High-yielding Wheat Cultivars Research Articles

Does Exogenous Application of salicylic acid induce salt stress tolerance in potentially high-yielding modern wheat cultivars?

Does Exogenous Application of salicylic acid induce salt stress tolerance in potentially high-yielding modern wheat cultivars?

Water Use Strategies and Shoot and Root Traits of High-Yielding Winter Wheat Cultivars under Different Water Supply Conditions

Drought is the most important factor limiting winter wheat yield in the North China Plain (NCP). Choosing high-yielding cultivars is an important measure to minimize the negative effects of drought stress. Field studies were conducted with 10 cultivars in the 2020–2022 seasons under three irrigation treatments (I0, without irrigation; I1, irrigated at jointing stage; I2, irrigated at jointing and anthesis stages) in the NCP to examine the water use strategies and root and shoot traits of high-yielding cultivars under different water supply conditions. The results showed that yield variation among cultivars was 21.2–24.6%, 23.7–25.9% and 11.6–15.3% for the I0, I1 and I2 treatments, respectively. Under water deficit conditions (I0 and I1), high-yielding cultivars reduced water use during vegetative stages and increased soil water use during reproductive stages, especially water use from deeper soil layers. Those cultivars with higher root length density (RLD) in deep soil layers exhibited higher water uptake. Each additional millimeter of water used after anthesis from the 100–200 cm soil layers increased grain yield by 23.6–29.6 kg/ha and 16.4–28.5 kg/ha under I0 and I1, respectively. This water use strategy enhanced dry matter accumulation after anthesis, decreased canopy temperature (CT) and increased relative leaf water contents (RLWC), which ultimately improved grain yield. For winter wheat grown under I2, cultivars that decreased water use after anthesis had higher water productivity (WP). Root length (RL), root weight (RW) and root:shoot ratio were each negatively correlated with grain yield, while above-ground biomass was positively correlated with grain yield. Therefore, higher dry matter accumulation and smaller root systems are two important traits of high-yielding cultivars under sufficient water supply conditions (I2) in the NCP.

Deciphering the genetic landscape of seedling drought stress tolerance in wheat (Triticum aestivum L.) through genome-wide association studies.

Wheat is an important cereal crop constrained by several biotic and abiotic stresses including drought stress. Understating the effect of drought stress and the genetic basis of stress tolerance is important to develop drought resilient, high-yielding wheat cultivars. In this study, we investigated the effects of drought stress on seedling characteristics in an association panel consisting of 198 germplasm lines. Our findings revealed that drought stress had a detrimental effect on all the seedling characteristics under investigation with a maximum effect on shoot length (50.94% reduction) and the minimum effect on germination percentage (7.9% reduction). To gain a deeper understanding, we conducted a genome-wide association analysis using 12,511 single nucleotide polymorphisms (SNPs), which led to the identification of 39 marker-trait associations (MTAs). Of these 39 MTAs, 13 were particularly noteworthy as they accounted for >10% of the phenotypic variance with a LOD score >5. These high-confidence MTAs were further utilized to extract 216 candidate gene (CGs) models within 1 Mb regions. Gene annotation and functional characterization identified 83 CGs with functional relevance to drought stress. These genes encoded the WD40 repeat domain, Myb/SANT-like domain, WSD1-like domain, BTB/POZ domain, Protein kinase domain, Cytochrome P450, Leucine-rich repeat domain superfamily, BURP domain, Calmodulin-binding protein60, Ubiquitin-like domain, etc. Findings from this study hold significant promise for wheat breeders as they provide direct assistance in selecting lines harboring favorable alleles for improved drought stress tolerance. Additionally, the identified SNPs and CGs will enable marker-assisted selection of potential genomic regions associated with enhanced drought stress tolerance in wheat.

