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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]

The combination of poorly drained soils and high rainfall can cause transient waterlogging and reduce yield of lentil. We screened 111 lentil lines for response to waterlogging in 2019 and 2020 using a pot assay outdoors. At 484 °Cd after emergence (38 d) in 2019 and 452 °Cd after emergence (42 d) in 2020, plants were waterlogged for 184 °Cd (11 d, 2019) and 167 °Cd (14 d, 2020) and allowed to recover for 323 °Cd (20 d, 2019) and 307 °Cd (26 d, 2020). We combined 2‐D digital images of canopy cover and plant height to derive a 3‐D trait that correlates with biomass to derive plant growth rate. Actual biomass at the end of recovery in the waterlogged plants varied 2.6‐fold with genotype, and genotypic and phenotypic correlations showed associations with plant growth rate both during (rg =.92; rp =.74) and after waterlogging (rg =.75; rp =.72); there was no trade‐off between maintenance of growth during waterlogging and growth during recovery. The ratio of biomass between waterlogged and control plants at the end of recovery was associated with growth rate during recovery (rg =.88, rp =.65) and biomass at the end of waterlogging (rg =.61, rp =.67). Broad‐sense heritability was 0.27 for growth rate during waterlogging, 0.37 for growth rate during recovery, 0.51 for biomass at the end of waterlogging and 0.47 for biomass at the end of recovery. High biomass at the end of recovery correlated with cooler canopies but correlations varied with season and measurement date, and heritability of canopy temperature was low. We identified genotypes with consistently higher tolerance to waterlogging and provide an improved understanding of the physiological response of lentil to hypoxia highlighting the importance of growth rate not only during waterlogging but also during recovery. [ABSTRACT FROM AUTHOR]

The contemporary lentil (Lens culinaris ssp. culinaris) industry in Australia started in the late 1980s. Yield in farmers' fields averages 1.2 t ha–1 nationally and has not increased over three decades. Lack of yield progress can be related to a number of non-mutually exclusive reasons: expansion of lentil to low-yielding environments, lack of genetic gain in yield, lack of progress in agronomic practices, and lack of adoption of superior technologies. The aims of this study were to (i) quantify the genetic gain in lentil yield since 1988, (ii) explore the variation in the expression of genetic gain with the environment, and (iii) identify shifts in crop phenotype associated with selection for yield and agronomic adaptation. We grew a historic collection of 19 varieties released between 1988 and 2019 in eight environments resulting from the factorial combination of two sowing dates, two water regimes, and two seasons. Across environments, yield varied 11-fold from 0.2 to 2.2 t ha–1. The rate of genetic gain averaged 20 kg ha–1 year–1 or 1.23% year–1 across environments and was higher in low-yield environments. The yield increase was associated with substantial shifts in phenology. Newer varieties had a shorter time to flowering and pod emergence, and the rate of change in these traits was more pronounced in slow-developing environments (e.g., earlier sowing). Thermal time from sowing to end of flowering and maturity were shorter in newer varieties, and thermal time from pod emergence to maturity was longer in newer varieties; the rate of change in these traits was unrelated to developmental drivers and correlated with environmental mean yield. Genetic gain in yield was associated with increased grain number and increased harvest index. Despite their shorter time to maturity, newer varieties had similar or higher biomass than their older counterparts because crop growth rate during the critical period increased with the year of release. Genotype-dependent yield increased over three decades in low-yield environments, whereas actual farm yield has been stagnant; this suggests an increasing yield gap requiring agronomic solutions. Genetic improvement in high-yield environments requires improved coupling of growth and reproduction. [ABSTRACT FROM AUTHOR]

Insufficient nitrogen applications may contribute to yield gaps in low rainfall environments of Western Australia (WA). This study tested a nitrogen nutrition index (NNI) for wheat tailored for low rainfall regions, which is based on rainfall-scaled dilution curves. We analyzed yield, shoot biomass, and nitrogen concentration from 32 field trials in WA. An empirical rainfall threshold of 400mm (summerþgrowing season rainfall) returned two parallel dilution curves accounting for the reduction of critical N in drier and lower yielding conditions. Scatterplots of relative yield and rainfall-adjusted NNI returned a robust boundary function that may lead to greater adoption by growers. The NNI defined in this research study can be applied and further tested by growers in WA, but may also apply to other low rainfall environments, to close nitrogen related yield gaps. [ABSTRACT FROM AUTHOR]

Nitrogen dilution curves relate a crop's critical nitrogen concentration (%Nc) to biomass (W) according to the allometric model %Nc = a W-b. This model has a strong theoretical foundation, and parameters a and b show little variation for well-watered crops. Here we explore the robustness of this model for water stressed crops. We established experiments to examine the combined effects of water stress, phenology, partitioning of biomass, and water-soluble carbohydrates (WSC), as driven by environment and variety, on the %Nc of wheat crops. We compared models where %Nc was plotted against biomass, growth stage and thermal time. The models were similarly scattered. Residuals of the %Nc - biomass model at anthesis were positively related to biomass, stem:biomass ratio, Δ 13C and water supply, and negatively related to ear:biomass ratio and concentration of WSC. These are physiologically meaningful associations explaining the scatter of biomass-based dilution curves. Residuals of the thermal time model showed less consistent associations with these variables. The biomass dilution model developed for well-watered crops overestimates nitrogen deficiency of water-stressed crops, and a biomass-based model is conceptually more justified than developmental models. This has implications for diagnostic and modeling. As theory is lagging, a greater degree of empiricism might be useful to capture environmental, chiefly water, and genotype-dependent traits in the determination of critical nitrogen for diagnostic purposes. Sensitivity analysis would help to decide if scaling nitrogen dilution curves for crop water status, and genotype-dependent parameters are needed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Review of phosphorus, potassium and sulphur effect on symbiotic N2 fixation. [•] Nodule mass and number are more responsive to nutrient deficit than shoot biomass. [•] N2 fixation is more responsive to P and K deficit than shoot and nodule mass. [•] The ratios N/K, N/P and N/S in shoots increased under nutrient deficiency. [•] Patterns of growth, N2 fixation and nutrient concentration were similar for P, K and S deficiency. [ABSTRACT FROM AUTHOR]

