Search

Genetic recombination produces new allelic combinations, thereby introducing variation for domestication. Allopolyploidization has increased the evolutionary potential of hexaploid common wheat by conferring the advantages of heterosis and gene redundancy, but whether a relationship exists between allopolyploidization and genetic recombination is currently unknown. To study the impact of allopolyploidization on genetic recombination in the ancestral D genome of wheat, we generated new synthetic hexaploid wheats by crossing tetraploid Triticum turgidum with multiple diploid Aegilops tauschii accessions, with subsequent chromosome doubling, to simulate the evolutionary hexaploidization process. Using the DArT-Seq approach, we determined the genotypes of two new synthetic hexaploid wheats with their parents, F2 plants in a diploid population (2x, D1D1 × D2D2) and its new synthetic hexaploid wheat-derived population (6x, AABBD1D1 × AABBD2D2). About 11% of detected SNP loci spanning the D genome of Ae. tauschii were eliminated after allohexaploidization, and the degree of segregation distortion was increased in their hexaploid offspring from the F2 generation. Based on codominant genotypes, the mean genetic interval length and recombination frequency between pairs of adjacent and linked SNPs on D genome of the hexaploid F2 population were 2.3 fold greater than those in the diploid F2 population, and the recombination frequency of Ae. tauschii was increased by their hexaploidization with T. turgidum. In conclusion, allopolyploidization increases genetic recombination of the ancestral diploid D genome of wheat, and DNA elimination and increased segregation distortion also occur after allopolyploidization. Increased genetic recombination could have produced more new allelic combinations subject to natural or artificial selection, helping wheat to spread rapidly to become a major global crop and thereby accelerating the evolution of wheat via hexaploidization.

The powdery mildew resistance gene Pm58 was traced to a 141.3-kb interval with the co-segregating marker Xkasp68500 in wheat breeding. Pm58 is a powdery mildew resistance gene identified in Aegilops tauschii accession TA1662 and effective in a common wheat background. To finely map Pm58, an F

Rye (Secale cereale L.) is an important genetic resource for improving the disease resistance of wheat. An increasing number of rye chromosome segments have been transferred into modern wheat cultivars via chromatin insertions. In this study, 185 recombinant inbred lines (RILs) derived from a cross between a common wheat accession containing rye chromosomes 1RS and 3R and a wheat-breeding founder parent (Chuanmai 42) from southwestern China were used to decipher the cytological and genetic effects of 1RS and 3R via fluorescence/genomic in situ hybridization and quantitative trait locus (QTL) analyses. Chromosome breakage was detected in the RIL population. Additionally, the recombination of chromosomes 1BS and 3D from Chuanmai 42 was completely suppressed by 1RS and 3R in the RIL population. In contrast to chromosome 3D of Chuanmai 42, rye chromosome 3R was significantly associated with white seed coats and decreased yield-related traits, as revealed by QTL and single marker analyses, whereas it had no effect on stripe rust resistance. Rye chromosome 1RS did not affect yield-related traits and it increased the susceptibility of plants to stripe rust. Most of the detected QTLs that positively affected yield-related traits were from Chuanmai 42. The findings of this study suggest that the negative effects of rye-wheat substitutions or translocations, including the suppression of the pyramiding of favorable QTLs on paired wheat chromosomes from different parents and the transfer of disadvantageous alleles to filial generations, should be considered when selecting germplasm to enhance wheat-breeding founder parents or to breed new varieties.

Powdery mildew, caused by fungal pathogen Blumeria graminis f. sp. tritici, is an agronomically important and widespread wheat disease causing severe yield losses. Deployment of broad‐spectrum disease resistance genes is the preferred strategy to prevent this pathogen. Chinese wheat landrace Honghuaxiaomai (HHXM) was resistant to all 23 tested B. graminis f. sp. tritici isolates at the seedling stage. The F1, F2, and F2:3 progenies derived from the cross HHXM × Yangmai 158 were used in this study, and genetic analysis revealed that a single dominant gene, designated PmHHXM, conferred resistance to B. graminis f. sp. tritici isolate E09. Bulked segregant analysis and molecular mapping initially located PmHHXM to the distal region of chromosome 4AL. To fine map PmHHXM, we identified two critical recombinants from 592 F2 plants and delimited PmHHXM to a 0.18-cM Xkasp475200 to Xhnu552 interval covering 1.77 Mb, in which a number of disease resistance–related gene clusters were annotated. Comparative mapping of this interval revealed a perturbed synteny among Triticeae species. This study reports the new powdery mildew resistance gene PmHHXM, which seems different from three known quantitative trait loci/genes identified on chromosome 4AL and has significant values for further genetic improvement. Analysis of the polymorphisms of 13 cosegregating markers between HHXM and 170 modern wheat cultivars indicates that Xhnu227 and Xsts478700 developed here are ideal for marker-assisted introgression of this locus in wheat breeding.

