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Background and Aims: Barley breeding has increased yield over the last century, but the associated changes in the phenotype are largely unknown. Our aim was to quantify the rate of genetic gain in a collection of Australian barley cultivars representing seven decades of breeding, and the associated changes in the phenotype. Methods: Thirteen barley cultivars were grown in the field at Roseworthy and Mintaro, South Australia, to evaluate shifts in phenology, yield, and its components. A subset of five cultivars was grown under controlled conditions to probe for changes in root traits and nutrient uptake. Results: Grain yield increased at 16.0 ± 5.3 kg ha−1 yr−1 or 0.43 ± 0.15% yr−1 at Roseworthy, where average yield was 3.1 t ha−1. There was no relation between yield and year of registration at Mintaro, where severe, extended frost disrupted reproduction. Changes in phenology with year of registration were not apparent. The main drivers of yield gain were grain number per m2 and harvest index, with a minor contribution of shoot biomass. Root length density, specific root length, root extension rate, and nutrient uptake per cm of root length increased with year of registration. Conclusions: The rate of genetic gain of Australian barley aligned with rates reported for other breeding programs worldwide and compared to 21.0 ± 2.3 kg ha−1 yr−1 for actual yield in Australian farms between 1961 and 2019. Changes in the growth and functionality of the root system highlight the indirect effects of selective pressure for yield and agronomic adaptation. [ABSTRACT FROM AUTHOR]

Owing to the interaction between genotype and environment (G x E), identifying traits to increase wheat yield and grain protein concentration simultaneously or increasing one without affecting the other remains a challenge. Phenotypic plasticity is an insightful perspective to understand G x E. To explore the relations of wheat yield and grain protein concentration in response to N input and its physiological basis from the perspective of phenotypic plasticity. We established a factorial experiment combining 14 winter wheat cultivars and four N fertilization rates (0, 45, 90 and 135 kg ha−1) in eight environments. We analyzed the interaction of cultivar and N combining a phenotypic plasticity framework and a three-phase model of grain yield and protein response to N input. The phases are: phase I, N supply limits both yield and grain protein; phase II, N supply limits grain protein but not yield; and phase III, N supply does not limit yield or grain protein concentration Grain yield plasticity was positively associated to yield in high-yielding environments without N limitations (phase II) with no cost in low yielding environments, and associated to harvest index. Grain protein plasticity was positively associated to protein in high protein environments without N limitations (phase III). Plasticity of grain protein concentration was negatively associated to grain number m −2, resulting in moderate negative association of protein plasticity and yield. Grain C:N ratio associated weakly and positively with yield plasticity and strongly and negatively for grain protein plasticity. This work proposes a yield-protein plasticity framework combined with a three-phase model that allows to disclose G × N interactions. Under our experimental conditions, we identified physiological mechanisms associated to yield and protein plasticity. Yield and protein plasticity can contribute guiding grower's cultivar selection towards high yield plasticity cultivars when aiming to high yield with acceptable protein levels or high protein plasticity cultivars to ensure high protein at the expense of lower yields. Yield plasticity brings opportunity to breed for high yielding cultivars while maintaining grain protein concentration. Accuracy of N recommendations models and mechanistic crop models can be improved by accounting for G × N interactions through plasticity of yield and grain protein. • We propose a yield-protein plasticity framework to assess G × N interactions. • Yield associated with yield plasticity in high yield non-N limiting environments. • Yield plasticity was unrelated with grain protein. • Protein plasticity associated negatively with yield. • Harvest index associated with yield plasticity in high yielding environments. [ABSTRACT FROM AUTHOR]

