Cereal Grain Yield Research Articles

Sorghum qTGW1a encodes a G-protein subunit and acts as a negative regulator of grain size.

Grain size is a major determinant of grain yield in sorghum and other cereals. Over 100 quantitative trait loci (QTLs) of grain size have been identified in sorghum. However, no gene underlying any grain size QTL has been cloned. Here, we describe the fine mapping and cloning of one grain size QTL. From an F8 recombinant inbred line population derived from a cross between inbred lines 654 and LTR108, we identified 44 grain size QTLs. One QTL, qTGW1a, was detected consistently on the long arm of chromosome 1 in the span of 4 years. Using the extreme recombinants from an F2:3 fine-mapping population, qTGW1a was delimited within a ~33 kb region containing three predicted genes. One of them, SORBI_3001G341700, predicted to encode a G-protein γ subunit and homologous to GS3 in rice, is likely to be the causative gene for qTGW1a. qTGW1a appears to act as a negative regulator of grain size in sorghum. The functional allele of the putatively causative gene of qTGW1a from inbred line 654 decreased grain size, plant height, and grain yield in transgenic rice. Identification of the gene underlying qTGW1a advances our understanding of the regulatory mechanisms of grain size in sorghum and provides a target to manipulate grain size through genome editing.

Analysis of relationship between cereal yield and NDVI for selected regions of Central Europe based on MODIS satellite data

Earth observation satellite technologies allow the status of crops to be assessed at various geographical scales. The most popular vegetation index for analyzing this status is the Normalized Difference Vegetation Index (NDVI). This article studies the relationship between the NDVI and cereal-grain yield in selected regions (corresponding to NUTS2 levels) of four Central European countries: Poland, Germany, the Czech Republic, and Slovakia. The remote sensing data cover the vegetation seasons (from the beginning of March until the end of June) of 2012–2016, and were obtained using the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor of NASA's Terra satellite. The average NDVI of the data was calculated for both the entire area and the arable-land area of the regions (according to the Corine Land Cover program). Statistical analysis includes correlation and linear regression analyses between cereal grain yield and mean NDVI for entire area and arable land of the regions in each year of the study. They are strongly correlated from the beginning of March until mid-May (most of the correlation coefficients for arable land are between 0.50 and 0.85), the strongest relationship being around the beginning of April in the Czech Republic and Slovakia (most of the correlation coefficients are between 0.80 and 1.00). In most regions of Poland, the relationships are quite strong, but in German regions they are weak and inconsistent. Regression coefficients (slopes) for relationships between the NDVI in the beginning of April and the grain yield of cereals range from 10.8 to 26.2. This means that an increase in the NDVI in early spring by 0.1 unit increases the grain yield of cereals by about 1.1–2.6 t/ha. The obtained results are promising because they prove the possibility of forecasting cereal grain yield at the regional level, three–four months before the harvest, which is important for planning food policy.

Molecular, cellular and Yin-Yang regulation of grain size and number in rice

Final grain size and grain number per plant, representing the sink capacity, are two major developmental traits determining grain yield of rice and other cereals. Understanding the regulatory mechanisms controlling grain size and number has become an important research field in plant science. Grain number and size are determined by the activity, size and number of inflorescence meristems, branch meristems and floral meristems, which are coordinately regulated by both rate and duration of cell division, cell expansion and cell differentiation. Current advances have revealed several signaling pathways controlling grain size and number, including G protein signaling, biosynthesis and signaling of BR, CK and IAA, MAPK signaling, peptide signaling, the ubiquitin-proteasome degradation pathway, epigenetic pathways and transcriptional regulation. This review provides a general overview of recent findings and future perspectives in molecular, cellular and Yin-Yang regulatory mechanisms of coordinating grain size and number in rice, which has substantial implications for breaking the yield bottleneck caused by the trade-off of grain size and number in crop genetic improvement. We also propose 16 key scientific questions underlying grain size and number in rice and other crops to call for an international coordinated effort in studying and solving these problems in the form of a project named GSGN16.

