Increase In Number Of Grains Research Articles

Chromosomal mapping of a major genetic locus from Agropyron cristatum chromosome 6P that influences grain number and spikelet number in wheat.

A novel locus on Agropyron cristatum chromosome 6P that increases grain number and spikelet number was identified in wheat-A. cristatum derivatives and across 3 years. Agropyron cristatum (2n = 4x = 28, PPPP), which has the characteristics of high yield with multiple flowers and spikelets, is a promising gene donor for wheat high-yield improvement. Identifying the genetic loci and genes that regulate yield could elucidate the genetic variations in yield-related traits and provide novel gene sources and insights for high-yield wheat breeding. In this study, cytological analysis and molecular marker analysis revealed that del10a and del31a were wheat-A. cristatum chromosome 6P deletion lines. Notably, del10a carried a segment of the full 6PS and 6PL bin (1-13), while del31a carried a segment of the full 6PS and 6PL bin (1-8). The agronomic characterization and genetic population analysis confirmed that the 6PL bin (9-13) brought about an increase in grain number per spike (average increase of 10.43 grains) and spikelet number per spike (average increase of 3.67) over the three growing seasons. Furthermore, through resequencing, a multiple grain number locus was mapped to the physical interval of 593.03-713.89Mb on chromosome 6P of A. cristatum Z559. The RNA-seq analysis revealed the expression of 537 genes in the del10a young spike tissue, with the annotation indicating that 16 of these genes were associated with grain number and spikelet number. Finally, a total of ten A. cristatum-specific molecular markers were developed for this interval. In summary, this study presents novel genetic material that is useful for high-yield wheat breeding initiatives to meet the challenge of global food security through enhanced agricultural production.

Integrated use of organic and synthetic fertilizers improves soil functioning, growth, yield and quality attributes of maize

The combined use of organic and chemical fertilizers may prove to be an excellent option for maintaining soil health, increasing fertilizer use efficiency, and improving crop quality and yield of maize. So, with this objective in mind a pot experiment was conducted to find out the effectiveness of organic and synthetic fertilizers on the yield and quality of maize crop. Two organic fertilizer levels (FYM and Press-mud @ 2% and 4% of each) were tested separately and in combination with recommended NPK fertilizers (160: 80: 60 kg ha-1). The experimental units were laid out in a completely randomized design (CRD) with five replications. The results showed that the combined use of NPK + press mud @ 4% caused a significant increase in grain numbers per cob (8.6%), weight of grains per cob (11.5%), grain yield, biological yield, harvest index, stalk yield, and oil and protein contents up to 11.5%, 6.3%, 19.7%, 12.6% and 12.0%, respectively as compared to the control treatment. The oil and protein contents were also improved significantly over the sole application of NPK fertilizer. Soil health was also improved due to the combined use of synthetic fertilizer with 4% press mud and 2% FYM. It is concluded that integrated use of NPK fertilizers and press mud @ 4% not only increased the quality and yield of maize, but it also improved soil health.

EXPLORING THE IMPACT OF SOIL AMENDMENTS ON FOOD SAFETY AND CROP PRODUCTIVITY FOR SUSTAINABLE AGRICULTURE

Aflatoxins impact the entire food supply chain, from agricultural fields to processing facilities, markets, and consumer tables. In peanut cultivation, this threat poses a constant challenge throughout the cultivation, processing, and consumption stages. To confront this challenge, an exhaustive study was undertaken with the aim of investigating the effects of targeted soil amendments; namely, Vermicompost, Lentil crop residue, and Sulphate of Potash applied during the pivotal sowing phase at two distinct locations, Chakwal and Attock. The research includes meticulous groundnut sample analysis to quantify aflatoxin levels, revealing a significant reduction across all soil amendments compared to the control group. Vermicompost stands out as the most effective, achieving a remarkable 64.8% reduction, followed closely by Sulphate of Potash at 62.4%. Statistical analysis highlights non-significant differences among amendments. Beyond aflatoxin mitigation, the study underscores the dual benefit of these soil amendments, contributing not only to mycotoxin control but also enhancing overall crop productivity. Percent increase in number of grains per plant ranged between 58.82% to 43.53% whereas in hundred grain weight it ranged between 17.10% and 10.55%. In summary, the study emphasizes the importance of strategic soil amendments, particularly Vermicompost and Sulphate of Potash, in mitigating aflatoxin contamination in peanuts. The dual benefit of improved crop productivity adds significance to the findings, offering a holistic approach to address the multifaceted dimensions of aflatoxin challenges in peanut cultivation.

