Variation For Wheat Improvement Research Articles

Heat shock protein TaHSP17.4, a TaHOP interactor in wheat, improves plant stress tolerance

Adaptation to drought and salt stresses is a fundamental part of plant cell physiology and is of great significance for crop production under environmental stress. Heat shock proteins (HSPs) are molecular chaperones that play a crucial role in folding, assembling, translocating, and degrading proteins. However, their underlying mechanisms and functions in stress tolerance remain elusive. Here, we identified the HSP TaHSP17.4 in wheat by analyzing the heat stress-induced transcriptome. Further analysis showed that TaHSP17.4 was significantly induced under drought, salt, and heat stress treatments. Intriguingly, yeast-two-hybrid analysis showed that TaHSP17.4 interacts with the HSP70/HSP90 organizing protein (HOP) TaHOP, which plays a significant role in linking HSP70 and HSP90. We found that TaHSP17.4- and TaHOP-overexpressing plants have a higher proline content and a lower malondialdehyde content than wild-type plants under stress conditions and display strong tolerance to drought, salt, and heat stress. Additionally, qRT-PCR analysis showed that stress-responsive genes relevant to reactive oxygen species scavenging and abscisic acid signaling pathways were significantly induced in TaHSP17.4- and TaHOP-overexpressing plants under stress conditions. Together, our findings provide insight into HSP functions in wheat and two novel candidate genes for improvement of wheat varieties.

Effect of gliadin from Psathrostachys huashanica on dough rheological properties and biscuit quality

Psathrostachys huashanica (P. huashanica), a wild relative of common wheat, is widely used in wheat variety improvement because of its many beneficial properties. In this study, we carried out preliminary analysis on the grain and flour quality of wheat-P. huashanica addition line 7182-6Ns and its wheat parents 7182, and found that 7182-6Ns had a higher protein content and great dough rheological characteristics and investigated the reasons for the changes. The results indicated that 7182-6Ns contained exogenous gliadin, which changed the gliadin composition and increased the ratio of gliadin in total gluten proteins, rebuilt gluten microstructure and thus optimized dough extensibility. As the addition of 7182-6Ns gliadin gradually increased to wheat flour, the diameter, crispness and spread rate of biscuit increased, the thickness and hardness decreased, and the colour improved. The current research provides a basis for understanding the introduction of exogenic gliadin to improve biscuit wheat varieties.

Identification and validation of QTLs for kernel number per spike and spike length in two founder genotypes of wheat

BackgroundKernel number per spike (KNS) and spike length (SL) are important spike-related traits in wheat variety improvement. Discovering genetic loci controlling these traits is necessary to elucidate the genetic basis of wheat yield traits and is very important for marker-assisted selection breeding.ResultsIn the present study, we used a recombinant inbred line population with 248 lines derived from the two founder genotypes of wheat, Bima4 and BainongAK58, to construct a high-density genetic map using wheat 55 K genotyping assay. The final genetic linkage map consists of 2356 bin markers (14,812 SNPs) representing all 21 wheat chromosomes, and the entire map spanned 4141.24 cM. A total of 7 and 18 QTLs were identified for KNS and SL, respectively, and they were distributed on 11 chromosomes. The allele effects of the flanking markers for 12 stable QTLs, including four QTLs for KNS and eight QTLs for SL, were estimated based on phenotyping data collected from 15 environments in a diverse wheat panel including 384 elite cultivars and breeding lines. The positive alleles at seven loci, namely, QKns.his-7D2–1, QKns.his-7D2–2, QSl.his-4A-1, QSl.his-5D1, QSl.his-4D2–2, QSl.his-5B and QSl.his-5A-2, significantly increased KNS or SL in the diverse panel, suggesting they are more universal in their effects and are valuable for gene pyramiding in breeding programs. The transmission of Bima4 allele indicated that the favorite alleles at five loci (QKns.his-7D2–1, QSl.his-5A-2, QSl.his-2D1–1, QSl.his-3A-2 and QSl.his-3B) showed a relatively high frequency or an upward trend following the continuity of generations, suggesting that they underwent rigorous selection during breeding. At two loci (QKns.his-7D2–1 and QSl.his-5A-2) that the positive effects of the Bima4 alleles have been validated in the diverse panel, two and one kompetitive allele-specific PCR (KASP) markers were further developed, respectively, and they are valuable for marker-assisted selection breeding.ConclusionImportant chromosome regions controlling KNS and SL were identified in the founder parents. Our results are useful for knowing the molecular mechanisms of founder parents and future molecular breeding in wheat.