Senescence is a key physiological process that can regulate crop grain yield. Patterns of leaf senescence and its association with grain yield for a short maturity maize hybrid were investigated in a factorial combination of two tillage treatments (conventional and no-till), three amounts of stubble (0, 3 and 5 t ha −1 ) and three N rates (0, 80 and 120 kg N ha −1 ) over three seasons in 2015 long rains, 2015/2016 short rains and 2016 long rains. Leaf senescence from flowering to harvest was assessed at (a) the whole-plant scale by the visual scoring of dry leaves and (b) the canopy-layer scale by measuring leaf greenness with a SPAD 502 chlorophyll meter. A bilinear model was used to quantify the patterns of senescence at the whole-plant scale. A logistic function was fitted to estimate the traits of senescence at three canopy layers (top, mid, bottom), including minimum and maximum SPAD, onset of senescence (EC90), time to loss of 50% maximum SPAD (EC50) and the rate of senescence in each layer. Nitrogen rate effect on patterns and traits of senescence were large and its interactions with stubble were more frequent than interactions between other treatments. Tillage and stubble amount had marginal effects. EC50 was delayed in the unfertilized controls compared with fertilized crops and was negatively correlated with grain yield. Rate of senescence was faster in fertilised crops compared with unfertilized controls at both whole-plant and canopy-layer scales. Grain yield, grain number and nitrogen remobilization efficiency were associated with faster rates of senescence in the top and mid leaves but with slower rates of senescence in the bottom layer leaves. We advance a sink-driven leaf senescence ideotype for high yield and efficient use of nitrogen for short maturity maize. [ABSTRACT FROM AUTHOR]

Oats likely emerged as part of the weedy grass assemblage in early wheat and barley crops. Some Avena species, such as A. fatua and A. sterilis, evolved into aggressive weeds, and the high interspecific competitive ability of cultivated oats (A. sativa) is valued agronomically to facilitate weed control in rotations. We tested the hypothesis, verified in many crops, that high yield of oats is related to low intraspecific competitive ability. Ten contemporary oat varieties, selected for grain yield and milling attributes, where grown in three environments. Response to competition was calculated as 100 x (Yb - Yc)/Yc, where Y is yield measured in border (b) and centre (c) rows. The same definition was used to calculate response to competition of yield components (biomass, harvest index, grain number, grain weight) and the components of grain number (panicle number and grains per panicle). Yield response to competition was affected by all three sources of variation, i.e. environment, variety and variety x environment interaction. The interaction demonstrates the plasticity of yield response to intraspecific competition; for example, the response to competition of variety Mortlock varied from 9% to 71% among environments. This plasticity in yield response to competition was partially related to variety-dependent responses to competition for biomass and harvest index, number of panicles and number of grains per panicle. We did not find the expected negative association between yield and variety-dependent response to competition. We discuss how this lack of correlation could relate to sampling issues, i.e. a limitation in the range of environments and varieties explored in this study, or reflect a legitimate feature of oat crops arising from early and contemporary selective pressures. [ABSTRACT FROM AUTHOR]

Controversy around the benefits of NT and stubble retention, and weaknesses in the underpinning science arise from a limited understanding of the mechanisms that operate in these systems. Two experiments were conducted at the Kenya Agricultural and Livestock Research Organization research station in Embu (0.515°S and 37.273°E) over three seasons during the 2015 long rains, 2015/2016 short rains and 2016 long rains to explore the mechanisms that regulate crop growth, nitrogen uptake and yield in maize ( Zea mays L.). In the first experiment, crops were grown in a factorial combination of conventional tillage (CT) and no-till (NT), three amounts of stubble (0, 3 and 5 t ha −1 ) and three N rates (0, 80 and 120 kg N ha −1 ). The second experiment investigated the interaction between tillage (CT, NT) and timing of N supply (80 kg N ha −1 ) that was supplied at sowing, six- (V6) and 12-leaf stage, with 5 t ha −1 of stubble. Grain yield ranged from 2.3 to 5.3 t ha −1 , with small effects from tillage and stubble retention. Nitrogen had the largest impact on grain yield and influenced crop response to tillage and stubble by modifying crop growth rate (CGR) and nitrogen nutrition index (NNI). However, the effects of N timing on crop growth, yield and traits associated with N use efficiency were independent of tillage system. High CGR between V6 and flowering was associated with high NNI, which led to increased grain number. The value of stubble in water storage at sowing, and crop growth and yield was greater in a dry season (<300 mm rainfall) compared with wet seasons (>600 mm). Irrespective of tillage system, moderate amounts of stubble, higher N rates and better matching of N supply to the critical window for yield determination could improve maize yields in sub-humid tropical environments. [ABSTRACT FROM AUTHOR]