Multi-scale simulation study on the evolution of stress waves and dislocations in Ti alloy during laser shock peening processing

This study investigates the effect of laser shock peening (LSP) on the evolution of stress waves and dislocations in Ti-6Al-4V alloy by multi-scale simulation. The finite element model on the macroscale and molecular dynamics model on the microscale were built, and multi-scale simulations based on the finite element and molecular dynamics were performed. Under the high pressure on material induced by LSP, elastic deformation and plastic deformation are generated. With the increase of stress wave traveling distance, its intensity gradually decays. The stress wave in the material completely vanishes eventually. The macroscale simulation shows that the average velocity of the stress wave equals 6.0 km/s and does not change much with the loading pressure. The microscale simulation shows that the average velocity of the stress wave in single crystal α-Ti is in the range of 7.1∼7.8 km/s. The average velocity of stress wave in polycrystals is always lower than that in the single crystal and has a trend to decrease with the increase of grain number until a stable value of around 6.0 km/s. Considering the induced shock pressure, the piston velocity should be below 0.4 km/s to recreate the LSP process. This paper provides a comprehensive understanding of the effect of LSP on the evolution of stress waves and dislocations and also provides a new numerical method to further study laser shock peening processing.

Straw Mulching Combined with Phosphorus Fertilizer Increases Fertile Florets of Wheat by Enhancing Leaf Photosynthesis and Assimilate Utilization

Lack of soil moisture and phosphorus deficiency limits wheat grain yield in dryland areas. However, the moisture-conserving effect of straw mulching combined with phosphor fertilization on fertile florets per spike (FFS) and grain yield remains unclear. During the 2020–2021 and 2021–2022 growing seasons, we investigated the combined effects of straw mulching (0 and 8000 kg ha−1) and phosphorus fertilization (0, 75, and 120 kg P2O5 ha−1) on spike development, assimilates’ availability, and the photosynthetic properties of flag leaves by conducting a field experiment. Compared with no straw mulch control, straw mulching increased fertile spike, grain number per spike (15.6%), and grain yield (22.6%), and grain number per spike was the most important contribution to increasing wheat grain yield (46%). An increase in grain number per spike is associated with FFS. Compared with no straw mulch control, straw mulching increased FFS by 19.5%, and it increased with increasing phosphorus fertilization levels. Moreover, straw mulching combined with phosphorus fertilization promoted the light compensation point (LCP), light saturation point (LSP), net photosynthetic rate (Pn), Chl b, and the maximal photochemical efficiency of photosystem II (Fv/Fm) of flag leaves to produce carbohydrates. Our study has shown that the primary factor for the divergence in FFS under straw mulching and phosphorus application was the efficiency of assimilate utilization in the spike, which ultimately led to increased grain number per spike and grain yield.

Post-Intensification Poaceae Cropping: Declining Soil, Unfilled Grain Potential, Time to Act.

