Second Chromosome Research Articles

UAV-based time-series phenotyping reveals the genetic basis of plant height in upland cotton.

Plant height (PH) is an important agronomic trait affecting crop architecture, biomass, resistance to lodging and mechanical harvesting. Elucidating the genetic governance of plant height is crucial because of the global demand for high crop yields. However, during the rapid growth period of plants the PH changes a lot on a daily basis, which makes it difficult to accurately phenotype the trait by hand on a large scale. In this study, an unmanned aerial vehicle (UAV)-based remote-sensing phenotyping platform was applied to obtain time-series PHs of 320 upland cotton accessions in three different field trials. The results showed that the PHs obtained from UAV images were significantly correlated with ground-based manual measurements, for three trials (R2 = 0.96, 0.95 and 0.96). Two genetic loci on chromosomes A01 and A11 associated with PH were identified by genome-wide association studies (GWAS). GhUBP15 and GhCUL1 were identified to influence PH in further analysis. We obtained a time series of PH values for three field conditions based on remote sensing with UAV. The key genes identified in this study are of great value for the breeding of ideal plant architecture in cotton.

FHB resistance conferred by Fhb1 is under inhibitory regulation of two genetic loci in wheat (Triticum aestivum L.).

Two loci inhibiting Fhb1 resistance to Fusarium head blight were identified through genome-wide association mapping and validated in biparental populations. Fhb1 confers Fusarium head blight (FHB) resistance by limiting fungal spread within spikes in wheat (type II resistance). However, not all lines with Fhb1 display the expected resistance. To identify genetic factors regulating Fhb1 effect, a genome-wide association study for type II resistance was first performed with 72 Fhb1-carrying lines using the Illumina 90K iSelect SNP chip. Of 84 significant marker-trait associations detected, more than half were repeatedly detected in at least two environments, with the SNPs distributed in one region on chromosome 5B and one on chromosome 6A. This result was validated in a collection of 111 lines with Fhb1 and 301 lines without Fhb1. We found that these two loci caused significant resistance variations solely among lines with Fhb1 by compromising the resistance. In1, the inhibitory gene on chromosome 5B, was in close linkage with Xwgrb3860 in a recombinant inbred line population derived from Nanda2419 × Wangshuibai and a double haploid (DH) population derived from R-43 (Fhb1 near isogenic line) × Biansui7 (with Fhb1 and In1); and In2, the inhibitory gene on chromosome 6A, was mapped to the Xwgrb4113-Xwgrb4034 interval using a DH population derived from R-43 × PH8901 (with Fhb1 and In2). In1 and In2 are present in all wheat-growing areas worldwide. Their frequencies in China's modern cultivars are high but have significantly decreased in comparison with landraces. These findings are of great significance for FHB resistance breeding using Fhb1.

Genome-wide association mapping of genomic regions associated with drought stress tolerance at seedling and reproductive stages in bread wheat.

Understanding the genetic architecture of drought stress tolerance in bread wheat at seedling and reproductive stages is crucial for developing drought-tolerant varieties. In the present study, 192 diverse wheat genotypes, a subset from the Wheat Associated Mapping Initiative (WAMI) panel, were evaluated at the seedling stage in a hydroponics system for chlorophyll content (CL), shoot length (SLT), shoot weight (SWT), root length (RLT), and root weight (RWT) under both drought and optimum conditions. Following that, a genome-wide association study (GWAS) was carried out using the phenotypic data recorded during the hydroponics experiment as well as data available from previously conducted multi-location field trials under optimal and drought stress conditions. The panel had previously been genotyped using the Infinium iSelect 90K SNP array with 26,814 polymorphic markers. Using single as well as multi-locus models, GWAS identified 94 significant marker-trait associations (MTAs) or SNPs associated with traits recorded at the seedling stage and 451 for traits recorded at the reproductive stage. The significant SNPs included several novel, significant, and promising MTAs for different traits. The average LD decay distance for the whole genome was approximately 0.48 Mbp, ranging from 0.07 Mbp (chromosome 6D) to 4.14 Mbp (chromosome 2A). Furthermore, several promising SNPs revealed significant differences among haplotypes for traits such as RLT, RWT, SLT, SWT, and GY under drought stress. Functional annotation and in silico expression analysis revealed important putative candidate genes underlying the identified stable genomic regions such as protein kinases, O-methyltransferases, GroES-like superfamily proteins, NAD-dependent dehydratases, etc. The findings of the present study may be useful for improving yield potential, and stability under drought stress conditions.