Late-season nitrogen (N) application has been proposed to boost grain yield and grain protein concentration (GPC) in cereals; however, its effects on bread and durum wheat have been inconsistent in field experiments. We performed a meta-analysis to (i) assess the effect of N applications to wheat after flag leaf visible (GS 37) on grain yield and GPC; and to assess the variation in these responses with (ii) N fertiliser management, (iii) environmental factors, and (iv) physiological traits. We searched ' Agronomy Journal ', ' Crop Science ', ' European Journal of Agronomy ', and ' Field Crops Research ' for articles published between 1980 and 2021 that allowed for a direct comparison of wheat yield and GPC between N application after GS 37 to an otherwise equally managed crop that received basal N fertilisation. We also collected other traits such as stover biomass and N uptake at plant maturity, and dough rheological properties, when available. The search resulted in 38 articles that, in addition to one unpublished trial from our group, evaluated 542 pairwise comparisons in 127 environments. Across studies, grain yield ranged from 1.15 to 10.63 Mg ha−1 and showed a negative relation with GPC, which ranged from 65 to 189 g kg−1. Late-season N fertilisation was consistently neutral for grain yield (I2, proportion of the overall variance due to variation in real effects rather than chance, 26.2 %) and increased GPC with a pooled estimate of 3.96 %. The response of GPC was heterogeneous (I2 = 84 %), suggesting the need for exploration of potential moderators of the response. Meta-regression suggested that increasing the proportion of late N relative to the total available N positively associated to increases in GPC, and the residuals of this analysis suggested that later applications increased GPC response, with no effect of N fertiliser source or placement. Environments with low temperature, high photothermal quotient, and long duration of the critical period associated with greater GPC response to late-season N applications. The relative response of GPC to late fertilisation correlated with the relative response of both stover N uptake and nitrogen concentration in stover at maturity, but not with stover biomass at maturity. Alveogram index and dough extensibility increased when late-season N increased GPC. Enhancing GPC through late N applications should consider associations between management, environmental, and physiological factors. Future research should focus on forecasting GPC response to late N, based on GPC response drivers identified in the current research. • Meta-analysis highlighted physiological drivers of wheat response to late N • Grain yield was unaffected by late N across a broad range of environments • Late N increased protein by 3.96% and its effects were heterogeneous • Protein increased linearly with the proportion of late N and with later applications • Higher protein response to late N associated to favourable growing conditions [ABSTRACT FROM AUTHOR]

• Splitting N in 3–4 applications improved wheat yield by 7 % and grain protein content by 5 %. • The effect of split N on yield was larger for winter wheat than for spring wheat. • Split N mitigated the negative relationship between yield and grain protein content. Management of nitrogen (N) fertilizer is critical to avoid the environmental consequences of both over-fertilization and excess reactive N in the system, and chronic under-fertilization and soil mining. Split N application seeks to improve nitrogen use efficiency in both small-holdings and large-scale mechanized farms, but lack of conclusive evidence on its benefits restricts the adoption of this practice. Here we report a global meta-analysis of split N application in wheat using 129 studies with 2661 comparisons. Split N in 3–4 applications improved yield by 7.0 % and grain protein by 5.2 % in relation to single application. The effect of split N on yield was larger for winter wheat than for spring wheat, while split N improved grain protein in both winter and spring wheat. Its effects on both yield and grain protein were larger under conventional tillage, in humid climate especially for winter wheat, in coarse textured soils, on less fertile soils, and at high N rate. Splitting N in 3–4 applications would increase annual production of winter wheat by 12.9 M t grain and 1.3 M t protein globally. By identifying the conditions where split N application is more likely to deliver agronomic benefits, our study would contribute to the targeted adoption of this practice. [ABSTRACT FROM AUTHOR]

