Stem Water-soluble Carbohydrates Research Articles

Stem traits promote wheat climate-resilience.

Wheat grain filling processes under post-anthesis stress scenarios depend mainly on stem traits and remobilization of stem water-soluble carbohydrates (WSC). A diverse panel of advanced semi-dwarf spring wheat lines, representing a natural variation in stem traits (WSC content, stem diameter, peduncle length, and stem wall width), was used to identify specific traits that reliably reflect the relationship between WSC and grain yield. The panel was phenotyped under various environmental conditions: well-watered, water-limited, and heat stress in Mexico, and terminal-drought in Israel. Environmental stresses reduced grain yield (from 626 g m-2 under well-watered to 213 g m-2 under heat), lower internode diameter, and peduncle length. However, stem-WSC generally peaked 3-4 weeks after heading under all environmental conditions except heat (where it peaked earlier) and expressed the highest values under water-limited and terminal-drought environments. Increased investment in internode diameter and peduncle length was associated with a higher accumulation of stem WSC, which showed a positive association with yield and kernel weight. Across all environments, there were no apparent trade-offs between increased crop investment in internode diameter, peduncle length, and grain yield. Our results showed that selecting for genotypes with higher resource investment in stem structural biomass, WSC accumulation, and remobilization could be a valuable strategy to ameliorate grain size reduction under stress without compromising grain yield potential. Furthermore, easy-to-measure proxies for WSC (stem diameter at specific internodes and length of the last internode, i.e., the peduncle) could significantly increase throughput, potentially at the breeding scale.

Determination of water-soluble carbohydrates by near-infrared spectroscopy for canola, maize, and sorghum stem fractions

Near infrared spectroscopy (NIRS) was evaluated as a rapid and non-destructive method for determining the concentration of water-soluble carbohydrates (WSC) in stem fractions for winter canola (Brassica napus L.), maize (Zea mays L.) and sorghum (Sorghum bicolor L. Moench) crops. For each crop at different growth stages, stem WSC concentration was determined using NIRS, and benchmarked against the anthrone reagent method, chemical lab analysis. Partial least squares regression was implemented to associate the WSC predicted via NIRS relative to those obtained by laboratory analysis. Spectral regions between 1100 and 1480 nm were critical for WSC determination. The predictive models resulted in coefficient of determinations of 0.93, 0.94, and 0.95, and a Root Mean Square Error of prediction of 10, 20, and 17 for winter-canola, maize and sorghum crops, respectively. The NIRS spectroscopy is a reliable method for WSC determination in stem tissues on these major field crops.

Grain-Filling Rate Improves Physical Grain Quality in Barley Under Heat Stress Conditions During the Grain-Filling Period.

Heat stress is a primary constraint to Australia's barley production. In addition to impacting grain yield, it adversely affects physical grain quality (weight and plumpness) and market value. The incidence of heat stress during grain filling is rising with global warming. However, breeding for new superior heat-tolerant genotypes has been challenging due to the narrow window of sensitivity, the unpredictable nature of heat stress, and its frequent co-occurrence with drought stress. Greater scientific knowledge regarding traits and mechanisms associated with heat tolerance would help develop more efficient selection methods. Our objective was to assess 157 barley varieties of contrasting genetic backgrounds for various developmental, agro-morphological, and physiological traits to examine the effects of heat stress on physical grain quality. Delayed sowing (i.e., July and August) increased the likelihood of daytime temperatures above 30°C during grain-filling. Supplementary irrigation of field trials ensured a reduced impact of drought stress. Heat tolerance appeared to be the primary factor determining grain plumpness. A wide variation was observed for heat tolerance, particularly among the Australian varieties. Genotypic variation was also observed for grain weight, plumpness, grain growth components, stay-green and stem water-soluble carbohydrates (WSC) content, and mobilisation under normal and delayed sown conditions. Compared to normal sowing, delayed sowing reduced duration of developmental phases, plant height, leaf size, head length, head weight, grain number, plumpness, grain width and thickness, stem WSC content, green leaf area retention, and harvest index (HI), and increased screenings, grain length, grain-filling rate (GFR), WSC mobilisation efficiency (WSCME), and grain protein content. Overall, genotypes with heavier and plumper grains under high temperatures had higher GFR, longer grain-filling duration, longer green leaf area retention, higher WSCME, taller stature, smaller leaf size, greater HI, higher grain weight/plumpness potentials, and earlier flowering. GFR played a significant role in determining barley grain weight and plumpness under heat-stress conditions. Enhancing GFR may provide a new avenue for improving heat tolerance in barley.

