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Waterlogging is a growing threat to wheat production in high-rainfall areas. In this study, a doubled haploid (DH) population developed from a cross between Yangmai 16 (waterlogging-tolerant) and Zhongmai 895 (waterlogging-sensitive) was used to map quantitative trait loci (QTL) for waterlogging tolerance using a high-density 660K single-nucleotide polymorphism (SNP) array. Two experimental designs, waterlogging concrete tank (CT) and waterlogging plastic tank (PT), were used to simulate waterlogging during anthesis in five environments across three growing seasons. Waterlogging significantly decreased thousand-kernel weight (TKW) relative to non-waterlogged controls, although the degree varied across lines. Three QTL for waterlogging tolerance were identified on chromosomes 4AL, 5AS, and 7DL in at least two environments. All favorable alleles were contributed by the waterlogging-tolerant parent Yangmai 16. QWTC.caas-4AL exhibited pleiotropic effects on both enhancing waterlogging tolerance and decreasing plant height. Six high-confidence genes were annotated within the QTL interval. The combined effects of QWTC.caas-4AL and QWTC.caas-5AS greatly improved waterlogging tolerance, while the combined effects of all three identified QTL (QWTC.caas-4AL, QWTC.caas-5AS, and QWTC.caas-7DL) exhibited the most significant effect on waterlogging tolerance. Breeder-friendly kompetitive allele-specific PCR (KASP) markers (K_AX_111523809, K_AX_108971224, and K_AX_110553316) flanking the interval of QWTC.caas-4AL, QWTC.caas-5AS, and QWTC.caas-7DL were produced. These markers were tested in a collection of 240 wheat accessions, and three superior polymorphisms of the markers distributed over 67 elite cultivars in the test population, from the Chinese provinces of Jiangsu, Anhui, and Hubei. The three KASP markers could be used for marker-assisted selection (MAS) to improve waterlogging tolerance in wheat.

IntroductionCytoplasmic male sterility (CMS) is an important tool for hybrid heterosis utilization. However, the underlying mechanisms still need to be discovered. An adequate supply of nutrients is necessary for anther development; pollen abortion would occur if the metabolism of carbohydrates were hampered.MethodsIn order to better understand the relationship between carbohydrate metabolism disorder and pollen abortion in S-CMS wheat, the submicroscopic structure of wheat anthers was observed using light microscopy and transmission electron microscopy; chloroplast proteome changes were explored by comparative proteomic analysis; sugar measuring and enzyme assays were performed; and the expression patterns of carbohydrate metabolism-related genes were studied using quantitative real-time PCR (qRT-PCR) method.ResultsThese results indicated that the anther and microspore in S-CMS wheat underwent serious structural damage, including premature tapetum degeneration, nutritional shortage, pollen wall defects, and pollen grain malformations. Furthermore, the number of chloroplasts in the anthers of S-CMS lines decreased significantly, causing abnormal carbohydrate metabolism, and disintegration of osmiophilic granules and thylakoids. Meanwhile, some proteins participating in the Calvin cycle and carbohydrate metabolism were abnormally expressed in the chloroplasts of the S-CMS lines, which might lead to chloroplast dysfunction. Additionally, several key enzymes and genes related to carbohydrate metabolism were significantly inhibited in S-CMS.DiscussionBased on these results, we proposed a carbohydrate metabolism pathway for anther abortion in S-type cytoplasmic male sterility, which would encourage further exploration of the pollen abortion mechanisms for CMS wheat.