• Excel x Kaspa RILs screened in dry, hot environment (yield 149 g m-2) and a wet, mild environment (477 g m-2). • Ranking of RILs was consistent between environments for pod wall ratio, the weight ratio between the pod wall and the whole pod including seeds. • A QTL for flowering time on chromosome 2 co-located with a QTL for a number of yield related traits including pod wall ratio. Trait-based selection to improve stress adaptation can complement direct selection for yield provided the trait meets six criteria: (1) it must be genetically correlated with yield in the target environments; (2) it should be less affected by the GxE interaction than yield; (3) it should not be associated with low yield in favourable conditions; (4) it must show genetic variation; (5) it must be genetically stable, persistent across generations and relevant in different genetic backgrounds, and (6) it must lend itself to rapid, cost-effective and reliable quantification. Against these criteria, this study focused on pod wall ratio, defined as the weight ratio between the pod wall and the whole pod including seeds. We explored the phenotypic and genetic associations of this trait with yield components in a field pea population of 102 recombinant inbred lines (RILs) from a cross between Excel and Kaspa grown in two environments: Roseworthy 2015 (average yield 149 g m−2) and Turretfield 2016 (477 g m−2). All three sources of variation, environment, line and their interaction, affected yield (all P < 0.0001). The ranking of RILs for yield varied between environments, reflecting the strong G x E. The ranking of RILs for pod wall ratio was maintained between environments. Broad-sense heritability was higher for pod wall ratio (≥ 0.83) than for yield (≤ 0.59). There was a narrow range of pod wall ratio, 0.07 to 0.25 at Roseworthy 2015 compared to 0.09 to 0.52 in Turretfield 2016. Pod wall ratio correlated with seeds per pod and harvest index in Roseworthy 2015, and with yield, seeds per pod and harvest index in Turretfield 2016. A QTL for flowering time on linkage group 2 co-located with a QTL for a number of traits including pod wall ratio, days to pod emergence, seeds per pod, seeds per m2, shoot biomass at harvest and grain yield. These markers are potentially valuable for breeding after validation in independent populations. [ABSTRACT FROM AUTHOR]

• Benchmarks of wheat N utilisation efficiency (NUtE) in Mediterranean conditions are needed. • We compiled a large set of data from Mediterranean and non-Mediterranean environments of Europe. • Mediterranean growing conditions narrowed N uptake contributing to lower final yields than in N Europe. • But they also reduced consistently NUtE (considering both average and maximum yields at each level of N uptake). • These effects on NUtE produced a trade-off with grain N concentration. Water and temperature stress during critical periods of grain yield formation are distinctive of wheat crops in Mediterranean environments. However, nitrogen (N) availability may also constrain grain yields in these environments. Benchmarks of yield response to N uptake in Mediterranean conditions are lacking, and extrapolation from non-Mediterranean environments is not warranted. We hypothesised that under Mediterranean environments (1) maximum N uptake would be lower, thus the range of N uptake would be narrower, and (2) N utilisation efficiency (NUtE, yield per unit N uptake) would be reduced along the whole range of N uptake than under non-Mediterranean conditions. To test these hypotheses, we compiled published data of yield and N uptake from Mediterranean (n = 340) and non-Mediterranean environments (n = 563) of Europe. Wheat in Mediterranean environments had lower average grain yield (4.1 vs 7.1 Mg ha−1), lower average N uptake (131 vs 166 kg N ha−1), lower average NUtE (33 vs 47 kg grain kg N−1), and higher average grain N concentration (2.4 vs 1.8%) than crops in non-Mediterranean environments. Boundary functions relating yield and nitrogen uptake captured the lower yield of wheat along the whole range of N uptake as hypothesised; these functions could be used for benchmarking wheat crops in Mediterranean regions of Europe, and possibly other Mediterranean environments. [ABSTRACT FROM AUTHOR]