Genome-wide association study revealed the reason for the decrease in grain iron concentration during wheat breeding process in China

Iron (Fe) deficiency affects over two billion people worldwide. Developing high-yielding wheat (Triticum aestivum L.) cultivars with high grain Fe concentration (GFeC) is a key step toward alleviating malnutrition in humans. In this study, we used a diversity panel of 388 wheat accessions to examine the GFeC in four field environments. We found that the mean GFeC of the four environments decreased with the release year. And GFeC showed poor correlation with grain yield or the three yield factors in the four environments. Importantly, wheat cultivars in the major wheat-producing region of China showed the lowest GFeC. The GFeC phenotype was used for a genome-wide association study (GWAS) using a 660 K single-nucleotide polymorphism (SNP) chip, and 17 quantitative trait loci (QTLs) were identified on chromosomes 3B, 4 A, 5 A, 6B, 6D, 7 A, 7B, and 7D. However, no universal QTLs were detected among the 17 identified QTLs and 2280 yield-related QTLs. Through allelic analysis, two homologous genes, TraesCS7A01G197400 and TraesCS7D01G198900, were identified as potential candidate genes for GFeC, while the favourable alleles for GFeC were lost during the selection breeding process in China. The insights gained from this study showed that the yield dilution effect was not applied to the decrease in GFeC, which should be mainly caused by the loss of favourable alleles during the wheat breeding process in China. Therefore, wheat breeders should pay more attention to other traits to improve GFeC rather than the yield dilution effect.

RNAseq of diverse spring wheat cultivars released during last 110 years

Here, we performed RNA-seq based expression analysis of root and leaf tissues of a set of 24 historical spring wheat cultivars representing 110 years of temporal genetic variations. This huge 130 tissues RNAseq dataset was initially used to study expression pattern of 97 genes regulating root growth and development in wheat. Root system architecture (RSA) is an important target for breeding stress-resilient and high-yielding wheat cultivars under climatic fluctuations. However, root transcriptome analysis is usually obscured due to challenges in root research due to their below ground presence. We also validated the dataset by performing correlation analysis between expression of RSA related genes in roots and leaves with 25 root traits analyzed under varying moisture conditions and 10 yield-related traits. The Pearson’s correlation coefficients between root phenotypes and expression of root-specific genes varied from −0.72 to 0.78, and strong correlations with genes such as DRO1, TaMOR, ARF4, PIN1 was observed. The presented datasets have multiple uses such as a) studying the change in expression pattern of genes during time, b) differential expression of genes in two very important tissues of wheat i.e., leaf and roots, and c) studying customized expression of genes associated with important phenotypes in diverse wheat cultivars. The initial findings presented here provided key insights into understanding the transcriptomic basis of phenotypic variability of RSA in wheat cultivars.

High-Zn wheat alleviates P-Zn antagonism by improving Zn activation, acquisition, and translocation at key growth stages

Context or problemApplication of phosphorus (P) fertilizer has achieved a remarkable increase in yield but has also resulted in decreased zinc (Zn) concentration and its bioavailability in cereal grains. ObjectivesSelecting, breeding, and understanding the mechanism for wheat cultivars with high-yield and high-grain Zn under P application is urgent and difficult, with the purpose of alleviating P-Zn antagonism and solving Zn malnutrition globally. MethodsIn a five-year field experiment on the southern Loess Plateau, China, selected high-yield wheat cultivars with contrasting grain Zn concentrations were assessed for rhizosphere Zn activation, root Zn acquisition, and Zn translocation among plant parts at the key growth stages under different P fertilization rates. ResultsResults showed that although the grain Zn concentration decreased with P application, it decreased less and still remained around 49–65 mg/kg in the grain of high Zn (HZn) cultivars. This was 58–72% higher than that of the low Zn (LZn) cultivars on soil with 2.7 mg/kg Olsen-P and 0.55 mg/kg DTPA-Zn due to 32.9–55.4% higher shoot Zn uptake in HZn cultivars at harvest. P application enhanced the rhizosphere Zn activation of HZn cultivars by 21.6% higher than that of LZn cultivars at the jointing stage. However, P application inhibited the root Zn acquisition of both types of cultivars, except for that of the HZn cultivars at the anthesis. The Zn translocation from root to shoot was remarkably enhanced at the grain-filling stage, but much more for HZn cultivars with P application, with the transfer factor being 154% for HZn cultivars and 7.9% for LZn cultivars, respectively. ConclusionsTherefore, HZn cultivars alleviated the P-Zn antagonism and achieved higher grain Zn concentration than the recommended target of 40–60 mg/kg, by maintaining higher rhizosphere Zn activation at the jointing stage, stable high Zn acquisition at the anthesis, and higher Zn translocation capacity from root to shoot during the grain-filling stage. ImplicationsBreeding and selecting cultivars with excellent acquisition performance and translocation capacity for Zn, accompanied by relatively lower soil available P and reasonable P application, may be an applicable Zn biofortification strategy for wheat and other cereals, overcoming the P-Zn antagonism.