The status and sustainability of Poaceae crops, wheat and barley, were examined in an Atlantic zone climate. Intensification had caused yield to rise 3-fold over the last 50 years but had also degraded soil and biodiversity. Soil carbon and nitrogen were compared with current growth and yield of crops. The yield gap was estimated and options considered for raising yield. Organic carbon stores in the soil (C-soil) ranged from <2% in intensified systems growing long-season wheat to >4% in low-input, short-season barley and grass. Carbon acquisition by crops (C-crop) was driven mainly by length of season and nitrogen input. The highest C-crop was 8320 kg ha-1 C in long-season wheat supported by >250 kg ha-1 mineral N fertiliser and the lowest 1420 kg ha-1 in short-season barley fertilised by livestock grazing. Sites were quantified in terms of the ratio C-crop to C-soil, the latter estimated as the mass of carbon in the upper 0.25 m of soil. C-crop/C-soil was <1% for barley in low-input systems, indicating the potential of the region for long-term carbon sequestration. In contrast, C-crop/C-soil was >10% in high-input wheat, indicating vulnerability of the soil to continued severe annual disturbance. The yield gap between the current average and the highest attainable yield was quantified in terms of the proportion of grain sink that was unfilled. Intensification had raised yield through a 3- to 4-fold increase in grain number per unit field area, but the potential grain sink was still much higher than the current average yield. Filling the yield gap may be possible but could only be achieved with a major rise in applied nitrogen. Sustainability in Poaceae cropping now faces conflicting demands: (a) conserving and regenerating soil carbon stores in high-input systems, (b) reducing GHG emissions and other pollution from N fertiliser, (c) maintaining the yield or closing the yield gap, and (d) readjusting production among food, feed, and alcohol markets. Current cropping systems are unlikely to satisfy these demands. Transitions are needed to alternative systems based on agroecological management and biological nitrogen fixation.

Effect of delayed sowing on grain number, grain weight, and protein concentration of wheat grains at specific positions within spikes

Delays in sowing have significant effects on the grain yield, yield components, and grain protein concentrations of winter wheat. However, little is known about how delayed sowing affects these characteristics at different positions in the wheat spikes. In this study, the effects of sowing date were investigated in a winter wheat cultivar, Shannong 30, which was sown in 2019 and 2020 on October 8 (normal sowing) and October 22 (late sowing) under field conditions. Delayed sowing increased the partitioning of 13C-assimilates to spikes, particularly to florets at the apical section of a spike and those occupying distal positions on the same spikelet. Consequently, the increase in grain number was the greatest for the apical sections, followed by the basal and central sections. No significant differences were observed between sowing dates in the superior grain number in the basal and central sections, while the number in apical sections was significantly different. The number of inferior grains in each section also increased substantially in response to delayed sowing. The average grain weights in all sections remained unchanged under delayed sowing because there were parallel increases in grain number and 13C-assimilate partitioning to grains at specific positions in the spikes. Increases in grain number m–2 resulted in reduced grain protein concentrations as the limited nitrogen supply was diluted into more grains. Delayed sowing caused the greatest reduction in grain protein concentration in the basal sections, followed by the central and apical sections. No significant differences in the reduction of the grain protein concentration were observed between the inferior and superior grains under delayed sowing. In conclusion, a 2-week delay in sowing improved grain yield through increased grain number per spike, which originated principally from an increased grain number in the apical sections of spikes and in distal positions on the same spikelet. However, grain protein concentrations declined in each section because of the increased grain number and reduced N uptake.

Supplemental irrigation at jointing improves spike formation of wheat tillers by regulating sugar distribution in ear and stem

