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Rht24is a major dwarfing allele that not only reduces plant height but also increases grain weight. The objective of this study was to trace the source, spread, and distribution of Rht24and determine its frequency in conjunction with other important dwarfing alleles for Rht1(Rht‐B1b), Rht2(Rht‐D1b), and Rht8. Allele‐specific cleaved amplified polymorphic sequence (CAPS) markers were developed for accurate and effective genotyping of Rht1and Rht2, and closely linked flanking markers were used for genotyping of Rht8and Rht24. Marker analysis showed that Rht24occurs at a higher frequency (84.2%) than other important dwarfing alleles in elite wheat (Triticum aestivumL.) varieties and usually couples with Rht2or Rht8. Genotyping of old varieties and landraces showed that Rht24was widely used in wheat breeding before the Green Revolution (GR). ‘Akakomugi’ and ‘Norin 10’, the donors of Rht8and GR genes Rht1and Rht2, respectively, harbored Rht24, so Rht24likely followed the transfer routes of GR genes and Rht8to spread worldwide. Pedigree analysis showed that many Chinese elite lines and backbone parents were derived from Akakomugi, contributing to the high frequency of Rht24in Chinese varieties. Additionally, Norin 10‐derived semidwarf varieties from the CIMMYT were widely used in Chinese wheat breeding. Finally, Rht24was also detected in 30 old Chinese varieties and landraces. Overall, these findings show that the presence of Rht24in modern Chinese elite varieties originated from Akakomugi, Norin 10, or Chinese landraces. Thus, Rht24was introgressed early, spread widely, and became genetically fixed in a wide range of modern Chinese wheat germplasm.

The puroindoline genes (Puroindoline a‐D1and Puroindoline b‐D1), located very near to the distal end of the short arm of chromosome 5D (distal to fraction arm length of 0.78) have a significant effect on grain hardness. Puroindoline b‐2(Pinb‐2) is another puroindoline gene family that exists as a homoeologous series on group 7 chromosomes. However, a more detailed localization (physical mapping) of the Pinb‐2genes has not been conducted. In the present study, 24 group 7 long‐arm chromosome deletion stocks of ‘Chinese Spring’ were used to physically map three Pinb‐2variant genes: Pinb‐2v1, Pinb‐2v2, and Pinb‐2v4. All three genes were found to be physically located on the most distal 0.11 to 0.16 fraction arm length of chromosomes 7AL, 7BL, and 7DL in Chinese Spring. These results contribute insight into wheat (Triticum aestivumL.) genome synteny, structure, and organization and provide a useful metric for germplasm and population relationships. Future studies may further resolve the physical mapping of Pinb‐2genes at the ends of group 7 chromosomes and contribute to a better understanding of the molecular and genetic basis of kernel hardness.

Lipoxygenase (LOX) activity in grain influences the color and processing quality of wheat (Triticumspp.)‐based products. Characterization of LOX genes and development of functional markers are of importance for marker‐assisted selection in common wheat (Triticum aestivumL.) breeding. In the present study, the full‐length genomic DNA (gDNA) sequence of a LOX gene (designated TaLox‐B1) located on chromosome 4BS was characterized by in silico cloning and experimental validation. Two complementary dominant sequence tagged site (STS) markers, LOX16 and LOX18, were developed based on the single nucleotide polymorphism (SNP) of two alleles at the TaLox‐B1locus, amplifying 489‐ and 791‐bp fragments in cultivars with higher and lower LOX activities, respectively. The two markers were mapped on chromosome 4BS using a doubled haploid (DH) population derived from Zhongyou 9507 × CA9632, a set of Chinese Spring nullisomic–tetrasomic lines, ditelosomic line 4BS, and Langdon (LDN) 4D(4B) chromosome substitution line. Quantitative trait loci (QTL) analysis indicated that TaLox‐B1co‐segregated with the two functional markers and was closely linked to simple sequence repeat (SSR) locus Xgwm251on chromosome 4BS with a genetic distance of 1.8 cM. LOX16 and LOX18 were validated on 198 Chinese wheat cultivars and advanced lines and showed highly significant (p< 0.01) associations with LOX activity. These results suggested that LOX16 and LOX18, co‐segregating with TaLox‐B1, could be used for the improvement of color attributes of noodles and other wheat‐based products in wheat breeding programs.