Genetic mapping of the wheat leaf rust resistance gene Lr2a and its importance in Canadian wheat cultivars.

Leaf rust resistance gene Lr2a was located to chromosome arm 2DS in three mapping populations, which will facilitate map-based cloning and marker-assisted selection of Lr2a in wheat breeding programs. Incorporating effective leaf rust resistance (Lr) genes into high-yielding wheat cultivars has been an efficient method of disease control. One of the most widely used genes in Canada is the multi-allelic resistance gene Lr2, with alleles Lr2a, Lr2b, Lr2c, and Lr2d. The Lr2a allele confers complete resistance to a large portion of the Puccinia triticina (Pt) population in Canada. In this study, Lr2a was genetically mapped in two doubled haploid populations developed from the crosses Superb/BW278 and Superb/86ISMN 2137, and an F2 population developed from the cross Chinese Spring/RL6016. Seedlings were tested with the Lr2a avirulent Pt races 74-2 MGBJ (Superb/BW278) and 12-3 MBDS (Superb/86ISMN 2137 and Chinese Spring/RL6016) in greenhouse assays and were genotyped with 90K wheat Infinium SNP and kompetitive allele-specific PCR (KASP) markers. Lr2a was mapped to a collinear position on chromosome arm 2DS in all three populations, within a 1.00cM genetic interval between KASP markers kwm1620 and kwm1623. This corresponded to a 305kb genomic region of chromosome 2D in Chinese Spring RefSeq v2.1. The KASP marker kwh740 was predictive of Lr2a in all mapping populations. A panel of 260 wheats were tested with three Pt isolates, which revealed that Lr2a is common in Canadian wheats. The KASP markers kwh740 and kwm1584 were highly associated with resistance at the Lr2 locus, while kwm1622 was slightly less correlated. Genetic mapping of the leaf rust resistance gene Lr2a and DNA markers developed here will facilitate its use in wheat breeding programs.

Investigating theBiochemical Responses in Wheat Cultivars Exposed to Thermal Power Plant Emission.

The current study aimed to assess how high concentrations of ozone (O3) and suspended particulate matter (SPM) alter biochemical properties of high yielding wheat cultivars (i.e., HD3086 and HD2967) grown under 10km radius in 8 villages, located around Thermal Power Plant (TPP), Auraiya, Uttar Pradesh, India. Significant foliar damage was brought on by O3 and SPM exposure in both wheat cultivars and noted for consecutive 2 years as per emission patterns, air movement and biochemical defense capabilities. The detected air pollutants at the chosen experimental site ranged from 34 to 46ppb O3 and 139-189µg/m3 SPM. Range of biochemical parameter for both cultivars are as pH 6.6-7.1, relative water content (RWC) 44-62%, chlorophyll 0.23-0.35mg/g, ascorbic acid (AA) 54-68mg/g and air pollution tolerance index (APTI) 47-72. It has been observed that SPM deposition had a meaningful impact (P-value = 0.05) on the chlorophyll, pH, RWC and APTI.

