Background: Peroxidase (POD) activity plays an important role in flour-based product quality, which is mainly associated with browning and bleaching effects of flour. Here, we performed a genome-wide association study (GWAS) on POD activity using an association population consisted with 207 wheat world-wide collected varieties. Our study also provide basis for the genetic improvement of flour color-based quality in wheat. Results: Twenty quantitative trait loci (QTLs) were detected associated with POD activity, explaining 5.59–12.67% of phenotypic variation. Superior alleles were positively correlated with POD activity. In addition, two SNPs were successfully developed to KASP (Kompetitive Allele-Specific PCR) markers. Two POD genes, TraesCS2B02G615700 and TraesCS2D02G583000, were aligned near the QTLs flanking genomic regions, but only TraesCS2D02G583000 displayed significant divergent expression levels (P < 0.001) between high and low POD activity varieties in the investigated association population. Therefore, it was deduced to be a candidate gene. The expression level of TraesCS2D02G583000 was assigned as a phenotype for expression GWAS (eGWAS) to screen regulatory elements. In total, 505 significant SNPs on 20 chromosomes (excluding 4D) were detected, and 9 of them located within 1 Mb interval of TraesCS2D02G583000. Conclusions: To identify genetic loci affecting POD activity in wheat grain, we conducted GWAS on POD activity and the candidate gene TraesCS2D02G583000 expression. Finally, 20 QTLs were detected for POD activity, whereas two QTLs associated SNPs were converted to KASP markers that could be used for marker-assisted breeding. Both cis- and trans-acting elements were revealed by eGWAS of TraesCS2D02G583000 expression. The present study provides genetic loci for improving POD activity across wide genetic backgrounds and largely improved the selection efficiency for breeding in wheat.

Resistant starch (RS) is a special group of starches which are slowly degraded and rarely digested in the gastrointestinal tract. It was recognized as a new type of dietary fiber that improved cardiovascular, cerebrovascular, and intestinal health. Breeding high-RS-content wheat is one of the most efficient and convenient approaches for providing an adequate amount of RS for a healthy diet. However, studies which aim to genetically illustrate RS content in wheat are still rare. In the present study, a panel of 207 wheat varieties were collected world-wide and planted under three locations. The RS content of each variety was measured, and 14 additive genetic loci were found to stably exist under more than two environments. Meanwhile, four genes were recognized as the putative candidates with annotated functions of β-amylase, α-1,4 glucan phosphorylase, sucrose transporter, and NAC domain protein. A kompetitive allele-specific PCR (KASP) marker was developed from the SNP AX-94546744, representing the genetic locus of β-amylase located. The AX-94546744-T allele can significantly increase the RS content compared to the AX-94546744-C allele. The genetic loci and KASP marker associated with RS content may be useful for wheat germplasm cultivation and variety breeding with a high RS content, further helping to improve the nutritional quality in wheat.

The wet gluten content (WGC) of wheat is a key indicator of wheat-processing quality, and its genetic basis is extremely critical in breeding. This study evaluated the WGC of 207 wheat accessions under three growing seasons from a natural population. Nine quantitative trait loci (QTLs) explained 7.61–15.18% of phenotypic variation in a genome-wide association study (GWAS) using a 660K SNP array. Among them, qWGC6B.2 on chromosome 6BL was consistently detected across multiple environments, accounting for 10.08–12.27% of variation. Incorporating grain transcriptome data led to the identification of TaWGC6B.1 (TraesCS6B02G386700), which is highly expressed in developing endosperm and strongly correlated with WGC. A competitive allele specific PCR (KASP) marker development and validation indicated that the Whaas68366_GG allele significantly enhanced gene expression and WGC. This study identified key genes and molecular markers, providing theoretical and technical support for WGC genetic improvement in wheat (Triticum aestivum L.).