LA ESTABILIDAD DE RENDIMIENTO EN GRANO DE CEREALES INVERNALES EN LA REGIÓN SUBHÚMEDASECA PAMPEANA

Winter cereals are important in agrosystems of the drysubhumid Pampas region. Environmental factors such as rainfall and temperature dominant in the definition of grain yield, there is usually a great interaction with the genotype. The triticale (X Triticosecale Wittmack) and durum wheat ( Triticum durum Desf.) may be alternatives to bread wheat ( Triticum aestivum L.) to stabilize the grain yields of winter cereals. The study was conducted in the Faculty of Agronomy of UNLPam Experimental Field, located at 36o 46 'S and 64o 17' W, 210 m above sea level. The tests were conducted for eight years, which compared the three species, (five varieties of bread wheat, four of durum wheat and two of triticale), with two fertility conditions. The two triticale`s genotypes and bread wheat “Buck guarani” had greater grain yield, while durum wheats showed average to low yields. The grain yield stability was not exclusive of one species, since triticale “Eronga 83”, bread wheat “ACA 601” and durum wheat “Ciccio” were stable, and bread wheat “Abate” and durum wheat “Buck cristal” were unstable. The CVi of Francis and Kannemberg and VEP of AMMI methods showed a good description of the clasification stability`s including all methods. The grain yield stability was not associated with higher yield potential.

Simulation of satellite reflectance data using high-frequency ground based hyperspectral canopy measurements for in-season estimation of grain yield and grain nitrogen status in winter wheat

Remote sensing allows the assessment of biomass and grain yield of cereals. An enhanced potential to detect specific traits is offered by proximal hyperspectral sensing, in contrast the potential of satellite remote sensing might still be leveraged up seen the degree of spatial and temporal resolution. Consequently, hyperspectral satellite data are still not readily available for most agricultural applications and ground truth validation done at high frequency throughout the season remains scarce. Here, we simulate multispectral satellite data through resampling ground based hyperspectral reflection (400–1000 nm). Spectral data were collected at 3 nm resolution at high temporal frequency during 5–14 growth stages over three winter wheat growing seasons for investigating the influence of year and seasonality. The field experiment comprised 24 different genotypes, which varied in morphology and phenology, grown at varying nitrogen application and additionally by varying the sowing time and fungicide intensity during the third season. Ground based reflectance data were resampled to fit the spectral resolution of the satellite sensors Landsat-8, Quickbird, RapidEye, WorldView-2 and Sentinel-2. The resulting spectral bands were used for calculating all possible normalized difference vegetation indices, which were correlated to grain yield, grain N uptake and grain N concentration. The index performance depended substantially on the growth stages and years. For grain yield, maximum linear relationships (R2) obtained from hyperspectral sensing over the season ranged from 0.65 in 2017 to 0.88 in 2015 compared to 0.40 to 0.79 for the best simulated multispectral sensor, Sentinel-2. In most cases, indices performed better for grain N uptake and less well for grain N concentration. Typically, correlations peaked at early to medium grain filling but decreased around ear emergence. Index performance from multispectral compared to hyperspectral data decreased over time during grain filling. The sensor ranking remained consistent with Sentinel-2 followed by Worldview-2 and RapidEye clearly outperforming the other sensors. Advantages are attributed to the red edge band for N-related traits and the better coverage of the NIR range between 800 and 1000 nm by the Sentinel-2. The results can possibly be extrapolated to the application of UAV and satellite sensing by elucidating optimized measurement stages and enhancing spectral properties of sensors.

Screening of barley genotypes for drought tolerance based on culm reserves contribution to grain yield

Grain filling determines the grain weight, a major component of grain yield in cereals. Grain filling in barley depends on current assimilation and culm reserves. A pot experiment was conducted at the Grilled House, Department of Crop Botany, Bangladesh Agricultural University, Mymensingh during October 2015–May 2016 to study the grain filling patterns and the contributions of culm reserves to grain yield under drought stress. The experiment consisted of two factors—barley cultivars (six cultivars) and drought stress treatments (control and drought stress). Drought stress was imposed by limiting the irrigation during grain filling period. The tillers were sampled at anthesis, milk-ripe and maturity to determine the changes in dry weights of different parts, viz., leaf lamina, culm with sheath, spikes, and grains; and to examine the contribution of culm reserves to grain yield. The result in this experiment revealed that the grain yield was reduced by 5–25% due to drought stress. The reduction in grain yield was attributable to reduce number of grains per spike and lighter grain weight due to the stress. Drought stress drastically reduced the grain filling duration by about 30% and the stress induced early leaf senescence. Photosynthesis rate and leaf greenness were also reduced in stress. The stress altered the contribution of culm reserves, water soluble carbohydrates (WSCs) in culms to grains. At milk ripe stage, accumulation reached its peak. It accumulated 29.0 to 70.0 mg and from 15.8 to 40.6 mg culm−1 in control and stressed plants, respectively. The residual culm WSCs ranged from 3.5 to 11.2 mg and 1.0 to 3.5 mg culm−1 under control and stress conditions, respectively. The highest contribution of culm WSCs to grain yield was observed in BARI barley2 and the lowest was in BARI barley5 both in control and stress condition. Among the cultivars studied, BARI barley2 produced higher yield with the higher contribution of culm reserves to grain yield under the drought stress.J. Bangladesh Agril. Univ. 16(1): 62-66, April 2018