High-density genetic mapping of Fusarium head blight resistance and agronomic traits in spring wheat.

Fusarium head blight (FHB) has rapidly become a major challenge to successful wheat production and competitive end-use quality in western Canada. Continuous effort is required to develop germplasm with improved FHB resistance and understand how to incorporate the material into crossing schemes for marker-assisted selection and genomic selection. The aim of this study was to map quantitative trait loci (QTL) responsible for the expression of FHB resistance in two adapted cultivars and to evaluate their co-localization with plant height, days to maturity, days to heading, and awnedness. A large doubled haploid population of 775 lines developed from cultivars Carberry and AC Cadillac was assessed for FHB incidence and severity in nurseries near Portage la Prairie, Brandon, and Morden in different years, and for plant height, awnedness, days to heading, and days to maturity near Swift Current. An initial linkage map using a subset of 261 lines was constructed using 634 polymorphic DArT and SSR markers. QTL analysis revealed five resistance QTL on chromosomes 2A, 3B (two loci), 4B, and 5A. A second genetic map with increased marker density was constructed using the Infinium iSelect 90k SNP wheat array in addition to the previous DArT and SSR markers, which revealed two additional QTL on 6A and 6D. The complete population was genotyped, and a total of 6,806 Infinium iSelect 90k SNP polymorphic markers were used to identify 17 putative resistance QTL on 14 different chromosomes. As with the smaller population size and fewer markers, large-effect QTL were detected on 3B, 4B, and 5A that were consistently expressed across environments. FHB resistance QTL were co-localized with plant height QTL on chromosomes 4B, 6D, and 7D; days to heading on 2B, 3A, 4A, 4B, and 5A; and maturity on 3A, 4B, and 7D. A major QTL for awnedness was identified as being associated with FHB resistance on chromosome 5A. Nine small-effect QTL were not associated with any of the agronomic traits, whereas 13 QTL that were associated with agronomic traits did not co-localize with any of the FHB traits. There is an opportunity to select for improved FHB resistance within adapted cultivars by using markers associated with complementary QTL.

Genome-wide association analysis reveals a novel pathway mediated by a dual-TIR domain protein for pathogen resistance in cotton

BackgroundVerticillium wilt is one of the most devasting diseases for many plants, leading to global economic loss. Cotton is known to be vulnerable to its fungal pathogen, Verticillium dahliae, yet the related genetic mechanism remains unknown.ResultsBy genome-wide association studies of 419 accessions of the upland cotton, Gossypium hirsutum, we identify ten loci that are associated with resistance against Verticillium wilt. Among these loci, SHZDI1/SHZDP2/AYDP1 from chromosome A10 is located on a fragment introgressed from Gossypium arboreum. We characterize a large cluster of Toll/interleukin 1 (TIR) nucleotide-binding leucine-rich repeat receptors in this fragment. We then identify a dual-TIR domain gene from this cluster, GhRVD1, which triggers an effector-independent cell death and is induced by Verticillium dahliae. We confirm that GhRVD1 is one of the causal gene for SHZDI1. Allelic variation in the TIR domain attenuates GhRVD1-mediated resistance against Verticillium dahliae. Homodimerization between TIR1-TIR2 mediates rapid immune response, while disruption of its αD- and αE-helices interface eliminates the autoactivity and self-association of TIR1-TIR2. We further demonstrate that GhTIRP1 inhibits the autoactivity and self-association of TIR1-TIR2 by competing for binding to them, thereby preventing the resistance to Verticillium dahliae.ConclusionsWe propose the first working model for TIRP1 involved self-association and autoactivity of dual-TIR domain proteins that confer compromised pathogen resistance of dual-TIR domain proteins in plants. The findings reveal a novel mechanism on Verticillium dahliae resistance and provide genetic basis for breeding in future.

