NRG2 family members of Arabidopsis and maize regulate nitrate signalling and promote nitrogen use efficiency.

Nitrogen (N) is an essential nutrient for plant growth, and most plants absorb it as nitrate. AtNRG2 has been reported to play an important role in nitrate regulation. In this study, we investigated the functions of AtNRG2 family members of Arabidopsis thaliana and maize in nitrate signalling and metabolism. Our results showed that both AtNRG2.10 and AtNRG2.15 regulated nitrate signalling and metabolism. Overexpression of AtNRG2.11 (AtNRG2) could promote plant growth and improve nitrogen use efficiency (NUE). In addition, the maize genome harbors 23 ZmNRG2 members. We detected the expression of these genes treated with nitrate and the expression of four genes was strongly induced with ZmNRG2.7 having the highest levels. Overexpression of ZmNRG2.7 in the atnrg2 mutant could restore the defects of atnrg2, suggesting that ZmNRG2.7 is involved in nitrate signalling and metabolism. Moreover, the overexpression lines of ZmNRG2.7 showed increased biomass and NUE. These findings demonstrate that at least a part of NRG2 family genes in Arabidopsis and maize regulate nitrate signalling and provide a molecular basis for improving the NUE of crops.

Novel allelic variations in Tannin1 and Tannin2 contribute to tannin absence in sorghum.

Sorghum is an important food crop commonly used for brewing, feed, and bioenergy. Certain genotypes of sorghum contain high concentrations of condensed tannins in seeds, which are beneficial, such as protecting grains from herbivore bird pests, but also impair grain quality and digestibility. Previously, we identified Tannin1 and Tannin2, each with three recessive causal alleles, regulate tannin absence in sorghum. In this study, via characterizing 421 sorghum accessions, we further identified three novel recessive alleles from these two genes. The tan1-d allele contains a 12-bp deletion at position 659 nt and the tan1-e allele contains a 10-bp deletion at position 771 nt in Tannin1. The tan2-d allele contains a C-to-T transition, which results in a premature stop codon before the bHLH domain in Tannin2, and was predominantly selected in China. We further developed KASP assays targeting these identified recessive alleles to efficiently genotype large populations. These studies provide new insights in sorghum domestication and convenient tools for breeding programs. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-024-01463-y.

Mapping QTL for Adult-Plant Resistance to Stripe Rust in a Chinese Wheat Landrace.

Wheat stripe (yellow) rust is a worldwide disease that seriously reduces wheat grain yield and quality. Adult-plant resistance (APR) to stripe rust is generally more durable but usually controlled by multiple genes with partial resistance. In this study, a recombinant inbred line population was developed from a cross between a Chinese wheat landrace, Tutoumai, with APR to stripe rust, and a highly susceptible wheat cultivar, Siyang 936. The population was genotyped by genotyping-by-sequencing and phenotyped for APR to stripe rust in four consecutive field experiments. Three QTLs, QYr.sdau-1BL, QYr.sdau-5BL, and QYr.sdau-6BL, were identified for APR to stripe rust, and explained 8.0-21.2%, 10.1-22.7%, and 11.6-18.0% of the phenotypic variation, respectively. QYr.sdau-1BL was further mapped to a 21.6 Mb region using KASP markers derived from SNPs identified by RNA-seq of the two parents. In the QYr.sdau-1BL region, 13 disease-resistance-related genes were differently expressed between the two parents, and therefore were considered as the putative candidates of QYr.sdau-1BL. This study provides favorable gene/QTL and high-throughput markers to breeding programs for marker-assisted selection of the wheat stripe rust APR genes.

High-resolution genome-wide association study and genomic prediction for disease resistance and cold tolerance in wheat.