MSD1 regulates pedicellate spikelet fertility in sorghum through the jasmonic acid pathway

Grain number per panicle (GNP) is a major determinant of grain yield in cereals. However, the mechanisms that regulate GNP remain unclear. To address this issue, we isolate a series of sorghum [Sorghum bicolor (L.) Moench] multiseeded (msd) mutants that can double GNP by increasing panicle size and altering floral development so that all spikelets are fertile and set grain. Through bulk segregant analysis by next-generation sequencing, we identify MSD1 as a TCP (Teosinte branched/Cycloidea/PCF) transcription factor. Whole-genome expression profiling reveals that jasmonic acid (JA) biosynthetic enzymes are transiently activated in pedicellate spikelets. Young msd1 panicles have 50% less JA than wild-type (WT) panicles, and application of exogenous JA can rescue the msd1 phenotype. Our results reveal a new mechanism for increasing GNP, with the potential to boost grain yield, and provide insight into the regulation of plant inflorescence architecture and development.

Natural variation and genetic make-up of leaf blade area in spring barley

Key messageGWAS analysis for leaf blade area (LA) revealed intriguing genomic regions associated with putatively novel QTL and known plant stature-related phytohormone and sugar-related genes.Despite long-standing studies in the morpho-physiological characters of leaf blade area (LA) in cereal crops, advanced genetic studies to explore its natural variation are lacking. The importance of modifying LA in improving cereal grain yield and the genes controlling leaf traits have been well studied in rice but not in temperate cereals. To better understand the natural genetic variation of LA at four developmental stages, main culm LA was measured from 215 worldwide spring barleys including 92 photoperiod-sensitive accessions [PHOTOPERIOD RESPONSE LOCUS 1 (Ppd-H1)] and 123 accessions with reduced photoperiod sensitivity (ppd-H1) locus under controlled greenhouse conditions (long-day; 16/8 h; ~ 20/~ 16 °C day/night). The LA of Ppd-H1-carrying accessions was always smaller than in ppd-H1-carrying accessions. We found that nine SNPs from the Ppd-H1 gene were present in the collection of which marker 9 (M9; G/T in the CCT-domain) showed the most significant and consistent effect on LA at all studied developmental stages. Genome-wide association scans (GWAS) showed that the accessions carrying the ppd-H1 allele T/M9 (late heading) possessed more genetic variation in LA than the Ppd-H1 group carrying G/M9 (early heading). Several QTL with major effects on LA variation were found close to plant stature-related heading time, phytohormone- and sugar-related genes. The results provide evidence that natural variation of LA is an important source for improving grain yield, adaptation and canopy architecture of temperate cereals.

Effects of 16‐Year Woodchip Mulching on Weeds and Yield in Organic Farming

Core Ideas Woodchip mulching significantly suppressed weeds under field conditions.Sixteen‐year woodchip mulching had no impact on grain yield of cereals or faba bean.There was a continuous decreasing trend of the relative yield with woodchip mulching.There was no impact of woodchip mulching on the weed seed bank after 16 yr. To test the possibility of using hedgerow woody waste for weed control in arable organic farming, a 16‐yr field trial with a typical organic crop rotation using three rates of woodchip mulching (WCM) was conducted in Southwest Germany. Winter cereals, fodder crops, and legumes representative for this region were included in the crop rotation. The woodchips were produced from cuttings of the hedgerows on the farm and were applied to the field in rates of 0, 80, and 160 m3 ha–1, respectively (control, WCM80, and WCM160). Weed infestations, including weed density in spring, weed biomass at crop harvest and weed seed bank, were measured in selected years. Crop yields were recorded yearly. Soil temperature and soil mineral N content were measured in selected years. In general, mean weed density was reduced in WCM160 (135 plants m–2) compared to WCM80 and the control (150 and 160 plants m–2, respectively). The relative weed density averaged across the two WCM levels was 91% of the control on average and showed no trend over time. The grain yield of cereals and faba bean (Vicia faba L.) did not significantly differ between the mulching treatments. The relative crop yield of plots with WCM compared to the control showed a decreasing trend over time. Soil temperature and diurnal temperature variation were lower in WCM160 compared to the control. Generally, combined with an adapted fertilizer application, WCM in a specific amount could be an efficient tool to control weeds in organic farming without yield loss.

