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Summary: Wheat fixes CO2 by photosynthesis into kernels to nourish humankind. Improving the photosynthesis rate is a major driving force in assimilating atmospheric CO2 and guaranteeing food supply for human beings. Strategies for achieving the above goal need to be improved. Here, we report the cloning and mechanism of CO2ASSIMILATION RATE AND KERNEL‐ENHANCED 1 (CAKE1) from durum wheat (Triticum turgidum L. var. durum). The cake1 mutant displayed a lower photosynthesis rate with smaller grains. Genetic studies identified CAKE1 as HSP90.2‐B, encoding cytosolic molecular chaperone folding nascent preproteins. The disturbance of HSP90.2 decreased leaf photosynthesis rate, kernel weight (KW) and yield. Nevertheless, HSP90.2 over‐expression increased KW. HSP90.2 recruited and was essential for the chloroplast localization of nuclear‐encoded photosynthesis units, for example PsbO. Actin microfilaments docked on the chloroplast surface interacted with HSP90.2 as a subcellular track towards chloroplasts. A natural variation in the hexaploid wheat HSP90.2‐B promoter increased its transcription activity, enhanced photosynthesis rate and improved KW and yield. Our study illustrated an HSP90.2–Actin complex sorting client preproteins towards chloroplasts to promote CO2 assimilation and crop production. The beneficial haplotype of Hsp90.2 is rare in modern varieties and could be an excellent molecular switch promoting photosynthesis rate to increase yield in future elite wheat varieties. [ABSTRACT FROM AUTHOR]

Plant architecture is a crucial influencing factor of wheat yield and adaptation. In this study, we cloned and characterized TaSPL14, a homologous gene of the rice ideal plant architecture gene OsSPL14 in wheat. TaSPL14 homoeologs (TaSPL14- 7A, TaSPL14-7B and TaSPL14-7D) exhibited similar expression patterns, and they were all preferentially expressed in stems at the elongation stage and in young spikes. Moreover, the expression level of TaSPL14-7A was higher than that of TaSPL14-7B and TaSPL14-7D. Overexpression of TaSPL14-7A in wheat resulted in significant changes in plant architecture and yield traits, including decreased tiller number and increased kernel size and weight. Three TaSPL14-7A haplotypes were identified in Chinese wheat core collection, and haplotype-based association analysis showed that TaSPL14-7A-Hap1/2 were significantly correlated with fewer tillers, larger kernels and higher kernel weights in modern cultivars. The haplotype effect resulted from a difference in TaSPL14- 7A expression levels among genotypes, with TaSPL14-7A-Hap1/2 leading to higher expression levels than TaSPL14-7A-Hap3. As favorable haplotypes, TaSPL14-7A-Hap1/2 underwent positive selection during global wheat breeding over the last century. Together, the findings of our study provide insight into the function and genetic effects of TaSPL14 and provide a useful molecular marker for wheat breeding. [ABSTRACT FROM AUTHOR]

Sulfur fertilizers play an important role in increasing the yield and improving the dough quality of bread wheat, but their regulatory mechanism remains unclear. In this study, 0 kg·ha-1 (S0) and 60 kg·ha-1 (S60) of sulfur were applied on the anthesis date; subsequently, immature wheat grains at 8, 13, and 18 days post-anthesis (DPA) were subjected to integrated transcriptomic and metabolomic analyses to investigate the changes in the gene/metabolite activity in a typical strong-gluten wheat, Gaoyou2018 (GY2018). Our data show that the S60 treatment could significantly increase the grain yield and grain protein content by 13.2 and 3.6%, respectively. The transcriptomic analysis revealed that 10,694 differentially expressed genes (DEGs) were induced by S60 from 8 to 18 DPA when compared with their corresponding no-sulfur controls, and most DEGs were mainly involved in lipid metabolism and amino acid metabolism pathways. Ninety-seven MYB transcription factors (TFs) were identified as responsive to the S60 treatment; of these, 66 showed significantly differential expression at 13 DPA, and MYB118 might participate in the process of sulfur metabolism by regulating glucosinolate synthesis. In total, 542 significantly enriched differentially expressed (DE) metabolites (DEMs) were identified following the S60 treatment, which mainly included secondary metabolites, carbohydrates, and amino acids. Several metabolites (e.g., glutathione, sucrose, GDP-alpha-D-glucose, and amino acids) exhibited altered abundances following the S60 treatment. The combination of transcriptomic and metabolomic analyses highlighted the important role of amino acid metabolism (especially cysteine, methionine, and glutathione metabolism) and starch and sucrose metabolism pathways after S60 application. Our results provide valuable information enhancing our understanding of the molecular mechanism of the response to sulfur and provide useful clues for grain protein quality formation and yield improvement in bread wheat. [ABSTRACT FROM AUTHOR]