Many organisms have dormant stages with an extension of their life span to increase longevity, and deeper dormancy is usually related to greater longevity. In cereal crops, seed dormancy is significantly associated with pre-harvest sprouting tolerance during seed development, as seed longevity is a valuable trait for seed banks and providing reliable crop seeds to farmers. In this study, we evaluated both seed dormancy and longevity in bread wheat based on germination and artificial aging tests. According to phenotypic clustering analysis, relative germination rate/potential and relative seedling vigor index were more effective to indicate seed longevity than relative electrical conductivity in wheat, while all the four investigated phenotypes of relative germination potential, relative germination rate, germination index and degree of seed dormancy fit well as a reflex of wheat seed dormancy. In the correlation analysis, the germination level of newly harvested grain negatively reflected its degree of seed dormancy, while the germination ability of grain after artificial aging reflected its seed longevity. However, in contrast to the current opinion in plant, seed dormancy was significantly negatively correlated to seed longevity in our study, and it was not an accidental phenomenon, for that the majority of accessions with high degree of seed dormancy had short seed longevity. To our knowledge, this is the first to report the negative association between seed dormancy and longevity in cereal crops. It would lead to further concerns about how to breed wheat with both prolonged seed longevity and deep dormancy to avoid pre-harvest sprouting.

Seed storability (SS), also called seed longevity, is a valuable trait for seed banks and providing reliable crop seeds to farmers, which is usually negatively correlated to lipoxygenase (LOX) activity. In this study, the seed storability of 60 accessions of CIMMYT core wheat germplasm panel (CIMCOG) was investigated through artificial aging (AA) test, including three parameters relative germination potential (RGP), relative germination rate (RGR) and relative seedling vigor index (RVI). Significant positive relationships were observed among RGP, RGR and RVI. And the genotypes at three LOX activity related QTLs/genes QLpx.caas-4B, QLpx.caas-1AL and TaLOX-B1 were also identified with published trait-associated molecular markers. For QLpx.caas-4B, a total of five alleles were detected at the locus of Xgwm251, and one marker-trait association was identified for RVI. Four and two alleles were detected at the loci of QLpx.caas-1AL and TaLoxB1 that were significantly associated with RGP, RGR and RVI, respectively. A total of 9 haplotypes were detected at three lipoxygenase activity related gene loci, and the haplotype of three lipoxygenase loci showed a significant association with RGP, RGR and RVI. The haplotype of Xgwm251-125bp + Xwmc312-247bp + TaLox-B1b produced seeds with the best storability in the CIMCOG, which could benefit the breeding for wheat with good seed storability.

Wheat is the crop most widely grown in the world and provides the daily protein and 20% food calories for 4.5 billion people. It is crucial to understand the genetic basis of grain hardness for improving wheat quality. In order to explore the molecular basis of the formation of wheat grain hardness, two wheat cultivars Chuanmai 66 and Shumai 969 with significant hardness difference in southwest wheat region were selected to analyze the proteins differential expression by TMT quantitative proteomics (tandem mass tags) and bioinformatic methods of function and pathway enrichment analysis. A total of 6020 effective proteins were identified and quantified, including 113 differentially expressed proteins (DEPs), of which 69 were up-regulated and 44 were down-regulated in soft wheat Chuanmai 66. These DEPs were enriched into 65 GO terms, including a biological process term, a cellular component term and six molecular function terms at extremely significant level. Based on the enrichment analysis, we suggested that nutrient reservoir activity proteins, enzyme inhibitor proteins and glutathione metabolism proteins might participate in the formation of wheat grain hardness, and grain hardness related proteins might mainly distribute in the extracellular region of cells and had defensive function. According to the phylogenetic analysis, it was inferred that puroindolines and its homologous proteins might be as not only wheat grain storage proteins, but also enzyme inhibitors regulating grain development. This study provides a basis for further exploring the genetic mechanism of wheat grain hardness.

