Search

Fusarium head blight (FHB) is a major disease of wheat in many wheat-growing regions affecting wheat yield and quality. Glenn is arguably the most FHB-resistant spring wheat cultivar in the USA. To decipher the genetics of FHB resistance in Glenn, a population of 112 recombinant inbred lines was developed from the cross Glenn × MN00261-4 and evaluated for various FHB related traits at multiple locations in two states (North Dakota and Minnesota) over 3 years. Quantitative trait loci (QTL) analysis detected 15 QTL for FHB resistance related traits and heading date (HD). One QTL for FHB incidence (INC; type I resistance), six QTL for FHB severity (SEV; type II resistance), one QTL for Fusarium damaged kernels (FDK; type IV resistance), four QTL for disease index (DI), and three QTL for HD were detected. Major QTL defined as those consistent across multiple environments and explaining > 10% of the phenotypic variation were detected on chromosomes 5BL, 6BS, and 7AS. They were associated with multiple FHB variables and HD. The stable 6BS QTL with a large effect for FHB SEV resistance corresponded to the Fhb2 gene in Sumai 3. In addition, potentially novel QTL were identified on 1AS, 5BL and 7DS. Our study showed that FHB resistance in the GM population was contributed by loci other than Fhb1. The major QTL detected for FHB resistance have potential for use in marker-assisted breeding for FHB resistance.

Hybrid necrosis in wheat (Triticum aestivum L.) is the premature death of leaves or plants caused by the interaction of two dominant complementary genes, Ne1 and Ne2, located on chromosomes 5B and ...

Neonicotinoids alone and in combination with pyrethroid insecticides are common in crop production and suppress target herbivores effectively. The goal of this research was to quantify the effects of these insecticides on primary and secondary pests of soybeans and their natural enemies. We examined the effects of neonicotinoids alone applied to soybean seeds (thiamethoxam), neonicotinoids and pyrethroids applied to leaves (imidacloprid + β-cyfluthrin), and a combination of these treatments on arthropod abundance in soybean fields at two locations over two years in eastern South Dakota. Foliar applications of the insecticides suppressed soybean aphids, Aphis glycines Matsumara (Hemiptera: Aphididae), while thrips, (Thysanoptera: Thripidae) increased in numbers following exposure to the neonicotinoid insecticides alone or in combination with the pyrethroid in one of the locations and were significantly correlated with their major predators. Spider mites (Tetranychus urticae Koch) were not significantly affected by treatments. We also noted suppression of several taxa of predators following exposure to the insecticides. While low abundance of arthropods in the first year of the study limits our inferences, we conclude that both insecticide classes effectively suppress the key pest of soybean, soybean aphids, while their impact on secondary pests and on predators is variable. This research provides important contribution to our understanding of target and non-target impacts of insecticides commonly used in crop protection.

Elevating resistance levels to bacterial leaf streak (BLS), caused by Xanthomonas campestris pv. translucens (Jones, Johnson, & Reddy) and Fusarium head blight (FHB) caused by Fusarium graminearum Schwabe (telomorph Gibberella zeae (Schwein.) Petch) are major objectives of several hard red spring wheat (Triticum aestivum L.; HRSW) breeding programs situated in the northern Great Plains of the USA. High grain yield significantly contributes to the success of HRSW cultivars. Other traits, such as disease resistance, are most useful when accompanied by high grain yield in a single genotype. The genotype by yield-trait (GYT) analysis method aids in selecting genotypes with elevated performance levels for traits of consideration in the presence of high grain yield. Replicated yield trial data was subjected to GYT analysis to demonstrate its utility for selecting HRSW genotypes for use as parents and further consideration toward cultivar release. Genotype selections were identified based on overall performance while strong and weak characteristics were also investigated. Several genotypes were selected for potential use as parents while three were chosen for further cultivar release consideration. Performance levels associated with two of the three candidate cultivars were greater than average for all traits considered.

Fusarium graminearum causes crown rot in wheat affecting seed germination, seedling establishment hence impacting crop productivity. Integrated disease management approaches includes cultural practices, use of good quality seed, resistant varieties, seed treatment. In this study, we surveyed wheat plant samples from South Dakota to determinethe prevalence and distribution of root rot pathogens. F. graminearum and Bipolaris sorokiniana were recovered from 100% and 48% of the root samples (n=39) collected, respectively. Further, we studied the effect of F. graminearum on the seed germination and seedling blight on spring wheat cultivars under greenhouse and field conditions. F. graminearum significantly affected the seed germination and seedling blight in 11 spring wheat cultivars, ranging from 75-96% and 0-9%, respectively in infested seed as compared to uninfested seed (control). The cultivars ‘Forefront’ and ‘Select’ were least impacted by the pathogen; whereas, ‘Russ’ and ‘Oxen’ showed a significant reduction in germination and higher seedling blight. Field experiments were conducted to determine the impact of source of inoculum, fungicide seed treatment and varieties on seed germination and seedling survival at two locations in 2015 and 2016. Cultivars Russ and Oxen showed poor seed germination and high seedling blight; whereas, Forefront, Selectand Briggs had higher germination and seedling survival. Fungicide treatment significantly increased seed germination. The source of inoculum was significant in 2015, however, it was not significant in 2016 due to less disease pressure. Our results showed that F. graminearum lowers seed germination and causes seedling blight in wheat cultivars and genetic variability exists incultivars. Hence the use of fungicide seed treatment can reduce the germination losses caused by the pathogen for fields likely to have high inoculum pressure or likely infested seed and use of tolerant cultivars like Forefront can further reduce the losses due to crown and root rot diseasent.

Author(s): Blake, NK; Pumphrey, M; Glover, K; Chao, S; Jordan, K; Jannick, JL; Akhunov, EA; Dubcovsky, J; Bockelman, H; Talbert, LE | Abstract: The Triticeae-CAP spring wheat nested association mapping population (Reg. No. MP-10, NSL 527060 MAP) consisting of recombinant inbred line (RIL) populations derived from 32 spring wheat (Triticum aestivum L.) accessions each crossed to a common spring wheat parent, ‘Berkut’, has been released. The spring wheat accessions consisted of 29 landraces and three cultivars. Each population consists of approximately 75 lines for a total of 2325 RILs (Reg. Nos. GSTR No. 14701–GSTR 17133). The RILs have all been genotyped with the Illumina wheat iSelect 90K single nucleotide polymorphism array using the Infinium assay method and through genotype-by-sequencing. This nested association mapping population provides a genotyped germplasm resource for the wheat community. A potential strategy for use of the material is to screen the parents for a trait of interest, followed by analysis of RIL of populations that are likely to be segregating for a target trait or sequence.