Characterization of candidate genes for ozone tolerance in winter wheat (Triticum aestivum L.) and associated physiological mechanisms

Rising tropospheric ozone causes global yield reduction in wheat and therefore necessitates the breeding of ozone-resistant wheat varieties. The aim of this study was to explore contrasting physiological responses and characterize candidate genes for ozone tolerance in wheat identified in a genome-wide association study. Four wheat genotypes were grouped into tolerant and sensitive haplotypes according to their genetic backgrounds at ozone tolerant loci, and were investigated under season-long ozone fumigation in open-top chambers. Only sensitive haplotypes showed a significant decrease in net photosynthetic rate and a significant increase in lipid peroxidation indicating oxidative stress. Moreover, tolerant and sensitive haplotypes of wheat showed consistently contrasting antioxidant responses to ozone in terms of apoplastic ascorbate, ascorbate peroxidase and peroxidase activity. Candidate genes located within an ozone tolerant locus on chromosome 5A 592.04–593.33 Mb were analyzed through gene expression. The gene TraesCS5A01G400500 putatively involved in peroxidase activity was only upregulated in tolerant haplotypes. The differential regulation was consistent with sequence polymorphisms in the promoter region, where the cis-elements, EVENINGAT and PREATPRODH were only present in tolerant haplotypes. Based on the consistency of differential expression and sequence polymorphisms between tolerant and sensitive haplotypes, TraesCS5A01G400500 might explain contrasting physiological responses after ozone fumigation. This study demonstrated consistent transcriptional regulation, sequence polymorphisms in a candidate gene and physiological responses to ozone in different haplotypes, which represents a step forward in the understanding of the molecular mechanism underlying ozone tolerance in wheat.

Historical Selection, Adaptation Signatures, and Ambiguity of Introgressions in Wheat.

Wheat was one of the crops domesticated in the Fertile Crescent region approximately 10,000 years ago. Despite undergoing recent polyploidization, hull-to-free-thresh transition events, and domestication bottlenecks, wheat is now grown in over 130 countries and accounts for a quarter of the world's cereal production. The main reason for its widespread success is its broad genetic diversity that allows it to thrive in different environments. To trace historical selection and hybridization signatures, genome scans were performed on two datasets: approximately 113K SNPs from 921 predominantly bread wheat accessions and approximately 110K SNPs from about 400 wheat accessions representing all ploidy levels. To identify environmental factors associated with the loci, a genome-environment association (GEA) was also performed. The genome scans on both datasets identified a highly differentiated region on chromosome 4A where accessions in the first dataset were dichotomized into a group (n = 691), comprising nearly all cultivars, wild emmer, and most landraces, and a second group (n = 230), dominated by landraces and spelt accessions. The grouping of cultivars is likely linked to their potential ancestor, bread wheat cv. Norin-10. The 4A region harbored important genes involved in adaptations to environmental conditions. The GEA detected loci associated with latitude and temperature. The genetic signatures detected in this study provide insight into the historical selection and hybridization events in the wheat genome that shaped its current genetic structure and facilitated its success in a wide spectrum of environmental conditions. The genome scans and GEA approaches applied in this study can help in screening the germplasm housed in gene banks for breeding, and for conservation purposes.

Genome-wide association mapping in elite winter wheat breeding for yield improvement

Increased grain yield (GY) is the primary breeding target of wheat breeders. We performed the genome-wide association study (GWAS) on 168 elite winter wheat lines from an ongoing breeding program to identify the main determinants of grain yield. Sequencing of Diversity Array Technology fragments (DArTseq) resulted in 19,350 single-nucleotide polymorphism (SNP) and presence-absence variation (PAV) markers. We identified 15 main genomic regions located in ten wheat chromosomes (1B, 2B, 2D, 3A, 3D, 5A, 5B, 6A, 6B, and 7B) that explained from 7.9 to 20.3% of the variation in grain yield and 13.3% of the yield stability. Loci identified in the reduced genepool are important for wheat improvement using marker-assisted selection. We found marker-trait associations between three genes involved in starch biosynthesis and grain yield. Two starch synthase genes (TraesCS2B03G1238800 and TraesCS2D03G1048800) and a sucrose synthase gene (TraesCS3D03G0024300) were found in regions of QGy.rut-2B.2, QGy.rut-2D.1, and QGy.rut-3D, respectively. These loci and other significantly associated SNP markers found in this study can be used for pyramiding favorable alleles in high-yielding varieties or to improve the accuracy of prediction in genomic selection.

Identification of Novel QTLs Associated with Frost Tolerance in Winter Wheat (Triticum aestivum L.).