Impact of Long-Term Manure and Mineral Fertilization on Accumulation of Non-Structural Carbohydrates in Lucerne Forage

Fertilization management affects both productivity and nutritive value of forage legumes. However, there are few studies about changes in lucerne non-structural carbohydrates under long-term fertilization. The aims of this study were to compare the effects of mineral fertilization and organic manure on lucerne plant parts (leaf, stem) starch and water-soluble carbohydrate (WSC) accumulation in association with canopy structure following 60 years of different fertilization management approaches. Treatments investigated were: two contrasting levels of mineral N, P2O5 and K2O application (0:0:0 and 91:71:175), each with and without farmyard manure. Changes were mainly reflected in WSC content where intensive mineral fertilization consistently reduced the stem and forage WSC in contrast to unfertilized control or manure alone. These changes could be associated with a dilution effect presented by the highest increase of maximal stem length at these treatments. Manure improved leaf and forage WSC despite the associated increase in maximal stem length and leaf weight ratio, probably as a result of improved soil environment together with the potentially increased presence of arbuscular mycorrhizal fungi. Results showed that manure fertilization has potential for improvement of lucerne WSC, despite some negative relationships between lucerne canopy traits and sugar content.

GWAS to Identify Novel QTNs for WSCs Accumulation in Wheat Peduncle Under Different Water Regimes.

Water-soluble carbohydrates (WSCs) play a vital role in water stress avoidance and buffering wheat grain yield. However, the genetic architecture of stem WSCs’ accumulation is partially understood, and few candidate genes are known. This study utilizes the compressed mixed linear model-based genome wide association study (GWAS) and heuristic post GWAS analyses to identify causative quantitative trait nucleotides (QTNs) and candidate genes for stem WSCs’ content at 15 days after anthesis under different water regimes (irrigated, rainfed, and drought). Glucose, fructose, sucrose, fructans, total non-structural carbohydrates (the sum of individual sugars), total WSCs (anthrone based) quantified in the peduncle of 301 bread wheat genotypes under multiple environments (E01-E08) pertaining different water regimes, and 14,571 SNPs from “35K Axiom Wheat Breeders” Array were used for analysis. As a result, 570 significant nucleotide trait associations were identified on all chromosomes except for 4D, of which 163 were considered stable. A total of 112 quantitative trait nucleotide regions (QNRs) were identified of which 47 were presumable novel. QNRs qWSC-3B.2 and qWSC-7A.2 were identified as the hotspots. Post GWAS integration of multiple data resources prioritized 208 putative candidate genes delimited into 64 QNRs, which can be critical in understanding the genetic architecture of stem WSCs accumulation in wheat under optimum and water-stressed environments. At least 19 stable QTNs were found associated with 24 prioritized candidate genes. Clusters of fructans metabolic genes reported in the QNRs qWSC-4A.2 and qWSC-7A.2. These genes can be utilized to bring an optimum combination of various fructans metabolic genes to improve the accumulation and remobilization of stem WSCs and water stress tolerance. These results will further strengthen wheat breeding programs targeting sustainable wheat production under limited water conditions.

