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Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The likelihood of success in developing modern cultivars depend on multiple factors, including the identification of suitable parents to initiate new crosses, and characterizations of genomic regions associated with target traits. The objectives of the present study were to (a) determine the best economic weights of four major wheat diseases (leaf spot, common bunt, leaf rust, and stripe rust) and grain yield for multi-trait restrictive linear phenotypic selection index (RLPSI), (b) select the top 10% cultivars and lines (hereafter referred as genotypes) with better resistance to combinations of the four diseases and acceptable grain yield as potential parents, and (c) map genomic regions associated with resistance to each disease using genome-wide association study (GWAS). A diversity panel of 196 spring wheat genotypes was evaluated for their reaction to stripe rust at eight environments, leaf rust at four environments, leaf spot at three environments, common bunt at two environments, and grain yield at five environments. The panel was genotyped with the Wheat 90K SNP array and a few KASP SNPs of which we used 23,342 markers for statistical analyses. The RLPSI analysis performed by restricting the expected genetic gain for yield displayed significant (p < 0.05) differences among the 3125 economic weights. Using the best four economic weights, a subset of 22 of the 196 genotypes were selected as potential parents with resistance to the four diseases and acceptable grain yield. GWAS identified 37 genomic regions, which included 12 for common bunt, 13 for leaf rust, 5 for stripe rust, and 7 for leaf spot. Each genomic region explained from 6.6 to 16.9% and together accounted for 39.4% of the stripe rust, 49.1% of the leaf spot, 94.0% of the leaf rust, and 97.9% of the common bunt phenotypic variance combined across all environments. Results from this study provide valuable information for wheat breeders selecting parental combinations for new crosses to develop improved germplasm with enhanced resistance to the four diseases as well as the physical positions of genomic regions that confer resistance, which facilitates direct comparisons for independent mapping studies in the future. [ABSTRACT FROM AUTHOR]