Irrigation at jointing increases spike numbers at wheat harvest, but the mechanisms underlying increased tiller spike formation rate (SR) during wheat production caused by irrigation have remained unclear. We therefore designed the supplemental irrigation (SI) treatments at jointing in which SI was received (SIJ) or did not receive (NSI) by wheat, and analyzed the morphological differentiation of young ears and physiological responses of young ears and stems to SI. Results shown that SIJ relative to NSI mainly improved the SR of the first primary tiller (T1) and second primary tiller (T2), which significantly increased the grain yield. The tillers SR positively correlated to the soluble sugar and sucrose contents in young ears, but negatively correlated to that in stems. SIJ significantly increased the soluble sugar and sucrose contents in young ears and reduced that in stems in both the main stem (MS) and tillers. Compared with MS, the young ear differentiation of T1 and T2 tillers that can form spikes was always behind by 0–2 developmental periods between jointing and flowering. Although SIJ decelerated the young ears differentiation of the MS and the T1 tiller, the increased sugar content in young ears causing a significant increase in grain numbers. Moreover, SIJ positively regulated the young ear differentiation of T2 tiller with more sucrose contained in young ears and less in stems to narrow gaps in young ear differentiation between T2 tiller and MS. Some T1 and T2 as well as other high-position tillers composed invalid tillers, where young ears mostly ceased differentiating at the stages of glume primordium present to carpel primordium present, and contained significantly less sugar than effective tillers. Significant morphological differences in young ears and nutritional physiological differences in tillers led to high-position tillers that were difficult to convert into effective tillers even under favorable conditions by SIJ. Overall, tillers can be converted into effective spikes by increasing sugar metabolism in young ears via SIJ when the discrepancy in young ear differentiation does not exceed two developmental stages compared to MS.

Physiological bases of cultivar differences in average grain weight in wheat: Scaling down from plot to individual grain in elite material

In recent decades, increases in wheat yield have been achieved mainly through increases in grain number per m 2 (GNM2) rather than through increases in average grain weight (AGW). Using AGW as a lever to increase yield would require avoidance of the negative relationship between GNM2 and AGW. It is usually supposed that this trade-off arises from an increase in the proportion of small grains as GNM2 rises. The proportional increase in small grains being the result either of (1) an increase in the proportion of secondary tillers in the spike population or (2) of an increase in the proportion of grains located in distal positions within each spike. Either or both of these two populational effects would tend to mask any true genotypic differences in AGW. The existence of these constitutive differences has already been proposed, but without considering the full extent of the populational confounding effects. Identification of a component of the constitutive genetic determinism of AGW - one that is truly independent of GNM2 - could contribute to cultivar developments that would lead to further increases in grain yield under future target environments. To address this question, we analysed populational effects on AGW in four, modern, well-adapted bread-wheat cultivars. The four chosen cultivars show similar grain yields but contrasting AGWs. The analysis of populational effects was carried out at three hierarchical levels (the plot, the spike and the single grain) and under two contrasting environmental conditions (well-watered vs water-deficit conditions). Regardless of the environment, no (or only slight) differences in individual spike size were observed between cultivars. Furthermore the weak relationship between spike size and AGWdemonstrates that AGW differences between cultivars cannot be attributed to spike-level populational effects. Meanwhile, the analysis of individual grain mass distributions, showed that the differences in AGW between cultivars, originated from shifts in the whole grain-mass distribution, rather than from shape changes in the grain-mass distribution. This clearly indicates that AGW differences between cultivars cannot be attributed to populational effects at the individual grain level. The analysis carried out at both spike and individual grain levels indicates that the AGW differences between cultivars are largely constitutive, so that increases in grain yield through AGW may be considered independently of the GNM2: AGW trade-off. Taken together, these findings offer a new perspective for the genetic improvement of wheat, and one that should lead to further increases in yield. • The trade-off between grain number (GNM2) and average grain weight (AGW) may limit wheat yield. • AGW differences between cultivars are not driven only by this trade-off. • AGW differences between cultivars have a constitutive nature. • Increasing AGW should be possible without negative effects on GNM2. • Increasing grain yield through AGW may be relevant to future target environments.