Role of Water Soluble Carbohydrates in Improving Drought Stress Tolerance in Wheat: An Overview

Abiotic factors such as drought and heat stress impairs photosynthetic assimilates, shortening the carbon supply to the developing grains leads to yield loss. Under water stress, stem water-soluble carbohydrates (WSCs) mainly fructans, play an important role in buffering yield during the grain filling period in wheat. The stem WSCs may contribute up to 20% of the total dry weight of grain under irrigated conditions and upto 70% of grain dry matter under drought stress. Additionally, it maintains physiological balance under water-stressed conditions by acting as signalling molecules to various phytochemicals and hormones. Therefore, this drought adaptive trait can be a potential breeding target for sustainable wheat production, especially for water limiting conditions. Despite the proven contribution of stem WSCs to water-stress tolerance in wheat and compensating grain yield, a comprehensive review on this trait is still missing in the literature. With this review, efforts are made to compile the available information on the physiological, genetic and molecular aspects of accumulation and remobilisation of stem WSCs to bring more attention of plant scientists to this trait. Furthermore, effective molecular marker systems such as KASP to target stable loci identified using GWAS, QTL or meta-QTL studies may bring precision to the selection and accelerate the WSCs based wheat breeding program.

Carbohydrate and Amino Acid Dynamics during Grain Growth in Four Temperate Cereals under Well-Watered and Water-Limited Regimes

Grain development in cereals depends on synthesis and remobilisation compounds such as water-soluble carbohydrates (WSCs), amino acids (AAs), minerals and environmental conditions during pre- and post-anthesis. This study analyses the impact of water stress on metabolite (WSCs, AAs and nitrogen) dynamics between the source (leaves and stems) and sink (grain) organs in triticale, bread wheat, durum wheat and barley. Plants were grown in glasshouse conditions under well-watered (WW) and water-limited (WL) regimes (from flag leaf fully expanded until maturity). The results showed that the stem WSC content and the apparent mobilisation of WSC to the grain were much higher in triticale and were associated with its larger grain size and grain number. In the four cereals, grain weight and the number of kernels per spike were positively associated with stem WSC mobilisation. After anthesis, the AA concentration in leaves was much lower than in the grain. In grain, the main AAs in terms of concentration were Asn, Pro and Gln in triticale, bread, and durum wheat, and Asn, Pro and Val in barley. The water-limited regime reduced grain weight per plant in the four cereal species, but it had no clear effects on WSC content and AAs in leaves and grain. In general, triticale was less affected by WL than the other cereals.

Genome-Wide Association of Stem Carbohydrate Accumulation and Remobilization during Grain Growth in Bread Wheat (Triticum aestivum L.) in Mediterranean Environments.

Water deficit represents an important challenge for wheat production in many regions of the world. Accumulation and remobilization of water-soluble carbohydrates (WSCs) in stems are part of the physiological responses regulated by plants to cope with water stress and, in turn, determine grain yield (GY). The genetic mechanisms underlying the variation in WSC are only partially understood. In this study, we aimed to identify Single Nucleotide Polymorphism (SNP) markers that account for variation in a suite of WSC and GY, evaluated in 225 cultivars and advanced lines of spring wheat. These genotypes were established in two sites in the Mediterranean region of Central Chile, under water-limited and full irrigation conditions, and assessed in two growing seasons, namely anthesis and maturity growth periods. A genome-wide association study (GWAS) was performed by using 3243 SNP markers. Genetic variance accounted for 5 to 52% of phenotypic variation of the assessed traits. A rapid linkage disequilibrium decay was observed across chromosomes (r2 ≤ 0.2 at 2.52 kbp). Marker-trait association tests identified 96 SNPs related to stem weight (SW), WSCs, and GY, among other traits, at the different sites, growing seasons, and growth periods. The percentage of SNPs that were part of the gene-coding regions was 34%. Most of these genes are involved in the defensive response to drought and biotic stress. A complimentary analysis detected significant effects of different haplotypes on WSC and SW, in anthesis and maturity. Our results evidence both genetic and environmental influence on WSC dynamics in spring wheat. At the same time, they provide a series of markers suitable for supporting assisted selection approaches and functional characterization of genes.

Evaluation of Physiological and Morphological Traits for Improving Spring Wheat Adaptation to Terminal Heat Stress.

