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Wheat resistance to Fusarium head blight (FHB) has often been associated with some undesirable agronomic traits. To study the relationship between wheat FHB resistance and agronomic traits, we constructed a linkage map of single nucleotide polymorphisms (SNPs) using an F6:8 population from G97252W × G97380A. The two hard winter wheat parents showed contrasts in FHB resistance, plant height (HT), heading date (HD), spike length (SL), spike compactness (SC), kernel number per spike (KNS), spikelet number per spike (SNS), thousand-grain weight (TGW) and grain size (length and width). Quantitative trait locus (QTL) mapping identified one major QTL (QFhb.hwwg-2DS) on chromosome arm 2DS for the percentage of symptomatic spikelets (PSS) in the spike, deoxynivalenol (DON) content and Fusarium damaged kernel (FDK). This QTL explained up to 71.8% of the phenotypic variation for the three FHB-related traits and overlapped with the major QTL for HT, HD, SL, KNS, SNS, TGW, and grain size. QTL on chromosome arms 2AL, 2DS, 3AL and 4BS were significant for the spike and grain traits measured. G97252W contributed FHB resistance and high SNS alleles at QFhb.hwwg-2DS, high KNS alleles at the QTL on 2AL and 2DS, and high TGW and grain size alleles at QTL on 3AL; whereas G97380A contributed high TGW and grain size alleles at the QTL on 2AL and 2DS, respectively, and the high KNS allele at the 4BS QTL. Combining QFhb.hwwg-2DS with positive alleles for spike and grain traits from other chromosomes may simultaneously improve FHB resistance and grain yield in new cultivars. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.) wild relatives are rich genetic resources for genetic improvement of wheat. The short arm of rye (Secale cereale L.) chromosome 1 (1RS) contains many beneficial genes for resistance to drought, insects, and diseases, therefore the 1RS wheat translocations have been widely used in wheat breeding programs worldwide. To facilitate marker‐assisted identification of 1RS in wheat breeding, we designed a set of Kompetitive allele‐specific polymerase chain reaction (KASP) markers to detect the translocations of 1RS with long arm from wheat chromosome 1A (1RS.1AL) and 1RS with long arm from wheat chromosome 1B (1RS.1BL) based on the sequence flanking single nucleotide polymorphisms (SNPs) generated by genotyping‐by‐sequencing (GBS) between wheat and rye panels. We identified a set of three SNP markers for diagnosis and differentiation of the two 1RS translocations in wheat. Among the three KASP markers, 1AS‐05056 is 1RS specific, and clearly separated the genotypes with 1RS (1RS.1AL and 1RS.1BL) from those without the two 1RS translocations; whereas 1AS‐29875 clearly identified the 1RS.1AL translocation and 1BS‐16654 separated 1RS.1BL from 1RS.1AL. The three new KASP markers together accurately identified the presence of 1RS translocation on either 1A or 1B chromosome in a panel of 95 representative U.S. winter wheat accessions, which were further validated in two additional U.S. hard winter wheat panels. Therefore, they can be used for routine screening of 1RS.1BL and 1RS.1AL translocation lines in wheat breeding programs. Core Ideas: 1RS, 1AS, and 1BS specific SNPs were identified by analyzing GBS‐SNPs from both wheat and rye panels.Three chromosome‐arm‐specific KASPs clearly detected the 1RS.1AL and 1RS.1BL translocations in wheat.Three KASP markers were diagnostic for 1RS.1AL and 1RS.1BL in two U.S. hard winter wheat panels. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB), caused by the fungus Fusarium graminearum Schwabe is an important disease of wheat that causes severe yield losses along with serious quality concerns. Incorporating the host resistance from either wild relatives, landraces, or exotic materials remains challenging and has shown limited success. Therefore, a better understanding of the genetic basis of native FHB resistance in hard winter wheat (HWW) and combining it with major quantitative trait loci (QTLs) can facilitate the development of FHB-resistant cultivars. In this study, we evaluated a set of 257 breeding lines from the South Dakota State University (SDSU) breeding program to uncover the genetic basis of native FHB resistance in the US hard winter wheat. We conducted a multi-locus genomewide association study (ML-GWAS) with 9,321 high-quality single-nucleotide polymorphisms (SNPs). A total of six distinct marker-trait associations (MTAs) were identified for the FHB disease index (DIS) on five different chromosomes including 2A, 2B, 3B, 4B, and 7A. Further, eight MTAs were identified for Fusarium-damaged kernels (FDK) on six chromosomes including 3B, 5A, 6B, 6D, 7A, and 7B. Out of the 14 significant MTAs, 10 were found in the proximity of previously reported regions for FHB resistance in different wheat classes and were validated in HWW, while four MTAs represent likely novel loci for FHB resistance. Accumulation of favorable alleles of reported MTAs resulted in significantly lower mean DIS and FDK score, demonstrating the additive effect of FHB resistance alleles. Candidate gene analysis for two important MTAs identified several genes with putative proteins of interest; however, further investigation of these regions is needed to identify genes conferring FHB resistance. The current study sheds light on the genetic basis of native FHB resistance in the US HWW germplasm and the resistant lines and MTAs identified in this study will be useful resources for FHB resistance breeding via marker-assisted selection. [ABSTRACT FROM AUTHOR]