Effect of N and CO2 supply on source size per grain at anthesis and its relationship with grain growth in wheat

AbstractRising atmospheric CO2 concentration ([eCO2]) increases the yield of wheat mainly by increasing grain number, but effects on single grain weight are variable. It is discussed whether single grain growth is limited by the sink or the source size under a non‐stress environment. This study explores the effect of e[CO2] combined with varying N supply on the source and sink size during grain filling. Source size was defined as the amount of stem reserves per grain (SRG) and the proportion of incident radiation intercepted by the green canopy per grain (fIRG) at anthesis. Data from a 2‐year free‐air CO2 enrichment experiment with wheat with three N levels (on average 38 [Nd], 190 [Nad] and 320 kg N ha−1 [Nex]) and two CO2 levels (393 and 600 ppm) on SRG, fIRG and grain filling rate (GFR) and duration (GFD) were evaluated. SRG ranged from 2.5 to 12.9 mg and fIRG from 4.0 × 0.001% to 6.8 x 0.001%. Rising N supply or e[CO2] decreased SRG and fIRG via their increases in grain number. Accordingly, there was a negative linear relationship between grain number and SRG (r2 ≥ 0.84) or fIRG (r2 ≥ 0.97). Increasing N supply decreased GFR, but increased GFD, and GFR was increased by e[CO2] under Nad and Nex. For GFR and final grain weight, there was a strong positive (r2 ≥ 0.85), and for GFD, a strong negative linear relationship (r2 ≥ 0.76) with fIRG under Nad and Nex. Under these N levels, fIRG supplied the largest share (&gt;86%) for grain growth and thus single grain growth was possibly source limited under Nad and Nex. Under high grain number such as under Nex and e[CO2], there might be a risk for low final grain weight due to the low SRG that is insufficient for buffering assimilate shortage under unfavourable environmental conditions in early grain filling.

Impact of varying N fertiliser rate and timing on yield formation and grain filling in winter and spring-sown oats

The influence of N timing and N rate on yield formation and grain-filling procedures in winter and spring-sown oats is unclear. Factorial trials investigating the effect of six rates of applied N fertiliser (0,30. 60. 90. 120 and 150 kg N ha−1) applied at three timings (Zadoks GS 21, 30 and 50) were conducted at four spring sown sites and three winter sown sites (Cv Husky) over the period 2016–2019 in the east of Ireland.Significant interactions were frequently observed on grain yield following spring and winter sowing, associated with increases in grain number where N was applied at early growth stages (GS 21, GS30) relative to GS50 application. This was linked with increases in panicles/m2 in response to available N during early developmental periods. Grain weight was maintained as the level of N applied at GS50 increased with reductions observed at earlier applications, but had no effect on yield.Responses to applied N rate were in the range of 0.5–1.9 t ha−1 in spring sown crops and 1.2–3 t ha−1 in winter sown crops, with grain yield reducing by 0.5–2.1 t/ha −1 (spring) and 1.2–1.5 t ha−1 (winter) as N application was delayed. N application timing impacted spikelet and grain number per panicle in winter crops, with spring crops unaffected.The relative importance of panicle number when spring sown, and grains/panicle when winter sown, is also discussed. This paper highlights the role of N application during early developmental in increasing the yield components contributing to grain number.

Population structure, allelic variation at Rht-B1 and Ppd-A1 loci and its effects on agronomic traits in Argentinian durum wheat

Exploring the genetic variability in yield and yield-related traits is essential to continue improving genetic gains. Fifty-nine Argentinian durum wheat cultivars were analyzed for important agronomic traits in three field experiments. The collection was genotyped with 3565 genome-wide SNPs and functional markers in order to determine the allelic variation at Rht-B1 and Ppd-A1 genes. Population structure analyses revealed the presence of three main groups, composed by old, modern and genotypes with European or CIMMYT ancestry. The photoperiod sensitivity Ppd-A1b allele showed higher frequency (75%) than the insensitivity one Ppd-A1a (GS105). The semi-dwarfism Rht-B1b and the Ppd-A1a (GS105) alleles were associated with increases in harvest index and decreases in plant height, grain protein content and earlier heading date, although only the varieties carrying the Rht-B1 variants showed differences in grain yield. Out of the two main yield components, grain number per plant was affected by allelic variants at Rht-B1 and Ppd-A1 loci, while no differences were observed in thousand kernel weight. The increases in grain number per spike associated with Rht-B1b were attributed to a higher grain number per spikelet, whereas Ppd-A1a (GS105) was associated with higher grain number per spikelet, but also with lower spikelets per spike.