Appropriate genotype selection and management can impact wheat (Triticum aestivum L.) yield in dryland environments, but their impact on yield components and their role in yield modulation are not well understood. Our objectives were to evaluate the yield response of commercial winter wheat genotypes to different management practices reflecting a stepwise increase in management intensity (including a reduction in crop density under high input), and to quantify how the different yield components modulate wheat yield. A factorial experiment evaluated six management (M) intensities ["farmer practice" (FP), "enhanced fertility" (EF), "ecological intensification" (EI), "increased foliar protection" (IFP), "water-limited yield" (Yw), and "increased plant productivity" (IPP)] and four winter wheat genotypes (G) in four Kansas environments (E). Average grain yield was 4.9 Mg ha–1 and ranged from 2.0 to 7.4 Mg ha–1, with significant two-way interactions (E × M and E × G). The EF usually maximized yields in dry environments, while EI, which consisted of EF plus one fungicide application, maximized yields in environments with greater water availability. Across all sources of variation, kernels m–2 and aboveground biomass were the strongest modulators of yield as compared to kernel weight and harvest index, while spikes m–2 and kernels spike–1 modulated yields at a similar magnitude. Foliar fungicides improved yield through increased green canopy cover duration and greater radiation intercepted during grain filling. When crop density was reduced from 2.7 to 1.1 million plants per hectare in an otherwise high-input system, plants produced more productive tillers (with genotype-specific response); however, reduced green canopy cover at anthesis and reduced cumulative solar radiation intercepted during grain filling limited wheat yield—although large differences in canopy cover or intercepted radiation were needed to cause modest changes in yield. Treatments more intensive than EI were not warranted as EF or EI maximized yields at all environments, and practices that promote biomass and kernels m–2 are to be targeted for future increases in wheat yield. [ABSTRACT FROM AUTHOR]

To provide food security for a growing world population, it will be necessary to increase yields of staple crops such as wheat (Triticum aestivum L.). Yield is a complex, polygenic trait influenced by grain weight and number, which are negatively correlated with one another. Spikelet number is an important determinant of grain number, but allelic variants impacting its expression are often associated with heading date, constraining their use in wheat germplasm that must be adapted for specific environments. Identification and characterization of genetic variants affecting spikelet number will increase selection efficiency through their deployment in breeding programs. In this study, a quantitative trait locus (QTL) on chromosome arm 6BL for spikelet number was identified and validated using an association mapping panel, a recombinant inbred line population, and seven derived heterogeneous inbred families. The superior allele, QSn.csu-6Bb, was associated with an increase of 0.248 to 0.808 spikelets per spike across multiple environments that varied for mean spikelet number. Despite epistatic interactions between QSn.csu-6B and three other loci (WAPO-A1, VRN-D3, and PPD-B1), genotypes with a greater number of superior alleles at these loci consistently exhibit higher spikelet number. The frequency of superior alleles at these loci varies among winter wheat varieties adapted to different latitudes of the US Great Plains, revealing opportunities for breeders to select for increased spikelet number using simple molecular markers. This work lays the foundation for the positional cloning of the genetic variant underlying the QSn.csu-6B QTL to strengthen our understanding of spikelet number determination in wheat. [ABSTRACT FROM AUTHOR]

