Wheat Doubled Haploid Population Research Articles

Registration of the PI 173438/WA 8137 wheat doubled haploid mapping population

AbstractA doubled haploid mapping population was developed from a cross between the hard red winter wheat (Triticum aestivum L. subsp. aestivum) landrace PI 173438 and WA 8137, a soft white winter wheat breeding line developed by the Washington State University winter wheat breeding program in Pullman, WA. The PI 173438/WA 8137 (Reg. no. MP‐16, NSL 543858 MAP) population consists of 437 individuals, with 358 of these individuals used to identify quantitative trait loci associated with snow mold (Typhula spp.) tolerance in PI 173438. Genotypic information was gathered on these individuals using genotype‐by‐sequencing and processed using a pipeline developed by the USDA Eastern Regional Small Grains Genotyping Laboratory. Twenty‐three linkage groups covering the whole genome with groups for the long and short arms of chromosomes 3D and 7D were constructed using 4,029 single nucleotide polymorphisms from the sequenced individuals. Quantitative trait loci associated with snow mold tolerance and snow mold recovery attributed to PI 173438 were successfully identified in this population. PI 173438 has also been used to identify other traits associated with snow mold tolerance, such as freezing tolerance and carbohydrate reserves, and has been important in research investigating dwarf and common bunt. This population may continue to expand current knowledge in these areas, and, given the landrace status of PI 173438, the population may be useful in identifying other novel traits of interest.

Grain protein concentration at elevated [CO2] is determined by genotype dependent variations in nitrogen remobilisation and nitrogen utilisation efficiency in wheat

Predictions for wheat grown under future climate conditions indicate a decline in grain protein concentration accompanied with an increase in yield due to increasing carbon dioxide concentrations. Currently, there is a lack of understanding as to the complete mechanism that governs the response of grain protein concentration (GPC) to elevated carbon dioxide (e[CO2]). We investigated the GPC of 18 wheat genotypes from a doubled haploid wheat population and the two parental genotypes, Kukri and RAC0875. In addition, other nitrogen and biomass related traits were analysed to further elucidate which traits are connected with the decline in GPC. Wheat was grown under ambient and elevated [CO2] in an environmentally controlled glasshouse. Plant nitrogen and biomass accumulation were measured at anthesis and maturity. We found that GPC declined under e[CO2] and that the response of GPC to e[CO2] was negatively correlated with nitrogen utilisation efficiency and harvest index. The extent that total biomass (anthesis), harvest index, photosynthesis, nitrogen utilisation and remobilisation efficiency, total nitrogen remobilisation and post-anthesis nitrogen uptake impacted GPC in response to e[CO2] varied across genotype, suggesting that multiple mechanisms are responsible for GPC decline at e[CO2] and that these mechanisms are effected differentially across genotypes.

QTL Mapping of Adult Plant Resistance to Stripe Rust in a Doubled Haploid Wheat Population.

Stripe rust caused by Puccinia striiformis Westend. f. sp. tritici. is a major bread wheat disease worldwide with yield losses of up to 100% under severe disease pressure. The deployment of resistant cultivars with adult plant resistance to the disease provides a long-term solution to stripe rust of wheat. An advanced line from the International Winter Wheat Improvement Program (IWWIP) 130675 (Avd/Vee#1//1-27-6275/Cf 1770/3/MV171-C-17466) showed a high level of adult plant resistance to stripe rust in the field. To identify the adult plant resistance genes in this elite line, a mapping population of 190 doubled haploid (DH) lines was developed from a cross between line 130675 and the universal stripe rust-susceptible variety Avocet S. The DH population was evaluated at precision wheat stripe rust phenotyping platform, in Izmir during 2019, 2020, and 2021 cropping seasons under artificial inoculations. Composite interval mapping (CIM) identified two stable QTLs QYr.rcrrc-3B.1, and QYr.rcrrc-3B.2, which were detected in multiple years. In addition to these two QTLs, five more QTLs, QYr.rcrrc-1B, QYr.rcrrc-2A, QYr.rcrrc-3A, QYr.rcrrc-5A, and QYr.rcrrc-7D, were identified, which were specific to the cropping year (environment). All QTLs were derived from the resistant parent, except QYr.rcrrc-3A. The significant QTLs explained 3.4–20.6% of the phenotypic variance. SNP markers flanking the QTL regions can be amenable to marker-assisted selection. The best DH lines with high yield, end-use quality, and stripe rust resistance can be used for further selection for improved germplasm. SNP markers flanking the QTL regions can aid in identifying such lines.

