Key message
Markers, located in
Dicer1
and
Ara6
genes, which are likely involved in cross-kingdom RNA trafficking, are associated with FHB resistance in GABI wheat population and were validated in ...biparental population.
Association studies are a common approach to detect marker-trait associations for Fusarium head blight (FHB) resistance in wheat (
Triticum aestivum
), although verification of detected associations is exceptional. In the present study, candidate-gene association mapping (CG) of genes from silencing and secretory pathways, which may be involved in wheat resistance against FHB and cross-kingdom RNA trafficking, was performed. Fourteen markers, located in nine genes, were tested for association with FHB resistance in 356 lines from the GABI (genome analysis of the biological system of plants) wheat population. Three markers located in the genes
Dicer1
and
Ara6
were shown to be significantly associated with the studied trait. Verification of this finding was performed using the recombinant inbred lines (RILs) population ‘Apache
×
Biscay’, segregating for four of our 14 selected markers. We could show association of the Ara6 marker with plant height as well as association with FHB resistance for three markers located in Rab5-like GTPase gene
Ara6
and
Dicer1
. These results confirmed the trait-marker associations detected also in the CG approach. Gene products of the associated genes are involved in response of the plant to pathogens, plant metabolism and may be involved in cross-kingdom RNA trafficking efficiency. The markers detected in the GABI wheat population, which were also validated in the biparental population, can potentially be used in wheat breeding.
Resistance to Fusarium head blight (FHB) is of great importance in wheat breeding programs in the northern hemisphere. In Europe, breeders prefer adapted germplasm as resistance donor because of high ...grain yield and quality demands. Our objective was to identify chromosomal regions affecting FHB resistance among 455 European soft winter wheat (Triticum aestivum L.) lines using a genome-wide association mapping approach and to analyze the importance of epistatic interactions. All entries were evaluated for FHB resistance by inoculation in two environments and several ratings. Wheat was genotyped by 115 simple sequence repeat markers randomly distributed across the genome and two allele-specific markers for Rht-B1 and Rht-D1 genes. The genome-wide scan revealed nine significant (P < 0.05) marker–phenotype associations on seven chromosomes including dwarfing gene Rht-D1. Using a Bonferroni–Holm correction, three significant associations remained on chromosomes 1B, 1D, and 2D. The proportion of the genotypic variance explained simultaneously by individual markers was 36% and increased to 50% when two digenic epistatic interactions were considered, one of them associated with Rht-B1. In conclusion, new genomic regions on chromosomes 1D and 3A could be found for FHB resistance in European wheat and the effect of epistatic interactions was substantial.
Recent increase in the availability of expressed sequence tag (EST) data has facilitated the development of microsatellite or simple sequence repeat (SSR) markers in a number of plant species groups, ...including cereals. As these SSRs are derived from ESTs/genes (EST-SSRs), they exhibit a higher potential for transfer through cross-amplification in related species than SSR markers generated from genomic DNA libraries. In this study, a sub-set of 165 EST-SSR markers from a total of 185 assigned to the genetic map of barley was examined for transferability to wheat, rye and rice. A higher proportion, i.e., 78.2% of barley markers showed amplification in wheat followed by 75.2% in rye and 42.4% in rice. Furthermore, in silico comparison of SSR-ESTs (ESTs containing SSRs) corresponding to 185 mapped barley EST-SSR loci against 1,369,182 publicly available cereal ESTs showed significant homology with ESTs of wheat (93.5%), rye (37.3%), rice (57.3%), sorghum (51.9%) and maize (51.9%). Sequence similarity of the barley ESTs with 379,944 ESTs of the two model dicot species,
Arabidopsis and
Medicago suggested theoretical transferability of barley markers into dicot species although at low frequency (9.7% in
Arabidopsis and 8.6% in
Medicago). In silico comparative mapping (sequence comparison) of mapped barley SSR-ESTs against the mapping data of rye, wheat and rice indicated the presence of orthologues of the barley SSR-ESTs in the respective species. Furthermore, nine barley EST-SSRs were experimentally mapped to a rye genetic linkage map and all could be located in the expected orthologous region compared to their position in barley.