Abstract Background Stripe rust (yellow rust) is a significant disease for bread wheat (Triticum aestivum L.) worldwide. A genome-wide association study was conducted on 240 Chinese wheat cultivars and elite lines genotyped with the wheat 90 K single nucleotide polymorphism (SNP) arrays to decipher the genetic architecture of stripe rust resistance in Chinese germplasm. Results Stripe rust resistance was evaluated at the adult plant stage in Pixian and Xindu in Sichuan province in the 2015–2016 cropping season, and in Wuhan in Hubei province in the 2013–2014, 2016–2017 and 2018–2019 cropping seasons. Twelve stable loci for stripe rust resistance were identified by GWAS using TASSEL and GAPIT software. These loci were distributed on chromosomes 1B, 1D, 2A, 2B, 3A, 3B, 4B (3), 4D, 6D, and 7B and explained 3.6 to 10.3% of the phenotypic variation. Six of the loci corresponded with previously reported genes/QTLs, including Sr2/Yr30/Lr27, while the other six (QYr.hbaas-1BS, QYr.hbaas-2BL, QYr.hbaas-3AL, QYr.hbaas-4BL.3, QYr.hbaas-4DL, and QYr.hbaas-6DS) are probably novel. The results suggest high genetic diversity for stripe rust resistance in this population. The resistance alleles of QYr.hbaas-2AS, QYr.hbaas-3BS, QYr.hbaas-4DL, and QYr.hbaas-7BL were rare in the present panel, indicating their potential use in breeding for stripe rust resistance in China. Eleven penta-primer amplification refractory mutation system (PARMS) markers were developed from SNPs significantly associated with seven mapped QTLs. Twenty-seven genes were predicted for mapped QTLs. Six of them were considered as candidates for their high relative expression levels post-inoculation. Conclusion The resistant germplasm, mapped QTLs, and PARMS markers developed in this study are resources for enhancing stripe rust resistance in wheat breeding.

The objective of this paper is to review progress made in wheat breeding for Fusarium head blight (FHB) resistance in China, the United States of America (USA), and Canada. In China, numerous Chinese landraces possessing high levels of FHB resistance were grown before the 1950s. Later, pyramiding multiple sources of FHB resistance from introduced germplasm such as Mentana and Funo and locally adapted cultivars played a key role in combining satisfactory FHB resistance and high yield potential in commercial cultivars. Sumai 3, a Chinese spring wheat cultivar, became a major source of FHB resistance in the USA and Canada, and contributed to the release of more than 20 modern cultivars used for wheat production, including the leading hard spring wheat cultivars Alsen, Glenn, Barlow and SY Ingmar from North Dakota, Faller and Prosper from Minnesota, and AAC Brandon from Canada. Brazilian wheat cultivar Frontana, T. dicoccoides and other local germplasm provided additional sources of resistance. The FHB resistant cultivars mostly relied on stepwise accumulation of favorable alleles of both genes for FHB resistance and high yield, with marker-assisted selection being a valuable complement to phenotypic selection. With the Chinese Spring reference genome decoded and resistance gene Fhb1 now cloned, new genomic tools such as genomic selection and gene editing will be available to breeders, thus opening new possibilities for development of FHB resistant cultivars. Keywords: Fhb1, Fusarium head blight resistance, Fusarium graminearum, Triticum aestivum, Wheat breeding

Fusarium head blight (FHB) is a devastating wheat disease worldwide. To decipher the genetic architecture of FHB resistance in Chinese germplasm, a Wheat Association Panel for Scab Research (WAPS) consisting of 240 leading Chinese wheat cultivars and elite lines was genotyped using the 90K single nucleotide polymorphism (SNP) arrays. The FHB response was evaluated in the field nurseries in Wuhan in Hubei Province over four consecutive years from 2014 to 2017. Five quantitative trait loci (QTL) were consistently identified on chromosome arms 1AS, 2DL, 5AS, 5AL, and 7DS using a mixed linear model (MLM), explaining 5.6, 10.3, 5.7, 5.4, and 5.6% of phenotypic variation, respectively. The QTL on 5AS, 5AL, and 7DS QTL are probably novel. The allelic frequency analysis indicated that cultivars from the Middle and Lower Yangtze River Valleys harbored more favorable alleles and were therefore more resistant than those from other regions. To facilitate in-house germplasm screening and marker-assisted selection (MAS), SNP-derived PCR markers were developed for the QTL regions on 1AS, 5AS, and 5AL QTL. In addition to the above five QTL, the WAPS population had a very low frequency of Fhb1, confirming that the gene is not widely used in Chinese wheat breeding programs. The resistant lines and molecular markers developed in this study are resources and information for enhancing FHB resistance in breeding populations by marker-assisted recurrent selection and gene stacking.