Low temperature (cold) and freezing stress is a major problem during winter wheat growth. Low temperature tolerance (LT) is an important agronomic trait in winter wheat and determines the plants' ability to cope with below-freezing temperatures; thus, the development of cold-tolerant cultivars has become a major goal of breeding in various regions of the world. In this study, we sought to identify quantitative trait loci (QTL) using molecular markers related to freezing tolerance in winter. Thirty-four polymorphic markers among 425 SSR markers were obtained for the population, including 180 inbred lines of F12 generation wheat, derived from crosses (Norstar × Zagros) after testing with parents. LT50 is used as an effective selection criterion for identifying frost-tolerance genotypes. The progeny of individual F12 plants were used to evaluate LT50. Several QTLs related to wheat yield, including heading time period, 1000-seed weight, and number of surviving plants after overwintering, were identified. Single-marker analysis illustrated that four SSR markers with a total of 25% phenotypic variance determination were linked to LT50. Related QTLs were located on chromosomes 4A, 2B, and 3B. Common QTLs identified in two cropping seasons based on agronomical traits were two QTLs for heading time period, one QTL for 1000-seed weight, and six QTLs for number of surviving plants after overwintering. The four markers identified linked to LT50 significantly affected both LT50 and yield-related traits simultaneously. This is the first report to identify a major-effect QTL related to frost tolerance on chromosome 4A by the marker XGWM160. It is possible that some QTLs are closely related to pleiotropic effects that control two or more traits simultaneously, and this feature can be used as a factor to select frost-resistant lines in plant breeding programs.

Multiple loci with cumulative effects on late maturity α-amylase (LMA) in wheat

Main conclusionThe cumulative action of combinations of alleles at several loci on the wheat genome is associated with different levels of resistance to late maturity α-amylase in bread wheat.Resistance to late maturity α-amylase (LMA) in bread wheat (Triticum aestivum L.) involves a complex interaction between the genotype and the environment. Unfortunately, the incidence and severity of LMA expression is difficult to predict and once the trait has been triggered an unacceptably low falling number, high grain α-amylase may be the inevitable consequence. Wheat varieties with different levels of resistance to LMA have been identified but whilst some genetic loci have been reported, the mechanisms involved in resistance and the interaction between resistance loci requires further research. This investigation was focused on mapping resistance loci in populations derived by inter-crossing resistant wheat varieties or crossing resistant lines with a very susceptible line and then mapping quantitative trait loci. In addition to the previously reported locus on chromosome 7B for which a candidate gene has been proposed, loci were mapped on chromosomes 1B, 2A, 2B, 3A, 3B, 4A, 6A and 7D. These loci have limited effects on their own but have a cumulative effect in combination with each other. Further research will be required to determine the nature of the causal genes at these loci, to develop diagnostic markers and determine how the genes fit into the pathway that leads to the induction of α-AMY1 transcription in the aleurone of developing wheat grains. Depending on the target environmental conditions, different combinations of alleles may be required to achieve a low risk of LMA expression.

Fine mapping of KLW1 that conditions kernel weight mainly through regulating kernel length in wheat (Triticum aestivum L.).

KLW1 was localized to a 0.6 cM interval near the centromere of chromosome 4B and found to be dominant in conditioning longer kernels and higher kernel weight. Kernel weight is a major wheat yield component and affected by kernel dimensions, filling process and kernel density. Because of this complexity, the mechanism underlying kernel weight is still far from clear. Qtgw.nau-4B or KLW1 was a major kernel weight QTL identified in the Nanda2419 × Wangshuibai population. We showed that introduction of the Nanda2419 allele into elite cultivar Wenmai6 resulted in longer kernels as well as higher kernel weight, without affecting other traits such as spike number per plant, plant height, spike length, spikelet number per spike, and kernel number per spike. KLW1 was dominant in conditioning higher kernel weight and functioned mainly through affecting kernel length. Using F2 plants derived from KLW1 NIL, a high-density genetic map covering the QTL was constructed. KLW1 was consequently confined to the 0.6cM Xwgrc4219-Xwgrc4067 interval by evaluating the recombinant lines in three field trials. KLW1 is complementary to KT1, the QTL on chromosome 5A of Nanda2419 for thicker and heavier kernels, in producing larger kernels with higher commercial value, augmenting its usefulness in wheat breeding.

Relocation of Sr48 to Chromosome 2D Using an Alternative Mapping Population and Development of a Closely Linked Marker Using Diverse Molecular Technologies.