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is a serious disease in bread wheat (Triticum aestivum L.). Identification and use of adult plant resistance (APR) resources are important for stripe rust resistance breeding. Bread wheat line C33 is an exotic germplasm that has shown stable APR to stripe rust for more than 10 years in Sichuan Province of China. Here, 183 recombinant inbred lines (RILs) derived from the cross between C33 and a susceptible line X440 were genotyped with diversity arrays technology (DArT) markers to identify resistance quantitative trait locus (QTL). Field trials were conducted in five years at Chengdu and Xindu of Sichuan Province, using maximum disease severity (MDS) as stripe rust reaction phenotypes. A total of four quantitative trait loci (QTLs) were detected, respectively designed as QYr.saas-3AS, QYr.saas-5AL, QYr.saas-5BL, and QYr.saas-7DS, explaining 4.14–15.21% of the phenotypic variances. QYr.saas-5BL and QYr.saas-7DS were contributed by C33. However, the level for stripe rust resistance contributed by them was not strong as C33, suggesting the presence of other unidentified QTLs in C33. QYr.saas-7DS corresponded to Yr18 and QYr.saas-5BL remains to be formally named. The RIL lines carrying combinations QYr.saas-5AL, QYr.saas-5BL, and QYr.saas-7DS showed comparability resistance with C33. The present study provides resources to pyramid diverse genes into locally adapted elite germplasm to improve the stripe rust resistance of bread wheat.

Synthetic hexaploid wheat (SHW) is a useful genetic resource that can be used to improve the performance of common wheat by transferring favorable genes from a wide range of tetraploid or diploid donors. From the perspectives of physiology, cultivation, and molecular genetics, the use of SHW has the potential to increase wheat yield. Moreover, genomic variation and recombination were enhanced in newly formed SHW, which could generate more genovariation or new gene combinations compared to ancestral genomes. Accordingly, we presented a breeding strategy for the application of SHW—the ‘large population with limited backcrossing method’—and we pyramided stripe rust resistance and big-spike-related QTLs/genes from SHW into new high-yield cultivars, which represents an important genetic basis of big-spike wheat in southwestern China. For further breeding applications of SHW-derived cultivars, we used the ‘recombinant inbred line-based breeding method’ that combines both phenotypic and genotypic evaluations to pyramid multi-spike and pre-harvest sprouting resistance QTLs/genes from other germplasms to SHW-derived cultivars; consequently, we created record-breaking high-yield wheat in southwestern China. To meet upcoming environmental challenges and continuous global demand for wheat production, SHW with broad genetic resources from wild donor species will play a major role in wheat breeding.

Paper description: Indole-acyl esters (ID), nitrogen (N) or phosphorous (P) fertilizers can mitigate the toxic effects of Cd and Pb on plant growth. The Box-Behnken three-variable partial factorial design was utilized to study the interaction effects of three factors on Jatropha curcas L growth. The c ombined effects of two or three factors on plant growth were studied using single factor experiments. Combined ID, N, and P treatments increased the ability of Jatropha curcas to grow on heavy metal-contaminated soils. This paper proposes a novel methodology that is related to the interaction effects of multiple factors on plants. Abstract: The effects of indole-acyl esters (ID), NH 4 NO 3 (N), and KH 2 PO 4 (P), on the mitigation of the toxic effects of Cd and Pb and their concentration in Jatropha curcas L. from contaminated soils was investigated. The concentrations of ID, N, and P were optimized (0.1 mL·L -1 , 7 mM, and 2.5 mM, respectively) and they were applied in various combinations to the contaminated soils of potted plants of J. curcas . The results showed that ID together with the N and P fertilizers, increased plant biomass and improved the mitigating effects of the N-P treatments on Cd and Pb toxicity. Plants growing under ID-N-IP treatments had high whole plant biomasses, high concentrations of P, N, Pb and Cd in whole plants, as well as enhanced activities of superoxide dismutase (SOD) and peroxidase (POD). These results point to the phytoremediation ability of J. curcas . We propose a new methodology that can be utilized to study the effects and interactions of multiple factors on plant growth. https://doi.org/10.2298/ABS190216050F Received: February 16, 2019; Revised: August 17, 2019; Accepted: August 19, 2019; Published online: August 30, 2019 How to cite this article: Fang Z, Wan H, Xu Y, Liu Q, Liang J, Shi X, Chen F. Indole-acyl esters improve the effect of nitrogen and phosphorous fertilization by mitigating the phytotoxicity and concentrations of cadmium and lead in Jatropha curcas L. in contaminated soils. Arch Biol Sci. 2019;71(4):677-86.