Wheat crop experiences high temperature stress during flowering and grain-filling stages, which is termed as “terminal heat stress”. Characterizing genotypes for adaptive traits could increase their selection for better performance under terminal heat stress. The present study evaluated the morpho-physiological traits of two spring wheat cultivars (Millet-11, Punjab-11) and two advanced lines (V-07096, V-10110) exposed to terminal heat stress under late sowing. Early maturing Millet-11 was used as heat-tolerant control. Late sowing reduced spike length (13%), number of grains per spike (10%), 1000-grain weight (13%) and biological yield (15–20%) compared to timely sowing. Nonetheless, higher number of productive tillers per plant (19–20%) and grain yield (9%) were recorded under late sowing. Advanced lines and genotype Punjab-11 had delayed maturity and better agronomic performance than early maturing heat-tolerant Millet-11. Advanced lines expressed reduced canopy temperature during grain filling and high leaf chlorophyll a (20%) and b (71–125%) contents during anthesis under late sowing. All wheat genotypes expressed improved stem water-soluble carbohydrates under terminal heat stress that were highest for heat-tolerant Millet-11 genotype during anthesis. Improved grain yield was associated with the highest chlorophyll contents showing stay green characteristics with maintenance of high photosynthetic rates and cooler canopies under late sowing. The results revealed that advanced lines and Punjab-11 with heat adaptive traits could be promising source for further use in the selection of heat-tolerant wheat genotypes.

Tolerance of Combined Drought and Heat Stress Is Associated With Transpiration Maintenance and Water Soluble Carbohydrates in Wheat Grains.

Wheat (Triticum aestivum L.) production is increasingly challenged by simultaneous drought and heatwaves. We assessed the effect of both stresses combined on whole plant water use and carbohydrate partitioning in eight bread wheat genotypes that showed contrasting tolerance. Plant water use was monitored throughout growth, and water-soluble carbohydrates (WSC) and starch were measured following a 3-day heat treatment during drought. Final grain yield was increasingly associated with aboveground biomass and total water use with increasing stress intensity. Combined drought and heat stress immediately reduced daily water use in some genotypes and altered transpiration response to vapor pressure deficit during grain filling, compared to drought only. In grains, glucose and fructose concentrations measured 12 days after anthesis explained 43 and 40% of variation in final grain weight in the main spike, respectively. Starch concentrations in grains offset the reduction in WSC following drought or combined drought and heat stress in some genotypes, while in other genotypes both stresses altered the balance between WSC and starch concentrations. WSC were predominantly allocated to the spike in modern Australian varieties (28–50% of total WSC in the main stem), whereas the stem contained most WSC in older genotypes (67–87%). Drought and combined drought and heat stress increased WSC partitioning to the spike in older genotypes but not in the modern varieties. Ability to maintain transpiration, especially following combined drought and heat stress, appears essential for maintaining wheat productivity.

Dynamic responses of accumulation and remobilization of water soluble carbohydrates in wheat stem to drought stress

Remobilization of stem water soluble carbohydrates (WSC) can supply crucial carbon resources for grain filling against drought stress. Here, spatiotemporal variations in post-anthesis WSC levels and compensatory effects for grain weight from different internodes of the main stem were investigated, when exposed two wheat genotypes with contrasting drought tolerance to drought-stressed and well-watered conditions. Analysis of variance revealed that stem WSC levels were predominantly affected by days after anthesis, water stress and their interactions. Compared with well-watered conditions, the peak time of WSC levels was curtailed by 7–14 days in drought-stressed plants. Drought stress highly promoted WSC levels (ca. 20–30%) in upper internodes during the early period of grain filling, but significantly reduced WSC levels (ca. 40–90%) in all internodes during the late period. The drought-tolerant genotype LJ196 was more superior in WSC partitioning than the drought-prone genotype XD18, due to its stronger capacity for stem WSC remobilization, especially for pre-anthesis reserves under drought stress. This was associated with a better grain filling and compensation to the loss of grain weight. The WSC levels induced by drought stress formed a high-to-low concentration gradient from the lower to the upper internodes. Presumably, it might favorably drive WSC flux from stem to developing kernels, indicative of higher WSC remobilization efficiency generally in lower internodes than in upper ones. These findings provide the well-understanding of the spatiotemporal pattern of post-anthesis WSC accumulation and remobilization along stem internodes and their roles in the wheat grain-filling process under drought stress.