Genetic Improvement for Grain Yield under Heat Stress Conditions in Bread Wheat (Triticum aestivum L.)

Extreme temperature is one of the abiotic stresses that causes significant yield reductions in wheat. Therefore, the current study aims to create heat-tolerant wheat plants with superior grain yield productivity by using traditional breeding. Two cycles of phenotypic directional selection for grain yield per plant were applied in two F2 populations. These populations were derived from crosses among four local wheat varieties. In the first cycle, a directional selection for grain yield per plant was performed under both the favorable environment (optimal sowing date) and heat stress environments (late sowing date). Under the favorable conditions, the responses of F3 plants to selection for grain yield per plant were positive and significantly higher (averaged 7.71%) than under heat stress conditions (averaged 8.20%). Moreover, the average of the concurrent response to selection for grain yield per plant in grain yield per spike had a positive and high percentage under the favorable (7.00%) and the heat stress environment (8.84%). Highly significant and positive responses were observed within the F3 plants of the two populations. The value of the average was greater under favorable (6.85%) than under the heat stress conditions (7.20%). Additionally, the 1000 kernel weight was highly significant and positive responses (5.35% and 6.11%) in both favorable and heat stress environments, respectively. Generally, the observed results indicating the F4 plants could be a promising source to introduce yield related traits to develop high-yielding wheat cultivars for heat-stressed environments.

TaMADS29 interacts with TaNF-YB1 to synergistically regulate early grain development in bread wheat.

Grain development is a crucial determinant of yield and quality in bread wheat (Triticum aestivum L.). However, the regulatory mechanisms underlying wheat grain development remain elusive. Here we report how TaMADS29 interacts with TaNF-YB1 to synergistically regulate early grain development in bread wheat. The tamads29 mutants generated by CRISPR/Cas9 exhibited severe grain filling deficiency, coupled with excessive accumulation of reactive oxygen species (ROS) and abnormal programmed cell death that occurred in early developing grains, while overexpression of TaMADS29 increased grain width and 1,000-kernel weight. Further analysis revealed that TaMADS29 interacted directly with TaNF-YB1; null mutation in TaNF-YB1 caused grain developmental deficiency similar to tamads29 mutants. The regulatory complex composed of TaMADS29 and TaNF-YB1 exercises its possible function that inhibits the excessive accumulation of ROS by regulating the genes involved in chloroplast development and photosynthesis in early developing wheat grains and prevents nucellar projection degradation and endosperm cell death, facilitating transportation of nutrients into the endosperm and wholly filling of developing grains. Collectively, our work not only discloses the molecular mechanism of MADS-box and NF-Y TFs in facilitating bread wheat grain development, but also indicates that caryopsis chloroplast might be a central regulator of grain development rather than merely a photosynthesis organelle. More importantly, our work offers an innovative way to breed high-yield wheat cultivars by controlling the ROS level in developing grains.

Molecular Mapping of Biofortification Traits in Bread Wheat (Triticum aestivum L.) Using a High-Density SNP Based Linkage Map.

A set of 188 recombinant inbred lines (RILs) derived from a cross between a high-yielding Indian bread wheat cultivar HD2932 and a synthetic hexaploid wheat (SHW) Synthetic 46 derived from tetraploid Triticum turgidum (AA, BB 2n = 28) and diploid Triticum tauschii (DD, 2n = 14) was used to identify novel genomic regions associated in the expression of grain iron concentration (GFeC), grain zinc concentration (GZnC), grain protein content (GPC) and thousand kernel weight (TKW). The RIL population was genotyped using SNPs from 35K Axiom® Wheat Breeder's Array and 34 SSRs and phenotyped in two environments. A total of nine QTLs including five for GPC (QGpc.iari_1B, QGpc.iari_4A, QGpc.iari_4B, QGpc.iari_5D, and QGpc.iari_6B), two for GFeC (QGfec.iari_5B and QGfec.iari_6B), and one each for GZnC (QGznc.iari_7A) and TKW (QTkw.iari_4B) were identified. A total of two stable and co-localized QTLs (QGpc.iari_4B and QTkw.iari_4B) were identified on the 4B chromosome between the flanking region of Xgwm149-AX-94559916. In silico analysis revealed that the key putative candidate genes such as P-loop containing nucleoside triphosphatehydrolase, Nodulin-like protein, NAC domain, Purine permease, Zinc-binding ribosomal protein, Cytochrome P450, Protein phosphatase 2A, Zinc finger CCCH-type, and Kinesin motor domain were located within the identified QTL regions and these putative genes are involved in the regulation of iron homeostasis, zinc transportation, Fe, Zn, and protein remobilization to the developing grain, regulation of grain size and shape, and increased nitrogen use efficiency. The identified novel QTLs, particularly stable and co-localized QTLs are useful for subsequent use in marker-assisted selection (MAS).