Identification of QTL and underlying genes for root system architecture associated with nitrate nutrition in hexaploid wheat

The root system architecture (RSA) of a crop has a profound effect on the uptake of nutrients and consequently the potential yield. However, little is known about the genetic basis of RSA and resource adaptive responses in wheat (Triticum aestivum L.). Here, a high-throughput germination paper-based plant phenotyping system was used to identify seedling traits in a wheat doubled haploid mapping population, Savannah×Rialto. Significant genotypic and nitrate-N treatment variation was found across the population for seedling traits with distinct trait grouping for root size-related traits and root distribution-related traits. Quantitative trait locus (QTL) analysis identified a total of 59 seedling trait QTLs. Across two nitrate treatments, 27 root QTLs were specific to the nitrate treatment. Transcriptomic analyses for one of the QTLs on chromosome 2D, which was found under low nitrate conditions, revealed gene enrichment in N-related biological processes and 28 differentially expressed genes with possible involvement in a root angle response. Together, these findings provide genetic insight into root system architecture and plant adaptive responses to nitrate, as well as targets that could help improve N capture in wheat.

Yield-Related QTL Clusters and the Potential Candidate Genes in Two Wheat DH Populations.

In the present study, four large-scale field trials using two doubled haploid wheat populations were conducted in different environments for two years. Grain protein content (GPC) and 21 other yield-related traits were investigated. A total of 227 QTL were mapped on 18 chromosomes, which formed 35 QTL clusters. The potential candidate genes underlying the QTL clusters were suggested. Furthermore, adding to the significant correlations between yield and its related traits, correlation variations were clearly shown within the QTL clusters. The QTL clusters with consistently positive correlations were suggested to be directly utilized in wheat breeding, including 1B.2, 2A.2, 2B (4.9–16.5 Mb), 2B.3, 3B (68.9–214.5 Mb), 4A.2, 4B.2, 4D, 5A.1, 5A.2, 5B.1, and 5D. The QTL clusters with negative alignments between traits may also have potential value for yield or GPC improvement in specific environments, including 1A.1, 2B.1, 1B.3, 5A.3, 5B.2 (612.1–613.6 Mb), 7A.1, 7A.2, 7B.1, and 7B.2. One GPC QTL (5B.2: 671.3–672.9 Mb) contributed by cultivar Spitfire was positively associated with nitrogen use efficiency or grain protein yield and is highly recommended for breeding use. Another GPC QTL without negatively pleiotropic effects on 2A (50.0–56.3 Mb), 2D, 4D, and 6B is suggested for quality wheat breeding.

High density genetic mapping of stripe rust resistance in a ‘Strongfield’ / ‘Blackbird’ durum wheat population

Resistance breeding is an effective strategy against wheat stripe (yellow) rust caused by Puccinia striiformis f. sp. tritici (Pst). To identify and map quantitative trait loci (QTL) associated with stripe rust resistance, a durum wheat doubled haploid population (n = 87) derived from ‘Strongfield/Blackbird’ was evaluated for disease severity near Toluca, Mexico (2017–2019) and Lethbridge, Canada (2016–2019). The population was genotyped with the wheat 90 K Illumina iSelect single nucleotide polymorphism (SNP) array and simple sequence repeat (SSR) markers, and QTL analysis was performed with MapQTL 6. We identified stripe rust-resistance QTL contributed by ‘Blackbird’ on chromosomes 3A (2 loci, designated QYr.spa-3A.1, QYr.spa-3A.2) and 5B (QYr.spa-5B), and ‘Strongfield’ on 2B (QYr.spa-2B). All seem to represent QTL not reported previously. The QYr.spa-3A.2 was most consistently effective against Pst races across the Lethbridge and Toluca nurseries. With a LOD value of 4.9, QYr.spa-3A.2 explained a maximum phenotypic variation of 22.7% observed at the Toluca 2019 nursery. The QYr.spa-2B from ‘Strongfield’ and QYr.spa-3A.1 from ‘Blackbird’ expressed in multiple years at Toluca but were not detected at Lethbridge. QYr.spa-5B was identified in the Lethbridge 2016 environment. The identified QTL should be valuable in diversifying resistance genes used in breeding durum wheat cultivars with stripe rust resistance. ‘Blackbird’ was particularly useful for introducing the new QTL QYr.spa-3A.2 resistance that is effective in Canada and Mexico into traditional durum wheat germplasm. SNP markers associated with QTL will have application in marker-assisted breeding of resistance to Pst in durum wheat.

