The identification of stable quantitative trait locus (QTL) for yield-related traits and tightly linked molecular markers is important for improving wheat grain yield. In the present study, six yield-related traits in a recombinant inbred line (RIL) population derived from the Zhongmai 578/Jimai 22 cross were phenotyped in five environments. The parents and 262 RILs were genotyped using the wheat 50K single nucleotide polymorphism (SNP) array. A high-density genetic map was constructed with 1 501 non-redundant bin markers, spanning 2 384.95 cM. Fifty-three QTLs for six yield-related traits were mapped on chromosomes 1D (2), 2A (9), 2B (6), 2D, 3A (2), 3B (2), 4A (5), 4D, 5B (8), 5D (2), 7A (7), 7B (3) and 7D (5), which explained 2.7–25.5% of the phenotypic variances. Among the 53 QTLs, 23 were detected in at least three environments, including seven for thousand-kernel weight (TKW), four for kernel length (KL), four for kernel width (KW), three for average grain filling rate (GFR), one for kernel number per spike (KNS) and four for plant height (PH). The stable QTLs QKl.caas-2A.1, QKl.caas-7D, QKw.caas-7D, QGfr.caas-2B.1, QGfr.caas-4A, QGfr.caas-7A and QPh. caas-2A.1 are likely to be new loci. Six QTL-rich regions on 2A, 2B, 4A, 5B, 7A and 7D, showed pleiotropic effects on various yield traits. TaSus2-2B and WAPO-A1 are potential candidate genes for the pleiotropic regions on 2B and 7A, respectively. The pleiotropic QTL on 7D for TKW, KL, KW and PH was verified in a natural population. The results of this study enrich our knowledge of the genetic basis underlying yield-related traits and provide molecular markers for high-yield wheat breeding.

Psathyrostachys huashanica Keng (2n=2x=14, NsNs) is regarded as a valuable wild relative species for common wheat cultivar improvement because of its abundant beneficial agronomic traits.  However, although the development of many wheat–P. huashanica-derived lines provides a germplasm base for the transfer of excellent traits, the lag in the identification of P. huashanica chromosomes in the wheat background has limited the study of these lines.  In this study, three novel nondenaturing fluorescence in situ hybridization (ND-FISH)-positive oligo probes were developed.  Among them, HS-TZ3 and HS-TZ4 could specifically hybridize with P. huashanica chromosomes, mainly in the telomere area, and HS-CHTZ5 could hybridize with the chromosomal centromere area.  We sequentially constructed a P. huashanica FISH karyotype and idiogram that helped identify the homologous groups of introduced P. huashanica chromosomes.  In detail, 1Ns and 2Ns had opposite signals on the short and long arms, 3Ns, 4Ns, and 7Ns had superposed two-color signals, 5Ns and 6Ns had fluorescent signals only on their short arms, and 7Ns had signals on the intercalary of the long arm.  In addition, we evaluated different ways to identify alien introgression lines by using low-density single nucleotide polymorphism (SNP) arrays and recommended the SNP homozygosity rate in each chromosome as a statistical pattern.  The 15K SNP array is widely applicable for addition, substitution, and translocation lines, and the 40K SNP array is the most accurate for recognizing transposed intervals between wheat and alien chromosomes.  Our research provided convenient methods to distinguish the homologous group of P. huashanica chromosomes in a common wheat background based on ND-FISH and SNP arrays, which is of great significance for efficiently identifying wheat–P. huashanica-derived lines and the further application of Ns chromosomes

Large grain is a favorable trait for appearance quality and large sink potential in wheat breeding.  A stable QTL QGl.caas-5BS for grain length was previously identified in a recombinant inbred line population from the cross of Zhongmai 871 (ZM871) and its sister line Zhongmai 895 (ZM895).  Here, a BC₁F₆ residual heterozygous line was selected from the cross of ZM871/ZM895//ZM871 population, and six heterozygous recombinant plants were identified in the BC₁F₇ population from self-pollination of the heterozygous line.  QGl.caas-5BS was delimited into an interval of approximately 2.2 Mb flanked by markers Kasp_5B33 and Kasp_5B2 (25.3-27.5 Mb) through phenotyping and genotyping the secondary mapping populations derived from these heterozygous recombinant plants.  Five genes were predicted as candidates of QGl.caas-5BS based on sequence polymorphism and differential expression analyses.  Further mutation analysis showed that TraesCS5B02G026800 is likely the causal gene of QGl.caas-5BS.  A gene-specific marker Kasp_5B_Gl for TraesCS5B02G026800 was developed, and a significant genetic effect of QGl.caas-5BS on grain length was identified in a validation population including 166 cultivars using the marker.  These findings lay a good foundation for map-based cloning of QGl.caas-5BS and provide a breeding-applicable marker for the improvement of grain length in wheat.