Effects of elevated atmospheric CO2 and its interaction with temperature and nitrogen on yield of barley (Hordeum vulgare L.): a meta-analysis

AimsThe general aim of this meta-analysis is to synthesize and summarize the mean response of barley yield variables to elevated CO2 (eCO2) and how temperature and nitrogen (N) affect the CO2-induced yield responses of barley.MethodsA meta-analysis procedure was used to analyze five yield variables of barley extracted from 22 studies to determine the effect size and the magnitude concerning eCO2 and its interaction with temperature and N.ResultsCO2 enrichment increased aboveground biomass (23.8%), grain number (24.8%), and grain yield (27.4%). The magnitude of the responses to eCO2 was affected by genotype, temperature, nitrogen, and CO2 exposure methods. Genotype “Anakin” shows the highest CO2 response of aboveground biomass (47.1%), while “Bambina” had the highest grain number (58.4%). Grain yield response was observed to be higher for genotypes “Alexis” (38.1%) and “Atem” (33.7%) under eCO2. The increase of aboveground biomass and grain yield was higher when plants were grown under eCO2 in combination with higher N (151–200 kg ha−1). The interaction between eCO2 and three different temperature levels was analyzed to identify the impacts on barley yield components. The results revealed that the CO2-induced increase in grain number and grain yield was higher in combination with a temperature level of 21–25 °C as compared to lower levels (< 15 and 16–20 ℃). The response of barley yield to eCO2 was higher in growth chambers than in other CO2 exposure methods. Moreover, a higher response of aboveground biomass and grain yield to eCO2 was observed for pot-grown plants compared to field-grown.ConclusionsOverall, results suggest that the maximal barley production under eCO2 will be obtained in combination with high N fertilizer and temperature levels (21–25 °C).

Effect of Different Sowing Methods on Water Use Efficiency and Grain Yield of Wheat in the Loess Plateau, China

Research has revealed that summer fallow sowing improves the water use efficiency (WUE) and grain yield of winter wheat. However, wheat yields differ yearly with crop management. A field experiment over 8 years was established in the Loess Plateau to determine the role of precipitation and soil water storage in wheat yield formation under conservation tillage. The average WUE values were 7.8, 11.0, and 12.6 t·ha−1, while the average evapotranspiration (ET) values were 334.7, 365.5, and 410 mm when the yields were 3.0, 3.0–4.5, and over 4.5 t·ha−1, respectively. Compared to drill sowing (DS), high water consumption during early growth increased the spike number, grain number, and yield. In years of intermediate or low yields, wide-space sowing (WS) and furrow sowing (FS) improved the ET, WUE, spike number, grain number, and yield of wheat compared to (DS) drill sowing. When the wheat yield was 3.0–4.5 t·ha−1, higher soil water intake during jointing, anthesis, and anthesis–maturity increased the tiller number, 1000-grain weight, and yield, related to the use of suitable tillers. Synchronous increases in grain number per spike and 1000-grain weight were observed with increased soil water content at jointing, maturity, and anthesis, as well as consumption of soil water in the latter part during the growing season.