Characterization of vegetative vigor of two doubled-haploid wheat populations

ABSTRACT Major and urgent interventions are needed in improving wheat (Triticum aestivum L.) grain yield to avert the predicted global crisis of food insecurity. Two doubled-haploid (DH) wheat populations were evaluated for normalized difference vegetative index (NDVI), vegetative index ratio (VI RATIO), plant height (PH) and ear length (EL) in four environments with an aim to select DH lines with strong vegetative vigor. Genotypes and environments showed significant (p < 0.001) effects and only PH showed a significant (p < 0.018) genotype-by-environment interaction. The NDVI vs. VI RATIO showed a negative correlation (r2 = −1 – −0.99) in all environments. Positive correlations existed for NDVI vs. PH (r2 = 0.31– 0.40) and PH vs. EL (r2 =0.41– 0.54), suggesting a possible simultaneous improvement. Almost 23% of DH lines with precise, fixed, maximum variation, and strong vegetative vigor formed potential material for efficiently enhancing yield potential of wheat, which in turn could improve yield.

Mapping of Major Fusarium Head Blight Resistance from Canadian Wheat cv. AAC Tenacious.

Fusarium head blight (FHB) is one of the most devastating wheat disease due to its direct detrimental effects on grain-yield, quality and marketability. Resistant cultivars offer the most effective approach to manage FHB; however, the lack of different resistance resources is still a major bottleneck for wheat breeding programs. To identify and dissect FHB resistance, a doubled haploid wheat population produced from the Canadian spring wheat cvs AAC Innova and AAC Tenacious was phenotyped for FHB response variables incidence and severity, visual rating index (VRI), deoxynivalenol (DON) content, and agronomic traits days to anthesis (DTA) and plant height (PHT), followed by single nucleotide polymorphism (SNP) and simple sequence repeat (SSR) marker genotyping. A high-density map was constructed consisting of 10,328 markers, mapped on all 21 chromosomes with a map density of 0.35 cM/marker. Together, two major quantitative trait loci for FHB resistance were identified on chromosome 2D from AAC Tenacious; one of these loci on 2DS also colocated with loci for DTA and PHT. Another major locus for PHT, which cosegregates with locus for low DON, was also identified along with many minor and epistatic loci. QTL identified from AAC Tenacious may be useful to pyramid FHB resistance.

Mapping Quantitative Trait Loci for Agronomic Traits in Winter Wheat under Different Soil Moisture Levels

Due to variable moisture conditions in the U.S. Great Plains, it is important to understand genetic control of crop traits under a range of soil moisture levels. Our objective was to identify quantitative trait loci (QTL) for yield, phenology, and morphological traits in wheat (Triticum aestivum L.) under different soil moisture conditions. Field evaluation of a winter wheat doubled haploid population (n = 185) derived from a cross between CO940610 and ‘Platte’ was carried out in Fort Collins and Greeley, Colorado, USA in 2007–2008 and 2008–2009, respectively. At each location, trials were grown under moderate drought stress and fully irrigated conditions. A total of 33 QTL for 11 traits was detected in two or more environments. A cluster of QTL for nine traits was found on chromosome 2B in the vicinity of the photoperiod response gene Ppd-B1. Other stable QTL clusters were detected on chromosome 6A and near the vernalization response gene Vrn-D3 on chromosome 7D. A QTL for grain yield on chromosome 5A was detected in three environments. With minor exceptions, the large-effect QTL were detected in both the water limited and fully irrigated environments, rather than being detected only under specific moisture levels.