Grain protein concentration (GPC) is considered one of the most important quality factors, and it has remained a major culling criterion in the Canadian wheat cultivar development and registration process. However, grain protein composition also plays a critical role in determining the end-use quality of cereal-based products. The objective of this study was to determine whether high-yielding, lower protein Canada Western Red Spring (CWRS) analog wheat lines can exhibit acceptable baking properties (comparable with CWRS cultivars) under contrasting soil nitrogen levels. Five CWRS-analog lines together with four CWRS and one Canada Prairie Spring Red wheat cultivar, representing wide ranges of quality and grain yield potential, were assessed for agronomic and quality traits in multi-environment trials at three locations and five nitrogen fertilizer rates. CWRS analog lines produced significantly higher grain yield and, on average, 0.9% less GPC than the CWRS cultivars. Despite the lower GPC, CWRS-analog lines such as W07786 exhibited suitable and stable baking performance across all nitrogen levels. Based on the genotype × trait biplot analysis, CWRS-analog baking properties were mainly associated with sodium dodecyl sulfate sedimentation and flour water absorption. Our findings revealed that it is possible to develop wheat cultivars with up to 15% higher grain yield than modern CWRS cultivars and comparable end-use characteristics by reducing current GPC requirements (by up to 1%) while simultaneously selecting for improved baking attributes. This would facilitate an increase in CWRS grain yield genetic gains while maintaining favorable end-use quality and improving the crop competitiveness in western Canada. On estime que la teneur en protéines du grain (TPG) est l'un des paramètres les plus importants de la qualité et elle demeure un des principaux critères d'élimination dans le processus canadien de développement et d'homologation de cultivars pour le blé. Cependant, la composition des protéines dans le grain joue elle aussi un rôle primordial dans la détermination de la qualité des produits céréaliers en fonction de leur usage final. Les auteurs voulaient établir si les lignées analogues au blé roux de printemps de l'Ouest canadien (CWRS) à haut rendement mais à plus faible teneur en protéines présentent des propriétés boulangères acceptables (c.-à-d. comparables à celles du blé CWRS) en présence d'une concentration d'azote contrastante dans le sol. À cette fin, ils ont évalué les caractères agronomiques et qualitatifs de cinq lignées analogues au CWRS, de quatre variétés du CWRS et d'un cultivar de blé roux de printemps Canada Prairie correspondant à un large éventail sur les plans de la qualité et du rendement grainier. Les évaluations se sont déroulées dans des conditions environnementales variées, à trois endroits, et à cinq taux de fertilisation avec des engrais azotés. Les lignées analogues au CWRS ont donné un rendement grainier sensiblement plus élevé et une TPG d'en moyenne 0,9 % inférieure à celle des variétés de CWRS. Malgré la plus faible TPG, les lignées analogues comme W07786 présentaient des propriétés boulangères adéquates et stables, à tous les taux de fertilisation. L'analyse par diagramme de double projection (génotype × caractère) révèle que les propriétés boulangères des lignées analogues au CWRS sout essentiellement associées à la sédimentation SDS et à l'absorption de l'eau par la farine. Les résultats indiquent qu'on pourrait développer des cultivars de blé donnant jusqu'à 15 % plus de grain que les variétés contemporaines de CWRS mais aux caractéristiques comparables pour l'usage final si on diminuait (de jusqu'à un pour cent) les exigences actuelles relatives à la TPG tout en sélectionnant de meilleures qualités boulangères. De cette façon, on augmenterait génétiquement le rendement grainier du CWRS tout en préservant une qualité adéquate selon la destination finale et en rehaussant la compétitivité de cette culture dans l'Ouest canadien. [Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Previous genome‐wide association studies in Canadian spring wheat (Triticum aestivum L.) cultivars were based on consensus linkage maps of small population sizes. Here, we used a panel of 192 spring wheat cultivars widely used in western Canada to (a) explore the allelic variation and effects of six known genes and (b) identify genomic regions associated with eight agronomic traits and grain characteristics using the International Wheat Genome Sequencing Consortium (IWGSC) RefSeq v2.0 map. The panel was evaluated for heading, maturity, plant height, lodging, grain yield, grain protein content, test weight, and kernel weight under four conventionally (high N) and three organically (low N) managed environments and genotyped with the wheat 90K single‐nucleotide polymorphism (SNP) array of which 23,342 SNPs were polymorphic. Using gene‐specific functional markers, the proportion of homozygous genotypes with favorable alleles was low for Fhb1 (7–8%), Rht‐D1 (14%), and Rht‐B1 (18%); moderate for Lr34/Yr18 (28–39%); and high for Glu‐A1 (78%) and Glu‐D1 (85%). We identified a total of 172 SNPs located at 94 genomic regions across 19 chromosomes of which 82 regions were associated with a single trait and 12 regions coincided with two to three traits. Twenty‐seven of the 94 regions (28%) were common between the conventional and organic managements systems; the remaining were management specific. Two of the identified regions on chromosome 5A (586.5–588.6 Mb) and 5B (575.8 Mb) coincided with the vernalization response Vrn‐A1 and Vrn‐B1 genes, respectively. The IWGSC RefSeq v2.0 physical positions presented here would serve as the basis for easily comparing independent discovery studies in the future. Core Ideas: The allelic variation and effects of six known genes in a panel of historical and modern Canadian spring wheat were investigated.The effect of low and high nitrogen management systems on QTL detection were compared using eight phenotypic traits.Some coincident genomic regions associated with negatively correlated traits were uncovered.The IWGSC RefSeq v2.0 physical map of 23,342 of the wheat 90K SNP array presented here would serve as a basis for comparing QTL results. [ABSTRACT FROM AUTHOR]