Agronomic assessment of the durum

The wheat Green Revolution Rht-B1b and Rht-D1b dwarfing alleles are associated with increased grain yields but also with reduced early growth and seedling emergence, especially if sowing conditions are unfavourable. The gibberellic acid-responsive, mutagen-derived Rht18 dwarfing gene was backcrossed from durum wheat (Triticum turgidum subsp. durum L.) cv. Icaro into tall bread wheat (Triticum aestivum L.) cv. Halberd using phenotypic selection for reduced plant height. The Rht18 allele was confirmed among homozygous BC1F2-derived, F5:7 recombinant inbred lines by using a chromosome 6AS-linked, microsatellite molecular marker (Xwms4608), and then assessed for agronomic performance across multiple field sites ranging in yield from 3.6 to 6.4 t/ha. The Rht18-containing lines were significantly (P &lt; 0.05) shorter in height (−24%) and reduced in plant lodging (−51%) compared with tall sister lines. Reductions in plant height were associated with significant increases in grain yield (+16%), reflecting increases in grain number (+21%), number of spikes (+7%) and number of grains per spike (+12%). Coleoptile length, early shoot biomass and ground cover percentage were unaffected by the presence of the Rht18 dwarfing gene. Comparisons of effects of gibberellic acid-insensitive Rht-B1b and Rht18 on early growth and agronomic performance were assessed separately for a set of 30 BC5F6-derived Halberd near-isogenic lines in the field in 2015. Ground cover and coleoptile length were significantly greater for Rht18 lines, whereas plant height, lodging, harvest index, grain number and yield were similar for Rht-B1b and Rht18 sister lines. Reduced lodging and increased grain number and yield, together with greater coleoptile length, indicate a potentially useful role for Rht18 in improving wheat performance.

Promena prinosa i osnovnih agronomskih osobina pšenice tokom poslednjih 90 godina u Panonskoj niziji

This study aimed to quantify the changes in grain yield and main agronomic traits in winter wheat cultivars registered during the past 90 years . A field trial with 18 winter wheat cultivars registered from 1930 to 2016 was conducted at the experimental field Rimiski šančevi during two growing seasons . The following agronomic traits were measured: grain yield, stem height, spike length, heading date, hectolitre mass, 1000 grain weight, and grain number per unit area . The results of this study showed that there was a significant genotypic effect on the studied traits . Du-ring the past 90 years, grain yield increased at rate of 50 kg ha -1 per year of cultivar release . Grain yield improvement was followed by stem height decrease (0 .4 cm per year of cultivar release) and earlier heading date in modern cultivars, which were 7 -8 days earlier than the older ones . Modern wheat cultivars were characterized by a higher grain number per unit area than the ol-der ones while during the past 90 years, the 1000 grain weight was not significantly related to the year of cultivar release . Further grain yield improvement should be related to a further increase of grain number per unit area while maintaining a higher 1000 grain weight.

Genotypic differences in wheat yield determinants within a NAM population based on elite parents

Future grain yield (GY) improvements require the identification of beneficial traits within the context of high yield potential and not just based on the pleiotropic effect of traits such as crop height and heading date. We evaluated 1937 lines from Nested Association Mapping (NAM) population derived from 13 bi-parental varietal crosses under field conditions. We selected 493 lines with similar time to anthesis to that of the two checks used in the study (across and within each family) which reduced the range of plant height in the selected lines. Yield components were measured in these 493 lines from which 231 lines were selected by excluding lines with lowest number of grains so excluded low yielding lines. Later the subset of 231 lines were evaluated in two field experiments (2016−17, CS1 and 2017−18, CS2). Numerical and physiological components of grain yield were measured. The two-step selection maximised GY within an acceptable range of variation for height and anthesis. GY in 231 lines showed very high G × E interaction. Taking both seasons together, we selected lines from upper and lower quartile GY groups to identify stable beneficial trait combinations for improved GY. Differences in GY were explained by grain number driven by increased spike dry weight at anthesis (SDWa) and fruiting efficiency (FE). Increased GY was accompanied by sink limitation. The data points towards increases in grain number as the route towards future GY increases in wheat breeding.