Kernel weight is a key determinant of yield in wheat (Triticum aestivum L.). Starch consists of amylose and amylopectin and is the major constituent of mature grain. Therefore, starch metabolism in the endosperm during grain filling can influence kernel weight. In this study, we sequenced 87 genes involved in starch metabolism from 300 wheat accessions and detected 8,141 polymorphic sites. We also characterized yield-related traits across different years in these accessions. Although the starch contents fluctuated, thousand kernel weight (TKW) showed little variation. Polymorphisms in six genes were significantly associated with TKW. These genes were located on chromosomes 2A, 2B, 4A, and 7A; none were associated with starch content or amylose content. Variations of 15 genes on chromosomes 1A and 7A formed haplotype blocks in 26 accessions. Notably, accessions with higher TKWs had more of the favorable haplotypes. We thus conclude that these haplotypes contribute additive effects to TKW.

Starch is a major component of wheat (Triticum aestivum L.) endosperm and is an important part of the human diet. The functions of many starch synthesis genes have been elucidated. However, little is known about their regulatory mechanisms in wheat. Here, we identified a novel NAC transcription factor, TaNAC019-A1 (TraesCS3A02G077900), that negatively regulates starch synthesis in wheat and rice (Oryza sativa L.) endosperms. TaNAC019-A1 was highly expressed in the endosperm of developing grains and encoded a nucleus-localized transcriptional repressor. Overexpression of TaNAC019-A1 in rice and wheat led to significantly reduced starch content, kernel weight, and kernel width. The TaNAC019-A1 -overexpression wheat lines had smaller A-type starch granules and fewer B-type starch granules than wild-type. Moreover, TaNAC019-A1 could directly bind to the 'ACGCAG' motif in the promoter regions of ADP-glucose pyrophosphorylase small subunit 1 (TaAGPS1-A1 , TraesCS7A02G287400) and TaAGPS1-B1 (TraesCS7B02G183300) and repress their expression, thereby inhibiting starch synthesis in wheat endosperm. One haplotype of TaNAC019-B1 (TaNAC019-B1-Hap2 , TraesCS3B02G092800) was positively associated with thousand-kernel weight and underwent positive selection during the Chinese wheat breeding process. Our data demonstrate that TaNAC019-A1 is a negative regulator of starch synthesis in wheat endosperm and provide novel insight into wheat yield improvement. [ABSTRACT FROM AUTHOR]

Kernel weight is a key determinant of yield in wheat (Triticum aestivum L.). Starch consists of amylose and amylopectin and is the major constituent of mature grain. Therefore, starch metabolism in the endosperm during grain filling can influence kernel weight. In this study, we sequenced 87 genes involved in starch metabolism from 300 wheat accessions and detected 8,141 polymorphic sites. We also characterized yield-related traits across different years in these accessions. Although the starch contents fluctuated, thousand kernel weight (TKW) showed little variation. Polymorphisms in six genes were significantly associated with TKW. These genes were located on chromosomes 2A, 2B, 4A, and 7A; none were associated with starch content or amylose content. Variations of 15 genes on chromosomes 1A and 7A formed haplotype blocks in 26 accessions. Notably, accessions with higher TKWs had more of the favorable haplotypes. We thus conclude that these haplotypes contribute additive effects to TKW. [ABSTRACT FROM AUTHOR]