Grain filling patterns of barley as affected by high temperature stress

Grain filling determines the grain weight, a major component of grain yield in cereals. Grain filling in barley depends on current assimilation and culm reserves (mainly water-soluble carbohydrates). Nowadays barley is facing heat stress problem which is mostly responsible to reduce the yield of barley. A field experiment was conducted at the Field Lab, Department of Crop Botany, BangladeshAgriculturalUniversity, Mymensingh during November 2015 to March 2016 to study the grain filling patterns and the contributions of culm reserves to grain yield under heat stress. The experiment consisted of two factors—barley cultivars and heat stress. The heat stress was imposed by late sowing. The tillers were sampled once a week during grain filling period to determine the changes in dry weights of different parts, viz., leaves, culm with sheath, spikes, and grains; and to examine the contribution of culm reserves to grain yield. The results in the experiment revealed that the grain yield was reduced by 22-28% due to the stress. The grain yield varied from 52 to 150 g m−2 with the mean of 102 g m−2 under control while it varied from 37 to 116 g m−2 with the mean of 75 g m−2 under heat stress. Among the cultivars studied BARI Barley5, BARI Barley2 and BARI Barley1, seemed as high yielders while BARI Barley3, BARI Barley4, BARI Barley6 as the low yielders under heat stress treatment. The reduction in grain yield was attributable mainly to lighter grain weight due to the stress. Heat stress drastically reduced the grain filling duration by 45–50%. However, the stress increased the grain filling rate by 6–53%. The amount of reserves remobilized to grain varied among the cultivars ranging from 4.8 to 12.77 mg spike−1 in control and from 1.73 to 6.25 mg spike−1 in stressed plants. The stressed barley plants exhibited lower accumulation of reserves in culm but they showed almost its complete remobilization to the grain. The contribution of culm reserves to grain yield varied from 1.13 to 19.52%, and 1.09 to 2.11% in control and in stressed plants, respectively. In conclusion, culm reserve is the important attributes in grain yield in Bangladeshi barley cultivars but the contribution remains almost unaffected due the post-anthesis heat stress.J. Bangladesh Agril. Univ. 15(2): 174-181, December 2017

The Genetic Control of Reproductive Development under High Ambient Temperature

Ambient temperature has a large impact on reproductive development and grain yield in temperate cereals. However, little is known about the genetic control of development under different ambient temperatures. Here, we demonstrate that in barley (Hordeum vulgare), high ambient temperatures accelerate or delay reproductive development depending on the photoperiod response gene PHOTOPERIOD1 (Ppd-H1) and its upstream regulator EARLY FLOWERING3 (HvELF3). A natural mutation in Ppd-H1 prevalent in spring barley delayed floral development and reduced the number of florets and seeds per spike, while the wild-type Ppd-H1 or a mutant Hvelf3 allele accelerated floral development and maintained the seed number under high ambient temperatures. High ambient temperature delayed the expression phase and reduced the amplitude of clock genes and repressed the floral integrator gene FLOWERING LOCUS T1 independently of the genotype. Ppd-H1-dependent variation in flowering time under different ambient temperatures correlated with relative expression levels of the BARLEY MADS-box genes VERNALIZATION1 (HvVRN1), HvBM3, and HvBM8 in the leaf. Finally, we show that Ppd-H1 interacts with regulatory variation at HvVRN1. Ppd-H1 only accelerated floral development in the background of a spring HvVRN1 allele with a deletion in the regulatory intron. The full-length winter Hvvrn1 allele was strongly down-regulated, and flowering was delayed by high temperatures irrespective of Ppd-H1 Our findings demonstrate that the photoperiodic and vernalization pathways interact to control flowering time and floret fertility in response to ambient temperature in barley.