Powdery mildew, caused by fungal pathogen

Background: Genetic recombination produces different allelic combinations potentially, providing new variations to the selection pools for domestication. Allopolyploidization increases evolutionary potential of the hexaploid common wheat by taking its advantages of heterosis and gene redundancy. May there be any relationship between allopolyploidization and genetic recombination? To study the impact of allopolyploidization on genetic recombination in different ancestral genomes of wheat, we generated synthetic hexaploid wheat by crossed tetraploid Triticum turgidum with diploid Aegilops tauschii to simulate its evolutionary hexaploidization process. Results: Using Wheat Breeder’s Genotyping Array, the genotypes of F2 individuals were investigated in both tetraploid (A1A1B1B1 x A2A2B2B2) and their synthetic hexaploid wheat derived populations (A1A1B1B1DD x A2A2B2B2DD). And the genotypes of the diploid population (D1D1 x D2D2) and their synthetic hexaploid wheat derived population (AABBD1D1 x AABBD2D2) were obtained with DArT-Seq™ technology. Based on genotypes of F2 populations, the genetic recombination frequency of homologous chromosome were consequently calculated in ancestral tetraploid AABB (4x), diploid DD (2x) and their synthetic hexaploid AABBDD (6x) plants, respectively. The recombination frequency of the ancestral diploid genome DD from Aegilops tauschii was found enhanced significantly more than 2 folds after their hexaploidization, while no significant changes was found in their ancestral tetraploid genome AABB via hexaploidization.Conclusions: Allopolyploidization enhancing genetic recombination of the ancestral diploid genome is found to increase the evolutionary potential of wheat, which is beneficial for wheat to conquer their narrow origination of D genome, quickly spread and make it a major crop of the world.

Allopolyploidy increases its evolutionary potential by fixing heterosis and the advantage of gene redundancy. Allelic combinations generated from genetic recombination potentially provide many variations to the selection pools for evolution. May there be any relationship between allopolyploidization and genetic recombination? To study the impact of polyploidy on genetic recombination, we selected wheat as a model and simulated its evolution pathway of allopolyploidy by developing synthetic hexaploid wheat. The change of homologous chromosome recombination were investigated on their diploid DD and tetraploid AABB genomes after their allohexaploidization, respectively. The genetic recombination of the ancestral diploid genome ofAegilops tauschiiwas enhanced significantly more than 2 folds after their hexaploidization. Hexaploidization enhancing genetic recombination of the ancestral diploid D genome was firstly reported to be a new way to increase evolutionary potential of wheat, which is beneficial for wheat to conquer their narrow origination of D genome, quickly spread and make it a major crop of the world. Finally, re-synthetizing hexaploid wheat using diverseAe. tauschiispecies with tetraploid wheat can be considered as a pleiotropic strategy to speed adaptive evolution of bread wheat in breeding processes by increasing both gene allele types and genetic recombination variations.