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease of wheat (Triticum aestivum L.). Deployment of resistant wheat cultivars is one of the best strategies to mitigate disease‐associated risks. The genotype P2711 possesses effective stripe rust resistance under field conditions in western Canada, however, the genetic basis of this resistance is unknown. To identify resistance, a recombinant inbred line (RIL) population comprised of 252 RILs was developed from the cross AAC Cameron/P2711. This population was evaluated for stripe rust severity at the adult plant stage in Creston, BC (in 2018, 2019, and 2020) and Lethbridge, AB (in 2018 and 2020), and was genotyped using the wheat 90K iSelect single nucleotide polymorphism (SNP) assay. A high‐density genetic map comprised of 8,915 markers was constructed covering all the wheat chromosomes. Four resistance quantitative trait loci (QTLs) were contributed by P2711 and three from AAC Cameron. QYr.lrdc‐2A.1, corresponding to the Yr17 gene, was the most stable QTL and detected in four out of five environments, whereas QYr.lrdc‐2B was the second most stable QTL. These two QTL along with QYr.lrdc‐5A showed a significant reduction in stripe rust severity when present together. Where most of the QTLs detected in both locations, QYr.lrdc‐1A.1 and QYr.lrdc‐1A.2, both were detected only in Creston, BC. Stable QTLs on chromosome 2A, 2B, and 5A, and their closely associated markers identified in this study could be utilized in marker‐assisted selection for stripe rust resistant cultivar development. Core Ideas: This study discovered seven stripe rust resistance quantitative trait loci (QTLs) in AAC Cameron/P2711 recombinant inbred line population.QTLs identified on chromosomes 2A, 2B, and 5A were the three most stable and effective QTLs.QTL of chromosome 2A is conditioned by the presence of Yr17 gene in P2711.We have identified a novel QTL QYr.lrdc‐5A for stripe rust resistance from resistant parent P2711. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Early seeding has been suggested as a method of increasing the grain yield and grain yield stability of wheat (Triticum aestivum L.) in the Northern Great Plains. The point at which early seeding results in a decrease in grain yield has not been clearly identified. Changes in climatic conditions have increased frost-free periods and increased temperatures during grain filling, which can either be taken advantage of or avoided by seeding earlier. Field trials were conducted in western Canada from 2015 to 2018 to evaluate an ultra-early wheat planting system based on soil temperature triggers as opposed to calendar dates. Planting began when soil temperatures at 5 cm depth reached 0°C and continued at 2°C intervals until 10°C, regardless of calendar date. Conventional commercial spring wheat genetics and newly identified cold tolerant spring wheat lines were evaluated to determine if ultra-early wheat seeding systems required further development of specialized varieties to maintain system stability. Ultra-early seeding resulted in no detrimental effect on grain yield. Grain yield increased at sites south of 51° latitude N, and was unaffected by ultra-early seeding at sites north of 51° latitude N. Grain protein content, kernel weight, and bulk density were not affected by ultra-early seeding. Optimal seeding time was identified between 2 and 6°C soil temperatures. A greater reduction in grain yield was observed from delaying planting until soils reached 10°C than from seeding into 0°C soils; this was despite extreme environmental conditions after initial seeding, including air temperatures as low as −10.2°C, and as many as 37 nights with air temperatures below 0°C. Wheat emergence ranged from 55 to 70%, and heads m−2 decreased with delayed seeding while heads plant−1 did not change. Cold tolerant wheat lines did not increase stability of the ultra-early wheat seeding system relative to the conventional spring wheat check, and are therefore not required for growers to adopt ultra-early seeding. The results of this study indicate that growers in western Canada can successfully begin seeding wheat earlier, with few changes to their current management practices, and endure less risk than delaying seeding until soil temperatures reach 10°C or greater. [ABSTRACT FROM AUTHOR]

Marker-assisted breeding provides an opportunity for wheat breeders to introgress/pyramid genes of interest into breeding lines and to identify genes and/or quantitative trait loci in germplasm to be used as parents. Molecular markers were deployed to assist selection for disease resistance, agronomic and quality traits in several wheat cultivars released for commercial cultivation in Canada. Marker-assisted breeding is routinely used in most wheat breeding programmes for rust resistance (leaf, stem and stripe rust), orange wheat blossom midge resistance, high grain protein concentration, Fusarium head blight and common bunt resistance. Markers are being used selectively within breeding programmes to target traits that relate to market class or regional adaptation. For example, marker-assisted breeding for low lipoxygenase activity and low grain cadmium is being performed in durum breeding programmes and for enhancing stem solidness in programmes targeting resistance to the wheat stem sawfly. Markers are also being utilized for ergot resistance in durum wheat. Increased gluten strength is being selected with a marker for the overexpression of the Bx7 high-molecular-weight glutenin subunit. Marker-assisted breeding is also being used to pyramid resistance genes against a group of stem rust races related to TTKS ( Ug99), a disease that poses a serious threat to global wheat production. Development of tightly linked diagnostic markers and high-throughput genotyping with SNP markers will result in more effective molecular wheat breeding in the near future and will open the door to genomic selection. [ABSTRACT FROM AUTHOR]