Exotic alleles contribute to heat tolerance in wheat under field conditions

Global warming poses a major threat to food security and necessitates the development of crop varieties that are resilient to future climatic instability. By evaluating 149 spring wheat lines in the field under yield potential and heat stressed conditions, we demonstrate how strategic integration of exotic material significantly increases yield under heat stress compared to elite lines, with no significant yield penalty under favourable conditions. Genetic analyses reveal three exotic-derived genetic loci underlying this heat tolerance which together increase yield by over 50% and reduce canopy temperature by approximately 2 °C. We identified an Ae. tauschii introgression underlying the most significant of these associations and extracted the introgressed Ae. tauschii genes, revealing candidates for further dissection. Incorporating these exotic alleles into breeding programmes could serve as a pre-emptive strategy to produce high yielding wheat cultivars that are resilient to the effects of future climatic uncertainty.

Identification of a pleiotropic QTL cluster for Fusarium head blight resistance, spikelet compactness, grain number per spike and thousand-grain weight in common wheat

Simultaneously improving Fusarium head blight (FHB) resistance and grain yield is challenging in wheat breeding. The correlations between spikelet compactness (SC), grain number per spike (GNS), thousand-grain weight (TGW) and FHB resistance remains unclear in common wheat. Identification of major quantitative trait loci (QTL) conferring FHB resistance and yield components, and development of breeder-friendly markers for the QTL are prerequisites for marker-assisted selection (MAS). Here, a recombinant inbred line (RIL) population derived from a cross between a resistant cultivar Yangmai 12 (YM12) and a susceptible cultivar Yanzhan 1 (YZ1) was used to map QTL for FHB resistance and yield components. A total of 22 QTL were identified; among these, six are likely to be new for corresponding traits. A QTL cluster (Qclu.yas-2D) for FHB type II resistance, SC, GNS, and TGW was detected on chromosome 2D. Breeder-friendly kompetitive allele-specific PCR (KASP) markers flanking the interval of Qclu.yas-2D were developed and validated in a diverse panel of 166 wheat cultivars and advanced lines. The YM12 alleles of Qclu.yas-2D significantly increased FHB resistance, SC, and GNS but decreased TGW in the validation population. The KASP markers developed for Qclu.yas-2D have great potential for breeding high-yielding wheat cultivars with enhanced FHB resistance.

Studying the effect of the OsGATA rice transcription factor on salt stress tolerance in wheat

This study shows the possibility of using the OsGATA rice transcription factor in transgenic lines of high-yielding wheat cultivars to increase their tolerance to salinity, which was confirmed using physiological and biochemical methods according to standard protocols. Wheat plants were grown in an artificial climate under optimal growing conditions. Genetic transformation methods were used to introduce the GATA gene into the genome of the used wheat genotypes. Transgenic lines were selected on selective media under in vitro conditions.The results of the experimental work showed that the expression of the GATA gene under salt stress may be responsible for the increased compartmentalization of Na+ in the vacuole, which provides improved salt tolerance. As a result of the experiment, collections of T1 transgenic wheat lines from cvs. ‘Zlata’, ‘Emir’ and ‘Agata’ expressing the GATA gene were obtained and studied for salt tolerance. Lines Zl.01, Zl.02, Zl.03 and Ag.02 were selected with PCR. Under NaCl salinity conditions, some of the transgenic lines showed a statistically significant increase in salinity resistance. The results of the study laid the foundation for studying GATA genes in wheat and for producing salinity-tolerant lines without growth defects or reduced productivity.

