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Waterlogging is a stress that affects wheat (Triticum aestivum L.) and barley (Hordeum vulgare L. ssp. distichum) yield. This work aimed at analysing the impact of a waterlogging event during pre‐anthesis (critical period) on yield, its numerical components and their relationships with plant growth rate in wheat and barley. Two pot experiments were carried out under contrasting environmental conditions (early and late sowing date), in which six wheat and six barley cultivars were exposed to control and waterlogging conditions imposed c. 18 days prior to anthesis. Measurements included total above‐ground biomass at the beginning and at the end of the waterlogging treatment and at maturity, when grain yield and its numerical components were also measured. Wheat showed higher yield losses (−76%) due to waterlogging than barley (−49%). Grain yield was explained by both numerical components (the number of grains per plant and grain weight), which better correlated with the relative growth rate of plants during the post‐stress recovery than during the waterlogging period. Plant growth during the recovery period should be targeted as a key factor to estimate yield losses from waterlogging in these cereals. [ABSTRACT FROM AUTHOR]

The use of physiological traits for indirect selection may help to increase wheat yield potential. Fruiting efficiency (FE, grain number per unit of spike dry weight at anthesis −SDWa-) may be an alternative to 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 present paper 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 under different Nitrogen (N) availability at sowing [(i) low – Ni: ca. 50 kg N ha −1 ; (ii) middle −130 kg N ha −1 and (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 stem elongation (200N + SH). The FE showed G × E interaction (year × genotype and genotype × treatment) but it 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 main stem spikes, but the difference among cultivars was maintained. Thus, canopies of the same genotype with 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 FE at plot level and FE in main stems, for all treatments and cultivars, suggesting that sampling the main stem spikes represents the FE at plot level in dense canopies. A G × E cross-over interaction was observed when the sowing was delayed one month (200N + LS) from the optimum date because B19 reached anthesis later 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 for a wide range of SDWa values (from 90 to 188 g m −2 ). The B19, selected as a high FE genotype, showed higher 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, the genotypes with higher FE had more GN under a wide range of environments. Nevertheless, the SDWa and GW were negatively correlated with FE (for SDWa r = −0.73 p < 0.005, without considering 200N + SH; and for GW r = −0.48 p < 0.01 for all treatments or r = −0.75 p < 0.08 for genotypes only). Then, special attention should be given to SDWa and GW when selecting for higher FE in a breeding program. [ABSTRACT FROM AUTHOR]

Warm nights are a widespread predicted feature of climate change. This study investigated the impact of high night temperatures during the critical period for grain yield determination in wheat and barley crops under field conditions, assessing the effects on development, growth and partitioning crop-level processes driving grain number per unit area ( GN). Experiments combined: (i) two contrasting radiation and temperature environments: late sowing in 2011 and early sowing in 2013, (ii) two well-adapted crops with similar phenology: bread wheat and two-row malting barley and (iii) two temperature regimes: ambient and high night temperatures. The night temperature increase (ca. 3.9 °C in both crops and growing seasons) was achieved using purpose-built heating chambers placed on the crop at 19:000 hours and removed at 7:00 hours every day from the third detectable stem node to 10 days post-flowering. Across growing seasons and crops, the average minimum temperature during the critical period ranged from 11.2 to 17.2 °C. Wheat and barley grain yield were similarly reduced under warm nights (ca. 7% °C−1), due to GN reductions (ca. 6% °C−1) linked to a lower number of spikes per m2. An accelerated development under high night temperatures led to a shorter critical period duration, reducing solar radiation capture with negative consequences for biomass production, GN and therefore, grain yield. The information generated could be used as a starting point to design management and/or breeding strategies to improve crop adaptation facing climate change. [ABSTRACT FROM AUTHOR]

Further improvements in wheat yields are critical, for which increases in grain number would be required. In the recent past, higher grain number was achieved through increased growth of the juvenile spikes before anthesis, due to the reduction in stem growth. As current cultivars have already an optimum height, alternatives must be identified for further increasing grain number. One of them is increasing fruiting efficiency (grains set per unit of spike dry weight at anthesis). Fruiting efficiency is the final outcome of the fate of floret development and differences in this trait within modern cultivars would be related to higher survival of floret primordia. Then there are two alternative physiological pathways to improve fruiting efficiency by allowing a normal development of most vulnerable floret primordia: an increased allocation of assimilates for the developing florets before anthesis, or reduced demand of the florets for maintaining their normal development. Both alternatives may be possible, and it might be critical to recognize which of them is the actual cause of differences in fruiting efficiency. When considering this trait in breeding we must be aware of potential trade-offs and therefore it must be avoided that increases in fruiting efficiency be constitutively related to decreases in either spike dry weight at anthesis or grain weight. In this review we described fruiting efficiency and its physiological bases, analyzing genetic variation and considering potential drawbacks that must be taken into account to avoid increases in fruiting efficiency being compensated by other traits. [ABSTRACT FROM AUTHOR]

The understanding of ecophysiological basis of wheat (Triticum aestivum L.) grain yield potential provides a useful framework to complement conventional breeding aimed at achieving genetic gains. This study analyzed the ecophysiological performance of an elite wheat mapping population (105 double-haploid lines derived from two modern cultivars, Bacanora and Weebil, with similar phenology but different and stable combinations of grain number per area unit (GN) and grain weight (GW) resulting in high grain yield) grown in four contrasting high-yielding environments, to determine the most successful strategies to increase grain yield potential. Main effect of environment on grain yield was significant (p < 0.0001) but the genotypic component was larger than genotype × environment interaction (30%). A robust and positive relationship between grain yield and biomass production was observed across all environments (r² > 0.82, p < 0.0001), and relatively high harvest indexes were expressed (0.39-0.51). While GN was clearly the dominant numerical component in terms of association with grain yield (r² > 0.51, p < 0.0001), a wide range in both components (i.e., GN and GW) was observed across all environments. This population represents a valuable resource for prebreeding studies, as the transgressive segregation in physiological and numerical yield components in combination with favorable expression of all agronomic traits could allow a fine phenotyping and mapping to identify key traits and quantitative trait loci linked with grain yield. [ABSTRACT FROM AUTHOR]

Highlights • Late foliar diseases during grain filling reduced yield throughout grain weight. • Higher source-sink ratio lower yield penalties due to late foliar disease infections. • Yield penalties related to late foliar diseases is a complex interaction where the source-sink ratio plays an important role. Abstract 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Diseases reduced yield similarly in old and modern cultivars. • Protein shows change due to the predominance of biotrophic and necrotrophic diseases. • Foliar diseases reduced milling quality parameters more than breadmaking quality. • Quality parameters were more penalized in modern cultivars. • Alveoli and breadcrumbs did not show modifications, agreeing with breadmaking parameters. [ABSTRACT FROM AUTHOR]