Low falling number and discounting grain when it is downgraded in class are the consequences of excessive late-maturity α-amylase activity (LMAA) in bread wheat (Triticum aestivum L.). Grain expressing high LMAA produces poorer quality bread products. To effectively breed for low LMAA, it is necessary to understand what genes control it and how they are expressed, particularly when genotypes are grown in different environments. In this study, an International Collection (IC) of 18 spring wheat genotypes and another set of 15 spring wheat cultivars adapted to South Dakota (SD), USA were assessed to characterize the genetic component of LMAA over 5 and 13 environments, respectively. The data were analysed using a GGE model with a mixed linear model approach and stability analysis was presented using an AMMI bi-plot on R software. All estimated variance components and their proportions to the total phenotypic variance were highly significant for both sets of genotypes, which were validated by the AMMI model analysis. Broad-sense heritability for LMAA was higher in SD adapted cultivars (53%) compared to that in IC (49%). Significant genetic effects and stability analyses showed some genotypes, e.g. 'Lancer', 'Chester' and 'LoSprout' from IC, and 'Alsen', 'Traverse' and 'Forefront' from SD cultivars could be used as parents to develop new cultivars expressing low levels of LMAA. Stability analysis using an AMMI bi-plot revealed that 'Chester', 'Lancer' and 'Advance' were the most stable across environments, while in contrast, 'Kinsman', 'Lerma52' and 'Traverse' exhibited the lowest stability for LMAA across environments.

The unique ability of wheat (Triticum aestivum L.) flour to produce cohesive dough has helped to make it the most widely used cereal crop for bread and other baked food products. Measurement of end-use qualities, such as loaf volume, is ideally carried out through assessing loaves of bread; however, this is resource intensive. Predictive testing methods are more often utilized to identify wheat genotypes with potentially acceptable loaf volume, although more accurate predictive methods would be beneficial. Our objectives were to study the influence of weather observations on bread loaf volume and flour and dough quality data, to use a neural network (NN) model to predict loaf volume with select input data, and to compare the best multiple regression models identified with their NN counterparts. Weather data collected at 20 days after heading (DAH) showed the highest correlations with bread loaf volume when compared with prior intervals. A NN model containing maximum, minimum, and nighttime temperatures pr...

Stagonospora nodorum blotch (SNB), caused by Phaeosphaeria nodorum, and Septoria tritici blotch (STB), caused by Mycosphaerella graminicola, are the main pathogens of the Septoria disease complex of wheat (Triticum aestivum) in North America. This study was conducted to determine the disease reaction of 126 elite hard red spring, white, and durum wheat cultivars and advanced breeding lines collected from the northern Great Plains of the United States and Canada to SNB and STB. Seedlings of the 126 wheat genotypes were evaluated for resistance to SNB and STB under controlled environmental conditions. Moreover, these 126 wheat genotypes also were infiltrated with culture filtrate of P. nodorum isolate Sn2000. Based on disease reactions, three cultivars (McNeal, Dapps, and Oklee) and 12 advanced breeding lines (CA-901-580W, 97SO254-8-1, MN03291, MN03308, WA007925, MT0245, ND756, ND801, ND803, ND808, ND809, and ND811) adapted to the northern Great Plains were found to be resistant to both Septoria diseases and insensitive to the culture filtrate. Additionally, eight genetically diverse lines and cultivars, including two tetraploid wheat genotypes, were identified to be resistant to both Septoria diseases. These results suggest that the wheat genotypes contain a broad genetic base for resistance to the Septoria diseases in the northern Great Plains of the United States and Canada, and the resistant sources identified in this study may be utilized in wheat-breeding programs.

Summary Recombination affects the fate of alleles in populations by imposing constraints on the reshuffling of genetic information. Understanding the genetic basis of these constraints is critical for manipulating the recombination process to improve the resolution of genetic mapping, and reducing the negative effects of linkage drag and deleterious genetic load in breeding. Using sequence‐based genotyping of a wheat nested association mapping (NAM) population of 2,100 recombinant inbred lines created by crossing 29 diverse lines, we mapped QTL affecting the distribution and frequency of 102 000 crossovers (CO). Genome‐wide recombination rate variation was mostly defined by rare alleles with small effects together explaining up to 48.6% of variation. Most QTL were additive and showed predominantly trans‐acting effects. The QTL affecting the proximal COs also acted additively without increasing the frequency of distal COs. We showed that the regions with decreased recombination carry more single nucleotide polymorphisms (SNPs) with possible deleterious effects than the regions with a high recombination rate. Therefore, our study offers insights into the genetic basis of recombination rate variation in wheat and its effect on the distribution of deleterious SNPs across the genome. The identified trans‐acting additive QTL can be utilized to manipulate CO frequency and distribution in the large polyploid wheat genome opening the possibility to improve the efficiency of gene pyramiding and reducing the deleterious genetic load in the low‐recombining pericentromeric regions of chromosomes., Significance Statement This study offers insights into the genetic basis of recombination rate variation in allopolyploid wheat and its effect on the distribution of deleterious SNPs across the genome. The identified trans‐acting additive recombination rate QTL can be utilized to manipulate crossover frequency and distribution in the large polyploid wheat genome opening the possibility to improve the efficiency of gene pyramiding and reducing the deleterious genetic load in the low recombining pericentromeric regions of chromosomes.