Seed germination and biochemical responses of two Elytrigia elongata accessions exposed to abiotic stresses

AbstractElytrigia elongata, a rhizomatous and sparse‐type perennial herb of the Triticeae tribe, with stronger drought and salt tolerance, is an important wild genetic resource for wheat variety improvement. However, no precise information about seed germination and biochemical responses of this species to drought, salinity and mixed saline–alkaline stresses is available. Hence, this experiment was conducted to investigate the effects of three abiotic stresses on seed germination and physiological characteristics of two E. elongata accessions. The results showed that drought and mixed saline–alkaline stresses impair seed germination and bud seedling growth of E. elongata. However, seed germination and bud seedling growth were promoted by 50 mmol/L, but inhibited by 100–200 mmol/L salinity treatments. The malondialdehyde (MDA) content was increased and the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in the bud seedlings were significantly increased (p <.05) with increasing osmotic stress from 0 to −0.4 MPa, and salinity and mixed saline–alkaline from 0 to 150 mmol/L, but reduced at −0.75 MPa osmotic stress and 200 mmol/L salinity and mixed saline–alkaline stresses. Under the same salinity and mixed saline–alkaline treatment, the activities of SOD and CAT of EE030 were higher than those of EE024 except in 200 mmol/L salinity treatment; however, the MDA content of EE030 was lower than that of EE024, except in 150 mmol/L salinity treatment. In conclusion, the results of this study demonstrated that E. elongata seeds are more tolerant to salinity stress than to drought and mixed saline–alkaline stresses, and EE030 seed are more tolerant to three abiotic stresses than are the seeds of EE024.

Wheat Variety Improvement for Climate Resilience

High temperature stress unfavorably affects plant growth and reduces grain yield (GY). This study was conducted with an aim to identify the terminal heat tolerance of one hundred and two wheat genotypes with three checks. They were sown under normal (non-stress) and late (stress) conditions at Regional Agricultural Research Station (RARS), Tarahara; RARS, Nepalgunj and National Wheat Research Program (NWRP), Bhairahawa, Nepal. The trial was sown in Augmented design during 2014/15 winter season as a Nepal heat tolerance wheat screening nursery (NHTWSN). Grain yield, maturity, stress susceptibility and tolerant indices were estimated to assess the heat tolerance of the genotypes. Combined analysis among the tested wheat lines (102 new entries + 3 checks) showed that KACHU//KIRITATI/WBLL1 ((Heat tolerance index (HTI) = 1.78) possessed the highest level of heat tolerance, followed by SLVS /3/ CROC_1/ AE.SQUARROSA (224)// OPATA/5/ VEE/LIRA//BOW/3/BCN/4/KAUZ/6/ 2*KA/NAC//TRCH (HTI=1.57) while SUP152/VILLA JUAREZ F2009 (HTI=0.83) appeared to be the least heat tolerant. Correlation analysis showed that yield under stress environment had positive (r=0.083) and significant (p<0.05) association with that of non-stress environment. Grain yield (Kg/ha) under both environments had significant positive correlation with mean productivity (MP), geometric mean productivity (GMP) and HTI. Thirty seven wheat genotypes possessing heat tolerance will be considered in further heat tolerance trial and can also be used directly in varietal development and in the crossing program to breed more heat tolerant genotypes.

Effectiveness of Genomic Selection by Response to Selection for Winter Wheat Variety Improvement.