Strong early vigour plays a crucial role in wheat yield improvement by enhancing resource utilization efficiency. Synthetic hexaploid wheat (SHW) combines the elite genes of tetraploid wheat with Aegilops tauschii and has been widely used in wheat genetic improvement for its abundant genetic variation. The two SHWs Syn79 and Syn80 were derived from the crossing of the same tetraploid wheat DOY1 with two different Ae. tauschii accessions, AT333 and AT428, respectively. The Syn80 possessed better early vigour traits than Syn79, theretically caused by their D genome from Ae. tauschii. To dissect their genetic basis in a hexaploid background, 203 recombinant inbred lines (RILs) derived from the cross of Syn79 x Syn80 were developed to detect quantitative trait loci (QTL) for four early biomass related traits: plant height (PH), tiller number (TN), shoot fresh weight (SFW) and shoot dry weight (SDW) per plant, under five different environmental conditions. Determined from the data of SNP markers, two genome regions on 1DS and 7D were stably associated with the four early biomass related traits showing pleiotropic effects. Four stable QTLs QPh.saas-1DS, QTn.saas-1DS, QSfw.saas-1DS and QSdw.saas-1DS explaining 7.92, 15.34, 9.64 and 10.15% of the phenotypic variation, respectively, were clustered in the region of 1DS from AX-94812958 to AX-110910133. Meanwhile, QPh.saas-7D, QTn.saas-7D, QSfw.saas-7D and QSdw.saas-7D were flanked by AX-109917900 and AX-110605376 on 7D, explaining 16.12, 24.35, 15.25 and 13.37% of the phenotypic variation on average, respectively. Moreover, these genomic QTLs on 1DS and 7D enhancing biomass in the parent Syn80 were from Ae. tauschii AT428. These findings suggest that these two QTLs from Ae. tauschii can be expressed stably in a hexaploid background at the jointing stage and be used for wheat improvement.

Wheat, an important human energy source, is critical for global food security. Grain hardness is a major determinant of wheat quality. Although the genetic bases of wheat grain hardness have been investigated, the mechanisms underlying the effects of nitrogen on wheat quality remain largely unknown. In the same wheat cultivar, grain hardness and protein content decreased in plants treated with low nitrogen as compared to those treated with high nitrogen, while starch content increased. High-throughput tandem mass tags (TMT) quantitative proteomics identified 6061 effective proteins in cultivar Shumai 969; 88 of these proteins were differentially expressed in the low-nitrogen plants as compared to the high-nitrogen plants (31 upregulated and 57 downregulated). Several storage proteins, including α-gliadins, γ-gliadins, ω-gliadins, high molecular weight glutenin subunits, and three globulin proteins, were downregulated in the low-nitrogen plants as compared to the high-nitrogen plants. The differentially expressed proteins associated with the 10 significantly enriched Gene Ontology terms and the 5 significantly enriched biochemical metabolic pathways might play a role in the determination of wheat grain hardness. This study provides a baseline for the effects of nitrogen application on wheat grain quality and identifies candidate genes for the targeted breeding of superior wheat varieties with specific end-use properties.

This paper proposed three types of milling cutter, including the normal one, the modified cutter with high damping alloy sleeve, the modified cutter with high damping sleeve and gasket, these three type of cutters are identified with type A, type B and type C respectively. The testing items including cutting force, surface smoothness and fatigue life of above three type of cutter are conducted under different working conditions respectively. The result shows that the milling cutter with high damping alloy behaves better and could improve the related performance dramatically. Specifically, the cutting force of the cutters including type B and C is lower obviously than type A at three different directions, and type C cutter has the lowest cutting force and has the best anti-vibration effects. Additionally, under working condition 1, the surface smoothness of the three type of cutters have the similar behavior. But under working condition 2, the high damping milling cutter has at least 30% improvement. Finally, at the aspect of the fatigue life, the milling cutter with high damping alloy has at least 54.55% better performance than the normal cutter, and the wear of the high damping cutter is at least 38.13% less than normal cutter.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating fungal diseases of wheat worldwide. It is essential to discover more sources of stripe rust resistance genes for wheat breeding programs. Specific locus amplified fragment sequencing (SLAF-seq) is a powerful tool for the construction of high-density genetic maps. In this study, a set of 200 recombinant inbred lines (RILs) derived from a cross between wheat cultivars Chuanmai 42 (CH42) and Chuanmai 55 (CH55) was used to construct a high-density genetic map and to identify quantitative trait loci (QTLs) for stripe rust resistance using SLAF-seq technology. A genetic map of 2828.51 cM, including 21 linkage groups, contained 6732 single nucleotide polymorphism markers (SNP). Resistance QTLs were identified on chromosomes 1B, 2A, and 7B, Qyr.saas-7B was derived from CH42, whereas Qyr.saas-1B and Qyr.saas-2A were from CH55. The physical location of Qyr.saas-1B, which explained 6.24&ndash, 34.22% of the phenotypic variation, overlapped with the resistance gene Yr29. Qyr.saas-7B accounted for up to 20.64% of the phenotypic variation. Qyr.saas-2A, a minor QTL, was found to be a likely new stripe rust resistance locus. A significant additive effect was observed when all three QTLs were combined. The combined resistance genes could be of value in breeding wheat for stripe rust resistance.

