row barley the variations in GN are more frequently related to the number of spikes m−2, due to its higher tillering capacity than wheat, whereas in bread wheat both grain number spike−1 and the number of spikes m−2 contribute to the establishment of GN. The higher tillering capacity and leaf area index at the beginning of the crop cycle in two-row barley allows a higher radiation accumulation than in bread wheat. We hypothesize that the higher early vigor of two-row barley, associated with its greater leaf area exposure relative to wheat, represents an initial advantage that is capitalized at the end of the cycle as higher biomass accumulation driven by a larger GN and consequently higher grain yield. The main objective of this work was to compare different physiological traits of bread wheat and two-row barley growing together under different temperature and radiation conditions. We evaluated two genotypes of each species, with similar phenology, growing under four different environments without water or nutritional deficiencies. Numerical yield components, biomass, radiation interception and harvest index were measured. Despite no differences being observed between genotypes of bread wheat and two-row barley in terms of total grain yield and total grain number when exposed to different environments, each species had a different strategy for establishing the final yield. Although two-row barley showed initial advantages in radiation interception, bread wheat genotypes accumulated more intercepted photosynthetic active radiation (iPAR) and used it in a more efficient way than two-row barley, thus allowing a higher biomass accumulation. Both species showed a reduction in grain weight due to increases in mean night and high temperatures. Grain weight reductions were higher in bread wheat than in two-row barley, and were directly associated with shortening of the duration of grain filling without consequences for the grain-filling rate. This suggested a direct effect of temperature on grain development rather than a growth limitation due to a lack of source. Fil: Alvarez Prado, Santiago. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina Fil: Gallardo, Jose M.. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina Fil: Kruk, Betina Claudia. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina 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. Universidad de Buenos Aires. Facultad de Agronomía; Argentina

Predicting phenology, in particular heading time, is crucial to avoid and/or minimize risk of damage offrost, drought and high temperatures during grain filling. Although some of the major genes controllingdevelopment, associated with photoperiod and vernalization responses, were identified, the associationbetween the molecular characterization of those genes and photoperiod sensitivity, vernalizationresponses and earliness per se has been poorly studied. The present study was conducted to determinethe effects of photoperiod and vernalization genes (and their allelic combination characterized by molecularapproach) on heading time and its correlation with the phenological parameters determined by fieldexperiments in a wide range of Argentine bread wheat commercial cultivars. Additionally, the associationbetween photoperiod and vernalization responses with earliness per se was analyzed. Molecularcharacterization showed that most of the commercial Argentine wheat cultivars available in the marketcorrespond to spring growth habit with dominant insensitive photoperiod alleles (SI) followed by springhabit sensitive to photoperiod (SS), while winter insensitive (WI) habit represented a minority group. Allgenotypes included in the present study (even those classified as SI and WI) were photoperiod sensitivewhen that trait was quantified from a physiological analysis as the slope of the relationship betweenduration of a particular phase and mean photoperiod sensed during the period between emergence andheading. SI showed lower photoperiod sensitivity than SS and WI, without clear differences betweenboth later groups. In all cases, photoperiod sensitivity was the main attribute that determined the differencesin time to heading even when vernalization requirements were not completely fulfilled in the WI.The genotypes with different photoperiod and vernalization allele combinations showed a wide range ofduration of earliness per se. However, differences in earliness per se did not show any particular associationwith the groups classified by molecular markers for photoperiod and vernalization. The informationincluded in the present study can be used to build a gene-based model for predicting phenology. However,the variations in photoperiod and/or vernalization sensitivity within the same allelic combinationcould still determine mismatching in the prediction of the models based on Ppd-1 and Vrn-1 genes. Fil: Gomez, Dionisio Tomas. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Córdoba. Estación Experimental Agropecuario Marcos Juarez; Argentina Fil: Vanzetti, Leonardo Sebastián. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Córdoba. Estación Experimental Agropecuario Marcos Juarez; Argentina Fil: Helguera, Marcelo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Córdoba. Estación Experimental Agropecuario Marcos Juarez; Argentina Fil: Lombardo, Lucio Andrés. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Córdoba. Estación Experimental Agropecuario Marcos Juarez; Argentina Fil: Fraschina, Jimena. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Córdoba. Estación Experimental Agropecuario Marcos Juarez; 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; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina

Background and aims Crop tolerance to waterlogging depends on factors such as species sensitivity and the stage of development that waterlogging occurs. The aim of this study was to identify the critical period for waterlogging on grain yield and its components, when applied during different stages of crop development in wheat and barley. Methods Two experiments were carried out (E1: early sowing date, under greenhouse; E2: late sowing date, under natural conditions). Waterlogging was imposed during 15-20 days in 5 consecutive periods during the crop cycle (from Leaf 1 emergence to maturity). Results The greatest yield penalties occurred when waterlogging was applied from Leaf 7 appearance on the main stem to anthesis (from 34 to 92% of losses in wheat, and from 40 to 79% in barley for E1 and E2 respectively). Waterlogging during grain filling reduced yield to a lesser degree. In wheat, reductions in grain number were mostly explained by reduced grain number per spike while in barley, by variations in the number of spikes per plant. Conclusions The time around anthesis was identified as the most susceptible period to waterlogging in wheat and barley. Exposing the crop to more stressful conditions, e.g. delaying sowing date, magnified the negative responses to waterlogging, although the most sensitive stage (around anthesis) remained unchanged. Fil: de San Celedonio, Romina Paola. 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: 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; Argentina 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

Highlight Long days during post-flowering postpone elongation and active growth of dominant pods within a node, which extends flowering and allows pod set at usually dominated positions., In soybean, long days during post-flowering increase seed number. This positive photoperiodic effect on seed number has been previously associated with increments in the amount of radiation accumulated during the crop cycle because long days extend the duration of the crop cycle. However, evidence of intra-nodal processes independent of the availability of assimilates suggests that photoperiodic effects at the node level might also contribute to pod set. This work aims to identify the main mechanisms responsible for the increase in pod number per node in response to long days; including the dynamics of flowering, pod development, growth and set at the node level. Long days increased pods per node on the main stems, by increasing pods on lateral racemes (usually dominated positions) at some main stem nodes. Long days lengthened the flowering period and thereby increased the number of opened flowers on lateral racemes. The flowering period was prolonged under long days because effective seed filling was delayed on primary racemes (dominant positions). Long days also delayed the development of flowers into pods with filling seeds, delaying the initiation of pod elongation without modifying pod elongation rate. The embryo development matched the external pod length irrespective of the pod’s chronological age. These results suggest that long days during post-flowering enhance pod number per node through a relief of the competition between pods of different hierarchy within the node. The photoperiodic effect on the development of dominant pods, delaying their elongation and therefore postponing their active growth, extends flowering and allows pod set at positions that are usually dominated.