Different leguminous pre-crops increased yield of succeeding cereals in two consecutive years

ABSTRACTLeguminous pre-crops are an important source of green manure in organic crop rotations for improving soil fertility and achieving high yields of cereals. We aimed to study the potential of various leguminous species, other than the traditionally cultivated red clover (Trifolium pratense L.), as green manure pre-crops for subsequent cereals. The use of different legume species enables to exploit advantages of specific legumes in organic cereal production. In order to test the legumes as pre-crops for cereals, we carried out trials located in the temperate climate zone of northeast Europe (58°44′59.41″ N, 26°24′54.02″ E). We sowed the following perennial legumes as pre-crops: red clover, alsike clover (Trifolium hybridum L.) and Washington lupine (Lupinus polyphyllus Lindl.), biennial white sweet clover (Melilotus albus Medik.) and annual Alexandria clover (Trifolium alexandrinum L.), and crimson clover (Trifolium incarnatum L.). Timothy (Phleum pratense L.) was used as a control. The leguminous pre-crops were followed by three spring cereals (barley, oat and spring wheat) and two winter cereals (rye and winter wheat). We tested the first-year after-effect (all cereals) and second-year after-effect (only barley and oat) of pre-crops on the grain yield of cereals. Perennial and biennial legume species produced the highest dry matter yield and contained the highest amount of nutrients, especially nitrogen, compared to annual species. All subsequent cereals produced significant extra yields after each leguminous pre-crop in the following two years, although the effect was smaller in the second year. The most suitable pre-crops for spring cereals were red and alsike clover followed by lupine, whereas the best pre-crops for winter cereals were sweet clover and annual clovers. Our results show the potential of various leguminous pre-crop species as valuable sources of green manure in organic crop rotation.

Fine-mapping of qGW4.05, a major QTL for kernel weight and size in maize.

BackgroundKernel weight and size are important components of grain yield in cereals. Although some information is available concerning the map positions of quantitative trait loci (QTL) for kernel weight and size in maize, little is known about the molecular mechanisms of these QTLs. qGW4.05 is a major QTL that is associated with kernel weight and size in maize. We combined linkage analysis and association mapping to fine-map and identify candidate gene(s) at qGW4.05.ResultsQTL qGW4.05 was fine-mapped to a 279.6-kb interval in a segregating population derived from a cross of Huangzaosi with LV28. By combining the results of regional association mapping and linkage analysis, we identified GRMZM2G039934 as a candidate gene responsible for qGW4.05. Candidate gene-based association mapping was conducted using a panel of 184 inbred lines with variable kernel weights and kernel sizes. Six polymorphic sites in the gene GRMZM2G039934 were significantly associated with kernel weight and kernel size.ConclusionThe results of linkage analysis and association mapping revealed that GRMZM2G039934 is the most likely candidate gene for qGW4.05. These results will improve our understanding of the genetic architecture and molecular mechanisms underlying kernel development in maize.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0768-6) contains supplementary material, which is available to authorized users.

Awns reduce grain number to increase grain size and harvestable yield in irrigated and rainfed spring wheat.

Genotypic variation in ear morphology is linked to differences in photosynthetic potential to influence grain yield in winter cereals. Awns contribute to photosynthesis, particularly under water-limited conditions when canopy assimilation is restricted. We assessed performance of up to 45 backcross-derived, awned-awnletted NILs representing four diverse genetic backgrounds in 25 irrigated or rainfed, and droughted environments in Australia and Mexico. Mean environment grain yields were wide-ranging (1.38-7.93 t ha(-1)) with vegetative and maturity biomass, plant height, anthesis date, spike number, and harvest index all similar (P >0.05) for awned and awnletted NILs. Overall, grain yields of awned-awnletted sister-NILs were equivalent, irrespective of yield potential and genetic background. Awnletted wheats produced significantly more grains per unit area (+4%) and per spike (+5%) reflecting more fertile spikelets and grains in tertiary florets. Increases in grain number were compensated for by significant reductions in grain size (-5%) and increased frequency (+0.8%) of small, shrivelled grains ('screenings') to reduce seed-lot quality of awnletted NILs. Post-anthesis canopies of awnletted NILs were marginally warmer over all environments (+0.27 °C) but were not different and were sometimes cooler than awned NILs at cooler air temperatures. Awns develop early and represented up to 40% of total spikelet biomass prior to ear emergence. We hypothesize that the allocation of assimilate to large and rapidly developing awns decreases spikelet number and floret fertility to reduce grain number, particularly in distal florets. Individual grain size is increased to reduce screenings and to increase test weight and milling quality, particularly in droughted environments. Despite the average reduction in grain size, awnless lines could be identified that combined higher grain yield with larger grain size, increased grain protein concentration, and reduced screenings.