The Ug99-effective stem rust resistance gene Sr48 was mapped to chromosome 2A based on its repulsion linkage with Yr1 in an Arina/Forno recombinant inbred line (RIL) population. Attempts to identify markers closely linked to Sr48 using available genomic resources were futile. This study used an Arina/Cezanne F5:7 RIL population to identify markers closely linked with Sr48. Using the Arina/Cezanne DArTseq map, Sr48 was mapped on the short arm of chromosome 2D and it co-segregated with 12 markers. These DArTseq marker sequences were used for BlastN search to identify corresponding wheat chromosome survey sequence (CSS) contigs, and PCR-based markers were developed. Two simple sequence repeat (SSR) markers, sun590 and sun592, and two Kompetitive Allele-Specific PCR (KASP) markers were derived from the contig 2DS_5324961 that mapped distal to Sr48. Molecular cytogenetic analysis using sequential fluorescent in situ hybridization (FISH) and genomic in situ hybridization (GISH) identified a terminal translocation of chromosome 2A in chromosome 2DL of Forno. This translocation would have led to the formation of a quadrivalent involving chromosomes 2A and 2D in the Arina/Forno population, which would have exhibited pseudo-linkage between Sr48 and Yr1 in chromosome 2AL. Polymorphism of the closet marker sunKASP_239 among a set of 178 wheat genotypes suggested that this marker can be used for marker-assisted selection of Sr48.

Genetic analysis and exploration of major effect QTLs underlying oil content in peanut.

AhyHOF1, likely encoding a WRI1 transcription factor, plays critical roles in peanut oil synthesis. Although increasing the oil content of peanut to meet growing demand has long been a primary aim of breeding programs worldwide, the mining of genetic resources to achieve this objective has obviously lagged behind that of other oil crops. In the present study, we developed an advanced recombinant inbred line population containing 192 F9:11 families derived from parents JH5 and KX01-6. We then constructed a high-resolution genetic map covering 3,706.382cM, with an average length of 185.32cM per linkage group, using 2840 polymorphic SNPs. Two stable QTLs, qCOA08_1 and qCOA08_2 having the highest contributions to genetic variation (16.1% and 20.7%, respectively), were simultaneously detected in multiple environments and closely mapped within physical intervals of approximately 2.9Mb and 1.7Mb, respectively, on chromosome A08. In addition, combined analysis of whole-genome and transcriptome resequencing data uncovered a strong candidate gene encoding a WRI1 transcription factor and differentially expressed between the two parents. This gene, designated as High Oil Favorable gene 1 in Arachis hypogaea (AhyHOF1), was hypothesized to play roles in oil accumulation. Examination of near-inbred lines of #AhyHOF1/#Ahyhof1 provided further evidence that AhyHOF1 increases oil content, mainly by affecting the contents of several fatty acids. Taken together, our results provide valuable information for cloning the favorable allele for oil content in peanut. In addition, the closely linked polymorphic SNP markers within qCOA08_1 and qCOA08_2 loci may be useful for accelerating marker-assisted selection breeding of peanut.

Genome-wide association analysis of Fusarium crown rot resistance in Chinese wheat landraces

A novel locus for Fusarium crown rot (FCR) resistance was identified on chromosome 1B at 641.36-645.13Mb using GWAS and could averagely increase 39.66% of FCR resistance in a biparental population. Fusarium crown rot can cause considerable yield losses. Developing and growing resistance cultivars is one of the most effective approaches for controlling this disease. In this study, 361 Chinese wheat landraces were evaluated for FCR resistance, and 27 with the disease index lower than 30.00 showed potential in wheat breeding programs. Using a genome-wide association study approach, putative quantitative trait loci (QTL) for FCR resistance was identified. A total of 21 putative loci on chromosomes 1A, 1B, 2B, 2D, 3B, 3D, 4B, 5A, 5B, 7A, and 7B were significantly associated with FCR resistance. Among these, a major locus Qfcr.sicau.1B-4 was consistently identified among all the trials on chromosome 1B with the physical regions from 641.36 to 645.13Mb. A polymorphism kompetitive allele-specific polymerase (KASP) marker was developed and used to validate its effect in an F2:3 population consisting of 136 lines. The results showed the presence of this resistance allele could explain up to 39.66% of phenotypic variance compared to its counterparts. In addition, quantitative real-time polymerase chain reaction showed that two candidate genes of Qfcr.sicau.1B-4 were differently expressed after inoculation. Our study provided useful information for improving FCR resistance in wheat.