Mapping of novel salt tolerance QTL in an Excalibur\u2009\xd7\u2009Kukri doubled haploid wheat population

Key messageNovel QTL for salinity tolerance traits have been detected using non-destructive and destructive phenotyping in bread wheat and were shown to be linked to improvements in yield in saline fields.Soil salinity is a major limitation to cereal production. Breeding new salt-tolerant cultivars has the potential to improve cereal crop yields. In this study, a doubled haploid bread wheat mapping population, derived from the bi-parental cross of Excalibur × Kukri, was grown in a glasshouse under control and salinity treatments and evaluated using high-throughput non-destructive imaging technology. Quantitative trait locus (QTL) analysis of this population detected multiple QTL under salt and control treatments. Of these, six QTL were detected in the salt treatment including one for maintenance of shoot growth under salinity (QG(1–5).asl-7A), one for leaf Na+ exclusion (QNa.asl-7A) and four for leaf K+ accumulation (QK.asl-2B.1, QK.asl-2B.2, QK.asl-5A and QK:Na.asl-6A). The beneficial allele for QG(1–5).asl-7A (the maintenance of shoot growth under salinity) was present in six out of 44 mainly Australian bread and durum wheat cultivars. The effect of each QTL allele on grain yield was tested in a range of salinity concentrations at three field sites across 2 years. In six out of nine field trials with different levels of salinity stress, lines with alleles for Na+ exclusion and/or K+ maintenance at three QTL (QNa.asl-7A, QK.asl-2B.2 and QK:Na.asl-6A) excluded more Na+ or accumulated more K+ compared to lines without these alleles. Importantly, the QK.asl-2B.2 allele for higher K+ accumulation was found to be associated with higher grain yield at all field sites. Several alleles at other QTL were associated with higher grain yields at selected field sites.

QTL analysis for stomatal density and size in wheat spike organ

Plant changes its own photosynthetic rate and transpiration rate through regulating stomatal aperture, stomatal density and stomatal distribution. In this study, stomatal density, length and width of wheat spike organs, including palea, lemma and glume, at the third day after flowering were investigated, using a wheat doubled haploid population from a cross of Hanxuan10 and Lumai 14 in 2012 and 2013. And quantitative trait loci (QTL) of the above three traits were analyzed. There were stomata in the abaxial surface of palea, lemma and glume, but not in the adaxial surface for DH lines and their parents. A total of fourteen additive QTLs for those traits were identified. On the marker interval Xgwm291-Xgwm410-WMC340 on chromosome 5A, QMLsd-5A for stomatal density at middle of lemma and QDGsd-5A for stomatal density at down of glume, and QAGsl-5A for stomatal length at apex of glume were detected in 2012 and 2013，but with opposite direction of additive effect. In the previous study, Qsd-5A.3 and Qsd-5A.4 for stomatal density of wheat leaf, and Qsl-5A.1 for stomatal length of wheat leaf were also detected at the same marker region, and also with opposite direction of additive effect. These findings provided genetic basis for significantly negative correlation between stomatal density and length for wheat leaf and spike organs, but also implied stomatal density and length for wheat leaf and spike organs may be governed by the same or pleiotropic genes.