Coordinated regulation of vegetative and reproductive branching in rice

Grasses produce tiller and panicle branching at vegetative and reproductive stages; the branching patterns largely define the diversity of grasses and constitute a major determinant for grain yield of many cereals. Here we show that a spatiotemporally coordinated gene network consisting of the MicroRNA 156 (miR156/)miR529/SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) and miR172/APETALA2 (AP2) pathways regulates tiller and panicle branching in rice. SPL genes negatively control tillering, but positively regulate inflorescence meristem and spikelet transition. Underproduction or overproduction of SPLs reduces panicle branching, but by distinct mechanisms: miR156 and miR529 fine-tune the SPL levels for optimal panicle size. miR172 regulates spikelet transition by targeting AP2-like genes, which does not affect tillering, and the AP2-like proteins play the roles by interacting with TOPLESS-related proteins (TPRs). SPLs modulate panicle branching by directly regulating the miR172/AP2 and PANICLE PHYTOMER2 (PAP2)/Rice TFL1/CEN homolog 1 (RCN1) pathways and also by integrating other regulators, most of which are not involved in tillering regulation. These findings may also have significant implications for understanding branching regulation of other grasses and for application in rice genetic improvement.

Regulation of grain yield in rice under well-watered and drought stress conditions by GUDK

Increasing the grain yield of cereals, which is stable under unfavorable environmental stress, is a major objective to sustain production and feed the growing world population. Recently, we functionally characterized a receptor-like cytoplasmic kinase, named GROWTH UNDER DROUGHT KINASE (GUDK), revealing its role in regulating grain yield under well-watered and drought stress conditions by transphosphorylating the OsAP37 transcription factor. GUDK is induced under several stresses and its loss-of-function increased the sensitivity of rice seedlings to salinity, osmotic stress, and abscisic acid treatment. In addition to reduced tolerance of gudk mutant plants to drought stress at vegetative stage, a significant reduction in grain yield was observed under well-watered and drought stress conditions at reproductive stage. Gene co-expression analysis supports the role of GUDK in regulating important biological processes both under control and stress conditions. Thus, our results suggest that GUDK has the potential to regulate grain yield both under favorable and unfavorable conditions.

Canopy temperature for simulation of heat stress in irrigated wheat in a semi-arid environment: A multi-model comparison

Even brief periods of high temperatures occurring around flowering and during grain filling can severely reduce grain yield in cereals. Recently, ecophysiological and crop models have begun to represent such phenomena. Most models use air temperature (Tair) in their heat stress responses despite evidence that crop canopy temperature (Tc) better explains grain yield losses. Tc can deviate significantly from Tair based on climatic factors and the crop water status. The broad objective of this study was to evaluate whether simulation of Tc improves the ability of crop models to simulate heat stress impacts on wheat under irrigated conditions. Nine process-based models, each using one of three broad approaches (empirical, EMP; energy balance assuming neutral atmospheric stability, EBN; and energy balance correcting for the atmospheric stability conditions, EBSC) to simulate Tc, simulated grain yield under a range of temperature conditions. The models varied widely in their ability to reproduce the measured Tc with the commonly used EBN models performing much worse than either EMP or EBSC. Use of Tc to account for heat stress effects did improve simulations compared to using only Tair to a relatively minor extent, but the models that additionally use Tc on various other processes as well did not have better yield simulations. Models that simulated yield well under heat stress had varying skill in simulating Tc. For example, the EBN models had very poor simulations of Tc but performed very well in simulating grain yield. These results highlight the need to more systematically understand and model heat stress events in wheat.