Wheat (Triticum aestivum L.) market grades and prices are determined in part by test weight (TW). Millers value high TW because it is typically associated with higher flour extraction rates and better end-use quality. Test weight is expected to be influenced by other directly quantifiable grain attributes such as grain length (GL), grain width (GW), shape, single-grain-density (SGD), thousand-grain-weight (TGW), and packing efficiency (PE). The objectives of this study were to: (1) determine the primary morphological grain attributes that comprise TW measurements for winter and spring wheat classes; and (2) determine TW stability and genotype and genotype × environment interactions (GEIs) of the attributes that comprise TW. A market class representative group of 32 hard spring and 24 hard winter wheat cultivars was grown at several locations in South Dakota in 2011 and 2012. A regularized multiple regression algorithm was used to develop a TW model and determine what grain attribute reliably predicts TW. A GGE biplot was used for stability and GEI analyses whereas a linear mixed model was used for variance analyses. Data were collected on eight grain traits: TW, SGD, TGW, protein concentration, GW, GL, shape, size, and PE. Observations showed that in both spring and winter wheat, SGD accounted for over 90% of the phenotypic variation of TW. Cultivars with stable and high TW were identified in both wheat classes. Apart from TW; significant (p

Fusarium head blight (FHB) is a highly detrimental disease of wheat. A quantitative trait locus for FHB resistance, Qfhb1, is the most utilized source of resistance in wheat-breeding programs, but very little is known about its resistance mechanism. In this study, we elucidated a prospective FHB resistance mechanism by investigating the proteomic signatures of Qfhb1 in a pair of contrasting wheat near-isogenic lines (NIL) after 24 h of inoculation of wheat florets by Fusarium graminearum. Statistical comparisons of the abundances of protein spots on the 2D-DIGE gels of contrasting NILs (fhb1+ NIL = Qfhb1 present, fhb1- NIL = Qfhb1 absent) enabled us to select 80 high-ranking differentially accumulated protein (DAP) spots. An additional evaluation confirmed that the DAP spots were specific to the spikelet from fhb1- NIL (50 spots), and fhb1+ NIL (seven spots). The proteomic data also suggest that the absence of Qfhb1 makes the fhb1- NIL vulnerable to Fusarium attack by constitutively impairing several mechanisms including sucrose homeostasis by enhancing starch synthesis from sucrose. In the absence of Qfhb1, Fusarium inoculations severely damaged photosynthetic machinery, altered the metabolism of carbohydrates, nitrogen and phenylpropanoids, disrupted the balance of proton gradients across relevant membranes, disturbed the homeostasis of many important signaling molecules induced the mobility of cellular repair, and reduced translational activities. These changes in the fhb1- NIL led to strong defense responses centered on the hypersensitive response (HSR), resulting in infected cells suicide and the consequent initiation of FHB development. Therefore, the results of this study suggest that Qfhb1 largely functions to either alleviate HSR or to manipulate the host cells to not respond to Fusarium infection.

Wheat stem sawfly (WSS), Cephus cinctus Norton (Hymenoptera: Cephidae), has recently emerged as a key pest of wheat (Triticum aestivum L.) in the Great Plains and Canadian provinces. The expanding impact of WSS has caused considerable economic losses to wheat production. Solid-stem varieties of wheat remain the only effective measure of suppression of WSS, and the goal of this research was to test whether five solid- and hollow-stem varieties of winter and spring wheat reduce survival of WSS in South Dakota. We reported that solid-stem varieties had significantly lower numbers of WSS larvae, and this effect was especially evident when WSS infestation rates exceeded 15%. We also observed that the yield of solid-stem varieties was significantly lower than hollow-stem varieties when the abundance of WSS was low, but not when populations of WSS were relatively high. We did not observe consistent differences in grain quality between solid- and hollow-stem varieties, however, and in case of protein levels of grain, solid-stem wheat varieties performed better than hollow-stem wheat. We conclude that solid-stem varieties of wheat appear to effectively suppress WSS survival, and reduced yield of these varieties is less apparent when populations of C. cinctus are high enough to affect the yield of hollow-stem wheat. This is the first report to describe the effectiveness of solid-stem varieties of wheat on WSS in South Dakota. More research in the state is necessary before more robust conclusions can be drawn.

Bread loaf volume is an important economic criterion. Breeders, millers, and bakers need measurements allowing them to evaluate dough performance during processing. Strain hardening is an important dough property. It describes the stability of the gas cell walls and the ability of cells to expand further; therefore, the higher the strain hardening index (n), the better the baking performance. Dough exhibits strain hardening during uniaxial extensibility tests. However, obtaining n from an extensibility test is time consuming. The objectives of this study were to identify the extensibility parameters that contribute to n. Three parameters were retained in the model (R2 = 0.90): dough strength (Rmax), extensional delay (EDiff), and initial slope of the curve (Ei). Rmax was the largest contributor and was proportional to the dough strain hardening properties. EDiff and Ei had a detrimental effect on n. The appropriateness of the model was validated with two sample sets (19 genotypes, 12 environments). Signif...

Pyramiding QTL for FHB resistance from multiple sources presents an opportunity to enhance the Fhb1 derived resistance of elite spring wheat germplasm. Conventionally, pyramiding QTL using a marker assisted-selection approach requires preliminary mapping studies to identify the resistance QTL from each parental line and validation studies to assess the QTL effects in multiple genetic backgrounds. This study evaluates IBD-based linkage analysis for the purpose of mapping, validation and marker-assisted pyramiding of resistance QTL simultaneously in breeding populations. Eight hundred and twenty nine segregating F1 progeny from 43 four-way crosses among multiple sources of resistance were evaluated in the greenhouse and in field-based progeny tests. IBD-based linkage analysis was conducted using a mixed model extension of Haseman-Elston sib-pair regression. QTL for FHB resistance were identified on chromosomes 2A, 2B, 3B and 7B, cumulatively explaining 18–21 % of the variance for FHB severity in different evaluations. The QTL on chromosome 3B corresponded with Fhb1, and the QTL on chromosomes 2B and 7B are corroborated by previous mapping studies. The QTL mapped to chromosome 2A potentially represents a novel source of resistance derived from elite North American spring wheat germplasm. Marker haplotypes for these QTL regions are being used for marker-assisted selection of resistance alleles in subsequent generations of these breeding populations.