Selection of drought tolerant and sensitive genotypes from wheat DH population

Drought has significant effect on wheat production by decreasing grain yield. Phenotyping the populations is a useful tool for understanding the interactions between phenotype and genotype. 135 doubled haploid (DH) genotypes and their parental varieties Plainsman (Pl) and Cappelle Desprez (CD) were phenotyped in glasshouse under well-watered (WW) and drought-stress (DS) conditions. The response of plant height, heading time, aboveground biomass, grain yield, root dry mass harvest index (HI) under both conditions, and stress tolerance index (STI) and water consumption in WW conditions was studied. We found 20% decrease in the plant growth, 66% decrease in the aboveground biomass, and 77% decrease in the grain yield. Under WW conditions, high water consumption was not related to high yields, STI, and HI. The tolerant and the sensitive genotypes were selected. In the WW and water consumption treatment, the sensitive genotype group had better grain yield performance, but under DS, the tolerant group had higher grain yield. The average yield loss was 59% in the tolerant group compared to the WW treatment, and the sensitive yield loss was 68%. Correlation was found between the grain yield and root dry mass in the tolerant group. There was significant difference between the tolerant and sensitive groups on water consumption, as the sensitive genotypes had higher water need. We found strong positive correlation between the water consumption and the grain yield in the tolerant group. This study showed that the tolerant genotypes had improved water regulating efficiency.

Quantifying rooting at depth in a wheat doubled haploid population with introgression from wild emmer.

Background and AimsThe genetic basis of increased rooting below the plough layer, post-anthesis in the field, of an elite wheat line (Triticum aestivum ‘Shamrock’) with recent introgression from wild emmer (T. dicoccoides), is investigated. Shamrock has a non-glaucous canopy phenotype mapped to the short arm of chromosome 2B (2BS), derived from the wild emmer. A secondary aim was to determine whether genetic effects found in the field could have been predicted by other assessment methods.MethodsRoots of doubled haploid (DH) lines from a winter wheat (‘Shamrock’ × ‘Shango’) population were assessed using a seedling screen in moist paper rolls, in rhizotrons to the end of tillering, and in the field post-anthesis. A linkage map was produced using single nucleotide polymorphism markers to identify quantitative trait loci (QTLs) for rooting traits.Key ResultsShamrock had greater root length density (RLD) at depth than Shango, in the field and within the rhizotrons. The DH population exhibited diversity for rooting traits within the three environments studied. QTLs were identified on chromosomes 5D, 6B and 7B, explaining variation in RLD post-anthesis in the field. Effects associated with the non-glaucous trait on RLD interacted significantly with depth in the field, and some of this interaction mapped to 2BS. The effect of genotype was strongly influenced by the method of root assessment, e.g. glaucousness expressed in the field was negatively associated with root length in the rhizotrons, but positively associated with length in the seedling screen.ConclusionsTo our knowledge, this is the first study to identify QTLs for rooting at depth in field-grown wheat at mature growth stages. Within the population studied here, our results are consistent with the hypothesis that some of the variation in rooting is associated with recent introgression from wild emmer. The expression of genetic effects differed between the methods of root assessment.

Time-course expression QTL-atlas of the global transcriptional response of wheat to Fusarium graminearum.

SummaryFusarium head blight is a devastating disease of small grain cereals such as bread wheat (Triticum aestivum). The pathogen switches from a biotrophic to a nectrotrophic lifestyle in course of disease development forcing its host to adapt its defence strategies. Using a genetical genomics approach, we illustrate genome‐wide reconfigurations of genetic control over transcript abundances between two decisive time points after inoculation with the causative pathogen Fusarium graminearum. Whole transcriptome measurements have been recorded for 163 lines of a wheat doubled haploid population segregating for several resistance genes yielding 15 552 at 30 h and 15 888 eQTL at 50 h after inoculation. The genetic map saturated with transcript abundance‐derived markers identified of a novel QTL on chromosome 6A, besides the previously reported QTL Fhb1 and Qfhs.ifa‐5A. We find a highly different distribution of eQTL between time points with about 40% of eQTL being unique for the respective assessed time points. But also for more than 20% of genes governed by eQTL at either time point, genetic control changes in time. These changes are reflected in the dynamic compositions of three major regulatory hotspots on chromosomes 2B, 4A and 5A. In particular, control of defence‐related biological mechanisms concentrated in the hotspot at 4A shift to hotspot 2B as the disease progresses. Hotspots do not colocalize with phenotypic QTL, and within their intervals no higher than expected number of eQTL was detected. Thus, resistance conferred by either QTL is mediated by few or single genes.