Highlights: [•] We investigated the relationships between yield components considering phenotypic plasticity. [•] Grains per m2 and spikes per m2 were coarse regulators while all components may be responsible for fine regulation of yield. [•] We showed that the rankings of responses of yield components depend on the nature of the driver, i.e. genotype or environment. [•] Strong trade-offs between components were found for small changes in yield or in grains per m2 for both environmental and genetic factor. [•] For large changes, trade-offs were weaker, but much stronger for components of yield than of grains per m2, particularly for genetic drivers. [Copyright &y& Elsevier]

Low temperature during the critical period of wheat can cause floret sterility, grain abortion, yield reduction, and economic losses. We tested the hypothesis that selection for yield improved frost tolerance. We measured phenology, yield and its components, including the distribution of grains within the spike, in a factorial experiment combining 12 wheat varieties released from 1973 to 2015, two sowing dates (mid-April and early or mid-May), two thermal regimes, ambient control and frost-protected, and two seasons. To protect crops from frost we used moveable, lightweight passive heating chambers before each frost event (≤ 0 °C). The rate of genetic gain in yield aligned with frost severity: it ranged from negligible under severe frost to 0.79 ± 0.05% y−1 in unfrosted crops. The chambers diminished but did not fully prevent frost; across sources of variation grain yield was 179 ± 20.1 g m−2 in ambient control and 264 ± 13.3 g m−2 in frost-protected treatments. Frost intensity was calculated as the cumulative, canopy-level minimum temperature below 2 °C during the period from −300 to + 100 °C d centred at anthesis. For the pooled data, yield declined with frost intensity at 1.24 ± 0.12% °C−1. Across varieties and environments, frost-protected crops set 29 ± 3.0 grains spike−1 compared with 19 ± 2.7 in ambient control. We did not find random grain abortion within spikelets, but random sterile spikelets. Average grain weight (weighed by the relative contributions of these grains to the number of grains per spike) in main shoot spike did not vary with thermal regime. Selection for yield did not improve frost tolerance. Preventing spring radiation frost improved spike fertility by increasing the proportion of grains in distal positions with no reduction in grain weight potential within spikelets in relation to controls. We advanced damage functions relating yield and frost, which are useful for modelling, and maps of grain set in spikes that help understanding the physiology of yield in response to frost. • We advance damage functions relating yield and frost, which are useful for modelling. • We quantified frost intensity as the cumulative minimum temperature below 2 ℃ during the critical period. • Wheat grain yield declined, on average, at 1.24% °C−1 with frost intensity. • The rate of genetic change in yield, from 1973 to 2015, declined with frost severity. • Frost-protection improved the proportion of grains in distal positions with no reduction in grain weight. [ABSTRACT FROM AUTHOR]

• We measure yield and protein of shaded lentil in southern Australia and Chile. • The most sensitive period was pod emergence, between 50–126 °Cd after flowering. • Grain number and biomass accounted for most of the variation in yield. • Grain protein concentration varied according to a bi-linear model. • Protein yield tracks grain yield and is partially buffered by late season protein. Lentil is a cool season grain legume produced primarily in the Mediterranean and temperate regions of the world where water and heat stress in critical developmental windows constrain yield. The effect of stress on yield depends on the timing, intensity and duration of stress; here we focus on timing relative to phenological development. To determine the critical period for grain yield and grain protein, we compared unshaded controls and crops exposed to sequential 10–14 d shading periods using two locally adapted varieties at Roseworthy, south-eastern Australia, and Valdivia, southern Chile. Yield of unstressed controls varied from 1 t ha−1 at Roseworthy to 7 t ha-1 at Valdivia, and grain protein from 22.0 % at Valdivia to 27.6 % at Roseworthy. Irrespective of growing conditions, the most sensitive period was at 50–126 °Cd after flowering, around pod emergence. Grain number and biomass accounted for most of the variation in yield. Grain protein concentration varied according to a bi-linear model, with minor reduction (<10 %) before a developmental threshold (i.e. flowering at Valdivia, ∼ 200 °Cd after flowering at Roseworthy) and a linear increase after the threshold. Protein yield tracked grain yield, but the increased grain protein concentration partially buffered the effect of post-flowering stress. [ABSTRACT FROM AUTHOR]