KEY MESSAGE: High-resolution genome-wide association study (GWAS) facilitated QTL fine mapping and candidate gene identification, and the GWAS based genomic prediction models were highly predictive and valuable in wheat genomic breeding. Wheat is a major staple food crop and provides more than one-fifth of the daily calories and dietary proteins for humans. Genome-wide association study (GWAS) and genomic selection (GS) for wheat stress resistance and tolerance related traits are critical to understanding their genetic architecture for improvement of breeding selection efficiency. However, the insufficient marker density in previous studies limited the utility of GWAS and GS in wheat genomic breeding. Here, we conducted a high-resolution GWAS for wheat leaf rust (LR), yellow rust (YR), powdery mildew (PM), and cold tolerance (CT) by genotyping a panel of 768 wheat cultivars using genotyping-by-sequencing. Among 153 quantitative trait loci (QTLs) identified, 81 QTLs were delimited to ≤ 1.0 Mb intervals with three validated using bi-parental populations. Furthermore, 837 stress resistance-related genes were identified in the QTL regions with 12 showing induced expression by YR and PM pathogens. Genomic prediction using 2608, 4064, 3907, and 2136 pre-selected SNPs based on GWAS and genotypic correlations between the SNPs showed high prediction accuracies of 0.76, 0.73, and 0.78 for resistance to LR, YR, and PM, respectively, and 0.83 for resistance to cold damage. Our study laid a solid foundation for large-scale QTL fine mapping, candidate gene validation and GS in wheat.

Artificial selection in breeding extensively enriched a functional allelic variation in TaPHS1 for pre-harvest sprouting resistance in wheat.

Pre-harvest sprouting (PHS) causes significant losses in wheat yield and quality worldwide. Previously, we cloned a PHS resistance gene, TaPHS1, and identified two causal mutations for reduced seed dormancy (SD) and increased PHS susceptibility. Here we identified a novel allelic variation of C to T transition in 3'-UTR of TaPHS1, which associated with reduced SD and PHS resistance. The T allele occurred in wild wheat progenitors and was likely the earliest functional mutation in TaPHS1 for PHS susceptibility. Allele frequency analysis revealed low frequency of the T allele in wild diploid and tetraploid wheat progenitors, but very high frequency in modern wheat cultivars and breeding lines, indicating that artificial selection quickly enriched the T allele during modern breeding. The T allele was significantly associated with short SD in both T. aestivum and T. durum, the two most cultivated species of wheat. This variation together with previously reported functional sequence variations co-regulated TaPHS1 expression levels and PHS resistance in different germplasms. Haplotype analysis of the four functional variations identified the best PHS resistance haplotype of TaPHS1. The resistance haplotype can be used in marker-assisted selection to transfer TaPHS1 to new wheat cultivars.

Genome-wide member identification, phylogeny and expression analysis of PEBP gene family in wheat and its progenitors.

The phosphatidylethanolamine binding protein (PEBP) family comprises ancient proteins found throughout the biosphere that play an important role in plant growth and development, flowering, seed development and dormancy. However, not all PEBP genes have been identified or analyzed in common wheat (Triticum aestivum L.) and its progenitors. In this study, we identified the PEBP genes in common wheat, Triticum dicoccoides, Triticum urartu and Aegilops tauschii by searching whole genome sequences, and characterized these genes by phylogenetic and transcriptome analyses. A total of 76, 38, 16 and 22 PEBP genes were identified in common wheat, T. dicoccoides, T. urartu and Ae. tauschii, respectively. Phylogenetic analysis classified the PEBP genes into four subfamilies (PEBP-like, MFT-like, TFL-like and FT-like); the PEBP-like subfamily was identified as a new subfamily with genes in this subfamily were conserved in plants. Group 2, 3 and 5 chromosomes of common wheat and its progenitors contained more PEBP genes than other chromosomes. The PEBP genes were conserved in wheat during evolution, and tandem duplication played a more important role in the amplification of PEBP genes than segmental duplication. Furthermore, transcriptome analysis revealed that PEBP genes showed tissue/organ-specific expression profiles and some PEBP genes were induced to express by biotic stresses. Quantitative real-time PCR (qRT-PCR) analysis revealed that seven randomly selected PEBP genes expressed differently during seed germination under cold, drought, flood, heat and salt stress treatments, and five of these genes (TaPEBP1, TaPEBP5, TaPEBP9, TaPEBP66 and TaPEBP69) showed significantly higher expression under different stress treatments, indicating that these genes play important roles during seed germination under stress conditions.

High-Resolution Genome-wide Association Study Identifies Genomic Regions and Candidate Genes for Important Agronomic Traits in Wheat.