Development of genotyping by sequencing (GBS)- and array-derived SNP markers for stem rust resistance gene Sr42

The stem rust fungus, particularly race TTKSK (Ug99), poses a serious threat to world wheat production. Gene Sr42 or SrCad (which could be the same gene or an allele ofSr42) iseffective against race TTKSK. However, known genetic markers for Sr42 are mostly SSR markers which are generally labor intensive to use. In this study, we mapped a race TTKSK resistance gene derived from PI 595667 at the same locus as Sr42 on chromosome 6DS. Based on position, pedigree and infection-type information, we propose that this gene is SrCad (Sr42). We enriched the genetic map for the Sr42 region using genotyping by sequencing (GBS) and array-derived SNP markers. In total, 21 SNP markers were discovered, spanning a genetic distance of 27.2 cM. Nine of them are derived from GBS and twelve from the Illumina iSelect 90K SNP assay. Ten of the twenty-one SNP markers are closely linked (\2.2 cM, or co-segregating) with Sr42. We converted five of the closely linked SNP markers into uniplex KASP assays which will better facilitate marker-assisted selection. We validated the KASP assay in a doubled haploid wheat population derived from a three-way cross between accessions PI 410954, RB07, and Faller that shared an uncharacter- ized resistance gene mapped at approximately the same locus as PI 595667. The development of closely linked (co-segregating), codominant, sequence-based SNP assays will aid marker-assisted selection and map-based cloning of Sr42.

Genetic basis of traits related to stomatal conductance in wheat cultivars in response to drought stress

The genetic basis of stomatal conductance (g s), net photosynthetic rate (P N), and transpiration rate (E) was explored by using a wheat doubled haploid population from a cross of Hanxuan10 and Lumai 14. The above three traits were evaluated in wheat flag leaves at 10, 20, 30 days after anthesis under drought stress (DS) and well-watered (WW), and quantitative trait loci (QTL) were analyzed. Expression of the traits during the grain filling stage showed downward trends under both conditions, but expression of three phenotypes were stronger under WW than those under DS. Extremely significant positive correlations were established among the traits at all growth stages under both conditions. A total of 18 additive QTLs for those traits were identified on 10 chromosomes. Among them, two batches of nine additive QTLs were associated with the target traits under DS and WW, respectively. Two additive QTLs for g s and E, two for g s and P N, six for g s, P N, and E clustered at the same or near the region (colocation) of chromosomes 4A, 2B, and 7B, respectively. This provided genetic basis for close phenotype correlations among g s, P N, and E. Furthermore, QTLs for g s, P N, and E near Xgwm577 and Xgwm611 located on 7B chromosome were linked to previously reported QTLs regulating a SPAD value and the chlorophyll a/b ratio under dark-induced condition. This finding indicated that these QTLs on 7B chromosome might be involved in the process of wheat leaf senescence.

QTL for resistance to root lesion nematode (Pratylenchus thornei) from a synthetic hexaploid wheat source.

A whole genome average interval mapping approach identified eight QTL associated with P. thornei resistance in a DH population from a cross between the synthetic-derived wheat Sokoll and cultivar Krichauff. Pratylenchus thornei are migratory nematodes that feed and reproduce within the wheat root cortex, causing cell death (lesions) resulting in severe yield reductions globally. Genotypic selection using molecular markers closely linked to Pratylenchus resistance genes will accelerate the development of new resistant cultivars by reducing the need for laborious and expensive resistance phenotyping. A doubled haploid wheat population (150 lines) from a cross between the synthetic-derived cultivar Sokoll (P. thornei resistant) and cultivar Krichauff (P. thornei moderately susceptible) was used to identify quantitative trait loci (QTL) associated with P. thornei resistance. The resistance identified in the glasshouse was validated in a field trial. A genetic map was constructed using Diversity Array Technology and the QTL regions identified were further targeted with simple sequence repeat (SSR) and single-nucleotide polymorphism (SNP) markers. Six significant and two suggestive P. thornei resistance QTL were detected using a whole genome average interval mapping approach. Three QTL were identified on chromosome 2B, two on chromosome 6D, and a single QTL on each of chromosomes 2A, 2D and 5D. The QTL on chromosomes 2BS and 6DS mapped to locations previously identified to be associated with Pratylenchus resistance. Together, the QTL on 2B (QRlnt.sk-2B.1-2B.3) and 6D (QRlnt.sk-6D.1 and 6D.2) explained 30 and 48% of the genotypic variation, respectively. Flanking PCR-based markers based on SSRs and SNPs were developed for the major QTL on 2B and 6D and provide a cost-effective high-throughput tool for marker-assisted breeding of wheat with improved P. thornei resistance.