English

Sink size with spikelets number (m -2 ) is one of the critical factors determining grain yield in cereals including rice. Nitrogen and dry matter are regarded as the two main factors controlling the formation of sink size and the objectives of present study were to examine the potential mechanisms underlying the difference in sink size between the late maturing YLY6 and HY3 an early maturing and drought resistant variety. The difference in the contribution of N and dry matter to the formation of sink size between the two varieties was also investigated. Growth duration of YLY6 was 20 days longer than of HY3. YLY6 produced significantly larger sink size than HY3 due to more secondary branches and spikelets, which resulted in higher grain yield for YLY6. Application of N fertilizer increased spikelets number for both YLY6 and HY3. Sink size of HY3 significantly correlated with N accumulation from mid-tillering (MT) to panicle initiation stage (PI) (R 2 =0.68) and N concentration in stem at PI (R 2 =0.74). However, for the late-maturing variety-YLY6, formation of sink size was more associated with biomass accumulation from PI-FL (flowering, R 2 =0.82). Both N and biomass accumulation significantly contributed to the difference in sink size between HY3 and YLY6, with R 2 of 0.45 and 0.84, respectively. Taken together, this study indicated that contribution of N and dry matter to the formation of sink size was different in rice varieties with different growth duration. © 2016 Friends Science Publishers

Effect of Copper, Zinc and Boron on Green Leaf Retention and Grain Yield of Winter and Spring Cereals

Crop nutrition has a significant effect on disease incidence, resistance or tolerance of various crops. There is currently a lack of reliable recent UK-based research about the effect of copper, zinc and boron on disease incidence, green leaf area (GLA), green leaf retention (GLR) and grain yield of winter wheat, spring wheat and spring barley. Data analysis showed that these trace elements had positive effects on GLR. These positive effects may have been due to the role of copper, zinc and boron in the production of defence related compounds (phenolics and lignin), which may have reduced the disease incidence resulting in prolonged GLR. Grain yield was significantly enhanced by the application of these trace elements on the crop grown on high pH calcareous soil, which can be partly attributed to enhanced GLR. Also trace elements have a positive role in reproductive growth, flowering and male fertility. On average, zinc was found to be the most consistent trace element in terms of enhancing GLR and grain yield. Across all trials, it was noted that for every 10% increase in GLA from trace elements, grain yields increased by 4.2% in 2012-2013, by 4.4% in 2013-2014 in winter wheat and by 3.9% in spring wheat in 2014. These are remarkably consistent and indicate that increasing GLA by 10% by early dough stage was associated with a yield improvement of about 4%. These trace elements also had a positive effect on grain protein content (GPC). This research concluded that the trace elements had positive effects in enhancing GLA and yield. It can be speculated that with the use of these trace elements, there may be more scope for using less robust or reduced rates of fungicides to control foliar diseases, which may help to maximize farm profits.

Enhancement of photosynthetic performance, water use efficiency and grain yield during long-term growth under elevated CO2 in wheat and rye is growth temperature and cultivar dependent

The effects of long-term elevated CO2 on photosynthetic performance of winter (cv Musketeer) and spring (cv SR4A) rye (Secale cereale) and winter (cv Norstar) and spring (cv Katepwa) wheat (Triticum aestivum) grown at either 20/16°C (non-acclimated (NA)) or 5/5°C (cold acclimated (CA) and at either ambient (380μmolCmol−1) or elevated (700μmolCmol−1) CO2 were studied. Compared to NA counterparts, CA winter cereals exhibited a 30–40% increase in light and CO2-saturated rates of photosynthesis at both ambient and elevated CO2. This was accompanied by a 35–50% decrease in excitation pressure and non-photochemical energy dissipation. Concomitantly, biomass increased by 28–46% and grain yield per plant by 60%. In contrast, both CA spring cultivars exhibited a 45–60% inhibition of light- and CO2-saturated rates of photosynthesis at ambient CO2 as well as growth at elevated CO2 relative to NA controls. This inhibition was specific for photosynthesis since cold acclimation stimulated rates of respiration by 22–47% in all cultivars tested. This was accompanied by a 58% increase in excitation pressure and a 17% increase in non-photochemical energy dissipation in the cold acclimated spring rye and spring wheat. Consequently, biomass accumulation was reduced by about 25% in CA versus NA spring cultivars at elevated CO2. We conclude that the potential for enhancement of photosynthetic performance, water use efficiency and grain yield of cereals grown at elevated CO2 is both growth temperature and cultivar dependent.