Wheat (Triticum aestivum) is a major staple food crop worldwide. Genetic dissection of important agronomic traits is essential for continuous improvement of wheat yield to meet the demand of the world's growing population. We conducted a large-scale genome-wide association study (GWAS) using a panel of 768 wheat cultivars that were genotyped with 327 609 single-nucleotide polymorphisms generated by genotyping-by-sequencing and detected 395 quantitative trait loci (QTLs) for 12 traits under 7 environments. Among them, 273 QTLs were delimited to ≤1.0-Mb intervals and 7 of them are either known genes (Rht-D, Vrn-B1, and Vrn-D1) that have been cloned or known QTLs (TaGA2ox8, APO1, TaSus1-7B, and Rht12) that were previously mapped. Eight putative candidate genes were identified for three QTLs that enhance spike seed setting and grain size using gene expression data and were validated in three bi-parental populations. Protein sequence analysis identified 33 putative wheat orthologs that have high identity with rice genes in QTLs affecting similar traits. Large r2 values for additive effects observed among the QTLs for most traits indicated that the phenotypes of these identified QTLs were highly predictable. Results from this study demonstrated that significantly increasing GWAS population size and marker density greatly improves detection and identification of candidate genes underlying a QTL, solidifying the foundation for large-scale QTL fine mapping, candidate gene validation, and developing functional markers for genomics-based breeding in wheat.

Identification of candidate chromosome region of Sbwm1 for Soil-borne wheat mosaic virus resistance in wheat.

Soil-borne wheat mosaic virus (SBWMV) causes a serious viral disease that can significantly reduce grain yield in winter wheat worldwide. Using resistant cultivars is the only feasible strategy to reduce the losses caused by SBWMV. To fine map the resistance gene Sbwm1, 205 wheat accessions was genotyped using wheat Infinium iSelect Beadchips with 90 K SNPs. Association analysis identified 35 SNPs in 12 wheat genes and one intergenic SNP in the Sbwm1 region that showed a significant association with SBWMV resistance. Those SNPs were converted into Kompetitive Allele-Specific Polymerase assays (KASP) and analyzed in two F6-derived recombinant inbred line (RIL) populations derived from the crosses between two resistant cultivars 'Wesley' and 'Deliver' and a susceptible line 'OK03825-5403-6'. Linkage analysis mapped this gene on chromosome 5D at intervals of 5.1 cM and 3.4 cM in the two populations, respectively. The two flanking markers in both populations delimited the gene to a 620 kb region where 19 genes were annotated. Comparative analysis identified a syntenic region of 660 kb in Ae. tauschii with 18 annotated genes and a syntenic region in chromosome 1 of B. distachyon. The candidate region includes several disease resistance related genes and we identified a PTI1-like tyrosine-protein kinase 1 gene as a putative candidate gene for Sbwm1. The two flanking SNPs for Sbwm1 can effectively separate the resistant and susceptible lines in a new diversity panel of 159 wheat germplasm. The results from this study lay a solid foundation for the cloning, functional characterization and marker-assisted selection of Sbwm1.

QTL mapping of pre-harvest sprouting resistance in a white wheat cultivar Danby.

KEY MESSAGE: One major and three minor QTLs for resistance to pre-harvest sprouting (PHS) were identified from a white wheat variety "Danby." The major QTL on chromosome 3A is TaPHS1, and the sequence variation in its promoter region was responsible for the PHS resistance. Additive × additive effects were detected between two minor QTLs on chromosomes 3B and 5A, which can greatly enhance the PHS resistance. Pre-harvest sprouting (PHS) causes significant losses in yield and quality in wheat. White wheat is usually more susceptible to PHS than red wheat. Therefore, the use of none grain color-related PHS resistance quantitative trait loci (QTLs) is essential for the improvement in PHS resistance in white wheat. To identify PHS resistance QTLs in the white wheat cultivar "Danby" and determine their effects, a doubled haploid population derived from a cross of Danby × "Tiger" was genotyped using genotyping-by-sequencing markers and phenotyped for PHS resistance in two greenhouse and one field experiments. One major QTL corresponding to a previously cloned gene, TaPHS1, was consistently detected on the chromosome arm 3AS in all three experiments and explained 21.6-41.0% of the phenotypic variations. A SNP (SNP-222) in the promoter of TaPHS1 co-segregated with PHS in this mapping population and was also significantly associated with PHS in an association panel. Gene sequence comparison and gene expression analysis further confirmed that SNP-222 is most likely the causal mutation in TaPHS1 for PHS resistance in Danby in this study. In addition, two stable minor QTLs on chromosome arms 3BS and 5AL were detected in two experiments with allele effects consistently contributed by Danby, while one minor QTL on 2AS was detected in two environments with contradicted allelic effects. The two stable minor QTLs showed significant additive × additive effects. The results demonstrated that pyramiding those three QTLs using breeder-friendly KASP markers developed in this study could greatly improve PHS resistance in white wheat.