Transcription factors (TFs) play fundamental roles in the developmental processes of all living organisms. Squamosa Promoter Binding Protein-like (SBP/SBP-Box) is a major family of plant-specific TFs, which plays important roles in multiple processes involving plant growth and development. While some work has been done, there is a lot more that is yet to be discovered in the hexaploid wheat SBP (TaSBP) family. With the completion of whole genome sequencing, genome-wide analysis of SBPs in common hexaploid wheat is now possible. In this study, we used protein−protein Basic Local Alignment Search Tool (BLASTp) to hunt the newly released reference genome sequence of hexaploid wheat (Chinese spring). Seventy-four TaSBP proteins (belonging to 56 genes) were identified and clustered into five groups. Gene structure and motif analysis indicated that most TaSBPs have relatively conserved exon−intron arrangements and motif composition. Analysis of transcriptional data showed that many TaSBP genes responded to some biological and abiotic stresses with different expression patterns. Moreover, three TaSBP genes were generally expressed in the majority of tissues throughout the wheat growth and also responded to many environmental biotic and abiotic stresses. Collectively, the detailed analyses presented here will help in understanding the roles of the TaSBP and also provide a reference for the further study of its biological function in wheat.

Wheat cultivar Zhongmai 895 was earlier found to carry YR86 in an 11.6 Mb recombination-suppressed region on chromosome 2AL when crossed with Yangmai 16. To fine-map the YR86 locus, we developed two large F2 populations from crosses Emai 580/Zhongmai 895 and Avocet S/Zhongmai 895. Remarkably, both populations exhibited suppressed recombination in the same 2AL region. Collinearity analysis across Chinese Spring, Aikang 58, and 10+ wheat genomes revealed a 4.1 Mb chromosomal inversion spanning 708.5-712.6 Mb in the Chinese Spring reference genome. Molecular markers were developed in the breakpoint and were used to assess a wheat cultivar panel, revealing that Chinese Spring, Zhongmai 895, and Jimai 22 shared a common sequence named InvCS, whereas Aikang 58, Yangmai 16, Emai 580, and Avocet S shared the sequence named InvAK58. The inverted configuration explained the suppressed recombination observed in all three bi-parental populations. Normal recombination was observed in a Jimai 22/Zhongmai 895 F2 population, facilitating mapping of YR86 to a genetic interval of 0.15 cM corresponding to 710.27-712.56 Mb falling within the inverted region. Thirty-three high-confidence genes were annotated in the interval using the Chinese Spring reference genome, with six identified as potential candidates for YR86 based on genome and transcriptome analyses. These results will accelerate map-based cloning of YR86 and its deployment in wheat breeding. [ABSTRACT FROM AUTHOR]

Rht24 is 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 Rht24 and 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 Rht1 and Rht2, and closely linked flanking markers were used for genotyping of Rht8 and Rht24. Marker analysis showed that Rht24 occurs at a higher frequency (84.2%) than other important dwarfing alleles in elite wheat (Triticum aestivum L.) varieties and usually couples with Rht2 or Rht8. Geno- typing of old varieties and landraces showed that Rht24 was widely used in wheat breeding before the Green Revolution (GR). 'Akakomugi' and 'Norin 10', the donors of Rht8 and GR genes Rht1 and Rht2, respectively, harbored Rht24, so Rht24 likely followed the transfer routes of GR genes and Rht8 to spread worldwide. Pedigree analysis showed that many Chinese elite lines and backbone parents were derived from Akakomugi, contributing to the high frequency of Rht24 in Chinese varieties. Additionally, Norin 10-derived semidwarf varieties from the CIMMYT were widely used in Chinese wheat breeding. Finally, Rht24 was also detected in 30 old Chinese varieties and landraces. Overall, these findings show that the presence of Rht24 in modern Chinese elite varieties originated from Akakomugi, Norin 10, or Chinese landraces. Thus, Rht24 was introgressed early, spread widely, and became genetically fixed in a wide range of modern Chinese wheat germplasm. [ABSTRACT FROM AUTHOR]