Genome-wide association analysis of stem water-soluble carbohydrate content in bread wheat.

GWAS identified 36 potentially new loci for wheat stem water-soluble carbohydrate (WSC) contents and 13 pleiotropic loci affecting WSC and thousand-kernel weight. Five KASP markers were developed and validated. Water-soluble carbohydrates (WSC) reserved in stems contribute significantly to grain yield (GY) in wheat. However, knowledge of the genetic architecture underlying stem WSC content (SWSCC) is limited. In the present study, 166 diverse wheat accessions from the Yellow and Huai Valleys Winter Wheat Zone of China and five other countries were grown in four well-watered environments. SWSCC at 10 days post-anthesis (10DPA), 20DPA and 30DPA, referred as WSC10, WSC20 and WSC30, respectively, and thousand-kernel weight (TKW) were assessed. Correlation analysis showed that TKW was significantly and positively correlated with WSC10 and WSC20. Genome-wide association study was performed on SWSCC and TKW with 373,106 markers from the wheat 660K and 90K SNP arrays. Totally, 62 stable loci were detected for SWSCC, with 36, 24 and 19 loci for WSC10, WSC20 and WSC30, respectively; among these, 36 are potentially new, 16 affected SWSCC at two or three time-points, and 13 showed pleiotropic effects on both SWSCC and TKW. Linear regression showed clear cumulative effects of favorable alleles for increasing SWSCC and TKW. Genetic gain analyses indicated that pyramiding favorable alleles of SWSCC had simultaneously improved TKW. Kompetitive allele-specific PCR markers for five pleiotropic loci associated with both SWSCC and TKW were developed and validated. This study provided a genome-wide landscape of the genetic architecture of SWSCC, gave a perspective for understanding the relationship between WSC and GY and explored the theoretical basis for co-improvement of WSC and GY. It also provided valuable loci and markers for future breeding.

Coordination of carbon and nitrogen accumulation and translocation of winter wheat plant to improve grain yield and processing quality

The objective of this work was to characterize the accumulation of carbon (C) and nitrogen (N), and the translocation of wheat (Triticum aestivum L.) cultivars to achieve both high-quality and high-yield. Twenty-four wheat cultivars, including 12 cultivars containing high-quality gluten subunit 5 + 10 at Glu-D1, and 12 cultivars with no Glu-D1 5 + 10, were planted at Yuanyang and Xuchang in Henan Province, during 2016–2017, and 2017–2018 cropping seasons. Wheat cultivars containing Glu-D1 5 + 10 had an advantage in grain quality traits. Significant difference (P < 0.05) was observed for grain protein concentration (GPC) between 5 + 10 group and no 5 + 10 group. Grain yield (GY) was significantly correlated with kernel number (KN) (r = 0.778, P < 0.01), thousand-kernel weight (TKW) (r = 0.559, P < 0.01), dry matter accumulation at post-anthesis (r = 0.443, P < 0.05), and stem water-soluble carbohydrate (WSC) accumulation (r = 0.487, P < 0.05) and translocation amount (r = 0.490, P < 0.05). GPC, dough stability time (DST) and nitrogen agronomic efficiency (NAE) were significantly correlated with nitrogen accumulation (NAA) at maturity stage (r = 0.524, = 0.404, = 0.418, P < 0.01, < 0.05, < 0.05, respectively), and nitrogen translocation amount (r = 0.512, = 0.471, = 0.405, P < 0.05, < 0.05, < 0.05, respectively). These results suggest that good-quality, high-yield, and high-efficiency could achieve through the selection of high-quality wheat cultivars and coordination of C and N accumulation and translocation. High-quality gluten subunit gene Glu-D1 5 + 10 and stem WSC could be used as a selection index for breeding and production of high-quality and high-yield wheat.