Virus-like particle vaccine by intranasal vaccination elicits protective immunity against respiratory syncytial viral infection in mice.

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory infection in infants and children, but there is still no licensed vaccine available. In this report, we developed virus-like particle (VLP) vaccines based on the Bac-to-Bac baculovirus expression system, consisting of an influenza virus matrix (M1) protein and the RSV fusion protein (F) or glycoprotein (G). These RSV VLPs were identified by western blot analysis and electron microscopy. Female BALB/c mice immunized intranasally (i.n.) with RSV-F VLPs, RSV-G VLPs, or both showed viral-specific antibody responses against RSV. Total IgG, IgG1, IgG2a, and mucosal IgA were detected in mice with RSV-F plus RSV-G VLPs, revealing potent cellular and mucosal immune responses. Moreover, we found that these mixed RSV VLPs conferred enhanced protection against live RSV challenges, showing significant decreases in lung viral replication and obvious attenuation of histopathological changes associated with viral infections. These results demonstrate that RSV-F plus RSV-G VLPs by intranasal vaccination is a promising vaccine candidate that warrants further evaluation using cotton rat and primate models.

Chromosome Pairing in Hybrid Progeny between Triticum aestivum and Elytrigia elongata.

In this study, the intergeneric hybrids F1, F2, BC1F1, BC1F2, and BC2F1 from Elytrigia elongata and Triticum aestivum crosses were produced to study their chromosome pairing behavior. The average E. elongata chromosome configuration of the two F1 hybrids agreed with the theoretical chromosome configuration of 21I+7II, indicating that the genomic constitution of this F1 hybrid was ABDStStEeEbEx. Compared with the BC1F1 generation, the BC2F1 generation showed a rapid decrease in the number of E. elongata chromosomes and the BC1F2 generation showed a more extensive distribution of E. elongata chromosomes. In addition, pairing between wheat and E. elongata chromosomes was detected in each of the wheat-E. elongata hybrid progenies, albeit rarely. Our results demonstrated that genomic in situ hybridization (GISH) using an E. elongata genomic DNA probe offers a reliable approach for characterizing chromosome pairing in wheat and E. elongata hybrid progenies.

Genome-wide association analysis on pre-harvest sprouting resistance and grain color in U.S. winter wheat.

BACKGROUND: Pre-harvest sprouting (PHS) in wheat can cause substantial reduction in grain yield and end-use quality. Grain color (GC) together with other components affect PHS resistance. Several quantitative trait loci (QTL) have been reported for PHS resistance, and two of them on chromosome 3AS (TaPHS1) and 4A have been cloned. METHODS: To determine genetic architecture of PHS and GC and genetic relationships of the two traits, a genome-wide association study (GWAS) was conducted by evaluating a panel of 185 U.S. elite breeding lines and cultivars for sprouting rates of wheat spikes and GC in both greenhouse and field experiments. The panel was genotyped using the wheat 9K and 90K single nucleotide polymorphism (SNP) arrays. RESULTS: Four QTL for GC on four chromosomes and 12 QTL for PHS resistance on 10 chromosomes were identified in at least two experiments. QTL for PHS resistance showed varied effects under different environments, and those on chromosomes 3AS, 3AL, 3B, 4AL and 7A were the more frequently identified QTL. The common QTL for GC and PHS resistance were identified on the long arms of the chromosome 3A and 3D. CONCLUSIONS: Wheat grain color is regulated by the three known genes on group 3 chromosomes and additional genes from other chromosomes. These grain color genes showed significant effects on PHS resistance in some environments. However, several other QTL that did not affect grain color also played a significant role on PHS resistance. Therefore, it is possible to breed PHS-resistant white wheat by pyramiding these non-color related QTL.

Independent mis-splicing mutations in TaPHS1 causing loss of preharvest sprouting (PHS) resistance during wheat domestication.