Two major quantitative trait loci control wheat dwarf virus resistance in four related winter wheat populations

Key messageQwdv.ifa-6A on chromosomes 6AL and Qwdv.ifa-1B on chromosome 1B are highly effective against wheat dwarf virus and act additively when combined.Wheat dwarf virus (WDV) is among the most damaging viral pathogens. Its prevalence has increased substantially in recent years, and it is predicted to increase even further due to global warming. There are limited options to control the virus. Growing resistant cultivars would safeguard crops, but most current wheat cultivars are highly susceptible. Thus, the aim of this study was to dissect the genetic architecture of WDV resistance in resistant germplasm and to identify quantitative trait loci (QTL) to support resistance breeding. QTL mapping was conducted using four related populations comprising 168, 105, 99 and 130 recombinant inbred lines. Populations were evaluated under field conditions for three years. Natural infestation was provoked by early autumn sowing. WDV symptom severity was visually assessed at two time points in spring. QTL analysis revealed two highly significant QTL with the major QTL Qwdv.ifa-6A mapping to the long arm of chromosome 6A between markers Tdurum_contig75700_411 (601,412,152 bp) and AX-95197581 (605,868,853 bp). Qwdv.ifa-6A descends from the Dutch experimental line SVP-72017 and was of high effect in all populations, explaining up to 73.9% of the phenotypic variance. The second QTL, Qwdv.ifa-1B, mapped to chromosome 1B and is putatively associated with the 1RS.1BL translocation, which was contributed by the CIMMYT line CM-82036. Qwdv.ifa-1B explained up to 15.8% of the phenotypic variance. Qwdv.ifa-6A and Qwdv.ifa-1B are among the first identified highly effective resistance QTL and represent valuable resources for improving WDV resistance in wheat.

Molecular Cytological Analysis and Specific Marker Development in Wheat-Psathyrostachys huashanica Keng 3Ns Additional Line with Elongated Glume.

Psathyrostachys huashanica Keng (2n = 2x = 14, NsNs) is an excellent gene resource for wheat breeding, which is characterized by early maturity, low plant height, and disease resistance. The wheat-P. huashanica derivatives were created by the elite genes of P. huashanica and permeate into common wheat through hybridization. Among them, a long-glume material 20JH1155 was identified, with larger grains and longer spike than its parents. In the present study, the methods of cytological observation, GISH, and sequential FISH analysis showed that 20JH1155 contained 21 pairs of wheat chromosomes and a pair of P. huashanica. There were some differences in 5A and 7B chromosomes between 20JH1155 and parental wheat 7182. Molecular marker, FISH, and sequence cloning indicated 20JH1155 alien chromosomes were 3Ns of P. huashanica. In addition, differentially expressed genes during immature spikelet development of 20JH1155 and 7182 and predicted transcription factors were obtained by transcriptome sequencing. Moreover, a total of 7 makers derived from Ph#3Ns were developed from transcriptome data. Taken together, the wheat-P. huashanica derived line 20JH1155 provides a new horizon on distant hybridization of wheat and accelerates the utilization of genes of P. huashanica.

Genome-wide association study for grain zinc concentration in bread wheat (Triticum aestivum L.).

Zinc (Zn) deficiency causes serious diseases in people who rely on cereals as their main food source. However, the grain zinc concentration (GZnC) in wheat is low. Biofortification is a sustainable strategy for reducing human Zn deficiency. In this study, we constructed a population of 382 wheat accessions and determined their GZnC in three field environments. Phenotype data was used for a genome-wide association study (GWAS) using a 660K single nucleotide polymorphism (SNP) array, and haplotype analysis identified an important candidate gene for GZnC. We found that GZnC of the wheat accessions showed an increasing trend with their released years, indicating that the dominant allele of GZnC was not lost during the breeding process. Nine stable quantitative trait loci (QTLs) for GZnC were identified on chromosomes 3A, 4A, 5B, 6D, and 7A. And an important candidate gene for GZnC, namely, TraesCS6D01G234600, and GZnC between the haplotypes of this gene showed, significant difference (P ≤ 0.05) in three environments. A novel QTL was first identified on chromosome 6D, this finding enriches our understanding of the genetic basis of GZnC in wheat. This study provides new insights into valuable markers and candidate genes for wheat biofortification to improve GZnC.