Recent technological advances in next-generation sequencing (NGS) technologies have dramatically reduced the cost of DNA sequencing, allowing species with large and complex genomes to be sequenced. ...Although bread wheat (
Triticum aestivum
L.) is one of the world’s most important food crops, efficient exploitation of molecular marker-assisted breeding approaches has lagged behind that achieved in other crop species, due to its large polyploid genome. However, an international public–private effort spanning 9 years reported over 65% draft genome of bread wheat in 2014, and finally, after more than a decade culminated in the release of a gold-standard, fully annotated reference wheat-genome assembly in 2018. Shortly thereafter, in 2020, the genome of assemblies of additional 15 global wheat accessions was released. As a result, wheat has now entered into the pan-genomic era, where basic resources can be efficiently exploited. Wheat genotyping with a few hundred markers has been replaced by genotyping arrays, capable of characterizing hundreds of wheat lines, using thousands of markers, providing fast, relatively inexpensive, and reliable data for exploitation in wheat breeding. These advances have opened up new opportunities for marker-assisted selection (MAS) and genomic selection (GS) in wheat. Herein, we review the advances and perspectives in wheat genetics and genomics, with a focus on key traits, including grain yield, yield-related traits, end-use quality, and resistance to biotic and abiotic stresses. We also focus on reported candidate genes cloned and linked to traits of interest. Furthermore, we report on the improvement in the aforementioned quantitative traits, through the use of (i) clustered regularly interspaced short-palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9)-mediated gene-editing and (ii) positional cloning methods, and of genomic selection. Finally, we examine the utilization of genomics for the next-generation wheat breeding, providing a practical example of using
in silico
bioinformatics tools that are based on the wheat reference-genome sequence.
Reciprocal recurrent genomic selection is a breeding strategy aimed at improving the hybrid performance of two base populations. It promises to significantly advance hybrid breeding in wheat. Against ...this backdrop, the main objective of this study was to empirically investigate the potential and limitations of reciprocal recurrent genomic selection. Genome-wide predictive equations were developed using genomic and phenotypic data from a comprehensive population of 1,604 single crosses between 120 female and 15 male wheat lines. Twenty superior female lines were selected for initiation of the reciprocal recurrent genomic selection program. Focusing on the female pool, one cycle was performed with genomic selection steps at the F
2
(60 out of 629 plants) and the F
5
stage (49 out of 382 plants). Selection gain for grain yield was evaluated at six locations. Analyses of the phenotypic data showed pronounced genotype-by-environment interactions with two environments that formed an outgroup compared to the environments used for the genome-wide prediction equations. Removing these two environments for further analysis resulted in a selection gain of 1.0 dt ha
−1
compared to the hybrids of the original 20 parental lines. This underscores the potential of reciprocal recurrent genomic selection to promote hybrid wheat breeding, but also highlights the need to develop robust genome-wide predictive equations.
The demands for increasing global crop production have prompted the development of new approaches relying on molecular marker technologies to investigate and improve the plant genome. The merits of ...molecular markers make them valuable tools in a range of research areas. This review describes novel approaches based on modern molecular marker technologies for characterization and utilization of genetic variation for wheat improvement. Large-scale genome characterization by DNA-fingerprinting has revealed no declining trends in the molecular genetic diversity in wheat as a consequence of modern intensive breeding thus opposing the genetic 'erosion' hypothesis. A great number of important major genes and quantitative trait loci have been mapped with molecular markers. Marker-assisted selection based on a tight linkage between a marker allele and a gene(s) governing a qualitative or quantitative trait is gaining considerable importance as it facilitates and accelerates cultivar improvement through precise transfer of chromosome regions carrying the gene of interest. The implementations of molecular markers in wheat genotyping, mapping and breeding complemented by specific approaches associated with the complex polyploid nature of common wheat are analyzed and presented.