Summary: Kernel size is an important trait determining cereal yields. In this study, we cloned and characterized TaDA1, a conserved negative regulator of kernel size in wheat (Triticum aestivum). The overexpression of TaDA1 decreased the size and weight of wheat kernels, while its down‐regulation using RNA interference (RNAi) had the opposite effect. Three TaDA1‐A haplotypes were identified in Chinese wheat core collections, and a haplotype association analysis showed that TaDA1‐A‐HapI was significantly correlated with the production of larger kernels and higher kernel weights in modern Chinese cultivars. The haplotype effect resulted from a difference in TaDA1‐A expression levels between genotypes, with TaDA1‐A‐HapI resulting in lower TaDA1‐A expression levels. This favourable haplotype was found having been positively selected during wheat breeding over the last century. Furthermore, we demonstrated that TaDA1‐A physically interacts with TaGW2‐B. The additive effects of TaDA1‐A and TaGW2‐B on kernel weight were confirmed not only by the phenotypic enhancement arising from the simultaneous down‐regulation of TaDA1 and TaGW2 expression, but also by the combinational haplotype effects estimated from multi‐environment field data from 348 wheat cultivars. A comparative proteome analysis of developing transgenic and wild‐type grains indicated that TaDA1 and TaGW2 are involved in partially overlapping but relatively independent protein regulatory networks. Thus, we have identified an important gene controlling kernel size in wheat and determined its interaction with other genes regulating kernel weight, which could have beneficial applications in wheat breeding. [ABSTRACT FROM AUTHOR]

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

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.

Background: Inducing mutations are considered to be an effective way to create novel genetic variations and hence novel agronomical traits in wheat. This study was conducted to assess the genetic differences between Shi4185 and its mutant line Fu4185, produced by gamma radiation with larger grain, and to identify quantitative trait loci (QTLs) for thousand kernel weight (TKW). Results: Phenotypic analysis revealed that the TKW of Fu4185 was much higher than that of Shi4185 under five different environments. At the genomic level, 110 of 2019 (5.4 %) simple sequence repeats (SSR) markers showed polymorphism between Shi4185 and Fu4185. Notably, 30 % (33 out of 110) polymorphic SSR markers were located on the D-genome, which was higher than the percentage of polymorphisms among natural allohexaploid wheat genotypes, indicating that mutations induced by gamma radiation could be a potential resource to enrich the genetic diversity of wheat D-genome. Moreover, one QTL, QTkw.cau-5D, located on chromosome 5DL, with Fu4185 contributing favorable alleles, was detected under different environments, especially under high temperature conditions. Conclusions: QTkw.cau-5D is an environmental stable QTL, which may be a desired target for genetic improvement of wheat kernel weight. [ABSTRACT FROM AUTHOR]

Wheat thousand kernel weight (TKW) is a complex trait, and is largely controlled by several kernel traits, including kernel length (KL) and kernel width (KW). In order to reveal the genetic relationship between TKW and these kernel traits (KW and KL) as accurate as possible, we applied both unconditional and conditional mapping analyses to three distinct genetic populations, one DH population and two RIL populations. This report describes the identifications of 36 unconditional and conditional additive QTLs and 30 pairs of unconditional and conditional epistatic QTLs, all of which are closely associated with TKW. While the conditional additive locus Qtkw1B, detected in the RIL2 population, exhibited the largest contribution, explaining 14.12 % of TKW variance, the unconditional epistatic QTLs Qtkw3A-2/ Qtkw5B.1, detected in the DH population, accounted for 11.95 % of phenotypic variance. This study also showed that, compared with unconditional mapping, conditional mapping resulted in very different numbers and different extent of effects of additive and epistatic QTLs that were associated with TKW when TKW was conditioned on kernel traits (KW and KL). These data strongly suggest that KW and KL indeed play a significant role in determining TKW. Furthermore, we demonstrated that the effects of the 25 additive QTLs for TKW were either entirely or largely determined by KW, while the effects of the other 25 additive QTLs for TKW were either entirely or largely affected by KL. We conclude that the conditional mapping can be useful for a better understanding of the interrelationship between the yield contributing traits at the QTL level. [ABSTRACT FROM AUTHOR]

