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Ferrante A.,University of Lleida | Savin R.,University of Lleida | Slafer G.A.,University of Lleida | Slafer G.A.,Catalonian Institution for Research and Advanced Studies
Journal of Experimental Botany | Year: 2010

In Mediterranean durum wheat production, nitrogen (N) fertilization may be important to stabilize and increase yields. Wheat yield responses to N fertilization are usually related to grains per m2, which in turn is the consequence of processes related to floret development (floret initiation followed by floret death/survival) during stem elongation. The literature is rather scarce in terms of the relevance of floret developmental dynamics, determining the final number of grains in general terms and in particular regarding responsiveness to N. The aim of this study was to determine whether durum wheat responses to N under different water regimes are related to the dynamics of development of floret primordia to produce fertile florets. During the 2006-2007 and 2007-2008 growing seasons, experiments with a factorial combination of two N levels (0 and 100 or 250kg N ha-1) and two levels of water availability (rainfed and irrigated) were carried out (although the water regime was only effective in the second season). The response of yield was largely a consequence of that in grain number per spike. Floret initiation was similar for both N levels in each experiment and water regime, for which the survival of a higher proportion of initiated florets was critical in the response of the crop. The diminished rate of floret abortion during the late part of stem elongation in response to N was associated with a slightly accelerated rate of floret development which allowed a higher proportion of the primordia initiated to reach the stage of fertile floret by flowering. © 2010 The Author.


Ferrante A.,University of Lleida | Savin R.,University of Lleida | Slafer G.A.,University of Lleida | Slafer G.A.,Catalonian Institution for Research and Advanced Studies
Field Crops Research | Year: 2015

Future increases in grain number may be achieved through improving fruiting efficiency (FE; grains set per unit spike dry weight at anthesis). In recent experiments it was found a negative relationship between the average weight of the grains and FE. The objective of this paper was to determine whether this negative relationship was constitutive (i.e. the increased FE caused all grains to be smaller) or resulted from the increased proportion of grains of smaller potential size. Four experiments, involving 8 different environmental conditions, were carried out during two consecutive growing seasons (2008-2009 and 2009-2010) in which two durum wheat cultivars contrasting in FE and average grain weight were compared. In these conditions we determined FE and carried out a comprehensive study analysing in detail the weights of each individual grain along each of the spikelets. Averaging all experimental conditions, there was a negative relationship between average grain weight (GW) and fruiting efficiency (FE). Donduro with low FE produced in average heavier grains than Vitron. However, when considering individual grains there were, in general, no differences in GW. Therefore, the negative relationship between average grain weight and FE would not be constitutive, and would mostly represent the increase in the proportion of distal grains within the spikelets or of grains from apical spikelets as a consequence of an increased FE, reducing the average size of the grain but mostly unaffecting the size of particular grains. This provides further and stronger support to the idea of using FE as a criterion to further raise yield potential in wheat breeding programmes. © 2015 Published by Elsevier B.V.


Ferrante A.,University of Lleida | Savin R.,University of Lleida | Slafer G.A.,University of Lleida | Slafer G.A.,Catalonian Institution for Research and Advanced Studies
Journal of Experimental Botany | Year: 2013

Survival of floret primordia initiated seems critical for the determination of grain number and yield in wheat, and understanding what determines floret mortality would help in the development of more robust physiological models of yield determination. The growth of the juvenile spikes has been frequently considered the determinant of grain number, implying that floret development would depend on resource availability and that the onset of floret death would be related to spike growth. However, this model has been recently challenged from a study concluding that floret death started when the most advanced floret primordia reached a particular developmental stage. As the few previous studies on this relationship involved photoperiod treatments which affect both floret development and the onset of spike growth, conclusions cannot be considered mechanistic. This comprehensive study analysed in detail floret development in wheat as affected by resource availability (mainly soil nitrogen levels) and found that the onset of floret death may occur when development of the most advanced florets ranged from stages 5 to 9 and that the average and standard deviation of floret developmental stage coinciding with the onset of floret death was not related to the level of availability of resources. These results provide further support to the model relating the onset of floret death with the initiation of active growth of the juvenile spike in which florets are developing. © The Author(2) [2013].


Ferrante A.,University of Lleida | Savin R.,University of Lleida | Slafer G.A.,University of Lleida | Slafer G.A.,Catalonian Institution for Research and Advanced Studies
Journal of Experimental Botany | Year: 2013

