Wheat grain morphology is an important breeding target due to its impact on yield and end-use properties. However, the genetic basis of grain roundness, which is a major determinant of grain morphology, remains largely unexplored. In this study, F₂ and recombinant inbred line (RIL) populations from a Zhongkemai 138 (ZKM138)×Chinese Spring (CS) cross were employed to analyze the genetic basis of grain shape variation. Kompetitive allele specific PCR (KASP) markers were developed according to single nucleotide polymorphisms (SNPs) from bulked segregant exome sequencing (BSE-Seq) of F₂ and Wheat 55K SNP array data online. Those SNPs were then used to construct two genetic maps of the F₂ and RIL populations, spanning 148.89 cM (30 KASP markers) and 129.82 cM (25 KASP markers), respectively. Using the traditional QTL mapping method based on these two maps, a stable quantitative trait locus (QTL) for grain roundness (GR), QGr.cib-5A, could be repeatedly detected in the interval of 444.8–455.5 Mb on chromosome 5A. Further conditional QTL mapping analysis revealed that grain width was the major contributor to GR at this locus. In addition, the use of two tightly linked markers, 5A4-15 and 55k-31, showed a 96.27% transmissibility of ZKM138-derived alleles in 134 ZKM138 derivatives, along with a 7.38% increase in GR and a 65.19% distribution among worldwide varieties. Finally, TraesCS5A02G236400, which may encode a hydroxyproline-rich glycoprotein family protein, was deduced to be the candidate gene. Collectively, these results can facilitate wheat grain shape improvement and enhance the market value of wheat.

Wheat stripe rust caused by Puccinia striiformis f. sp. tritici (Pst) is a devastating disease threaten food security in China and worldwide. Epidemics of wheat stripe rust have been under control through applying resistant cultivars and crop protection approaches. However, due to climate change, innovation of cropping system, improvement of breeding technology, yield level enhancement of wheat cultivars, variation in structure and frequency of virulence genes in Pst populations in the new era, the current status of stripe rust resistance genes in wheat breeding programs need to be evaluated. The results could provide useful information for applying stripe rust resistance genes to develop new wheat cultivars with broad-spectrum and durable rust resistance. After multiple year’s stripe rust resistance survey, genetic analysis, molecular tagging and mining of stripe rust resistance genes in wheat cultivars and advanced breeding lines, the current status of major stripe rust resistance genes utilization was reviewed. We summarized the present situations of major stripe rust resistance gene discovery and germplasm innovation, the most frequently used stripe rust resistance genes, new strategy for pyramiding adult plant partial resistance and all stage resistance, and molecular marker assisted selection for developing wheat cultivars with broad spectrum and durable resistance in China. This review also proposes the major research areas in wheat stripe rust resistance breeding in the new era.

Grain size and weight are key components of wheat yield. Exploitation of major underlying quantitative trait loci (QTL) can improve yield potential in wheat breeding. A recombinant inbred line (RIL) population was constructed to detect QTL for thousand-grain weight (TGW), grain length (GL) and grain width (GW) across eight environments. Genomic regions associated with grain size and grain weight were identified on chromosomes 4A and 6A using bulked segregant exome sequencing (BSE-Seq) analysis. After constructing genetic maps, six major QTL detected in at least four individual environments and in best linear unbiased estimator (BLUE) datasets, explained 7.50%–23.45% of the phenotypic variation. Except for QGl.cib-4A, the other five QTL were co-located in two regions, namely QTgw/Gw.cib-4A and QTgw/Gw/Gl.cib-6A. Interactions of these QTL were analyzed. Unlike QTgw/Gw/Gl.cib-6A, QTgw/Gw.cib-4A and QGl.cib-4A had no effect on grain number per spike (GNS). The QTL were validated in a second cross using Kompetitive Allele Specific PCR (KASP) markers. Since QTgw/Gw.cib-4A was probably a novel locus, it and the KASP markers reported here can be used in wheat breeding. TraesCS4A03G0191200 was predicted to be potential candidate gene for QTgw/Gw.cib-4A based on the sequence differences, spatiotemporal expression patterns, gene annotation and haplotype analysis. Our findings will be useful for fine mapping and for marker-assisted selection in wheat grain yield improvement.