Bacterial leaf streak (BLS; caused by Xanthomonas campestris pv. translucens) has become a serious disease of wheat (Triticum aestivum) in the Midwest USA. This study was conducted to map quantitative trait loci (QTL) controlling resistance to BLS in spring wheat using an identity by descent (IBD) mapping approach. The mapping population consisted of 825 individuals representing 60 families. Resistance phenotyping was carried out in greenhouse and field research plots. QTL analysis was performed using both linkage and association-based approaches. Two genomic regions near the simple sequence repeat loci Xwmc522 and Xbarc134, on chromosomes 2A and 6B, respectively, were significantly associated with resistance in both greenhouse and field evalua- tions. The Xwmc291 and Xbarc3, loci were also significantly associated with greenhouse evaluations of resistance, and Xgwm550 was significantly associ- ated with field observations. Variance explained by the significant markers ranged from 0.56 to 29.56 %, Xwmc522 was most associated with resistance, and narrow-sense heritability for resistance was 0.28. This study demonstrates that the IBD mapping technique is a viable alternative to traditional bi-parental mapping for detecting markers associated with complex traits, like partial disease resistance in breeding populations. This information is potentially useful for marker- assisted selection and should ultimately accelerate development of resistant cultivars.

Rye (Secale cereale L.) chromosome translocation is reported to enhance yield attributes in common wheat (Triticum aestivum L.). We used 1RS translocations within the spring wheat cultivar “Pavon76” to measure and identify the translocation that is suitable to withstand moisture stress conditions without significant loss in yield potential. Four lines were grown under two water regimes in greenhouse environment in 2011 and 2012. The rye translocation increased root and shoot biomass in some cases, reduced plant height, and delayed maturity in some cases. The 1RS.1BL translocation produced the highest grain yield associated with the lowest root and shoot biomass under both well watered and water stressed conditions. Root and shoot biomass were recorded the highest for 1RS.1AL under well watered condition. However it produced the least biomass for both traits under water stressed conditions. In most cases, lines were not statistically differentiated for seminal root angle, abscisic acid concentration, water use efficiency, and grain yield. Results from our study show that the 1RS.1BL translocation is more suited to produce high grain yield under moisture limiting conditions.

Consumer health awareness has recently favored food products thought to aid in disease prevention. Wheat (Triticum aestivum L.) produces phenolic compounds shown to play an inhibitory role on several diseases. Value may be added to wheat if phenolic compounds were consistently produced to the extent that diseases could be mitigated through consumption of more wheat products. Our objectives were to determine whether genotypes differed significantly in phenolic compound concentrations when grown over diverse South Dakota production environments and to determine heritability estimates for each compound. Total phenolic content, antioxidant activity, and total orthorphenolic content values were collected from spring wheat genotypes grown at five South Dakota locations in 2008 and 2009 and winter wheat genotypes grown at three locations in 2006 and 2007. Phenolic compounds were more variable among spring wheat genotypes, and heritability estimates were moderate. It appears that focused breeding efforts could su...

Rye (Secale cereale L.) serves as an alternative host of Pyrenophora tritici-repentis (PTR) the cause of tan spot on wheat. Rye is cultivated as a forage or cover crop and overlaps with a significant portion of wheat acreage in the U.S. northern Great Plains; however, it is not known whether the rye crop influences the evolution of PTR races. We evaluated a global collection of 211 rye accessions against tan spot and assessed the diversity in PTR population on rye in South Dakota. All the rye genotypes were inoculated with PTR races 1 and 5, and infiltrated with Ptr ToxA and Ptr ToxB, at seedling stage. We observed 21% of the genotypes exhibited susceptibility to race 1, whereas, 39% were susceptible to race 5. All 211 accessions were insensitive to both the Ptr toxins. It indicates that though rye exhibits diversity in reaction to tan spot, it lacks Ptr ToxA and ToxB sensitivity genes. This suggests that unknown toxins or other factors can lead to PTR establishment in rye. We characterized the race structure of 103 PTR isolates recovered from rye in South Dakota. Only 22% of the isolates amplified Ptr ToxA gene and were identified as race 1 based on their phenotypic reaction on the differential set. The remaining 80 isolates were noted to be race 4. Our results show that races 1 and 4 are prevalent on rye in South Dakota with a higher frequency of race 4, suggesting a minimal role of rye in the disease epidemiology.

Bacterial leaf streak (caused by Xanthomonas campestris pv. translucens) has reemerged as a potential threat in spring wheat (Triticum aestivum) production areas in the northern Great Plains. As with other foliar bacterial diseases, chemical control under field situations is neither economical nor practical. Development of resistant genotypes will be needed for adequate management of the disease. There is currently limited information on sources of resistance in hard spring wheat germplasm. The main objective was to develop and apply a robust screening tool for evaluating germplasm against bacterial leaf streak, and to identify resistance sources for this disease. Inoculated field experiments were conducted in Brookings and Codington Counties, SD in 2009 and 2010 using a virulent local isolate (XctSD-017) inoculated after tillering stage. Forty-five hard red spring wheat genotypes with diverse genetic backgrounds were evaluated for disease severity, with ratings made at 7-day intervals from heading through dough stage. Results of this study showed clear differences in level of resistance among the 45 genotypes, with no immunity expressed. SD4205 was found resistant to the disease with the lowest area under the disease progress curve across location–years. Other genotypes showing moderate levels of resistance included SD4148, SD4176, ‘Alsen’, SD4023, ‘Faller’, SD4024, ‘Knudson’, and SD4199. Grain weight was negatively correlated to disease, as was days to heading. The resistance identified appeared to be quantitative in nature and was expressed through slower disease progress and reduced severity.

Genetic data collected from various plant breeding and genetic studies may not be replicated in field designs although field variation is always present. In this study, we addressed this problem using spring wheat (Triticum aestivum L.) trial data collected from two locations. There were no intralocation replications and an extended additive-dominance (AD) model was used to account for field variation. We numerically evaluated the data from simulations and estimated the variance components. For demonstration purposes we also analyzed three agronomic traits from the actual spring wheat data set. Results showed that these data could be effectively analyzed using an extended AD model, which was more comparable to a conventional AD model. Actual data analysis revealed that grain yield was significantly influenced by systematic field variation. Additive effects were significant for all traits and dominance effects were significant for plant height and time-to-flowering. Genetic effects were predicted and used to demonstrate that most spring wheat lines developed by the South Dakota State University breeding program (SD lines) exhibited good general combining ability effects for yield improvement. Thus, this study provides a general framework to appropriately analyze data in situations where field crop data are collected from non-replicated designs.