Background Although rapeseed (Brassica napus L.) mutant forming multiple siliques was morphologically described and considered to increase the silique number per plant, an important agronomic trait in this crop, the molecular mechanism underlying this beneficial trait remains unclear. Here, we combined bulked-segregant analysis (BSA) and whole genome re-sequencing (WGR) to map the genomic regions responsible for the multi-silique trait using two pools of DNA from the near-isogenic lines (NILs) zws-ms (multi-silique) and zws-217 (single-silique). We used the Euclidean Distance (ED) to identify genomic regions associated with this trait based on both SNPs and InDels. We also conducted transcriptome sequencing to identify differentially expressed genes (DEGs) between zws-ms and zws-217. Results Genetic analysis using the ED algorithm identified three SNP- and two InDel-associated regions for the multi-silique trait. Two highly overlapped parts of the SNP- and InDel-associated regions were identified as important intersecting regions, which are located on chromosomes A09 and C08, respectively, including 2044 genes in 10.20-MB length totally. Transcriptome sequencing revealed 129 DEGs between zws-ms and zws-217 in buds, including 39 DEGs located in the two abovementioned associated regions. We identified candidate genes involved in multi-silique formation in rapeseed based on the results of functional annotation. Conclusions This study identified the genomic regions and candidate genes related to the multi-silique trait in rapeseed. Electronic supplementary material The online version of this article (10.1186/s12864-019-5675-4) contains supplementary material, which is available to authorized users.

Table S2. Information about the mapped reads based on the transcriptome sequencing data. (DOCX 15 kb)

Table S7. GO annotations of the 104 genes with non-synonymous mutation SNPs in the associated regions. (DOCX 34 kb)

Table S8. GO annotations of the 19 genes with frame-shift mutation InDels in the associated regions. (DOCX 17 kb)

Figure S1. Whole genome with associated regions. (DOCX 209 kb)

Table S1. Summary of the transcriptome sequencing data. (DOCX 15 kb)

High molecular weight (HMW) glutenin, one of the important storage proteins of wheat, mainly confers end-use quality of wheat grain. Among the loci of HMW-GS, the locus D1 determines the breaking quality of bread wheat dough mostly. Synthetic hexaploid wheat (SHW) inherits vast genetic diversity in the D genome of Aegilops tauschii and has gradually been used as a bridge-tool for wheat improvement. Therefore, more and more HMW-GS subunit types of Ae. tauschii have been introgressed into the common wheat with irresistible application of SHW in wheat breeding. However, the traditional SDS-PAGE couldn’t distinguish Dtx5 of Ae. tauschii from Dx5 of common wheat. In this study, we developed two AS-PCR markers based on three SNPs in the HMW-GS D1 sequences of Ae. tauschii and common wheat. The sharp and stable fragments amplified by designed AS-PCR primers indicated their availability and convenience in Dtx5 and Dx5 identification. And Dx5 of common wheat obtained the amplified fragments by AS-PCR primers, while no fragment was amplified for Dtx5 of Ae. tauschii. And the amplified results were consistent in both pairs of AS-PCR primers. Moreover, Dtx5 is more highly homologous with Dx2 than Dx5 from their protein sequences.

Aegilops tauschii, the diploid D genome progenitor of the hexaploid wheat, has been used to improve modern common wheat by creating synthetic hexaploid wheat (SHW) as a bridging mechanism for wheat breeding. Most Ae. tauschii accessions have hairiness on the leaf sheath, whereas the hexaploid common wheat is usually glabrous. In this study a major QTL for leaf sheath hairiness (LSH) was detected on the long arm of chromosome 4D in two recombinant inbred line (RIL) populations produced from SHW-derived cultivar Chuanmai 42. The QTL peak was flanked by markers Xbarc48 and Xbarc1183/D_GB5Y7FA01AGCKH_224, and explained more than 75 % of the phenotypic variation. The QTL allele for LSH was contributed by Chuanmai 42, and originated from Ae. tauschii. In both RIL populations the QTL allele producing hairy leaf sheath was significantly and positively associated with increased grain yield, grain weight and grain weight per spike. Moreover, most Chuanmai 42-derived cultivars have inherited the hairy leaf sheath character. These findings suggest that the hairy leaf sheath gene in Chuanmai 42 can be applied in marker-assisted selection (MAS) as a morphologically selectable marker in breeding for high yield.