The variability for quality attributes existing in a collection of 154 durum landraces from 20 Mediterranean countries and 18 modern cultivars was determined with the ultimate goal of identifying potential quality-enhancing genotypes for use in breeding programs. Field experiments were conducted during 3 years under rainfed conditions in northeastern Spain. Environmental effects were the most important in determining protein content, grain yield and yellow color index of the endosperm (grain flour), and the least important in determining EU quality index (QI), gluten strength and grain filling rate. QI is a weighed composite index determined from protein content, gluten strength, yellow color index and thousand kernel weight. Multivariate analysis detected four groups; three including landraces and one comprising modern cultivars. Landraces from the eastern Mediterranean countries had the highest mean QI and the widest variability for individual quality traits, but were characterized by relatively small grains. Landraces from the western Mediterranean countries had greater grain filling rates and heavier grains. Protein content, gluten strength and yellow color index were similar between eastern and western groups. The low QI and reduced variability characterizing the landrace group from the north Balkan Peninsula support the hypothesis of a different origin for this group. Modern cultivars, as a group, were the most productive and showed high QI, but they had the lowest grain protein content and phenotypic variability. Landraces that could be used as sources of quality-improving attributes and/or those that could be used in breeding programs without substantial quality handicaps were identified from different groups. Landraces can be particularly useful in breeding programs to improve gluten strength, grain weight and accelerate grain filling rate. [ABSTRACT FROM AUTHOR]

Cell wall invertase (CWI) is a critical enzyme for sink tissue development and carbon partition, and has a high association with kernel weight. Characterization of Cwi genes and development of functional markers are of importance for marker-assisted selection in wheat breeding. In the present study, the full-length genomic DNA sequence of a Cwi gene located on wheat chromosome 2A, designated TaCwi- A1, was characterized by in silico cloning and experimental validation. TaCwi- A1 comprises seven exons and six introns, with 3,676 bp in total, and an open reading frame (ORF) of 1,767 bp. A pair of complementary dominant markers, CWI21 and CWI22, was developed based on allelic variations at the TaCwi- A1 locus. A 404-bp PCR fragment was amplified by CWI21 in varieties with lower kernel weights, whereas a 402-bp fragment was generated by CWI22 in the varieties with higher kernel weights. The markers CWI21 and CWI22 were located on chromosome 2AL using a F population from a cross Doumai/Shi 4185, and a set of Chinese Spring nullisomic-tetrasomic lines. They were linked to the SSR locus Xbarc15- 2AL with a genetic distance of 10.9 cM. QTL analysis indicated that TaCwi- A1 could explain 4.8% of phenotypic variance for kernel weight over 2 years. Two sets of Chinese landraces and two sets of commercial wheat varieties were used to validate the association of CWI21 and CWI22 with kernel weight. The results indicated that the functional markers CWI21 and CWI22 were closely related to kernel weight and could be used in wheat breeding for improving grain yield. [ABSTRACT FROM AUTHOR]

Heat is an important abiotic stress during wheat ( Triticum aestivum L.) grain-filling in South Asia. A study was undertaken to determine effectiveness of selection for reduction in 1000-kernel weight (TKWR) under heat stress to increase grain yield. Selection was made for low and high TKWR and selected progenies were evaluated in timely and late seeded trials at two locations in Nepal in 2003. One thousand kernel weight (TKW), biomass yield, grain yield, harvest index (HI), grain-filling duration (GFD) and area under spot blotch progress curve per day (AUDPC/day) were examined. The low and high TKWR groups did not differ significantly for TKW, biomass yield, grain yield, HI, days to heading, GFD and AUDPC/day under timely seeding. However, low TKWR lines showed higher TKW, biomass yield, grain yield, HI, and GFD and lower AUDPC/day than the lines with high TKWR under late seeding. Realized heritability estimates for TKWR ranged from 0.68 to 0.85. The findings show that selection for low TKWR could be used as an indirect selection criterion to identify high grain yielding lines under terminal heat stress. [ABSTRACT FROM AUTHOR]