Genetic dissection of stem WSC accumulation and remobilization in wheat (Triticum aestivum L.) under terminal drought stress

BackgroundThe accumulation and remobilization of stem water soluble carbohydrates (WSC) are determinant physiological traits highly influencing yield potential in wheat against drought stress. However, knowledge gains of the genetic control are still limited. A hexaploid wheat population of 120 recombinant inbred lines were developed to identify quantitative trait loci (QTLs) and to dissect the genetic basis underlying eight traits related to stem WSC under drought stress (DS) and well-watered (WW) conditions across three environments.ResultsAnalysis of variance (ANOVA) revealed larger environmental and genotypic effects on stem WSC-related traits, indicating moderate heritabilities of 0.51–0.72. A total of 95 additive and 88 pairs of epistatic QTLs were identified with significant additive and epistatic effects, as well as QTL× water environmental interaction (QEI) effects. Most of additive QTLs and additive QEIs associated with drought-stressed environments functioned genetic effects promoting pre-anthesis WSC levels and stem WSC remobilization to developing grains. Compared to other genetic components, both genetic effects were performed exclusive contributions to phenotypic variations in stem WSC-related traits. Nineteen QTL clusters were identified on chromosomes 1B, 2A, 2B, 2D, 3B, 4B, 5A, 6A, 6B and 7A, suggestive of the genetic linkage or pleiotropy. Thirteen additive QTLs were detectable repeatedly across two of the three water environments, indicating features of stable expressions. Some loci were consistent with those reported early and were further discussed.ConclusionStem WSC-related traits were inherited predominantly by additive and QEI effects with a moderate heritability. QTL cluster regions were suggestive of tight linkage or pleiotropy in the inheritance of these traits. Some stable and common loci, as well as closely linked molecular markers, had great potential in marker-assisted selection to improve stem WSC-related traits in wheat, especially under drought-stressed environments.

Abscisic acid associated with key enzymes and genes involving in dynamic flux of water soluble carbohydrates in wheat peduncle under terminal drought stress

Remobilization of stem water soluble carbohydrates (WSC) can supply crucial carbon resources for grain filling under drought stress, while the regulatory metabolism associated with abscisic acid (ABA) is still limited. Two cultivars, LJ196 (drought-tolerant) and XD18 (drought-prone), were pot-grown under well-watered (WW) and drought-stressed (DS) conditions. Concentrations of WSC components and ABA, and fructan metabolizing enzymes and genes were investigated in peduncle after anthesis. When compared with those under the WW, LJ196 remained higher grain yield and grain-filling rate than XD18 under the DS. During the early period of grain filling (0–14 DAA), DS increased concentrations of total WSC and its components, but thereafter substantially reduced them. The gene expression levels and enzymatic activities of fructan 1-exohydrolases (1-FEH) and fructan 6-exohydrolases (6-FEH) showed similar trends, whereas those of fructan: fructan 1-fructosyltransferase (1-FFT), and sucrose: fructan 6-fructosyltransferase (6-SFT) were depressed and declined over the period of examination. LJ196 still showed higher levels of ABA and fructan metabolizing. The ABA concentration under the DS was positively and significantly correlated with total WSC and fructan concentration, and expression levels of these enzymes and genes as well, with more prominently with those of 6-FEH. Presumably, ABA could enhance fructan hydrolysis by strongly up-regulating the gene expression and enzymatic activity of 6-FEH to accelerate WSC remobilization. However, stem WSC induced by DS could be not fully remobilized to grains, due to its weaker correlation with grain-filling rate and finally indicating lower grain yield. The findings would provide useful information for wheat production under water-deficit environments.

Stem carbohydrate dynamics during post anthesis period in diverse wheat genotypes under different environments

The contribution of stem water soluble carbohydrates (SWSCs) to grain biomass of wheat ranges from 10 to 20% under irrigated condition and 40 to 60% under stresses such as terminal heat and drought. Genetic variation in SWSC and its mobilization can be useful to increase the grain yield of wheat under harsh environments. Hence, a set of 16 genotypes varying in spike morphology and grain yield was grown in field under timely sown, late sown and terminal drought stress conditions. The anthrone method was used to measure the SWSC concentration in the dried peduncle and penultimate internodes in three replicates at 3 growth stages starting from anthesis. The effect of delay in sowing and terminal drought on the SWSC concentration was significant from anthesis to 14 days after anthesis. Significant genetic variation was observed in the rate of post anthesis change in SWSC during the early grain filling period under the three conditions which partially contributed to the variation in grain yield per spike among the genotypes. Due to sterile florets and/or shorter grain filling duration, all the genotypes did not have a correlation between grain weight per spike and rate of decrease of SWSCs. Thus, our experiments reconfirm the significance of SWSC in present cultivars of wheat and also the scope for exploiting the genetic variation in this trait.