Spring wheat (Triticum aestivum L.) is one of the most imperative staple food crops, with an annual production of 765 million tons globally to feed ∼40% world population. Genetic diversity in available germplasm is crucial for sustainable wheat improvement to ensure global food security. A diversity panel of 184 Pakistani wheat accessions was genotyped using 123,596 high-quality single nucleotide polymorphism (SNP) markers generated by genotyping-by-sequencing with 42% of the SNPs mapped on B, 36% on A, and 22% on D sub-genomes of wheat. Chromosome 2B contains the most SNPs (9,126), whereas 4D has the least (2,660) markers. The mean polymorphic information content, genetic diversity, and major allele frequency of the population were 0.157, 0.1844, and 0.87, respectively. Analysis of molecular variance revealed a higher genetic diversity (80%) within the sub-population than among the sub-populations (20%). The genome-wide linkage disequilibrium was 0.34 Mbp for the whole wheat genome. Among the three subgenomes, A has the highest LD decay value (0.29 Mbp), followed by B (0.2 Mbp) and D (0.07 Mbp) genomes, respectively. The results of population structure, principal coordinate analysis, phylogenetic tree, and kinship analysis also divided the whole population into three clusters comprising 31, 33, and 120 accessions in group 1, group 2, and group 3, respectively. All groups were dominated by the local wheat accessions. Estimation of genetic diversity will be a baseline for the selection of breeding parents for mutations and the genome-wide association and marker-assisted selection studies. [ABSTRACT FROM AUTHOR]

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a disease of global importance, and new powdery mildew resistance genes that can be directly used in cultivar development are urgently needed. A recombinant inbred line population from 'CI 17884' × 'Bainong 418' was genotyped using single nucleotide polymorphism markers generated from genotyping-by-sequencing, and evaluated for responses to Great Plains Bgt isolates OKS(14)-B-3-1 and NEI-1-3. Genetic mapping identified a powdery mildew resistance gene, designated PmBN418, on a 1BL.1RS translocation segment in Bainong 418. Given that PmBN418 conferred resistance to Bgt isolates virulent to Pm8 that resides on the chromosome arm 1RS translocated from rye (Secale cereale L.) cv. 'Petkus', PmBN418 is either a new gene or a new allele of Pm8. Phenotypic and genomic data analyses indicated segregation distortion of the powdery mildew resistance gene due to reduced transmission of the wheat (Triticum aestivum L.)-rye 1BL.1RS translocation segment from Bainong 418, while the wheat-Triticum speltoides translocation segment 7S#1 in CI 17884 was preferentially transmitted. Bainong 418, a high-yielding cultivar with good resistance to several U.S. Bgt isolates, is a useful resistance source for wheat breeding, and the availability of the Kompetitive Allele Specific PCR (KASP) marker KASP-1RS-1 makes marker-assisted introgression of PmBN418 into locally adapted cultivars feasible. [ABSTRACT FROM AUTHOR]

Moderate heat stress accompanied by short episodes of extreme heat during the post-anthesis stage is common in most US wheat growing areas and causes substantial yield losses. Sink strength (grain number) is a key yield limiting factor in modern wheat varieties. Increasing spike fertility (SF) and improving the partitioning of assimilates can optimize sink strength which is essential to improve wheat yield potential under a hot and humid environment. A genome-wide association study (GWAS) allows identification of novel quantitative trait loci (QTLs) associated with SF and other partitioning traits that can assist in marker assisted breeding. In this study, GWAS was performed on a soft wheat association mapping panel (SWAMP) comprised of 236 elite lines using 27,466 single nucleotide polymorphisms (SNPs). The panel was phenotyped in two heat stress locations over 3 years. GWAS identified 109 significant marker-trait associations (MTAs) (p ≤ 9.99 x 10−5) related to eight phenotypic traits including SF (a major component of grain number) and spike harvest index (SHI, a major component of grain weight). MTAs detected on chromosomes 1B, 3A, 3B, and 5A were associated with multiple traits and are potentially important targets for selection. More than half of the significant MTAs (60 out of 109) were found in genes encoding different types of proteins related to metabolism, disease, and abiotic stress including heat stress. These MTAs could be potential targets for further validation study and may be used in marker-assisted breeding for improving wheat grain yield under post-anthesis heat stress conditions. This is the first study to identify novel QTLs associated with SF and SHI which represent the major components of grain number and grain weight, respectively, in wheat. [ABSTRACT FROM AUTHOR]