Wheat is one of the founder crops of Western agriculture. This study reconstructs agronomic conditions, potential yields, and kernel weight in the beginnings of cultivation of domesticated free-threshing wheat, c. 8000 BC. The carbon and nitrogen stable isotope compositions and the dimensions of fossil grains of naked wheat (Triticum aestivum/durum) were analysed. Samples were collected in Tell Halula and Akarçay Tepe, two Neolithic archaeological sites from the Middle Euphrates (the claimed core area for wheat domestication). The samples analysed include the oldest reported remains of naked wheat. Consistently wetter conditions but lower kernel weights were found in the Neolithic compared with the present day. Besides, the estimated yields were clearly beyond what is expected from the gathering of wild stands of cereals. Patterns of phenotypic adaptation achieved by wheat after its diffusion through the Mediterranean were also assessed. On the one hand, the study looked at variation in morphophysiological traits as related to local climate in a set of 68 durum wheat landraces from the Middle Euphrates. On the other hand, an assessment was made of regional adaptation around the Mediterranean Basin in a set of 90 landraces, traditional varieties, and modern cultivars from different origins by characterizing agronomic and morphophysiological variability. Significant relationships were observed between phenotypic variation among landraces from the Middle Euphrates and both minimum temperatures and the ratio of precipitation to potential evapotranspiration of the sites of origin. In addition, consistent differences in grain yield, plant structure, and water status were found among genotypes following both north–south and east–west gradients across the Mediterranean. These differences are associated with contrasting environmental and selection pressures. [ABSTRACT FROM PUBLISHER]

The honeycomb nil interplant competition selection procedure has been proposed as effective breeding methodology in developing high yielding and broadly adapted wheat varieties. The objective of this research were to (i) evaluate the performance under low and high nitrogen (N) fertility of a set of honeycomb vs traditional pedigree selected bread wheat varieties and (ii) to compare the effectiveness of honeycomb vs traditional pedigree selection in developing high yielding and broadly adapted wheat varieties. Seven F2 populations, which underwent honeycomb selection in the F2 for grain yield (GY), were the basic material for the derived F9 varieties used in this study. Three population were selected as promising (HC-PR) and four were discarded (HC-D). From each HC-PR the selected material entered honeycomb selection through the F6 and the high and corresponding low yielding genotypes (HY and LY) were advanced to the F9. The honeycomb F2 discarded material from each HC-PR entered traditional pedigree selection and resulted in developing the corresponding F9 varieties (TPS). Then for each HC-PR a set of three varieties, including the HY its LY counterpart and their corresponding TPS, was formed. A 4th set including four F9 varieties, one from each HC-D, developed through traditional pedigree (TPS) was also formed. These 13 varieties along with four commercial check varieties were grown with 0, 90 and 180 KgN ha−1 in a 2 year field study. Grain (GY) and biomass (BY) yield, harvest index (HI) and 1000 kernel weight (Kwg) were recorded. Both, the TPS and LY varieties yielded equal to or significantly outyielded their HY counterparts at all N treatments. This yielding superiority was associated with higher HI and heavier kernels. In the same manner the TPS varieties of the 4th set were equal to or superior than the HY for GY, HI and Kwg. Data indicated that honeycomb method selected mainly for environmental effects and/or high biomass yielding ability combined with poor N using efficiency genotypes. Data indicated that the honeycomb breeding methodology was nearly equal to or less effective than the traditional pedigree. [Copyright &y& Elsevier]

Simple Summary: Improving 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. [ABSTRACT FROM AUTHOR]