Prediction performance for winter wheat grain yield and end-use quality traits. Prediction accuracies evaluated by cross-validations are significantly overestimated. Nonparametric algorithms outperform the parametric alternatives in cross-year predictions. Strategically designing training population improves response to selection. Response to selection varies across growing seasons and environments. Considering the practicality of applying genomic selection (GS) in the line development stage of a hard red winter (HRW) wheat (Triticum aestivum L.) variety development program (VDP), the effectiveness of GS was evaluated by prediction accuracy and by the response to selection across field seasons that demonstrated challenges for crop improvement under significant climate variability. Important breeding targets for wheat improvement in the southern Great Plains of the United States, including grain yield, kernel weight, wheat protein content, and sodium dodecyl sulfate (SDS) sedimentation volume as a rapid test for predicting bread-making quality, were used to estimate the effectiveness of GS across harvest years from 2014 (drought) to 2016 (normal). In general, nonparametric algorithms reproducing kernel Hilbert space (RKHS) and random forest (RF) produced higher accuracies in both same-year cross-validations (CVs) and cross-year predictions for the purpose of line selection. Further, the stability of GS performance was greatest for SDS sedimentation volume but least for wheat protein content. To ensure long-term genetic gain, our study on selection response suggested that across this sample of environmental variability, and though there are cases where phenotypic selection (PS) might be still preferred, training conducted under drought or in suboptimal conditions could provide an encouraging prediction outcome when selection decisions were made in normal conditions. However, it is not advisable to use training information collected from a normal season to predict trait performance under drought conditions. Finally, the superiority of response to selection was most evident if the training population (TP) can be optimized.

Estimating and attributing benefits from wheat varietal innovations in South African agriculture

ABSTRACTIt is well accepted that biological innovations, particularly varietal improvements, have greatly contributed to agricultural yield and output growth in the past. At the same time, public funding for breeding programmes such as at the Agricultural Research Council in South Africa has dwindled. In an effort to confirm the importance of continued funding of varietal improvement programmes, this paper estimates the benefits from wheat varietal innovations and attributes them to the different institutional sources (public, private and others) that have contributed to varietal changes in South Africa. The empirical analyses used data on market shares of wheat varieties planted by farmers and annual quantities of wheat produced across different wheat-production areas in South Africa (summer dryland, dryland winter, and irrigation). A vintage regression model was estimated to calculate the proportional yield gain from wheat varietal improvements. The results indicated that the rate of gain in yield as a result of releases of new wheat varieties (variety research) was 0.8 per cent per year (equivalent to 19.84 kg/ha/year) for dryland summer varieties, and 0.5 per cent for both irrigation (equivalent to 32.20 kg/ha/year) and dryland winter varieties (equivalent to 16.65 kg/ha/year). The attribution of benefits among different institutional sources confirms that not accounting for attribution of benefits by source and time period results is overestimation of benefits to any specific research programme. Attribution of benefits by institutional source showed that Sensako dominated, while the share of the ARC-SGI substantially declined, after deregulation of the wheat sub-sector. The results highlight the impact of the decline in public funding for wheat variety improvement research after deregulation and provide a strong argument for continued public funding for variety improvement in South Africa.

Perspectives of Use of Transcription Factors for Improving Resistance of Wheat Productive Varieties to Abiotic Stresses by Transgenic Technologies

To increase the wheat productivity in a rapidly changing climate and extreme weather conditions, new varieties that are adaptive to the stresses of the environment are needed. Improvement of wheat varieties by the methods of transgenic technologies has been carried out for more than 20 years. Complex resistance to extreme temperatures, drought, salinity, pathogens, and insects are introduced to productive varieties. By now, the ISB database (Information Systems for Biotechnology—A National Resource in Agbiotech Information) lists 585 cases of transgenic wheat plants resistant to multiple environmental stresses [1]. To improve productive varieties by the methods of transgenic technology, it is necessary to have (1) genes that determine resistance to stress, (2) effective systems of genetic transformation, and (3) factors regulating the expression of a large number of stress response genes. Genes encoding transcription factors (TFs) have attracted particular attention because they are the main regulators of cellular processes; therefore, they are excellent candidates for the modification of complex multigene controlled traits of crops. Under different stress conditions, TFs regulate the stress-responsive genes by binding specifically to cis-elements in their promoters and induce the activation or suppression of their transcription. The results of crop improvement using transgenic technologies and the use of TF indicate that this approach can form the basis for the next generation of biotech crops. The review presents data on various families of TF and some of their properties, as well as prospects and achievements of the use of TF in the genetic engineering improvement of wheat.