Response of Wheat Cultivars to Organic and Inorganic Nutrition: Effect on the Yield and Soil Biological Properties

The deterioration of soil biological health is the most important aspect associated with the sustainability of cereal-based food production systems. The application of organic nutrient sources is widely accepted and recommended for sustaining crop productivity and preserving soil fertility. Therefore, a study was carried out to assess the effects of different levels of farmyard manure (FYM10: 10 t ha−1, FYM20: 20 t ha−1, FYM30: 30 t ha−1), including inorganic fertilizer (NPK) on the soil and the biological properties of five high-yielding wheat cultivars (HD 2967, DPW 621-50, PBW 550, and WH 1105) over a three-year period (2014–2015 to 2016–2017). The results showed that the application of NPK produced significantly higher yields compared to different levels of FYM and the control during all the study years. The continuous addition of a higher rate of FYM at 30 t ha−1 was found to be beneficial in terms of enhancing crop yield gain, thereby bridging the yield gap to only 7.2% in the third year; the gap was 69.1% in the first year with NPK application. The microbial population and microbial biomass carbon were significantly higher in the FYM treatments compared to the NPK treatment. The activities of different soil enzymes were observed to be significantly maximum in the FYM30 treatment. Similarly, the addition of FYM significantly improved the soil respiration and microbial activity over the NPK and control treatments. Based on the principal component analysis, fluorescein diacetate, bacteria, fungi, and actinomycetes were observed as sensitive biological parameters for the assessing of soil biological health. The soil biological index (SBI) determined with the sensitive parameters was in the decreasing order of FYM30 (0.70), FYM20 (0.61), FYM10 (0.55), NPK (0.18), and control (0.15). Considering both the SBI and the sustainability yield index together, the performance of WH 1105 was found to be better compared to the rest of the wheat cultivars. Our results conclude that the application of FYM in the long run increases the crop yield (24.3 to 38.9%) and improves the soil biological process, leading to the improved biological index of the soil.

Characteristics of lodging resistance of high-yield winter wheat as affected by nitrogen rate and irrigation managements

High yields of wheat are mainly obtained through a high level of nitrogen and irrigation supplementation. However, excessive nitrogen and irrigation supplication increase the risk of lodging. The main objectives of this work were to clarify the capacity of lodging resistance of wheat in response to nitrogen and irrigation, as well as to explore the effective ways of improving lodging resistance in a high-yield wheat cultivar. In this study, field experiments were conducted in the 2015–2016 and 2016–2017 growing seasons. A wheat cultivar Jimai 22 (JM22), which is widely planted in the northern of Huang-Huai winter wheat region, was grown at Tai'an, Shandong Province, under three nitrogen rates and four irrigation treatments. The lodging risk was increased with increased nitrogen rate, as indicated by increasing lodging index (LI) and lodging rate across both growing seasons. With nitrogen increasing, the plant height, the basal internode length and the center of gravity height, which were positively correlated with LI, increased significantly. While the density of the basal 2nd internode (for culm and leaf sheath) and cell wall component contents, which were negatively correlated with LI, decreased conspicuous along with nitrogen increased. Increasing irrigation supplementation increased the 2nd internode culm wall thickness, breaking strength and leaf sheath density within limits which increased stem strength. Among the treatments, nitrogen application at a rate of 240 kg ha–1 and irrigation application at 600 m3 ha–1 at both the jointing and anthesis stages resulted in the highest yield and strongest stem. A suitable plant height ensures sufficient biomass for high yield, and higher stem stiffness, which was primarily attributed to thicker culm wall, greater density of the culm and leaf sheaths and higher cell wall component contents are the characteristics that should be taken into account to improving wheat lodging resistance.