Wheat yield depends on the number of grains per square metre, which in turn is related to the number of fertile florets at anthesis. The dynamics of floret generation/degeneration were studied in contrasting conditions of nitrogen (N) and water availability of modern, well-adapted, durum wheats in order to understand further the bases for grain number determination. Experiments were carried out during the 2008-2009 and 2009-2010 growing seasons at Lleida (NE Spain). The first experiment involved four cultivars (Claudio, Donduro, Simeto, and Vitron) and two contrasting N availabilities (50 kgN ha-1 and 250 kgN ha-1; N50 and N250) while experiment 2 included the two cultivars most contrasting in grain setting responsiveness to N in experiment 1, and two levels of N (N50 and N250), under irrigated (IR) and rainfed (RF) conditions. In addition, a detillering treatment was imposed on both cultivars under the IR+N250 condition. The number of fertile florets at anthesis was increased by ~30% in response to N fertilization (averaging across treatments and spikelet positions). The effect of N and water availability was evident on floret developmental rates from the third floret primordium onwards, as these florets in the central spikelets of all genotypes reached the stage of a fertile floret in N250 while in N50 they did not. In this study, clear differences were found between the cultivars in their responsiveness to N by producing more fertile florets at anthesis (through accelerating developmental rates of floret primordia), by increasing the likelihood of particular grains to be set, or by both traits. © 2012 The Author. Published by Oxford University Press [on behalf of the Society for Experimental Biology]. All rights reserved.


Ferrante A.,University of Lleida | Savin R.,University of Lleida | Slafer G.A.,University of Lleida | Slafer G.A.,Catalonian Institution for Research and Advanced Studies
Field Crops Research | Year: 2012

Yield differences among wheat cultivars and its responsiveness to resource availability are usually related to grain number per m 2, and further increases in grain number are required, but now beyond differences in time to anthesis and plant height (that are mostly optimised in traditional growing regions). The objective of this paper was to determine and quantify differences in yield physiology between different modern well adapted durum wheats grown in contrasting conditions (in addition we also tested if a higher amount of resources due to removal of competition could affect yield through the same determinants to nitrogen (N) availability).Four experiments were carried out during two growing seasons (2008-09 and 2009-2010); all in all under eight different growing conditions (Gc1-Gc8). In the first season four different modern cultivars were used and in the second season we selected the two highest-yielding cultivars, which differed in their responses to N in terms of spike fertility.Yield was closely related to biomass and N uptake due to both growing conditions and genotypic effects in all experiments. The existence of variation among modern cultivars in these yield determinants is relevant as further increases in yield must be achieved beyond further increases in partitioning. Yield differences among cultivars were based on their differences in grains per m 2 or average grain weight depending on which cultivars were compared. Overall grain number was related to spike dry weight at anthesis, and no evidences were found for a direct involvement of N in grain number determination, beyond the general effect of N availability on spike dry matter. However, this overall effect was mainly driven by growing conditions whilst differences between genotypes seemed associated with either spike dry weight at anthesis or fruiting efficiency, which varied significantly between cultivars. Interestingly, grain weight was consistently higher in the cultivars with lower fruiting efficiency than in cultivars maximising the number of grains set per unit of spike dry weight at anthesis suggesting a constitutive component for the commonly reported negative relationship between grain weight and grain number. In conclusion, the main differences in yield between modern, well adapted wheats were related to their biomass and N uptake and to the sink-strength during post-anthesis, being this strength increased either by having more grains or grains of potentially greater size, depending on the specific cultivar and as a consequence of a trade-off between fruiting efficiency and grain size. © 2012 Elsevier B.V.


Marti J.,University of Lleida | Slafer G.A.,University of Lleida | Slafer G.A.,Catalonian Institution for Research and Advanced Studies
Field Crops Research | Year: 2014

It is frequently assumed that durum wheat is more tolerant to stress than bread wheat. Unfortunately few research papers compare the performance of both species side-by-side under a wide range of environments in field conditions. We aimed to compare durum and bread wheat performance in a field study under contrasting treatments of water and nitrogen during three experimental seasons. In addition we compiled a comprehensive database with data from field experiments in which both species were grown in the same field conditions. A cross-over interaction of yield from bread vs. durum wheat was found, but oppositely to the hypothesis, bread outyielded durum wheat in the low-yielding conditions while durum wheat tended to have higher potential yield. We then divided the database in decades in which the cultivars were released and found that in the 1960s bread wheat outyielded durum wheat in almost any comparison whilst in the 2000s durum wheat outyielded bread wheat in most comparisons. Grain weight was constitutively higher in durum than in bread wheat, likely associated with a lower fruiting efficiency in the former; but in both types of wheat grain number per m2 was the component responsible for yield sensitivity to environmental changes. Differences in yield were also related to differences in water and nitrogen use efficiencies: under low-yielding conditions bread wheat was consistently more efficient than durum wheat and under high-yielding conditions durum wheat was more efficient. © 2013 Elsevier B.V.