The wheat stem sawfly [Cephus cinctus Norton (Hymenoptera: Cephidae)] (WSS) has been a serious pest of wheat (Triticum aestivum L.) since the late 19th century. Adoption of solid-stemmed cultivars, which are available only in the spring bread wheat class in Canada, can mitigate damage but the trait that confers resistance tends to be variable. Five other classes of wheat are grown within the geographical range of C. cinctus and are vulnerable to WSS infestation, and the entire production area for durum (T. turgidum L.) in western Canada, Montana, and western North Dakota lies within the geographic range of C. cinctus. Our objective was to test the hypothesis that the response of hollow- and solid-stemmed cultivars to sowing density (150, 250, 350, or 450 seeds m-2) would differ and subsequently affect infestation patterns of WSS and an endemic parasitoids. The lowest rates of infestation occurred in the hollow-stemmed durum cultivar AC Avonlea and declined with increased sowing density. Wheat pith expression was optimized at the lowest sowing density but the same level produced low and variable grain yield. In the solid-stemmed cultivar Lillian, pith expression was most stable at 250 or 350 seeds m-2. For all cultivars, grain yield was optimized at the higher seeding rates of 350 and 450 seeds m-2. Solid-stemmed wheat should be seeded at low to moderate density to maximize resistance to WSS, but hollow-stemmed cultivars should be seeded at higher seeding rates to optimize yield, lower WSS infestation, and to increase overall crop competitiveness. [ABSTRACT FROM AUTHOR]

Characterizing variety testing sites and identification of sites with negligible genotype x environment crossover interaction is important for plant breeders wishing to identify superior germplasm and (or) cultivars for a wide range of environments. Long-term multilocation grain yield data from the regional hard red spring wheat (Triticum aestivum L.) variety trials from 1981 to 2002 (472 location years assessing 64 wheat genotypes) in Alberta, Canada, were employed for this study. The shifted multiplicative model (SHMM) and the site regression model (SREG) were used to group testing sites into subsets with reduced crossover interaction. Both models identified yearly subsets of testing sites with negligible crossover interaction. However, the yearly site groupings did not generally follow a repeatable pattern over years. Clustering did not correspond with provincial agroclimatic classification, nor did it correspond with site-specific yield potential. Genotype × environment patterns were therefore inconsistent over the years, mainly because of complex, highly variable, and unpredictable year × location effects. We identified sites appearing to be more discriminative and predictive of average genotype performance. This suggests that regional variety trials may be conducted at a fewer more representative locations predictive of average varietal performance. We conclude that the spring wheat growing areas in Alberta (and in the northern Great Plains in general) belong to a single megaenvironment with unpredictable crossover interaction patterns. Because of the highly variable and unpredictable genotype × environment interaction patterns in Alberta, genotypic selection targeting wide adaptation is recommended. Although genotype × environment patterns were not repeatable, the yearly high yielding and stable varieties were repeatedly selected over years. These varieties were the most popular varieties grown by farmers during the testing time period. [ABSTRACT FROM AUTHOR]

The cabbage maggot, Delia radicum (L.), is a serious pest of cruciferous crops in temperate regions of North America and Europe. The effects of undersowing rutabaga, Brassica napus L. subsp, rapifera Metzg. (Brassicaceae), with white clover, Trifolium repens L. (Leguminosae), on second-generation cabbage maggot and its natural enemies were studied in Newfoundland in 1997 and 1998. In 1997, totals of 1311 and 724 eggs were recovered from bare and undersown plots, respectively. More eggs were present in bare plots than undersown plots on various specific dates. In 1997, rutabagas from bare plots weighed more than those from undersown plots, although damage ratings were similar, suggesting that competition, not cabbage maggot feeding, caused the yield differences. In 1998, there were few cabbage maggots present and little damage or yield reduction in either treatment. Similar numbers of cabbage maggot pupae were extracted and reared from each treatment in each year. In 1997, of the pupae reared from undersown plots, 48% produced cabbage maggot flies, 14% produced parasitic Hymenoptera, and 8% produced Aleochara bilineata Gyllenbal (Coleoptera: Staphylinidae); 19% of the pupae from bare plots produced cabbage maggot flies, 8% produced parasitic Hymenoptera, and 36% produced A. bilineata. More A. bilineata were captured in pitfall traps in bare plots than in undersown plots. The effect of clover on carabid beetles was species specific. There were more Bembidion lampros (Herbst) and Amara bifrons (Gyllenhal) in bare plots in 1997, and more Pterostichus melanarius (Illiger) in undersown plots in both years. Despite consistently lower egg numbers in undersown plots than in bare plots, the numbers of pupae in the two treatments were similar at the end of the season. We speculate that this may be due to differential, density-dependent mortality of immature stages of cabbage maggot caused by predators and parasitoids. [ABSTRACT FROM AUTHOR]