Preharvest sprouting (PHS) is one of the major constraints of wheat production in areas where prolonged rainfall occurs during harvest. TaPHS1 is a gene that regulates PHS resistance on chromosome 3A of wheat, and two causal mutations in the positions +646 and +666 of the TaPHS1 coding region result in wheat PHS susceptibility. Three competitive allele-specific PCR (KASP) markers were developed based on the two mutations in the coding region and one in the promoter region and validated in 82 wheat cultivars with known genotypes. These markers can be used to transfer TaPHS1 in breeding through marker-assisted selection. Screening of 327 accessions of wheat A genome progenitors using the three KASP markers identified different haplotypes in both diploid and tetraploid wheats. Only one Triticum monococcum accession, however, carries both causal mutations in the TaPHS1 coding region and shows PHS susceptibility. Five of 249 common wheat landraces collected from the Fertile Crescent and surrounding areas carried the mutation (C) in the promoter (-222), and one landrace carries both the causal mutations in the TaPHS1 coding region, indicating that the mis-splicing (+646) mutation occurred during common wheat domestication. PHS assay of wheat progenitor accessions demonstrated that the wild-types were highly PHS-resistant, whereas the domesticated type showed increased PHS susceptibility. The mis-splicing TaPHS1 mutation for PHS susceptibility was involved in wheat domestication and might arise independently between T. monococcum and Triticum aestivum.

Genotyping-by-sequencing (GBS) identified SNP tightly linked to QTL for pre-harvest sprouting resistance.

KEY MESSAGE: Using a GBS-SNP map, a QTL for pre-harvest sprouting resistance on 4AL of Totoumai A was delimited to 2.9-cM interval, and SNP closely linked to several other QTL were identified. Pre-harvest sprouting (PHS) of wheat is a major constraint to wheat production in many wheat-growing areas worldwide, because it reduces both wheat grain yield and the end-use quality. To identify markers tightly linked to the quantitative trait loci (QTL) for PHS resistance and seed dormancy (SD), we evaluated 155 recombinant inbred lines (RIL) derived from a cross between a PHS-resistant parent 'Tutoumai A' and a PHS-susceptible parent 'Siyang 936' for single-nucleotide polymorphisms (SNP) using genotyping-by-sequencing (GBS), and for PHS resistance and SD using both field and greenhouse grown plants. Two SNP, GBS109947 and GBS212432, were mapped to a major QTL region for PHS resistance and SD on chromosome 4AL, and delimited the QTL to a 2.9-cM interval. Two and nine additional SNP were mapped to minor QTL regions for SD on chromosome 5B and 5A, respectively. Critical SNP in these QTL regions were converted into KBioscience Competitive Allele-Specific PCR (KASP) assays that can be easily used for marker-assisted selection to improve PHS resistance.

Genome-wide association analysis identified SNPs closely linked to a gene resistant to Soil-borne wheat mosaic virus.

KEY MESSAGE: Using association and linkage mapping, two SNP markers closely linked to the SBWMV resistance gene on chromosome 5D were identified and can be used to select the gene in breeding. Soil-borne wheat mosaic virus (SBWMV) disease is a serious viral disease of winter wheat growing areas worldwide. SBWMV infection can significantly reduce grain yield up to 80 %. Developing resistant wheat cultivars is the only feasible strategy to reduce the losses. In this study, wheat Infinium iSelect Beadchips with 9 K wheat SNPs were used to genotype an association mapping population of 205 wheat accessions. Six new SNPs from two genes were identified to be significantly associated with the gene for SBWMV resistance on chromosome 5D. The SNPs and Xgwm469, an SSR marker that has been reported to be associated with the gene, were mapped close to the gene using F6-derived recombinant inbred lines from the cross between a resistant parent 'Heyne' and a susceptible parent 'Trego'. Two representative SNPs, wsnp_CAP11_c209_198467 and wsnp_JD_c4438_5568170, from the two linked genes in wheat were converted into KBioscience Competitive Allele-Specific Polymerase assays and can be easily used in marker-assisted selection to improve wheat resistance to SBWMV in breeding.

Cloning and characterization of a critical regulator for preharvest sprouting in wheat.