Zeta (ζ)‐carotene desaturase (ZDS) is a key enzyme in the carotenoid biosynthetic pathway, which determines the yellow pigment (YP) content in wheat (Triticum aestivumL.) grains. In the present study, the full‐length DNA sequence of a ZDS gene on wheat chromosome 2DL, designated TaZds‐D1, was characterized. The TaZds‐D1gene has an open reading frame of 1707 bp, including 13 introns and 14 exons, and a deduced peptide containing 568 amino acid residues with a predicted molecular weight of 62.5 kDa. The TaZds‐D1gene was located on chromosome 2DL based on polymerase chain reaction amplifications of Chinese Spring nullisomic‐tetrasomic lines, Langdon–Chinese Spring D‐genome chromosome disomic substitution lines, and Rusty D‐genome chromosome disomic substitution lines as well as linkage analysis. Two allelic variants, TaZds‐D1aand TaZds‐D1b, were detected in Chinese wheat cultivars, and a functional marker, YP2D‐1, was developed based on the sequence polymorphism between TaZds‐D1aand TaZds‐D1b. A major quantitative trait locus, located at the TaZds‐D1region in the marker interval of YP2D‐1 and Xgwm157on chromosome 2DL, explained 18.4% of the phenotypic variance for YP content in a doubled haploid population derived from the cross Zhongyou 9507/CA 9632. This confirmed the association between allelic variation at the TaZds‐D1locus and YP content.

Phytoene synthase (PSY) genes are involved in the biosynthesis of carotenoid pigments in durum wheat [Triticum turgidumL. subsp durum(Desf.) Husn.], significantly influencing grain yellowness. This study was conducted to identify new allelic variants at the Psy‐A1and Psy‐B1loci in durum wheat, and to evaluate the applicability of functional markers developed from common wheat (Triticum aestivumL.) for durum wheat breeding. Two new allelic variants, Psy‐A1dand Psy‐A1e, were identified at the Psy‐A1locus, and both the codominant markers YP7Aand YP7A‐2can be used to discriminate the two haplotypes, yielding 194‐ and 231‐bp polymerase chain reaction (PCR) products with YP7Aand 1001‐ and 1684‐bp fragments with YP7A‐2, respectively. At the Psy‐B1locus, three allelic variants were identified. Psy‐B1ewas also found in common wheat, whereas Psy‐B1fand Psy‐B1gwere detected only in durum wheat. The codominant marker YP7B‐1can be used to distinguish Psy‐B1fand Psy‐B1g, generating 151‐ and 153‐bp PCR fragments, respectively, and the dominant marker YP7B‐4was specific to haplotype Psy‐B1e, producing a 717‐bp PCR product. In a set of 100 CIMMYT durum wheat lines with widely variable grain yellowness, the frequencies of Psy‐A1d, Psy‐A1e, Psy‐B1e, Psy‐B1f, and Psy‐B1gwere 99, 1, 0, 67, and 33%, respectively, and the genotype Psy‐B1fshowed a significant association with higher grain yellowness, whereas the presence of Psy‐B1gled to lower yellowness. A phylogenetic tree generated from the gene sequences of the allelic variants at Psy‐A1and Psy‐B1loci indicated two parallel lineages of durum–common wheat, suggesting that more than one tetraploid T. turgidumL. subsp. dicoccon(Schrank) Thell. genotypes were involved in the origin of common wheat. Our results suggested that Psy‐B1fshould be paid more attention in durum breeding programs for its association with elevated grain yellowness.