Key message
Genotypes with recombination events in the
Triticum ventricosum
introgression on chromosome 7D allowed to fine-map resistance gene Pch1, the main source of eyespot resistance in European ...winter wheat cultivars.
Eyespot (also called Strawbreaker) is a common and serious fungal disease of winter wheat caused by the necrotrophic fungi
Oculimacula yallundae
and
Oculimacula acuformis
(former name
Pseudocercosporella herpotrichoides
). A genome-wide association study (GWAS) for eyespot was performed with 732 microsatellite markers (SSR) and 7761 mapped SNP markers derived from the 90 K iSELECT wheat array using a panel of 168 European winter wheat varieties as well as three spring wheat varieties and phenotypic evaluation of eyespot in field tests in three environments. Best linear unbiased estimations (BLUEs) were calculated across all trials and ranged from 1.20 (most resistant) to 5.73 (most susceptible) with an average value of 4.24 and a heritability of
H
2
= 0.91. A total of 108 SSR and 235 SNP marker–trait associations (MTAs) were identified by considering associations with a −log
10
(
P
value) ≥3.0. Significant MTAs for eyespot-score BLUEs were found on chromosomes 1D, 2A, 2D, 3D, 5A, 5D, 6A, 7A and 7D for the SSR markers and chromosomes 1B, 2A, 2B, 2D, 3B and 7D for the SNP markers. For 18 varieties (10.5%), a highly resistant phenotype was detected that was linked to the presence of the resistance gene
Pch1
on chromosome 7D. The identification of genotypes with recombination events in the introgressed genomic segment from
Triticum ventricosum
harboring the
Pch1
resistance gene on chromosome 7DL allowed the fine-mapping of this gene using additional SNP markers and a potential candidate gene Traes_7DL_973A33763 coding for a CC-NBS-LRR class protein was identified.
Parental selection is at the beginning and contributes significantly to the success of any breeding work. The value of a cross is reflected in the potential of its progeny population. Breeders invest ...substantial resources in evaluating progeny to select the best performing genotypes as candidates for variety development. Several proposals have been made to use genomics to support parental selection. These have mostly been evaluated using theoretical considerations or simulation studies. However, evaluations using experimental data have rarely been conducted. In this study, we tested the potential of genomic prediction for predicting the progeny mean, variance, and usefulness criterion using data from an applied breeding population for winter barley. For three traits with genetic architectures at varying levels of complexity, ear emergence, plant height, and grain yield, progeny mean, variance, and usefulness criterion were predicted and validated in scenarios resembling situations in which the described tools shall be used in plant breeding. While the population mean could be predicted with moderate to high prediction abilities amounting to 0.64, 0.21, and 0.39 in ear emergence, plant height, and grain yield, respectively, the prediction of family variance appeared difficult, as reflected in low prediction abilities of 0.41, 0.11, and 0.14, for ear emergence, plant height, and grain yield, respectively. We have shown that identifying superior crosses remains a challenging task and suggest that the success of predicting the usefulness criterion depends strongly on the complexity of the underlying trait.
Winter rye is a versatile crop widely used for food and industry. Although rye is resistant to abiotic stressors and many phytopathogens, it is severely damaged by pink snow mold (SM)—a progressive ...disease caused by the psychrotolerant fungus Microdochium nivale under the snow cover or during prolonged periods of wet and cool conditions. Due to little use of the SM resistance sources in contemporary breeding, varieties with at least moderate resistance to SM are limited. Our study aimed to integrate field assessment under natural conditions and an artificially enriched infection background with laboratory techniques for testing rye accessions and selecting SM resistant sources for applied breeding programs and genetic research. We revealed valuable sources of SM resistance and split rye accessions, according to the level of the genetic divergence of the SM resistance phenotype. This allowed us to select the most distinct donors of the SM resistance, for their use as parental forms, to include novel variability sources in the breeding program for achieving high genetic variability, as well as enhanced and durable SM resistance, in progeny. The rye accessions analyzed here, and the suggested options for their use in breeding, are valuable tools for rye breeding.
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