Control of late maturity alpha-amylase in wheat by the dwarfing gene Rht-D1b and genes on the 1B/1R translocation

The occurrence of late maturity alpha-amylase (LMA) was investigated using two doubled haploid wheat populations segregating for the dwarfing gene Rht-D1b and the 1B/1R translocation. Genotypes were assessed in the field and in controlled environments where a cold-shock treatment was used to induce LMA. Results from field-grown genotypes from the cross Spark × Rialto suggest that the absence of Rht-D1b or the presence of the 1B/1R translocation increases the expression of LMA.These two genetic factors were found to act independently and to have a positive interaction (complementary epistasis). In Option × Potent genotypes fixed for Rht-D1b, the 1B/1R effect was similar to that seen in the equivalent Spark × Rialto genotypes. Under controlled environment conditions, genotypes with the 1B/1R translocation showed a higher occurrence of LMA under both control and cold-shock conditions. 1B/1R was present in the majority of genotypes expressing LMA under control and cold-shock conditions. The results point to the novel finding that the 1B/1R translocation increases the expression of alpha-amylase in LMA-prone germplasm independently of effects of Rht-D1b, whereas previously it had been thought to act by a modification of the Rht-D1b effect.

QTLs for water absorption and flour yield identified in the doubled haploid wheat population Lang/QT8766

Two key quality traits in milling wheat are flour yield (FY) and water absorption (WA). Ideally, breeders would prefer to use markers to select promising lines rather than time consuming rheology tests. In this study, we measured FY and WA on a wheat mapping population (Lang/QT8766) of 162 individuals grown in two replicated field experiments at three locations over 2 years. We also carried out near infrared reflectance spectroscopy (NIRS) predictions on the grain for these traits to see if NIRS phenotypic data could provide useful mapping results when compared to the reference phenotypic data. Several common QTLs were identified for FY and WA by both sets of data. The QTL on chromosome 4D was a consistently recurring QTL region for both traits. The QTL on chromosome 2A was positively linked to protein content which was supported by genetic correlation data. The results also indicated it was possible to obtain useful phenotypic data for mapping FY and WA using NIRS data. This would save time and costs as NIRS is quicker and cheaper than current rheology methods.

Quantitative genetic analysis and mapping of leaf angle in durum wheat

The leaf erectness profile has been used to optimize plant architecture since erect leaves can enhance photosynthesis and dry matter production by greater sunlight capture. Brassinosteroid is a recent class of phytohormones that has been related to a more erect profile. There are no reports in the literature of the genetic variability of leaf angle in doubled haploid durum wheat populations; most studies on leaf angle have focused on the inheritance. Our aim was to study the genetic variation in flag and penultimate leaf angle in a durum wheat doubled haploid mapping population, identifying and mapping quantitative trait loci influencing leaf angle. An F(1)-derived doubled haploid population of 89 lines from the cross Strongfield/Blackbird was used to construct a genetic map using 423 molecular marker loci. Two greenhouse experiments and one field test were conducted using an alpha lattice in a randomized complete block design with three replicates. The leaf angle was measured on flag and penultimate leaf with a protractor at three different growth stages. The results indicated poor to moderate correlations between the position of the leaf angle and the growth stage. Transgressive segregation beyond Strongfield and Blackbird of leaf angle was observed for all environments. Putative trait loci were identified on chromosomes 2A, 2B, 3A, 3B, 4B, 5B and 7A. This work helps to understand the genetics of leaf angle in durum wheat.