Quality Characteristics of Noodle Made from Domestic Early Maturity and High Yield Wheat Cultivars

Yeon Jae Jo, Tae Yong You, Tae Whan Shin, Ho Jun Sung, Hye Won Lee, Ji Eun Kwak, Tae-Su Kang, Junsoo Lee, and Heon Sang Jeong. Journal of the Korean Society of Food Science and Nutrition 2022;51:170-6. https://doi.org/10.3746/jkfn.2022.51.2.170

Quality Characteristics of Bread Made from Domestic Early Maturity and High Yield Wheat Cultivars

Tae Yong You, Yeon Jae Jo, Tae Hwan Shin, Ji Eun Kwak, Yun Jeong Lee, Tae Su Kang, Junsoo Lee, and Heon Sang Jeong. Journal of the Korean Society of Food Science and Nutrition 2021;50:1358-64. https://doi.org/10.3746/jkfn.2021.50.12.1358

Association Mapping of Agronomic traits in Bread Wheat using a high Density 90k SNP Array

A genome-wide association study (GWAS) was performed using a high-density infinium 90K SNP array. We identified a total markers traits associations (MTAs) (p ?0.000) for the following plant traits; days taken to 50% heading(DH), days to 50% maturity (DM), plant height (Ph) cm, flag leaf area cm2 (FLA), tillers number per plant, spike length (SL) cm and grain yield per plant (GP) g. Most of the SNPs were identified in the A and B genome as compared to the D genome. The significant associated SNPs were mainly distributed on the chromosome 2B, 3B, 5A, and 5B. Nine SNPs on chromosome 5A, 2B and 2D were identified having pleiotropic effects The correlation analysis showed a significant positive association among SL, NT, GP. Which depicted that these traits are promising for breeding high yielding wheat cultivars. This study provided useful information of the valuable genetic loci for marker-assisted breeding.

Improving Grain Yield via Promotion of Kernel Weight in High Yielding Winter Wheat Genotypes.

Simple SummaryImproving plant net photosynthetic rates and accelerating water-soluble carbohydrate accumulation play an important role in increasing the carbon sources for wheat kernel growth and yield. The objective of this study was to quantify the relative yield contribution by analyzing the photosynthesis rate of flag leaf, water-soluble carbohydrate content of flag leaf, flag leaf sheath and stem, and other agronomic and physiological traits in 15 wheat cultivars released in Shandong Province, China between 1969 and 2006. Our results suggest that increase of flag leaf photosynthesis and WSC had a positive effect of 0.593 on the TKW, and thus benefit for developing high yielding wheat cultivars.Improving plant net photosynthetic rates and accelerating water-soluble carbohydrate accumulation play an important role in increasing the carbon sources for yield formation of wheat (Triticum aestivum L.). Understanding and quantify the contribution of these traits to grain yield can provide a pathway towards increasing the yield potential of wheat. The objective of this study was to identify kernel weight gap for improving grain yield in 15 winter wheat genotypes grown in Shandong Province, China. A cluster analysis was conducted to classify the 15 wheat genotypes into high yielding (HY) and low yielding (LY) groups based on their performance in grain yield, harvest index, photosynthetic rate, kernels per square meter, and spikes per square meter from two years of field testing. While the grain yield was significantly higher in the HY group, its thousand kernel weight (TKW) was 8.8% lower than that of the LY group (p < 0.05). A structural equation model revealed that 83% of the total variation in grain yield for the HY group could be mainly explained by TKW, the flag leaf photosynthesis rate at the grain filling stage (Pn75), and flag leaf water-soluble carbohydrate content (WSC) at grain filling stage. Their effect values on yield were 0.579, 0.759, and 0.444, respectively. Our results suggest that increase of flag leaf photosynthesis and WSC could improve the TKW, and thus benefit for developing high yielding wheat cultivars.