Cossani C.M.,University of Lleida | Slafer G.A.,University of Lleida | Slafer G.A.,Catalonian Institution for Research and Advanced Studies | Savin R.,University of Lleida
Field Crops Research | Year: 2011

Under Mediterranean environments, farmers usually prefer to sow barley rather than wheat as it is generally believed that barley yields more under stressful conditions. As terminal stresses such as high temperature and water are common constraints in Mediterranean regions, higher grain weight stability may confer a clear advantage in order to maintain higher yields. The objective of the present study was to compare the stability in terms of grain weight and its components for barley, bread wheat, and durum wheat, exploring a wide range of nitrogen and water availabilities in experiments conducted in a Mediterranean region. Grain weight ranged from 23.8 to 47.7mg grain -1, being higher for durum wheat than barley and bread wheat. Durum wheat presented higher variability both in maximum grain filling rate and duration of grain filling period than bread wheat or barley. The three species responded similarly in terms of grain nitrogen content to changes in the environmental conditions explored. It is concluded that in terms of grain weight barley is as stable as bread wheat. However, durum wheat presented a lower stability than barley and bread wheat. © 2011 Elsevier B.V.


Ordonez R.A.,University of Lleida | Savin R.,University of Lleida | Slafer G.A.,University of Lleida | Slafer G.A.,Catalonian Institution for Research and Advanced Studies
Field Crops Research | Year: 2015

A major aim in breeding programs is to improve nitrogen use efficiency (NUE). The critical level of specific leaf nitrogen (SLNc) maximising growth and yield is a relevant trait influencing NUE. The relationship between growth or yield and SLN is hyperbolic indicating that levels of SLN higher than the critical would tend to decrease NUE. It has been recently proposed that maize breeding may profit of this relationship by phenotyping SLN and selecting for genotypes with SLN=SLNc (SLNSLNc would bring about high yields but at the expense of low NUE); being the SLNc=1.5gNm-2. For this proposal to be realistic, genotypic variation in SLNc should be negligible. We aimed to determine the degree of genetic variation in SLNc in a range of modern maize hybrids. For this purpose, we carried out four field experiments with 11 contrasting maize hybrids grown under fertilized (200kgNha-1) or unfertilized conditions in each of the four experiments. At silking, leaf area and N concentration of leaves were determined and at maturity, yield and biomass were measured. Analysing the whole dataset together (n=88) we found a very large range of all variables measured and calculated: yield varied between c. 6 and c. 18Mgha-1 and SLN from c. 0.7 to c. slightly more than 2.5gNm-2. Within that context we found a significant bi-linear regression between yield and SLN (p<0.001). Analyzing each hybrid individually we did find substantial variation among hybrids in SLNc, ranging between c.1.0 and c.s1.93gNm-2. The variation was also substantial calculating SLNc with an alternative methodology and if leaf N content instead of SLN were used as independent variable. Genotypic differences in SLNc were positively related to N uptake but unrelated to other traits for which hybrids varied, including yield potential. Additionally, genotypes with low SLNc show a tendency for a better NUtE. We concluded that it does not seem appropriate to phenotype for a particular value of SLNc as any particular threshold might bring about selected lines with either a yield potential lower than possible and/or with a relatively lower than possible NUE. © 2014 Elsevier B.V.


Elia M.,University of Lleida | Savin R.,University of Lleida | Slafer G.A.,University of Lleida | Slafer G.A.,Catalonian Institution for Research and Advanced Studies
Field Crops Research | Year: 2016

Efforts to enhance the yield of wheat require increases in the number of grains per m2 (GN) which depends on spike fertility, i.e. the number of fertile florets or grains per spike. Fruiting efficiency (FE), the number of grains set per unit spike dry weight at anthesis, has been proposed as an alternative trait to improve spike fertility and thus GN. The use of FE in realistic breeding programs requires genetic variation within well-adapted, high-yielding modern cultivars and a lack of trade-off with other yield components. We quantified FE variation within Spanish elite material and determined whether the variation implied trade-offs with spike dry weight or grain weight (GW). Field experiments under contrasting nitrogen conditions were carried out with nine elite genotypes (eight modern cultivars and one advanced line) in which the number of fertile florets and grains were determined for different spikelets and the whole spike. Furthermore, the partitioning of dry matter was investigated at anthesis and maturity. Overall, the yield was strongly related to GN because environmental and genetic factors contributed to this relationship, although as expected for elite material the environmental effect was much greater than the genotype. Environmental effects on GN mainly influenced spike dry weight at anthesis (SDWa) whereas most genotypic differences were due to FE variation. Averaging across environments, the FE was c. 110-170 grains gspike -1. Although some G×E interactions were observed, there was no reversal in ranking between genotypes with extreme FEs across environments, and genotypic differences across environmental conditions were consistent (h 2 =0.46). The relationship between FE and the individual weight of fertile florets tended to be negative, although rather than a constitutive reduction in floret size driving the improvements in FE, this relationship appeared to reflect the increased proportion of smaller grains (distal florets in each spikelet) due to changes in spike fertility. FE was not related to grain weight (either the average of all grains or that of the most proximal grains). Therefore, differences in FE among the elite genotypes did not imply constitutively-linked changes in grain weight. When chaff dry weight was used as a proxy for SDWa to estimate genotypic variation in FE, we observed the consistent underestimation of FE and also changes in the ranking of genotypes. © 2016 Elsevier B.V.

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