Genome-Wide Association Mapping of Fusarium Head Blight Resistance in Spring Wheat Lines Developed in the Pacific Northwest and CIMMYT.

Fusarium head blight (FHB) is a destructive disease of wheat in humid and semihumid areas of the world. It has emerged in the Pacific Northwest (PNW) in recent years because of changing climate and crop rotation practices. Our objectives in the present study were to identify and characterize quantitative trait loci (QTL) associated with FHB resistance in spring wheat lines developed in the PNW and the International Maize and Wheat Improvement Center. In total, 170 spring wheat lines were evaluated in field and greenhouse trials in 2015 and 2016. Fourteen lines showing consistent resistance in multiple environments were identified. These lines are valuable resources in wheat variety improvement of FHB resistance because they have no Sumai 3 or Sumai 3-related background. The 170 lines were genotyped using a high-density Illumina 90K single-nucleotide polymorphisms (SNP) assay and 10 other non-SNP markers. A genome-wide association analysis was conducted with a mixed model (Q+K). Consistent, significant SNP associations with multiple traits were found on chromosomes 1B, 2B, 4B, 5A, 5B, and 6A. The locus on chromosome 5B for reduced deoxynivalenol content may be novel. The identified QTL are being validated in additional mapping studies and the identified resistant lines are being used in variety development for FHB resistance and facilitated by marker-assisted selection.

Meiotic instability inAegilops cylindrica: a comparison with stable meiosis inTriticum monococcumsubsp.aegilopoides

Wild relatives of wheat are potential sources of genetic variation for wheat improvement. Meiosis is a complex and multistep process involving many genes in which the underlying mechanisms have yet to be fully elucidated. In this study, the meiotic behavior of eight genotypes of Triticum monococcum subsp. aegilopoides and eight genotypes of Aegilops cylindrica which naturally grow side-by-side in four different regions in West Iran was investigated. Immature spikes were fixed in Carnoy’s solution and stained with hematoxylin. Percentage of abnormalities at different meiotic stages and meiotic index were determined. Results indicated the higher meiotic abnormalities in Ae. cylindrica including laggards, chromosome stickiness and bridges, B chromosomes, chromosomal unequal distribution, asynchrony, micronuclei, abnormal localization of the daughter nucleus, absence of spindle fibers and 2n gamete formation. The meiotic index of 82.6% calculated for this species characterized it as having relatively unstable...

Stripe rust resistance and dough quality of new wheat - Dasypyrum villosum translocation lines T1DL•1V#3S and T1DS•1V#3L and the location of HMW-GS genes.

The transfer of agronomically useful genes from wild wheat species into cultivated wheat is one of the most effective approaches to improvement of wheat varieties. To evaluate the transfer of genes from Dasypyrum villosum into Triticum aestivum, wheat quality and disease resistance was evaluated in two new translocation lines, T1DL•1V#3S and T1DS•1V#3L. We examined the levels of stripe rust resistance and dough quality in the two lines, and identified and located the stripe rust resistant genes and high molecular weight glutenin subunit (HMW-GS) genes Glu-V1 of D. villosum. Compared to the Chinese Spring (CS) variety, T1DL•1V#3S plants showed moderate resistance to moderate susceptibility to the stripe rust races CYR33 and Su11-4. However, T1DS•1V#3L plants showed high resistance or immunity to these stripe rusts. The genes for resistance to stripe rust were located on 1VL of D. villosum. In comparison to CS, the dough from T1DS•1V#3L had a significantly shorter developing time (1.45 min) and stable time (1.0 min), a higher weakness in gluten strength (208.5 FU), and a lower farinograph quality index (18). T1DL•1V#3S had a significantly longer developing time (4.2 min) and stable time (5.25 min), a lower weakness in gluten strength (53 FU) and a higher farinograph quality index (78.5). We also found that T1DS•1V#3L had reduced gluten strength and dough quality compared to CS, but T1DL•1V#3S had increased gluten strength and dough quality. The results of SDS-PAGE analysis indicated that Glu-V1 of D. villosum was located on short arm 1VS and long arm 1VL. These results prove that the new translocation lines, T1DS•1V#3L and T1DS•1V#3L, have valuable stripe rust resistance and dough quality traits that will be important for improving wheat quality and resistance in future wheat breeding programs.