Increases in crop yields are important to ensure food supply for humanity. Global yield trends have been analyzed considering public national average data, mainly for cereals but not for rapeseed. As rapeseed and wheat compete for land in crop rotation, it is also important to know how the rapeseed-to-wheat yield ratio is modified in different environments so as to make rapeseed an attractive alternative for farmers around the world. The present study analyzed historical records of rapeseed from FAO determining yield stability trends over the last 40yr, as well as rapeseed competitiveness compared to wheat. Twelve countries representing a wide range of environments and farming systems were taken into account. Regressions were fitted to the rapeseed yield/time relationships and residuals of these regressions were used to evaluate trends in yield stability. Results showed a global rapeseed yield gain of 27kgha -1yr -1 along the past 40yr, although fluctuating among decades. In relative terms to 1970, world rapeseed yield increased 3.4%yr -1. Yield gain in different countries varied from 15 to 40kgha -1yr -1, exhibiting linear, bi- or tri-linear yield trends. Opposite yield trends were observed for Chile and the UK, with sustained yield gain for the former and leveling off for the latter since the mid 1980s. This does not seem to be related to the supply of environmental resources (both countries yielding >3000kgha -1). A high variability was detected in national yields (0-750kgha -1 or 0-60% of yield) and yield stability did not increase over the last 40yr in any country. Rapeseed and wheat yields, expressed in relative terms to their values for 1970, increased in a similar proportion over the last four decades. Global rapeseed-to-wheat ratio ranged 40-60% over the last 40yr, but rapeseed yields can increase up to 80-100% with respect to wheat in poor environments for wheat (4000kgha -1). It was concluded that rapeseed yields have increased steadily in the last 40yr in most studied countries, the yield gain was not accompanied by greater yield stability, and rapeseed competitiveness compared to wheat is at least 40-50% in environments with good supply of resources. © 2011 Elsevier B.V. Fil: Rondanini, Deborah Paola. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina Fil: Gomez, Nora Valentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cultivos Industriales; Argentina Fil: Agostini, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cultivos Industriales; 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; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina

In wheat, stem elongation phase (SEP) duration is critical for grain number (GN) per unit of area determination, as it is the phase in which the spikes grow. Lengthening SEP, for instance by photoperiodic sensitivity, without altering the cycle to anthesis (AT) has been proposed as an alternative way to increase spike dry weight, and in turn GN. As most works supporting this idea have modified only SEP by artificial manipulation (e.g. photoperiod extensions), it is relevant to evaluate this hypothesis in populations segregating for this attribute in natural conditions. The aim of this work was to analyse the variability in SEP duration relative to AT in two F4 populations; in order to select contrasting phenotypes to evaluate the impact of this attribute on grain yield components and to analyse the selection response of this attribute. These segregating populations (Las Rosas INTA × Triguero 230 (A) and Klein Estrella × ProINTA B. Alazan (B)) were derived from parental lines with similar flowering time but different relative duration of their pre-anthesis phases. Two field experiments with previous vernalization treatment in cool chamber were carried out. In 2006, F4 populations were characterized and from one of them (population B, which presented higher variability) four groups were selected, which presented contrasting phenotypes in the attribute under study. Progenies of these groups (F5), together with remnant F4 full-sib of each one, were studied during 2007. Grain yield per plant was higher, due to GN increases, when duration of the SEP was lengthened. However, selection response to longer SEP with similar cycle to AT could not be found, possibly as the result of a high environmental influence on this attribute. The phenotypic variability evidenced in this attribute was not clearly associated with major adaptation genes evaluated (i.e. Ppd and/or Vrn), suggesting that other minor genes could be associated.

The present work analysed whether grain weight is affected by changes in source:sink ratio in twenty-four durum wheat cultivars from Italy and Spain released through the 20th century grown under Mediterranean conditions. For this purpose, a field experiment was conducted during the 2002 growing-season in southeastern Spain. Sink strength was modified by removing half of the spikelets, of one side of the spike, one week after anthesis. Spikelet trimming had different effects on both average grain weight and individual grain weight at different positions within the spike. While old cultivars did not respond positively to spikelet trimming, and appear to be mainly sink-limited, intermediate and modern cultivars from Spain increased their grain weight in response to sink reductions, suggesting co-limitation by the sink and source. On the contrary, grain weight of intermediate and modern Italian cultivars remained relatively unchanged suggesting a sink-limitation to grain yield. The differential response to source-sink manipulations observed between Italian and Spanish cultivars could be attributed to their different genetic background, which determines their level of adaptation to harsh Mediterranean environments. Fil: Rharrabti, Y.. Universidad de Granada; España 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 Fil: Martos, V.. Universidad de Granada; España Fil: García Del Moral, L.F.. Universidad de Granada; España