Genetic expression of a trait is complicated and it is usually associated with many genes including their interactions (epistasis) and genotype-by-environment interactions. Genetic mapping currently focuses primarily on additive models or marginal genetic effects due to the complexity of epistatic effects. Thus, there exists a need to appropriately identify favorable epistatic effects for important biological traits. Several multifactor dimensionality reduction (MDR) based methods are important resources to identify high-order gene–gene interactions. These methods are mainly focused on human genetic studies. Many traits in plant systems are not only quantitatively inherited but also are often measured in repeated field plots under multiple environments. In this study, we proposed a mixed model based MDR approach, which is suitable for inclusion of various fixed and random effects. This approach was used to analyze a cotton data set that included eight agronomic and fiber traits and 20 DNA markers. The results revealed high order epistatic effects were detected for most of these traits using this modified MDR approach.

With 10 tables Abstract Preharvest sprouting (PHS) can greatly affect the consistent production of high-quality spring wheat (Triticum aestivum L.) in many regions worldwide including Western Canada. A worldwide collection of red- and white-seeded spring wheat genotypes with different levels of sprouting response were characterized for three PHS traits: falling number, germination index and sprouting index in three different environments in Manitoba, Canada. The data sets were analysed by the genotype and genotype × environment interaction model. Variance components were estimated, genotypic and their interaction effects with environments were predicted by using one of mixed linear model approaches: minimum norm quadratic unbiased estimation approach. Genotypic variance expressed as proportion to the phenotypic variance was higher compared to genotype × environment (G × E) interaction effects for all three PHS traits, suggesting that these genotypes can be used to develop high level of PHS-resistant cultivars regardless of environment. Strong correlations between PHS traits across environments suggest that all three traits are repeatable and reliable methods to determine PHS response in spring wheat depending on sample types (spike, grain or flour). Predicted genotypic effects, G × E interaction effects and the linear discriminant analysis revealed that white-seeded genotypes ‘AUS1408’, ‘SC8019-R1’ and Kanata, and red-seeded genotypes ‘AC Domain’, ‘AC Majestic’ and ‘Red RL4137’ would be useful PHS-resistant donors in spring wheat cultivar development programmes.

Much effort has been invested in identifying molecular markers in wheat (Triticum aestivum L.) linked to quantitative trait loci (QTL) that confer resistance to Fusarium head blight (FHB) caused by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein) Petch]. Even after several generations of crossing and selection by many wheat breeding programs, resistance of the Chinese spring wheat cultivar ‘Sumai 3’ (PI 481542) remains among the most effective. It therefore seems that undocumented resistance QTL present in Sumai 3 were not detected in various mapping studies. Using an extremely susceptible Tibetan landrace (‘Y1193-6’; unknown pedigree) in the creation of a mapping population with Sumai 3, the objective of this research was to identify undocumented resistance QTL in Sumai 3. This was accomplished through collecting disease index (DI) and Fusarium damaged kernel (FDK) phenotypic values along with 305 Diversity Array Technology (DArT) and 52 Simple Sequence Repeat (SSR) marker genotypes on 160 F2:6 recombinant inbred lines (RILs). Disease response evaluations were based on four (two greenhouse and two field) experiments where spray inoculation methods were used. Three QTL were identified on chromosome arms 3BS, 6BL and 2DS explaining 26.1, 10.7 and 18.9% of the phenotypic variation for DI, respectively. The same QTL were also significantly associated with reduced FDK scores and explained 28.0, 11.0 and 23.0% of phenotypic variation. Lines within the mapping population were placed in eight categories with respect to their various QTL combinations. Lines with no QTL were the most susceptible, whereas those with the Sumai 3-derived 3BS and 6BL QTL combined with the 2DS QTL from Y1193-6 were the most resistant. Though the 3BS and 6BL QTL are well-documented, the 2DS resistance QTL, which was contributed by the susceptible parent, confers increased susceptibility when derived from Sumai 3. In this study no new FHB QTL from Sumai 3 was discovered, but results suggest that Sumai 3 contains a QTL for susceptibility on chromosome arm 2DS. Selection against this QTL may potentially increase resistance levels among Sumai 3-derived populations.

Fusarium head blight (FHB) (caused by Fusarium graminearum Schwabe [telomorph Gibberella zeae (Schwein.) Petch]), is a major constraint on the production of spring wheat (Triticum aestivum L.). The objective of this research was to release a hard red spring wheat (HRSW) cultivar with enhanced levels of FHB resistance. ‘Select’ (Reg. No. CV-1056, PI 659554) HRSW was developed at South Dakota State University (SDSU) and released by the South Dakota Agricultural Experiment Station (SDAES) in February 2010. The cross ‘Briggs’ (PI 632970)/FN1500–118 was made during spring 2001. Briggs (BW114/’Bergen’ (PI 538768)//SD3097) was released by SDAES in fall 2001. FN1500–118 is an unreleased experimental breeding line developed by the SDSU-HRSW breeding program. The population was advanced via an early-generation bulk-testing program where F 4:7 seed was included in the 2005 preliminary yield trial, and the line was designated SD3948. SD3948 also was tested in the advanced yield trial from 2006 through 2009. Select was released for its high level of resistance to FHB when compared with most other HRSW cultivars developed by the SDSU-HRSW breeding program as well as for its high yield potential and grain volume weight in South Dakota and the northern Great Plains. Additionally, Select is moderately resistant to leaf rust (caused by Puccinia triticina Eriks.) and has an early heading date compared with many HRSW cultivars currently in production.

Dough extensibility affects processing ease, gas retention, and loaf volume of finished products. The Kieffer dough extensibility test was developed to assess extensibility of small dough samples and is therefore adapted for use in breeding programs. Information is lacking on relationships between wheat growing environments and dough properties measured by the Kieffer dough extensibility test. This study documents the variability of dough extensibility (Ext), maximum resistance to extension (Rmax), and area under the extensibility curve (Area) in relation to breadmaking quality, and the effect of wheat growing environments. Mixograph, Kieffer dough extensibility, and bake tests were performed on flour milled from 19 hard red spring wheat (Triticum aestivum L.) genotypes grown during three growing seasons (2007-2009) at six South Dakota locations. Although both genotype and environment had significant effects on Kieffer dough extensibility variables, environment represented the largest source of v...