Vacuolar invertase genes SbVIN1 and SbVIN2 are differently associated with stem and grain traits in sorghum (Sorghum bicolor)

In higher plants, vacuolar invertases play essential roles in sugar metabolism, organ development, and sink strength. In sorghum (Sorghum bicolor), two vacuolar invertase genes, SbVIN1 (Sobic. 004G004800) and SbVIN2 (Sobic. 006G160700) have been reported, but their enzymatic properties and functional differences are largely unknown. We combined molecular, biochemical and genomic approaches to investigate their roles in sorghum stem and grain traits. SbVIN1 and SbVIN2 showed different expression levels in internodes, leaves, and panicles, indicating that their importance in each organ was different. In an in vitro sucrose hydrolysis assay, proteins of both genes heterologously expressed in Pichia pastoris displayed similar enzyme properties including the same optimum reaction pH (5) and similar Km for sucroe (49 mmol L−1 and 45 mmol L−1 for SbVIN1 and SbVIN2, respectively). The optimum reaction temperatures of SbVIN1 and SbVIN2 were 45 °C and 65 °C, respectively. SbVIN2 showed higher tolerance to high temperature than SbVIN1. We characterized the sequence variation of these two vacuolar invertase genes in a panel of 216 diverse inbred lines of sweet and grain sorghum and performed gene-based association analysis. SbVIN1 showed significant associations with stem traits including stem length, stem diameter, internode number, stem fresh weight, and Brix, as well as grain traits including hundred-grain weight and grain width. Significantly associated variation sites were mainly in 5′ upstream and intron regions. SbVIN2 only associated with grain width and stem water-soluble carbohydrates (WSCs) content. We conclude that the vacuolar invertase genes SbVIN1 and SbVIN2 are differently associated with stem and grain traits in sorghum.

Dual-purpose winter wheat: interactions between crop management, availability of nitrogen and weather conditions

Dual-purpose wheat has been adopted in many farming systems, but interactions between management, supply of resources, and seasonal conditions are still not clearly elucidated. Two experiments were established in the Loess Plateau of China to measure yield and its components, evapotranspiration, water-use efficiency (yield per unit evapotranspiration), accumulation and apparent remobilisation of stem water soluble carbohydrates (WSC), and economic benefit of dual-purpose winter wheat. Experiment 1 combined factorially three defoliation treatments, i.e. winter defoliation (DC23), spring defoliation (DC29) and untreated control, two seeding rates (currently recommended, and 125% recommended), and over four seasons. Experiment 2 combined factorially two defoliation treatments (spring defoliation and control), two nitrogen rates (low: 120–150 kg N ha−1, high: 180–200 kg N ha−1), three levels of soil water at sowing (low: rainfed; medium: rain +67 mm; high: rain +133 mm), and over three seasons.Defoliation was largely neutral for grain yield and water-use efficiency, and improved translocation of WSC to grain by 8%, harvest index by 7% and net income by 15% across conditions. Grain yield was unaffected by the interaction between defoliation and seeding rate, but significantly impacted by interactions of defoliation × initial soil water level and defoliation × nitrogen rate. Defoliated wheat yield was greater at high than at medium and low initial soil water content, and at low than at high nitrogen rate. Spring defoliation produced similar yield as winter defoliation but the former increased forage income. Increasing seeding rate or nitrogen rate increased forage income but reduced net income due to lower grain income and higher cost. Thus, dual-purpose winter wheat was more profitable (i) when defoliated in spring, (ii) at the lower seeding density, (iii) under the lower nitrogen rate, and (iv) with higher soil water content at sowing. Apparent translocation of stem WSC partially mediated the effect of defoliation on grain yield. It is concluded that dual-purpose winter wheat is feasible under straw mulching in semiarid environment.