• We develop a novel method to non-destructively measure crop growth rate in lentil. • Lentil yield correlated non-linearly with crop growth rate. • Lentil yield correlated with biomass and crop growth rate in stressful conditions. • Lentil yield decoupled with biomass and crop growth in higher yielding conditions. • The association of lentil yield and harvest index was significant for all yields. Growth and yield can be decoupled in lentil whereby excessive vegetative growth leads to self-shading, reduced pod and seed set, low harvest index and higher risk of disease and lodging. We evaluated the degree of coupling between growth and yield in 20 lentil lines grown in eight environments varying in water and photothermal conditions returning a 10-fold yield range, from 21 to 221 g m−2. Calibration curves between shoot biomass and canopy cover measured with NDVI and green canopy cover measured with Canopeo app were improved with canopy height as a multiplication factor returning a 3-D trait. Calibration curves were used to phenotype shoot biomass and calculate crop growth rate. For the pooled data, yield correlated non-linearly with crop growth rate, with an x-intercept of 0.09 g m−2 [oCd]-1, suggesting a minimum plant size for reproduction, and an inflection point at 0.43 g m−2 [oCd]-1. Yield correlated with biomass and crop growth rate in the more stressful conditions (yield ≤ 107 g m−2) and was decoupled in higher yielding conditions (yield ≥ 170 g m−2). Yield associated with harvest index at all yield levels, but more strongly in high-yielding conditions. Biomass and harvest index correlated in environments with yield ≤ 107 g m−2, and decoupled under more favourable conditions (yield ≥ 170 g m−2). Yield associated with phenology under stress but not in favourable conditions. For the combination of lines and environments in this study, broad sense heritability was 0.96 for flowering time, 0.93 for harvest index, 0.89 for yield, 0.87 for crop growth rate and 0.39 for biomass. Selection for harvest index would improve yield across environments whereas selection for growth rate could further improve yield under stress. Agronomic practices to improve the coupling of yield and growth under favourable conditions need to be explored; for example, using precision seeding to reduce rectangularity of crop arrangement and favour penetration of radiation into the canopy and pod set. [ABSTRACT FROM AUTHOR]

• Harvest index is inconsistent across literature to describe genetic gain in reproductive allocation at maturity. • Allometric analysis was used to characterize genetic gain in reproductive allocation in R5 in seven soybean varieties. • Allometric analysis at the end of the seed set revealed an increase in relative allocation into pods. • Allocation to seed must have increased, but HI did not capture this necessary change in allocation. Seed yield is commonly expressed as the product of shoot biomass and harvest index (HI) at physiological maturity. However, HI is a size-dependent ratio unsuitable to describe shifts in reproductive partitioning in historical soybean [ Glycine max (L.) Merr.] studies where selection has enhanced shoot biomass. The aim of this work was to analyze allocation of biomass to reproductive organs in the onset of seed filling (R5) using allometric analysis in a set of historical soybean varieties. Seven varieties released between 1980 and 2013 were evaluated in field trials in Rossville (Kansas, United States) under two N fertilizer rates (0 and 670 kg N ha−1) in 2016 and 2017. Seed yield increased at a rate of 0.74 % yr−1 (p < 0.001); while the shoot biomass increased at a rate of 0.41 % yr−1 (p < 0.001), suggesting an increase in allocation to reproduction. However, the rate of increase in HI at maturity was not different from zero highlighting the inadequacy of this trait. Allometric exponents (slopes of the log-log relationships) relating pod and shoot biomass, pod and leaf, and pod and stem plant fractions increased linearly with the year of release (p < 0.05). Allometric analyses thus revealed genetic gains in reproductive allocation not detected by HI at maturity. The latter outcome highlights the contribution of improved reproductive partitioning to soybean yield gains, and the need for allometric analyses to account for size-dependence in allocation of shoot biomass. [ABSTRACT FROM AUTHOR]

Interactions between nitrogen and water may vary between N 2 fixing species and species that rely only mineral soil nitrogen. Here we compared above ground biomass accumulation (W), nitrogen uptake (N), evapotranspiration (ET) of alfalfa ( Medicago sativa L.) and tall fescue ( Festuca arundinacea Schreb.) during regrowth periods under contrasting supply of water (irrigated vs non-irrigated) and N (for non-fixing species). Using previously published data, we estimated the dynamics of the two components of ET, evaporation from soil (E) and transpiration (T), in order to analyse the impact of E/T, of the transpiration efficiency (TE = W/T) and the role of crop N nutrition on water use efficiency (WUE= W/ET). In tall fescue, limiting N supply reduced WUE by both increasing E/T ratio and decreasing TE. Water limitation in both alfalfa and tall fescue led to crop nitrogen deficit. This drought-induced N deficiency resulted in a proportional reduction in TE irrespective of the source of N for the plant. We propose that the ratio N/T, representing the apparent N concentration of water transpired by the crop, is relevant for analysing N-water interactions. Comparisons of dynamics of N/T ratio must be done at similar biomass or similar transpiration because N and T are related allometrically. [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]