Microsatellite analysis of genetic diversity and population genetic structure of Aegilops tauschii Coss. in Northern Iran

Genetic diversity and population genetic structure of Aegilops tauschii in Northern Iran were studied based on nine microsatellite loci. A high level of genetic diversity was observed from the accessions collected from six regions (provinces). These accessions include 79 samples of the two subspecies (tauschii and strangulata), the intermediate form (among morphologically distinguished subspecies) and ten accessions of Triticum aestivum. The nine microsatellites revealed a total of 141 alleles, with an average of 15.7 alleles per locus. A comparison of the parameters showing genetic diversity, including the observed heterozygosity (Ho), gene diversity (He) and Shannon’s information index (I) of Ae. tauschii accessions from different provinces in Northern Iran, indicated that subsp. tauschii possesses the highest genetic diversity, followed by intermediate form. Genetic distance between subsp. strangulata and subsp. tauschii was low, confirming high gene flow between these two subspecies. However, intermediate form was more distinct from both of them. It was also found that the genetic diversity of T. aestivum is obviously lower than that of Ae. tauschii accessions. Moreover, the level of genetic diversity for Gilan, Golestan and Mazanderan provinces was higher than for Ardebil, Ghazvin and Semnan provinces, suggesting that these regions may provide a readily available source of potentially useful variation for wheat improvement.

Genetic Contribution of Introduced Varieties to Wheat Breeding in China Evaluated Using Microsatellite Markers

The objective of the study was to understand the genetic contribution of introduced varieties to Chinese wheat ( Triticum aestivum L.) breeding at the genomic level. A total of 44 representative accessions, consisting of 11 introduced parents from the 1950s to the 1970s and 33 Chinese modern varieties that were released in different years, were evaluated using 363 microsatellite markers. The introduced accessions contained 76.3% of the alleles presented in the Chinese varieties examined. Comparing the genetic diversity of grouped accessions based on their origins and released ages, the exotic group had the largest average allele number per locus (3.9), followed by the 1980s group (3.5), and the 1960s and the 1970s groups had the smallest value (2.9 and 3.0, respectively). Analysis of genetic distance among groups showed an accordant result to that on allelic diversity. According to the allelic frequency, 33 loci of introduced varieties were selected preferentially and transmitted to Chinese accessions, and the allelic frequencies at these loci were all larger than 70%. These loci played an important role in the improvement of wheat varieties in China. The objective of the study was to understand the genetic contribution of introduced varieties to Chinese wheat ( Triticum aestivum L.) breeding at the genomic level. A total of 44 representative accessions, consisting of 11 introduced parents from the 1950s to the 1970s and 33 Chinese modern varieties that were released in different years, were evaluated using 363 microsatellite markers. The introduced accessions contained 76.3% of the alleles presented in the Chinese varieties examined. Comparing the genetic diversity of grouped accessions based on their origins and released ages, the exotic group had the largest average allele number per locus (3.9), followed by the 1980s group (3.5), and the 1960s and the 1970s groups had the smallest value (2.9 and 3.0, respectively). Analysis of genetic distance among groups showed an accordant result to that on allelic diversity. According to the allelic frequency, 33 loci of introduced varieties were selected preferentially and transmitted to Chinese accessions, and the allelic frequencies at these loci were all larger than 70%. These loci played an important role in the improvement of wheat varieties in China.

D hordeins of Hordeum chilense: a novel source of variation for improvement of wheat

