The awn can contribute to photosynthesis and carbohydrates, enhancing grain yield in wheat. We mapped QAwn.sxau-5A, a major QTL for awn development in wheat (Triticum aestivum). This QTL was delimited to a 994-kb interval at the B1 locus on chromosome 5A, which included the candidate gene encoding a zinc finger protein (TraesCS5A01G542800) as an awn length inhibitor (ALI). The Ali-A1 allele for the awnless trait showed abundant sequence differences in the promoter regions compared to the ali-A1 allele for the long-awn trait. The results of the swap experiment on the promoters from the two ALI-A1 alleles showed that the two promoters caused a difference in the protein level, indicating the gene was regulated at the transcript level. However, the ali-A1 allele contained an SNP that caused a premature stop codon in its coding region, resulting in a truncated protein compared to the functional Ali-A1 protein. The Ali-A1 protein contained two ethylene-responsive element binding factor-associated amphiphilic repression (EAR) motifs, one at the N terminus (EAR-N) and the other at the C terminus (EAR-C), and they were involved in interactions with the wheat co-repressor protein TOPLESS (TPL1). The ali-A1 protein retained the EAR-N motif but lost the EAR-C motif, resulting in the attenuated ability to interact with TPL1. The tpl1 mutant produced a longer awn compared to the wild type. Ali-A1 repressed the transcription of two downstream genes, TaLRP-A1 and TaARF-B1, involved in endogenous auxin concentrations and auxin responses in wheat. We concluded that the awn length is regulated not only by the ALI-A1 gene at transcript levels but also by Ali-A1 and TPL1 at the protein level in wheat.

Structural variation is an important source of genetic variation in wheat and have been important in the evolution of the wheat’s genome. Few studies have examined the relationship between structural variations and agronomy and drought tolerance. The present study identified structural chromosome variations (SCVs) in a doubled haploid (DH) population and backcross introgression lines (BC5F3) derived from Jinmai 47 and Jinmai 84 using fluorescence in situ hybridization (FISH). There are one simple translocation, 10 present/absent variations (PAVs), and one copy number variation (CNV) between Jinmai 47 and Jinmai 84, which distributed in 10 chromosomes. Eight SCVs were associated with 15 agronomic traits. A PAV recombination occurred on chromosome 2A, which was associated with grain number per spike (GNS). The 1BL/1RS translocation and PAV.2D were associated with significant reductions in plant height, deriving from the effects on LI2-LI4, LI2-LI4 and UI, respectively respectively. PAV.2D was also contributed to an increase of 3.13% for GNS, 1BL/1RS significantly increased spikelet number, grain length (GL), and grain thickness (GT). The effect of PAV.4A.1 on GL, PAV.6A on spike length (SL) and thousand-grain weight (TGW), PAV.6B on SL, GT and TGW were identified and verified. PAVs on chromosomes 2A, 6A, 1D, 2D, and a CNV on chromosome 4B were associated with the drought tolerance coefficients. Additive and interaction effects among SCVs were observed. Many previously cloned key genes and yield-related QTL were found in polymorphic regions of PAV.2B, PAV.2D, and CNV.4B. Altogether, this study confirmed the genetic effect of SCVs on agronomy and drought tolerance, and identification of these SCVs will facilitate genetic improvement of wheat through marker-assisted selection.

Powdery mildew, caused by the biotrophic fungus Blumeria graminis f. sp. tritici (Bgt), is a prevalent disease in common wheat (Triticum aestivum L.) and causes serious yield losses worldwide. We used a map-based approach to clone the major broad-spectrum powdery mildew resistance gene PmCH1357 from wheat breeding line CH1357. PmCH1357 was mapped to a 526 kb region containing only TraesCS5D01G044600. The TraesCS5D01G044600 sequence of the susceptibility allele in Taichung 29 (TC29) was identical to that in Chinese Spring, whereas the sequence of the resistance allele in CH1357 was identical to Pm2a previously cloned from the germplasm Ulka/*8Cc. The susceptibility allele in TC29 contained a 7 bp deletion in exon 1, resulting in loss of 856 of the 1277 amino acids in the predicted nucleotide-binding domain leucine-rich repeat containing Pm2a protein. PmCH1357/Pm2a sequence was also isolated from the Chinese wheat landraces and cultivars that were previously reported to possess the resistance gene Pm2b, Pm2c, PmLX66, or PmND399. The PmCH1357/Pm2a resistance allele was present in 10 of 495 accessions in core germplasm and contemporary cultivars from China and the USA. A newly developed diagnostic marker for the 7 bp InDel in the resistance gene can be used to eliminate the susceptibility allele in wheat breeding programs.