Ultra-early seeding of spring wheat (Triticum aestivum L.) on the northern Great Plains can increase grain yield and grain yield stability compared to current spring wheat planting systems. Field trials were conducted in western Canada from 2015 to 2018 to evaluate the impact of optimal agronomic management on grain yield, quality, and stability in ultra-early wheat seeding systems. Four planting times initiated by soil temperature triggers were evaluated. The earliest planting was triggered when soils reached 0–2.5 °C at a 5 cm depth, with the subsequent three plantings completed at 2.5 °C intervals up to soil temperatures of 10 °C. Two spring wheat lines were seeded at each planting date at two seeding depths (2.5 and 5 cm), and two seeding rates (200 and 400 seeds m−2). The greatest grain yield and stability occurred from combinations of the earliest seeding dates, high seeding rate, and shallow seeding depth; wheat line did not influence grain yield. Grain protein content was greater at later seeding dates; however, the greater grain yield at earlier seeding dates resulted in more protein production per unit area. Despite extreme ambient air temperatures below 0 °C after planting, plant survival was not reduced at the earliest seeding dates. Planting wheat as soon as feasible after soil temperatures reach 0 °C, and prior to soils reaching 7.5–10 °C, at an optimal seeding rate and shallow seeding depth increased grain yield and stability compared to current seeding practices. Adopting ultra-early wheat seeding systems on the northern Great Plains will lead to additional grain yield benefits as climate change continues to increase annual average growing season temperatures. [ABSTRACT FROM AUTHOR]

Some studies have investigated the potential of genomic selection (GS) on stripe rust, leaf rust, Fusarium head blight (FHB), and leaf spot in wheat, but none of them have assessed the effect of the reaction norm model that incorporated GE interactions. In addition, the prediction accuracy on common bunt has not previously been studied. Here, we investigated within-population prediction accuracies using the baseline M1 model and two reaction norm models (M2 and M3) with three random cross-validation (CV1, CV2, and CV0) schemes. Three Canadian spring wheat populations were evaluated in up to eight field environments and genotyped with 3158, 5732, and 23,795 polymorphic markers. The M3 model that incorporated GE interactions reduced residual variance by an average of 10.2% as compared with the main effect M2 model and increased prediction accuracies on average by 2-6%. In some traits, the M3 model increased prediction accuracies up to 54% as compared with the M2 model. The average prediction accuracies of the M3 model with CV1, CV2, and CV0 schemes varied from 0.02 to 0.48, from 0.25 to 0.84, and from 0.14 to 0.87, respectively. In both CV2 and CV0 schemes, stripe rust in all three populations, common bunt and leaf rust in two populations, as well as FHB severity, FHB index, and leaf spot in one population had high to very high (0.54-0.87) prediction accuracies. This is the first comprehensive genomic selection study on five major diseases in spring wheat.

Previous molecular characterization studies conducted in Canadian wheat cultivars shed some light on the impact of plant breeding on genetic diversity, but the number of varieties and markers used was small. Here, we used 28,798 markers of the wheat 90K single nucleotide polymorphisms to (a) assess the extent of genetic diversity, relationship, population structure, and divergence among 174 historical and modern Canadian spring wheat varieties registered from 1905 to 2018 and 22 unregistered lines (hereinafter referred to as cultivars), and (b) identify genomic regions that had undergone selection. About 91% of the pairs of cultivars differed by 20-40% of the scored alleles, but only 7% of the pairs had kinship coefficients of < 0.250, suggesting the presence of a high proportion of redundancy in allelic composition. Although the 196 cultivars represented eight wheat classes, our results from phylogenetic, principal component, and the model-based population structure analyses revealed three groups, with no clear structure among most wheat classes, breeding programs, and breeding periods. F ST statistics computed among different categorical variables showed little genetic differentiation (< 0.05) among breeding periods and breeding programs, but a diverse level of genetic differentiation among wheat classes and predicted groups. Diversity indices were the highest and lowest among cultivars registered from 1970 to 1980 and from 2011 to 2018, respectively. Using two outlier detection methods, we identified from 524 to 2314 SNPs and 41 selective sweeps of which some are close to genes with known phenotype, including plant height, photoperiodism, vernalization, gluten strength, and disease resistance., (© 2021. The Author(s).)