Genetic gains in grain yield and physiological traits of winter wheat in Hebei Province of China, from 1964 to 2007

Understanding the key characteristics associated with genetic progress is essential to future wheat breeding strategies. Our objectives were to investigate the genetic progress in grain yield (GY) and key characteristics in wheat (Triticum aestivumL.) cultivars released from 1964 to 2007 in Hebei province, China. Field experiments including 9 milestone cultivars were conducted during three growing seasons (2010–2011, 2011–2012, and 2012–2013) at Shijiazhuang of Hebei. Grain yield is significantly increased by the linear rate of 47.4 kg ha−1 yr−1 or 0.717% (R 2 = 0.909, P < 0.001) and mainly attributed to the increase of harvest index (HI) (r = 0.927, P < 0.01), kernels per spike (Skernel) (r = 0.919, P < 0.01) and thousand kernel weight (TKW) (r = 0.869, P < 0.01). Aboveground biomass (AGBM) has also important contribution to genetic gain in yield before 1997 (r = 0.838, P < 0.05). Although there is decline tendency in spikes m−2 due to decreased maximum tiller numbers (Mtiller) and increased percentage of ear-bearing tiller (ET%) after 70 s, changes of spikes m−2 have no significant effect on yield improvement. Grain yield has positive correlation with kernels m-2 (r = 0.767, P < 0.05) in spite of slower increasing rate of kernels m−2 after 1970s. Genetic gain of GY has close relation with decreased plant height (PH) (r = −0.811, P < 0.01), and PH of stone cultivars after 1970s were 70–80 cm which was optimum for grain yield. Days to heading (DH), days to anthesis (DA) and days to maturity (DM) of stone cultivars have no significant correlation with genetic gain. The significant HI increase mainly results from a significant increase in TKW (r = 0.811, P < 0.01) and Skernel (r = 0.919, P < 0.01). The increased TKW is positively associated with the maximum filling rate (Rmax) (r = 0.720, p < 0.05), average filling rate (Ra) (r = 0.836, p < 0.01), water-soluble carbohydrate (WSC) at anthesis in stem (WSC0) (r = 0.820, p < 0.05), Stem WSC 10 d after anthesis (WSC10) (r = 0.861, p < 0.01) and chlorophyll content (Chl) (r = 0.783, p < 0.05). Thus the physiological traits of Chl of flag leaf, stem WSC and high filling rate can be used to select criterions for further improving yield potential.

Root pruning enhances wheat yield, harvest index and water-use efficiency in semiarid area

Improved management practices are necessary to increase grain yield and water-use efficiency of rainfed winter wheat in semiarid environments. Yield and its components, evapotranspiration, and accumulation and apparent remobilisation of stem water soluble carbohydrates (WSC) were measured to understand the effects of root pruning and its interactions with seeding rate, water and nitrogen supply. Two factorial studies under straw mulching with continuous wheat were established in the Loess Plateau of China. Study 1 was repeated over four seasons and included six treatments from the combination of three root treatments, i.e. root pruning in winter before dormancy (RPw), root pruning at the re-green stage in spring (RPs) and untreated control (CK), and two seeding rates. Study 2 was repeated over three seasons and included twelve treatments from the combination of two root treatments (RPs and CK), two nitrogen rates and three pre-sowing soil water levels. Yield ranged from 2571 to 7722 kg ha−1, harvest index from 0.28 to 0.56, and water-use efficiency from 5 to 20 kg ha−1 mm−1. Root pruning improved grain yield, harvest index and water-use efficiency by 6–11% across environmental conditions. Grain yield increased more (i) by pruning roots in spring than in winter, (ii) in high plant density than in low plant density crops, and (iii) in low-yielding conditions. It is concluded that spring root pruning is a viable option to improve wheat yield and water use efficiency under straw mulching in semiarid environment.