Physiological and genetic analysis of a mapping population responsiveness to plant growth-promoting Azospirillum in wheat

Azospirillum brasilense is a plant growth-promoting rhizobacteria (PGPR) with the potential of being employed as an inoculant to decrease the use of chemical fertilizers. We investigated the ef fect of A. brasilense inoculation on a doubled haploid population derived from Opata / WSHD67.2(257) cross and detected Quantitative Trait Loci (QTL) for seven agronomic traits. The population was segregated, concerning their response to inoculation, into three subgroups: neutral, positive, and negative in a proportion of 60:25:15. A total of 18 major QTL and 83 minor QTL controlled the expression of measured traits. Nineteen QTL showed pleiotropic characteristics; chromosomes 5A, 7A, 7B, and 7D were distinguished as those with QTL controlling four of the seven phenotypes measured. The sequences of nearest markers to major QTL detected synteny to rice sequences that codified for at least 38 candidate genes described and discussed as a first step to understanding the interaction of wheat with A. brasilense.

Utilizing Genomics to Characterize the Common Oat Gene Pool—The Story of More Than a Century of Polish Breeding

This study was undertaken to investigate the diversity and population structure of 487 oat accessions, including breeding lines from the ongoing programs of the three largest Polish breeding companies, along with modern and historical Polish and foreign cultivars. The analysis was based on 7411 DArTseq-derived SNPs distributed among three sub-genomes (A, C, and D). The heterogeneity of the studied material was very low, as only cultivars and advanced breeding lines were examined. Principal component analysis (PCA), principal coordinate analysis (PCoA), and cluster and STRUCTURE analyses found congruent results, which show that most of the examined cultivars and materials from Polish breeding programs formed major gene pools, that only some accessions derived from Strzelce Plant Breeding, and that foreign cultivars were outside of the main group. During the 120 year oat breeding process, only 67 alleles from the old gene pool were lost and replaced by 67 new alleles. The obtained results indicate that no erosion of genetic diversity was observed within the Polish native oat gene pool. Moreover, current oat breeding programs have introduced 673 new alleles into the gene pool relative to historical cultivars. The analysis also showed that most of the changes in relation to historical cultivars occurred within the A sub-genome with emphasis on chromosome 6A. The targeted changes were the rarest in the C sub-genome. This study showed that Polish oat breeding based mainly on traditional breeding methods-although focused on improving traits typical to this crop, i.e., enhancing the grain yield and quality and improving adaptability-did not significantly narrow the oat gene pool and in fact produced cultivars that are not only competitive in the European market but are also reservoirs of new alleles that were not found in the analyzed foreign materials.

Nutritional Genomic Approach for Improving Grain Protein Content in Wheat.

Grain protein content (GPC) is a key aspect of grain quality, a major determinant of the flour functional properties and grain nutritional value of bread wheat. Exploiting diverse germplasms to identify genes for improving crop performance and grain nutritional quality is needed to enhance food security. Here, we evaluated GPC in a panel of 255 Triticum aestivum L. accessions from 27 countries. GPC determined in seeds from three consecutive crop seasons varied from 8.6 to 16.4% (11.3% on average). Significant natural phenotypic variation in GPC among genotypes and seasons was detected. The population was evaluated for the presence of the trait-linked single nucleotide polymorphism (SNP) markers via a genome-wide association study (GWAS). GWAS analysis conducted with calculated best linear unbiased estimates (BLUEs) of phenotypic data and 90 K SNP array using the fixed and random model circulating probability unification (FarmCPU) model identified seven significant genomic regions harboring GPC-associated markers on chromosomes 1D, 3A, 3B, 3D, 4B and 5A, of which those on 3A and 3B shared associated SNPs with at least one crop season. The verified SNP-GPC associations provide new promising genomic signals on 3A (SNPs: Excalibur_c13709_2568 and wsnp_Ku_c7811_13387117) and 3B (SNP: BS00062734_51) underlying protein improvement in wheat. Based on the linkage disequilibrium for significant SNPs, the most relevant candidate genes within a 4 Mbp-window included genes encoding a subtilisin-like serine protease; amino acid transporters; transcription factors; proteins with post-translational regulatory functions; metabolic proteins involved in the starch, cellulose and fatty acid biosynthesis; protective and structural proteins, and proteins associated with metal ions transport or homeostasis. The availability of molecular markers within or adjacent to the sequences of the detected candidate genes might assist a breeding strategy based on functional markers to improve genetic gains for GPC and nutritional quality in wheat.