Because of the large number of cultivars that require examination in the development of spring wheat (Triticum aestivum L.) cultivars, breeding programs use predictive methods to test end use quality. The Mixograph is a widely used predictive test with which end use quality of many genotypes can be assessed in a short time. By comparison, the Mixolab is a relatively new device with additional capability that might be used for the same purpose. Our objective was to document variability of, and relationships among, 20 parameters obtained from Mixolab, Mixograph, and bake tests. Tests were performed on flour from 18 genotypes grown in 20 environments. Both genotype and environment had significant effects on quality parameter values. Several Mixograph and Mixolab parameters were highly significantly correlated, particularly when genotype mean values over environments were considered. Correlations between loaf volume and Mixolab parameters within environments were inconsistent and suggest that average...

Resistance to the soybean aphid (Aphis glycines Matsumura) was characterized in segregating populations from crosses of soybean [Glycine max (L.) Merr.] accession PI 71506 to susceptible cultivars, and compared to Rag1 resistance from the cultivar ‘Dowling.’ Two susceptible adapted cultivars were crossed with PI 71506 or Dowling. In no-choice greenhouse assays, resistance corresponded to a single dominant gene model for both the PI 71506-derived and Dowling-derived populations. Segregation of aphid resistance in SD1111RR × PI 71506 F2:3 populations in aphid field-cage trials also fit a single-gene model, as did segregation of aphid resistance in the F2:5 generation. However, other genetic effects may also contribute to aphid resistance from PI 71506. Comparison with Rag1 resistance from Dowling indicated that PI 71506 resistance was weaker than that associated with Rag1, but antixenosis resistance from PI 71506 was effective against an Ohio aphid biotype that has overcome Rag1 resistance.

Aegilops tauschii, the D genome donor of wheat (Triticum aestivum L.), has strong seed dormancy and genes controlling the trait may be used to improve resistance of cultivars to preharvest sprouting (PHS). Thus, this research project was initiated to identify dormancy genes from Ae. tauschii-derived synthetic hexaploid wheat (SHW). Four permanent segregating populations, developed by crossing four SHW lines with a common wheat line, were grown under field conditions to evaluate dormancy with threshed seeds (kernels) and/or intact seeds on the spike from 2006 to 2008. Significant genotypic and year effects on both kernel and on-spike seed dormancy were detected in each population, with heritability estimates of about 0.4 (0.32-0.48) across the years. Seeds on the spikes were much more dormant than kernels, suggesting the presence of germination inhibitors in the covering tissues. Significant correlations between kernel and on-spike seed germination percentages were detected in all populations; the estimated correlation coefficient (r) was greater for genotypic (0.80) than for phenotypic (0.63) or environmental (0.51) components. Thus, available SHW lines could be an alternative source of dormancy genes for enhancing resistance of wheat cultivars to PHS.

Categorization of locations with similar environments helps breeders to efficiently utilize resources and effectively target germplasm. This study was conducted to determine the relationship among winter wheat (Triticum aestivum L.) yield testing locations in South Dakota. Yield trial data containing 14 locations and 38 genotypes from 8 year were analyzed for crossover genotype (G) × environment (E) interactions according to the Azzalini-Cox test. G × E was significant (P < 0.05) and contributed a small proportion of variation over the total phenotypic variation. This suggested that for efficient resource utilization, locations should be clustered. The data were further analyzed using the Shifted Multiplicative Model (SHMM), Spearman’s rank correlation and GGE biplot to group testing locations based on yield. SHMM analysis revealed four major cluster groups in which the first and third had three locations, with four locations in each of the second and fourth groups. Spearman rank correlations between locations within groups were significant and positive. GGE biplot analysis revealed two major mega-environments of winter wheat testing locations in South Dakota. Oelrichs was the best testing location and XH1888 was the highest yielding genotype. SHMM, rank correlation and GGE biplot analyses showed that the locations of Martin and Winner in the second group and Highmore, Oelrichs and Wall in the third group were similar. This indicated that the number of testing locations could be reduced without much loss of grain yield information. GGE biplot provided additional information on the performance of entries and locations. SHMM clustered locations with reduced cross-over interaction of genotype × location. The combined methods used in this study provided valuable information on categorization of locations with similar environments for efficient resource allocation. This information should facilitate efficient targeting of breeding and testing efforts, especially in large breeding programs.

Fusarium head blight (FHB) (caused by Fusarium graminearum Schwabe; telomorph Gibberella zeae (Schwein.) Petch), is a major constraint to spring wheat (Triticum aestivum L.) production. The objective of this research was to release a hard red spring wheat (HRSW) cultivar with enhanced FHB resistance. 'Brick' (Reg. No. 1043, PI 657697) HRSW was developed at South Dakota State University (SDSU) and released by the South Dakota Agricultural Experiment Station to Registered seed producers in March 2009. The cross ND2897/SD3219//SD3414 was created in spring 2000. ND2897 is an unreleased experimental line developed by the North Dakota State University HRSW breeding program, and SD3219 and SD3414 are both unreleased experimental lines developed by the SDSU-HRSW breeding program. The population was advanced via an early-generation bulk-testing program where F 4:6 seed was included in the 2004 preliminary yield trial, and the line was designated SD3851. SD3851 also was tested in the advanced yield trial from 2005 through 2008. Brick was released for its high level of resistance to FHB when compared to other HRSW cultivars developed by the SDSU-HRSW breeding program as well as its high yield potential and grain volume weight in South Dakota and the northern Great Plains. Additionally, Brick is moderately resistant to leaf rust (caused by Puccinia triticina Eriks.) and has an early heading date compared with HRSW cultivars currently in production.