The high molecular weight subunits of wheat (Triticum aestivum L.) glutenin (HMW-GS) are important in determining the bread-making quality of flour and dough. There is therefore interest in transferring orthologous HMW-GS present in other grass species into wheat by wide crossing in order to extend the range of end use properties. In this work, we have isolated and characterized two genes encoding D hordeins from Hordeum chilense (Roem. et Schult.) lines H1 and H7, representing two ecotypes. The fragments were 4,305 bp for line H1 and 4,227 for line H7 and contained the promoter, coding and terminator regions. Both sequences differ in the presence of single base changes (SNPs) and insertions/deletions in the open reading frame (ORF). The encoded proteins comprise 870 and 896 amino acids for lines H1 and H7, respectively. The primary structure is similar to those of D hordeins of cultivated barley (H. vulgare L.) and HMW-GS from wheat. However, the D hordeins from H. chilense are significantly larger than those from cultivated barley due to the presence of longer repetitive regions. The H. chilense D hordeins also differ from those of cultivated barley in the distribution of the cysteine residues: whereas the D hordeins of cultivated barley contain ten cysteines with four in the repetitive domain, only nine are present in the H. chilense proteins with two in the repetitive domain. As in the HMW-GS, the central part of the D hordein proteins comprises repeated sequences based on short peptide motifs. The repetitive domain is divided in three regions named as R1 (N-terminal repeats), R2 (central degenerate repeats) and R3 (C-terminal repeats). Hexapeptide motifs are present throughout the repetitive domains of D hordeins with a consensus motif of PFQGQQ in R1 and R2 and PHQGQQ in R3. In addition, the tetrapeptide motif TTVS, which is characteristic of D hordeins of cultivated barley is present in the repetitive domain close to the protein C-terminus.

Chromosome 1D as a possible location of a gene (s) controlling variation between wheat (Triticum aestivum L.) varieties for carbon isotope discrimination (Δ) under water-stress conditions

Carbon isotope discrimination (Δ) is an important character regarding to water-stress tolerance in wheat. In this study, F2 backcross reciprocal monosomic crosses between varieties Falchetto (low Δ) and 18 monosomic lines of Oxley (high Δ) were used to identify chromosomal location of the gene (s) responsible for carbon isotope discrimination and therefore to detect allelic variation between the two wheat varieties. F2 reciprocal monosomic families were initially assessed for dry matter production. F2 families belonging to the chromosomes that indicated allelic variation for dry matter production were then assessed for Δ. The results revealed that reciprocal families belonging to chromosomes 1B, 7B, 1D and 5D indicated significant differences from which the family having chromosome 1D from Falchetto had the highest difference from its relevant reciprocal. Assessing the reciprocals of this chromosome for evapotranspiration efficiency (ETE) at the F3 disomic generation indicated that the observed variation for Δ was translated into differences for ETE. These results indicate that chromosome 1D of Falchetto is promising in reducing Δ and that the improvement of wheat varieties for ETE can be done by selection for Δ. When selecting for Δ, managing the experiment is easier and there is no need to monitor the water use during the growth cycle.

Backcross reciprocal monosomic analysis of leaf relative water content, stomatal resistance, and carbon isotope discrimination in wheat under pre-anthesis water-stress conditions

Monosomic plants from an Australian variety (Oxley) having low stomatal resistance (SR), low leaf relative water content (LRWC), and high carbon isotope discrimination (Δ) were crossed with variety Falchetto having opposite characters in order to produce F2 backcross reciprocal monosomic families. The families were assessed under pre-anthesis water-stress conditions in a controlled growth chamber. F2 backcross reciprocal monosomic analysis suggested possible allelic variations between chromosomes 1A, 3A, 6A, 7A, 7B, 1D, and 4D of Falchetto and their homologues in Oxley for LRWC. This analysis also suggested possible allelic variation between chromosomes 5A, 1A, and 3A of Falchetto and their homologues in Oxley for SR. Extending the analysis to the F3 disomic generation and the assessment of LRWC at this generation confirmed that reciprocals for chromosomes 3A and 6A showed significant differences. F2 backcross reciprocal monosomic analysis for Δ suggested allelic variations on chromosomes 1D, 4D, and 5D. However, chromosome 1D from Falchetto had the highest difference from its homologue in Oxley. Assessing the reciprocals of this chromosome for vegetative evapotranspiration efficiency (ETEveg) at the F3 disomic generation indicated that the observed variation for Δ was translated into differences for ETEveg. These results indicate that chromosome 1D of Falchetto is promising in reducing Δ and that the improvement of wheat varieties for ETEveg can be done by selection for Δ. Finally, plieotropic effects of some chromosomes were observed for the characters under study. This suggests the existence of genetic factors on these chromosomes affecting more than one character. However, some pleiotropic effects could also be due to non-genetic developmental interactions.