Maize hybrids response to high plant density in the Guinea savannah of Nigeria

ABSTRACT Several maize (Zea mays L.) hybrids have been developed and commercialized in the Nigeria savannas, but limited informationis available on how they perform at plant densities higher than the recommended density of 53,333 plants ha-1. Therefore, field trials were conducted in northern Nigeria in 2015 and 2016 at two locations with contrasting rainfall amount to evaluate the performance of selected maize hybrids at plant densities of 53,333 and 88,888 plants ha-1. All maize hybrids had higher grain yields, total dry matter, ears m-2, and number of grains m-2 at 88,888 than at 53,333 plants ha-1 at both locations. The magnitude ofincreases in yield when plant density was increased to 88,888 plants ha-1 was, however, higher for the new hybrids than for the old commercial hybrids. In Tudun Wada, five hybrids produced significantly higher mean grain yields than the remaining hybrid sat both plant densities. One of the hybrids (M1227-12) produced the highest grain yield at both planting densities at this location. In Samaru Zaria, the hybrid M1227-12 produced the highest grain yield only at 53,333 plants ha-1 at this location, whereas M0926-8 produced the highest yield at 88,888 plants ha-1. The 500-grain weight was 7-8% lower at 88,888 plants ha-1 than at 53,333 plantsha-1, which was offset by a significant increase in grain number. Our results showed that farmers in the Nigeria savannas can increase planting density of hybrid maize to 88,888 plants ha-1 and significantly increase their yields.

Cultivar, Trait and Management System Selection to Improve Soft-Red Winter Wheat Productivity in the Eastern United States.

Wheat growing regions and seasons are diverse, mandating different varietal adaptation and management practices. Grain yield is the primary target for soft-red winter (SRW) wheat, due to lower protein content requirements. The growing season for SRW wheat in the eastern United States takes up to 9 months under variable environments, highlighting the importance of variety and management. In this study, we present the results of a 2-year field-based investigation of yield response of 30 wheat lines to different nitrogen treatments by dissecting yield to its components. For 5 out of the 30 lines, we performed in-tissue nitrogen analysis. Spring nitrogen (N) treatments were two levels of 0 kg N ha–1 (low N) and 112 kg N ha–1 (high N). On average, application of 112 kg N in the spring, in addition to fall N fertilizer, increased phytomass by 22% at maturity, enhanced fertile tiller numbers by 16%, and increased grain yield by 18% that coincided with a 26% increase in grain number per unit area. N in the grains, or the nitrogen harvest index, was lower (36% of total) in high N than in low N (40% of total) treatment, which indicated plants did not increase the in-grain utilization of N. The 18% higher grain yield with 112 kg N treatment occurred without considerable change in grain N content. However, lines with greater biomass produced greater yields in low N. Therefore, increasing tiller numbers and grain numbers for SRW wheat are the targeted traits for improving grain yield under N management, with less emphasis on the utilization of N in grains because N content is not critically influential for the marketability of soft wheat grains.

Co-Evolution of Sink and Source in the Recent Breeding History of Winter Wheat in Germany.

Optimizing the interplay between sinks and sources is of crucial importance for breeding progress in winter wheat. However, the physiological limitations of yield from source (e.g. green canopy duration, GCD) and sink (e.g. grain number) are still unclear. Furthermore, there is little information on how the source traits have been modified during the breeding history of winter wheat. This study analyzed the breeding progress of sink and source components and their relationships to yield components. Field trials were conducted over three years with 220 cultivars representing the German breeding history of the past five decades. In addition, genetic associations of QTL for the traits were assessed with genome-wide association studies. Breeding progress mainly resulted from an increase in grain numbers per spike, a sink component, whose variations were largely explained by the photosynthetic activity around anthesis, a source component. Surprisingly, despite significant breeding progress in GCD and other source components, they showed no direct influence on thousand grain weights, indicating that grain filling was not limited by the source strength. Our results suggest that, 1) the potential longevity of the green canopy is predetermined at the time point that the number of grains is fixed; 2) a co-evolution of source and sink strength during the breeding history contribute to the yield formation of the modern cultivars. For future breeding we suggest to choose parental lines with high grain numbers per spike on the sink side, and high photosynthetic activity around anthesis and canopy duration on the source side, and to place emphasis on these traits throughout selection.