Nitrogen (N) fertilization plays a central role for improving yield in wheat and high N use efficiency (NUE) is desired to protect ground and surface waters. Several studies showed that sulfur (S) fertilization may increase NUE, but no attempts have been made to explain whether this increase is due to greater recovery efficiency (RE), an enhanced internal efficiency (IE) or by an improvement of both efficiencies. The aim of this study was to analyze the effects of different N and S fertilizer rates, and their interaction on N uptake, its partition at maturity, NUE and its main components. Field experiments were carried out during two consecutive growing seasons in the Argentinean Pampas using a single bread-wheat genotype grown under different combinations of N and S fertilizer rates. Additional experiments were performed in farmer fields using N and S fertilization evaluating different genotypes in order to analyze the components of NUE in other environmental conditions. Plant N uptake increased linearly in response to N addition until rates of ca. 80 kg N ha −1 . Sulfur addition showed no effect at the lowest N fertilizer rate, but N uptake was increased when S was applied at the highest N rate, revealing a synergism between both nutrients. At the lowest S rate RE was 42%, and increased to 70% when S fertilizer was added. No changes in IE in response to S fertilization were observed. These results were also observed in farmer field experiments, in genotypes that showed different IE. This study showed that S addition increased NUE mainly by increasing the N recovery from the soil. Thus, the concurrent management of N and S is important for reducing the potential pollution of residual soil nitrate by increasing N recovery from the soil while sustaining high nitrogen use efficiency.

The critical period for yield determination in barley ( Hordeum vulgare L.) is situated in the pre-heading phases. During the latest part of the critical period one of the most important yield components (i.e. the number of grains per spike) is set in two- and six-rowed barley. In wheat, much is known about the role of the spike in assimilate acquisition for the establishment of grains per spike, but not in barley. This paper evaluates how biomass partitioning between vegetative and reproductive organs impacts floret development and primordia survival in response to radiation during different periods in the crop cycle, in barley lines. Field experiments were carried out using two- and six-rowed near isogenic barley lines differing only in spike type. Shading treatments were applied at different periods during the crop cycle (from 60 to 15 days before and after heading) reducing the intercepted radiation (ca. 70%). Dynamics of floret primordia initiation and mortality and of floret development for different spikelet positions along the spike were measured, and biomass partitioning between vegetative and reproductive structures was calculated. Pre-heading shading reduced fertile florets per spike ( P The amount of assimilates partitioned to the spike at heading affected the number of fertile florets per spike in both barley types. However, when spike biomass at heading was corrected by nitrogen concentration, the fitness of the relationship did not improve in relation to the first one. In relative terms, radiation restrictions during the immediate pre-heading phase increased the amount of biomass partitioned to the growing spike.

In barley no studies have attempted to pinpoint the critical period for grain number determination, and it is frequently stated that the critical period is similar to that of wheat. However, there are important differences between the species and among barley genotypes (i.e. two- and six-rowed types) suggesting that this assumption requires testing. The objectives of this paper were (i) to determine the critical period for grain number determination in two- and six-rowed barleys, and (ii) to identify which yield components were more sensitive to changes in incident radiation during that period. Two field experiments were conducted using two pairs of near isogenic lines differing only in the spike type. Shading was imposed at different periods throughout the crop cycle (from 60 days before heading to 15 days after) to reduce incident solar radiation approximately 70%. The critical period for grain number determination tended to be slightly earlier in two- (ca. between 40 and 10 days before heading) than in six-rowed barleys (ca. between 30 days before heading until that stage). In terms of the external phenology, the beginning of the critical period for setting grains was 10 days after the beginning of stem elongation, and 10 days before flag leaf appearance in two- and six-rowed lines, respectively. Changes in the number of grains per unit area were correlated with crop growth rate during the critical period for yield determination.