The Growth-regulating factors (GRF) are a family of plant-specific transcription factors that have roles in plant growth, development and stress response. In this study the diversity of the TaGRF3-2A (TraesCS2A02G435100) gene was investigated in Russian bread wheat germplasm by means of next generation sequencing and molecular markers, and the results compared with those from multiple wheat genome and exome sequencing projects. The results showed that an allele possessing c.495G>T polymorphism found in Bezostaya 1 and designated as TaGRF3-2Ab, is connected with earlier heading and better grain filling under conditions of the Krasnodar Krai. TaGRF3-2Ab is more frequent among Russian winter wheat cultivars than in other germplasms found in the world, implying that it is adaptive for the Chernozem region. A new rare mutation of the TaGRF3-2A was found in the spring wheat cultivar Novosibirskaya 67. The molecular markers developed will facilitate utilization of TaGRF3-2A mutations in future agronomic studies and wheat improvement. Albeit GRF3-2Ab may be good at maintaining high milling quality of the grain, it should be used with caution in breeding of winter wheat cultivars in the perspective of climate change. [ABSTRACT FROM AUTHOR]

Quantitative genetic theory was used to investigate selection differentials, expected and observed direct and correlated responses to simultaneous improvement of grain yield, kernel weight, and grain protein content in F3 and F4 populations of four spring wheat (Triticum aestivum L.) crosses. Selection in the F3 generation based on the Smith-Hazel index (SH) and yield was found to be superior to the other methods studied in identifying high-yielding lines, but resulted in substantial decrease in grain protein level. Consequently, a 1.0% increase in protein from selection for protein depressed grain yield as much as 536 kg/ha below the population mean, reducing the expected yield gains per generation selection cycle by 250%. The weight-free indices (EW), particularly the index involving only yield and kernel weight (EW3) and its linear approximation (EW4), and the desired gains indices were effective in improving protein content but were less efficient in selecting top-yielding lines. Selection in the opposite direction using truncation of the lowest 10% of the population based on weight-free-index involving yield, kernel weight and protein (EW2) reduced all traits significantly compared with the mean of the unselected population indicating the effectiveness of the unweighted selection index. The observed genetic gains (Ra) from selection based on yield, the SH, EW3 and EW4 indices were slightly lower than the expected advances per cycle (R) in populations from crosses 'Sinton' × 'Glenlea' (Cl) 'Glenlea' × 'NB505' (C2), and 'A2P5' × 'NB320' (C6) (Ra/R = 70 to 85%) but were higher in cross 'NB505' × 'A2P5' (C5) (Ra/R = 126 to 143%). It was concluded that weight-free and the desired gains indices can be used to improve wheat grain yield and grain protein simultaneously in F3 generation selection, as revealed by response to selection measured in the F4 generation. [ABSTRACT FROM AUTHOR]

Kernel weight and shape-related traits are inherited stably and increase wheat yield. Narrow genetic diversity limits the progress of wheat breeding. Here, we evaluated kernel weight and shape-related traits and applied genome-wide association analysis to a panel of wheat multiple synthetic derivative (MSD) lines. The MSD lines harbored genomic fragments from Aegilops tauschii. These materials were grown under optimum conditions in Japan, as well as under heat and combined heat–drought conditions in Sudan. We aimed to explore useful QTLs for kernel weight and shape-related traits under stress conditions. These can be useful for enhancing yield under stress conditions. MSD lines possessed remarkable genetic variation for all traits under all conditions, and some lines showed better performance than the background parent Norin 61. We identified 82 marker trait associations (MTAs) under the three conditions; most of them originated from the D genome. All of the favorable alleles originated from Ae. tauschii. For the first time, we identified markers on chromosome 5D associated with a candidate gene encoding a RING-type E3 ubiquitin–protein ligase and expected to have a role in regulating wheat seed size. Our study provides important knowledge for the improvement of wheat yield under optimum and stress conditions. The results emphasize the importance of Ae. tauschii as a gene reservoir for wheat breeding. [ABSTRACT FROM AUTHOR]