Fusarium head blight (FHB) negatively impacts grain yield and quality of wheat (Triticum aestivum L. em. Thell) worldwide, especially when warm, humid weather prevails during flowering and grain filling. Our objective was to determine the mechanism of genetic control of FHB resistance in selected winter and spring wheat germplasm. Six genotypes, ‘Nekota’ (A), ‘2137’ (B), ‘Harding’ (C), ‘Ning7840’ (D), ‘ND2710’ (E) and ‘BacUp’ (F), were included in a modified diallel. The F1 and F2 populations were evaluated in a greenhouse, whereas only F2 populations were evaluated in a mist-irrigated field nursery. Plants were artificially inoculated with Fusarium graminearum Schwabe isolates in both environments. Additive gene effects were more important than non-additive gene effects. General combining ability (GCA) effects were significant in both F1 and F2 populations in both environments. Specific combining ability (SCA) effects were significant only in the greenhouse environment for F2. Combining ability ratio (0....

Gliadins are monomeric proteins that are encoded by the genes at the loci Gli 1 and Gli 2 present on the short arm of homologous wheat chromosomes 1 and 6, respectively. Studies have suggested that gliadins may play an important role in determining the functional properties of wheat flour. The main objective of this study was to understand the functionality of gliadins with respect to tortilla quality. The important tortilla quality attributes are diameter, opacity, and shelf stability, designated here as rollability or the ability to roll or fold the tortilla without cracking. In this study gliadin functionality in tortilla quality was studied using near-isogenic wheat lines that have deletions in either Gli A1, Gli D1, Gli A2, or Gli D2 gliadin loci. The deletion lines are designated by the same abbreviations. Dough and tortillas were prepared from the parent line used to derive these deletion lines, each individual deletion line, and a control commercial tortilla flour. Quantitative and qualitative evaluations were performed on the dough and tortillas derived from the flour from each of these lines. None of the deletions in the gliadin loci altered the shelf stability versus that found for the parent to the deletion lines or control tortilla flour. However, deletions in the Gli 2 loci, in particular Gli A2 reduced the relative proportion of alpha- and beta-gliadins with a greater cysteine amino acid content and gluten cross-link function versus the chain-terminating omega-gliadins in Gli 1, which were still present. As such, the dough and gluten matrix appeared to have greater extensibility, which improved the diameter and overall quality of the tortillas while not altering the rollability. Deletions in the Gli 1 loci had the opposite result with increased cross-linking of alpha- and beta-gliadins, polymeric protein content, and a stronger dough that decreased the diameter and overall quality of the tortillas. The data suggest that altering certain Gli 2 loci through null alleles could be a viable strategy to develop cultivars improved for the specific functionality requirements needed for the rapidly growing tortilla market.

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe, is one of the most devastating wheat (Triticum aestivum L.) diseases. To effectively create wheat cultivars that possess optimal agronomic and FHB resistance levels, an understanding of trait relationships is needed. The objectives of this research were: (i) to use genotype × trait (GT) biplot analysis to determine associations among several agronomic and FHB resistance traits, and (ii) to compare and select genotypes based on agronomic and FHB performance using a collection of widely grown cultivars and elite experimental breeding lines. Genotype × trait biplots were constructed using data from 2004, 2005, and across the two years. In general, biplots revealed that desirable levels of agronomic performance were highly associated with desirable levels of FHB resistance. Through observing GT biplots and genotype grand means for 13 traits, we were unable to identify genotypes that produced the most grain and/or had the highest grai...

In wheat ( Triticum aestivum L), the synthesis of high molecular weight (HMW) glutenins (GS) is controlled by three heterologous genetic loci present on the long arms of group 1 wheat chromosomes. The loci Glu-A1, Glu-B1, and Glu-D1 and their allelic variants play important roles in the functional properties of wheat flour. This study focused on understanding the functionality of these protein subunits on tortilla quality. Near-isogenic wheat lines in which one or more of these loci were absent or deleted were used. Tortillas were prepared from each deletion line and the parent lines. The elimination of certain HMW-GS alleles alter distinct but critical aspects of tortilla quality such as diameter, shelf stability, and overall quality. Two deletion lines possessing HMW-GS 17 + 18 at Glu-B1 and deletions in Glu-A1 and Glu-D1 had significantly larger tortilla diameters, yet tortilla shelf life was compromised or unchanged from the parent lines used to develop the deletion lines or the commercial tortilla flour used as a control. Alternatively, a deletion line possessing Glu-A1 and Glu-D1 (HMW-GS 1, 5 + 10) and a deletion in Glu-B1 also significantly improved tortilla diameters. Whereas the increase in diameter was less than the line possessing only HMW-GS 17 + 18 at Glu-B1, the stability of the tortillas were, however, maintained and improved as compared to the parent lines containing a full compliment of HMW-GS. Thus, the presence of subunits 5 + 10 at Glu-D1 alone or in combination with subunit 1 at Glu-A1 appears to provide a compromise of improvement in dough extensibility for improved tortilla diameters while also providing sufficient gluten strength to maintain ideal shelf stability.

The narrow genetic base of elite soybean, Glycine max (L.) Merr., germplasm may impede further attempts to improve grain yield and other important agronomic characters. Germplasm collections of wild soybean, Glycine soja Siebold & Zucc., are a source of genetic variability for soybean breeding programs. The objectives of this research were to use genetic markers to characterize diversity among 60 G. soja accessions collected in China and to compare this diversity with 18 U.S. ancestral soybean genotypes, 12 Chinese G. max plant introductions (Pis), and 47 elite soybean lines from the northern USA. These accessions were genotyped with a set of 72 simple sequence repeat markers. The G. soja accessions were found to contain more alleles per locus (17) than the U.S. ancestral genotypes (5.8), the Chinese Pls (5.5), or the elite lines (4.5). Multivariate analyses were able to separate the G. max lines from the G. soja accessions and identify the most diverse subset of G. soja accessions. Multidimensional scaling separated G. soja accessions from high and low latitudes, while Ward's clustering method separated the G. soja accessions into distinct clusters that tended to include accessions from similar geographical regions. These data will be useful to breeders selecting G. soja accessions as parents in a breeding program and for establishing a core collection of G. soja to be used in future research.