The critical period for grain yield determination has not been determined for triticale. We aimed to identify it, determining the relative importance of both the major yield components and the dry matter acquisition by the spikes at anthesis. A field experiment was carried out with two triticales, differing in tillering capacity, subjected to shading treatments at five different timings from early tillering to maturity. Results showed that reductions in grain yield were more significant when shading was imposed during 3 weeks before and 1 week after anthesis. Reductions in grain yield by shading treatments were associated with lower number of grains per m2 more than with changes in the average grain weight. Reductions in grains per m2 were due to reductions in the number of fertile florets per spike, affecting grains per spike. The assimilate acquisition by the spikes during the critical period was a key determinant of floret survival. Grain number per m2 was related with photothermal quotient during 30 days before anthesis and spike dry weight at anthesis, though the goodness of the prediction compared with wheat, was lowered by poorer grain setting percentage.

A better understanding of responsiveness of time to anthesis to water stress in triticale and wheat might help to explain their differences in performance under stress and to identify which attributes or components of time to anthesis are most affected. Three experiments were carried out during the 2004 and 2005 growing seasons to (i) evaluate genotypic variability in phenology responsiveness to drought in triticale and to (ii) explore the variation in the duration of pre-anthesis phases occurring before and after the onset of stem elongation as well as their responsiveness to water stress. Important variation was found among triticale cultivars on time to anthesis, allowing classification of cultivars into long, intermediate and short cycle. Differences in the duration of the stem elongation phase (i.e. from terminal spikelet initiation (TS) to anthesis (ANT)) were as high as 200 °Cd for cultivars with similar time to flowering. Although water stress reduced the time to anthesis (in average by ca. 125 °Cd), cultivars showed a differential responsiveness to drought in phases occurring before or after TS. Some cultivars that were highly sensitive to drought in the emergence (Eme)–TS phase were insensitive in the phase TS–ANT and vice-versa. Water shortage tended to reduce the grain filling period and was most evident when a Mediterranean environment treatment was simulated.

Spike growth during the stem elongation phase is critical for the establishment of the number of fertile florets (FF). A longer period of spike growth would lead to an increased number of FF and grains in wheat. The aim of this study was: (i) to analyze in three different commercial cultivars the impact of a photoperiod extension (NP + 10) during the stem elongation phase on the number of FF and (ii) to determine whether the photoperiod extension effect might be reversed by increasing the availability of assimilates by a direct modification of the source/sink ratio at booting. The number of FF per spike was reduced by extended photoperiod in the experiment sown in an optimum date, though no differences were observed when sown much later, probably due to the poor environmental conditions of a spring sowing. The detrimental effect of lengthening the photoperiod on the number of FF per spike was reversed by trimming the spike at booting in two of the three cultivars analyzed. This reversion, together with the effect of photoperiod extension on FF associated with similar effects on spike growth, may be considered as a confirmation that, at least in part, the detrimental effects of photoperiod extension on FF would be mediated by changes in assimilate supply to the developing florets. No differences were observed between photoperiod treatments on the onset of rapid spike growth; however, extended photoperiod reduced the duration of spike growth phase without differences in the maximum rate of spike growth in two of the three cultivars. Although a positive association was found between the number of FF and spike dry weight at anthesis, differences among cultivars were observed in this relationship, suggesting different carbohydrates partitioning (i.e., FF per unit of spike weight) among them.

The stem elongation phase in wheat [Triticum aestivum (L.)] is considered critical for yield determination. A longer duration of this phase could hypothetically increase grain set and therefore yield. Genetic variation in the relative duration of the stem elongation phase having been reported, the aim was to pinpoint whether this variability was associated with sensitivity to photoperiod, vernalizing temperatures or to differences in intrinsic earliness. Pairs of cultivars identified as having different duration of the stem elongation phase (from the appearance of the first visible node to anthesis) were grown under natural (short) or extended photoperiod, with or without vernalization. Variability in the duration of this phase, in the cultivars analysed, was related to different sensitivity to photoperiod, while differences in the previous phases were related to sensitivity to both photoperiod (though different to the sensitivity of the following phase) and vernalization.