Sprouting of grains in mature spikes before harvest is a major problem in wheat (Triticum aestivum) production worldwide. We cloned and characterized a gene underlying a wheat quantitative trait locus (QTL) on the short arm of chromosome 3A for preharvest sprouting (PHS) resistance in white wheat using comparative mapping and map-based cloning. This gene, designated TaPHS1, is a wheat homolog of a MOTHER OF FLOWERING TIME (TaMFT)-like gene. RNA interference-mediated knockdown of the gene confirmed that TaPHS1 positively regulates PHS resistance. We discovered two causal mutations in TaPHS1 that jointly altered PHS resistance in wheat. One GT-to-AT mutation generates a mis-splicing site, and the other A-to-T mutation creates a premature stop codon that results in a truncated nonfunctional transcript. Association analysis of a set of wheat cultivars validated the role of the two mutations on PHS resistance. The molecular characterization of TaPHS1 is significant for expediting breeding for PHS resistance to protect grain yield and quality in wheat production.

Molecular cytogenetic identification of a novel dwarf wheat line with introgressed Thinopyrum ponticum chromatin.

Novel dwarfing germplasms and dwarfing genes are valuable for the wheat breeding. A novel semi-dwarf line, 31505-1, with reduced height compared with its common wheat parent, was derived from a cross between common wheat and Thinopyrum ponticum. Cytological studies demonstrated that 31505-1 contained 42 chromosomes and formed 21 bivalents at meiotic metaphase I. Genomic in situ hybridization (GISH) analysis showed that 31505-1 had no large Th. ponticum chromosome fragments. Fluorescence in situ hybridization (FISH) results revealed the absence of a pAs1 hybridization band on 2DL chromosome of 31505-1. Two SSR markers (Xwmc41 and Xcfd168) and two STS markers (Xmag4059 and Xmag3596), which were located on 2D chromosome, amplified unique bands of Th. Ponticum in 31505-1. These revealed presence of an introgressed Th. ponticum segment in 2DL chromosome of dwarf line 31505-1, although the alien segment could not be detected by GISH.

Bipolar hip arthroplasty.

Our aim was to compare hip arthroplasty with internal screw fixation in the repair of intertrochanteric fractures in elderly patients with osteoporosis. Of 112 included patient, 70 (81.81 ± 4.88 years) received hip arthroplasty with a prosthesis specially designed for intertrochanteric fractures, and 42 (83.46 ± 5.11 years) underwent plate-screw fixation. The hip arthroplasty group had significantly longer operation time, intraoperative blood loss, and total volume of blood transfused but had shorter time to beginning weight-bearing (5.94 ± 2.76 vs 23.68 ± 22.01 days) and higher postoperative Harris hip score (91.37 ± 4.80 vs 86.14 ± 5.46). In the arthroplasty group, there were 2 dislocations; and in the plate-screw fixation group, there were 5 internal fixation failures. Hip arthroplasty is preferable to internal fixation in elderly patients (age >80 years) with osteoporosis.

Characterization and precise mapping of a QTL increasing spike number with pleiotropic effects in wheat.

Tiller number (TN) and spike number per plant (SN) are key components of grain yield and/or biomass in wheat. In this study, an introgression line 05210, developed by introgression of chromosomal segments from a synthetic exotic wheat Am3 into an elite cultivar Laizhou953, showed a significantly increased TN and SN, but shorter spike length (SL) and fewer grain number per spike (GNS) than Laizhou953. To investigate the quantitative trait locus (QTL) responsible for these variations, the introgressed segments in 05210 were screened by SSR markers and one follow-up segregation population was developed from the cross 05210/Laizhou953. The population showed 3:1 segregation ratios for SN, SL and GNS, indicating that QTLs for these traits have been dissected into single Mendelian factors. Bulked segregation analysis showed that the markers located on the 4B introgressed segment were polymorphic between the two bulks. Therefore, they were further analyzed in the F(2) population to construct a linkage map. Three new QTLs, QSn.sdau-4B, QSl.sdau-4B and QGns.sdau-4B, were detected for SN, SL and GNS, respectively, which explained a large portion of the phenotypic variation (30.1-67.6%) for these traits with overlapping peaks. Correlation analysis and multiple-trait, multiple-interval mapping (MMIM) suggested pleiotropic effects of the QTL on SN, SL and GNS. Therefore, the QTL was designated as QSn.sdau-4B. By a progeny test based on F(3) families using SN, the QTL was mapped as a Mendelian factor to the proximal region of 4BL. It is a key QTL responsible for variation in spike number and size, which had not been reported previously. Thus, it is an important QTL for wheat to achieve high and stable biomass and grain yield. Dissection and mapping of this QTL as a Mendelian factor laid a solid foundation for map-based cloning of grain yield-related QTLs in wheat.