Elevated level of late maturity α-amylase activity (LMAA) can result in low falling number scores, reduced grain quality, and downgrade of wheat (Triticum aestivum L.) class. A mating population was developed by crossing parents with different levels of LMAA. The F2 and F3 hybrids and their parents were evaluated for LMAA, and data were analyzed using the R software package ‘qgtools’ integrated with an additive-dominance genetic model and a mixed linear model approach. Simulated results showed high testing powers for additive and additive × environment variances, and comparatively low powers for dominance and dominance × environment variances. All variance components and their proportions to the phenotypic variance for the parents and hybrids were significant except for the dominance × environment variance. The estimated narrow-sense heritability and broad-sense heritability for LMAA were 14 and 54 %, respectively. High significant negative additive effects for parents suggest that spring wheat cultivars ‘Lancer’ and ‘Chester’ can serve as good general combiners, and that ‘Kinsman’ and ‘Seri-82’ had negative specific combining ability in some hybrids despite of their own significant positive additive effects, suggesting they can be used as parents to reduce LMAA levels. Seri-82 showed very good general combining ability effect when used as a male parent, indicating the importance of reciprocal effects. High significant negative dominance effects and high-parent heterosis for hybrids demonstrated that the specific hybrid combinations; Chester × Kinsman, ‘Lerma52’ × Lancer, Lerma52 × ‘LoSprout’ and ‘Janz’ × Seri-82 could be generated to produce cultivars with significantly reduced LMAA level.

Tan spot, caused by Pyrenophora tritici-repentis, is a serious foliar disease of wheat (Triticum aestivum) in North America. Control of tan spot through management practices and fungicide application is possible; however, the use of resistant varieties is the most effective and economical means of controlling tan spot. This study was conducted to determine the disease reaction of 126 elite hard red spring, white, and durum wheat varieties and advanced breeding lines collected from the northern Great Plains of the United States and Canada to individual races/toxins of P. tritici-repentis. Seedling evaluation of the 126 genotypes was done under controlled environmental conditions with virulent races 2, 3, and 5 of P. tritici-repentis and toxins Ptr ToxA and Ptr ToxB. Based on disease reactions, two resistant varieties and two advanced breeding lines adapted to the northern Great Plains were found to be resistant to all the races and insensitive to the toxins tested. Additionally, six genetically diverse lines/varieties were identified to be resistant to tan spot; however, these sources may not be well adapted to the northern Great Plains. These results suggest that the wheat germ plasm contains a broad genetic base for resistance to the most prevalent races of P. tritici-repentis in North America, and the resistant sources identified in this study may be utilized in wheat breeding programs to develop tan spot resistant varieties.

Soybean [Glycine max (L.) Merr.j is primarily grown as a source of protein and oil. A quantitative trait locus (QTL) controlling seed protein concentration was previously mapped to linkage group (LG) I of soybean. The objectives of this study were to fine map the QTL and to determine if additional recombination could reduce the inverse phenotypic relationship between seed protein concentration and yield and oil concentration. The fine mapping was done with two sets of backcross populations that were tested in the field and with genetic markers. These populations were developed by the introgression of a high protein allele from the Glycine soja Sieb and Zucc. plant introduction (PI) 468916 into the genetic background of the breeding line A81-356022. The first set (Set 1) included three populations of backcross-four (BC 4 ) lines, and the second set (Set 2) included four populations of BC 5 lines. The populations segregated for different segments of the genomic region where the QTL maps. Tests of the two sets of populations resulted in the localization of the QTL for protein and oil to a 3-cM interval between the simple sequence repeat (SSR) marker Satt239 and the amplified fragment length polymorphism (AFLP) marker ACG9b. The results from the agronomic trait evaluations were inconsistent, making it difficult to definitively conclude whether the protein QTL controls these other traits through pleiotropy.

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is one of the most destructive soybean [Glycine max (L.) Merr.] pests worldwide. The most common source of SCN resistance used in soybean breeding in the northern USA is PI 88788. Previous research has shown that PI 88788 carries a major quantitative trait locus (QTL) conferring SCN resistance on linkage group (LG) G, which is believed to be rhgl. The objective of our research was to map and confirm additional SCN resistance QTL in Bell, a cultivar with resistance from PI 88788. One hundred four F 4 -derived lines (F4 population) developed from crossing the cultivars Bell and Colfax were tested for associations between 54 molecular markers and resistance to SCN populations PA3 (HG type 7, race 3) and PA14 (HG type 1.3.5.6.7, race 14). Three populations of near isogenic lines (NILs) were developed from F 4 plants heterozygous for a region on LG J where a significant QTL was identified in the F 4 population. The NIL populations were tested with genetic markers and also for resistance to both SCN populations. In the F 4 population, SCN resistance QTL were identified at both rhgl and on LG J. The LG J QTL was confirmed in NIL populations and was given the confirmed QTL designation cqSCN-003. The effect of cqSCN-003 was diminished in the NIL populations compared to the F4 population. This was at least partially the result of segregation distortion in the F 4 population between the region containing rhgl and the region containing cqSCN-003. These results show the importance of verifying QTL in confirmation populations to estimate accurately their effects.

Since its identification in the late 1990s, the stem rust pathogen (Puccinia graminis. f. sp. tritici (Pgt)) strain Ug99 (race TTKSK) has represented a worldwide wheat production threat due to its ability to overcome most of the resistance genes present in commercial cultivars. In order to address this challenge, resistance genes in wheat cultivars as well as in wild relatives have been identified. However, stem rust resistance breeding is facing a new challenge with the recent discovery in Ethiopia of a new race of Pgt (TRTTF) capable of defeating Sr13, SrTmp, and Sr1R Amigo genes that conferred resistance to the Ug99 race group. As part of an ongoing screening process at USDA-ARS Cereal Disease Laboratory, SD4279, an elite line from the hard red spring wheat breeding program at South Dakota State University, was found to be resistant to both races TTKSK and TRTTF. The objectives posed in this research were (1) to characterize the genetics of resistance to stem rust in SD4279 and (2) to identify molecular markers linked to race TTKSK (Ug99) and TRTTF resistance in SD4279. A mapping population composed of 92 F2:3 families was evaluated for resistance to TTKSK and TRTTF. A single-gene conferring resistance to TTKSK, likely Sr9h, was mapped on chromosome arm 2BL. Also, a single gene was located on chromosome arm 6AS conferring resistance to TRTTF. Based on the type of reaction and map location, we postulate that the 6AS resistance gene is Sr8a which has not been mapped previously using DNA markers.