The spike characteristics length, spikelet density and fertile floret number are related yield components and are important in cereal improvement. QSpl.nau-2D is a major quantitative trait locus controlling spike length (SPL) detected in the recombinant inbred line population developed by crossing wheat (Triticum aestivum) cultivars Nanda2419 with Wangshuibai. In this study, to validate its genetic effect and determine its precise location, QSpl.nau-2D’s near-isogenic line (NIL) was developed using Mianyang99-323 as the recurrent parent through marker-assisted selection. Field trials showed that the NIL not only had significantly longer spikes on average than the recurrent parent but also had significantly higher grain weight, but did not differ in spikelet number and kernel number per spike. In the F2 population derived from a cross of the NIL with Mianyang99-323, QSpl.nau-2D functioned like a single gene and conditioned the SPL in a partially dominant manner, and was thus designated as HL1 (for head length). To precisely map HL1, 89 recombinants, consisting of 11 genotypes, were identified in the NIL-derived F2 population of 674 plants by using markers in the Xwmc25–Xgpw4080 interval. Phenotyping these lines showed that the introduction of a 0.9-cM interval flanked by Xcfd53 and DG371 in Nanda2419 resulted in longer spikes and a higher grain weight in the NIL. The availability of markers closely linked to HL1 could facilitate its use in breeding programs.

Rht-B1c, allelic to the DELLA protein-encoding gene Rht-B1a, is a natural mutation documented in common wheat (Triticum aestivum). It confers variation to a number of traits related to cell and plant morphology, seed dormancy, and photosynthesis. The present study was conducted to examine the sequence variations of Rht-B1c and their functional impacts. The results showed that Rht-B1c was partially dominant or co-dominant for plant height, and exhibited an increased dwarfing effect. At the sequence level, Rht-B1c differed from Rht-B1a by one 2kb Veju retrotransposon insertion, three coding region single nucleotide polymorphisms (SNPs), one 197bp insertion, and four SNPs in the 1kb upstream sequence. Haplotype investigations, association analyses, transient expression assays, and expression profiling showed that the Veju insertion was primarily responsible for the extreme dwarfing effect. It was found that the Veju insertion changed processing of the Rht-B1c transcripts and resulted in DELLA motif primary structure disruption. Expression assays showed that Rht-B1c caused reduction of total Rht-1 transcript levels, and up-regulation of GATA-like transcription factors and genes positively regulated by these factors, suggesting that one way in which Rht-1 proteins affect plant growth and development is through GATA-like transcription factor regulation.

Understanding the genetics underlying yield formation of wheat is important for increasing wheat yield potential in breeding programs. Nanda2419 was a widely used cultivar for wheat production and breeding in China. In this study, we evaluated yield components and a few yield-related traits of a recombinant inbred line (RIL) population created by crossing Nanda2419 with the indigenous cultivar Wangshuibai in three to four trials at different geographical locations. Negative and positive correlations were found among some of these evaluated traits. Five traits had over 50 % trial-wide broad sense heritability. Using a framework marker map of the genome constructed with this population, quantitative trait loci (QTL) were identified for all traits, and epistatic loci were identified for seven of them. Our results confirmed some of the previously reported QTLs in wheat and identified several new ones, including QSn.nau-6D for effective tillers, QGn.nau-4B.2 for kernel number, QGw.nau-4D for kernel weight, QPh.nau-4B.2 and QPh.nau-4A for plant height, and QFlw.nau-5A.1 for flag leaf width. In the investigated population, Nanda2419 contributed all QTLs associated with higher kernel weight, higher leaf chlorophyll content, and a major QTL associated with wider flag leaf. Seven chromosome regions were related to more than one trait. Four QTL clusters contributed positively to breeding goal-based trait improvement through the Nanda2419 alleles and were detected in trials set in different ecological regions. The findings of this study are relevant to the molecular improvement of wheat yield and to the goal of screening cultivars for better breeding parents.