Browsing by Author "Griffey, Carl A."

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    Accelerated senescence and nitrogen remobilization in flag leaves enhance nitrogen use efficiency in soft red winter wheat
    Alpuerto, Jasper B.; Brasier, Kyle G.; Griffey, Carl A.; Thomason, Wade E.; Fukao, Takeshi (2021-01)
    Wheat (Triticum aestivum L.) production requires a large amount of nitrogen (N) supply because growers aim to achieve high grain yield and appropriate grain protein content simultaneously. A comprehensive understanding of the mechanisms that underpin efficient N usage at limited N in wheat can facilitate the development of new N-saving varieties in this major crop. Here, we performed comparative analysis of flag leaf responses to N availability in soft red winter wheat with contrasting N use efficiency (NUE); VA08MAS-369 (high NUE) and VA07W-415 (low NUE). This study demonstrated that accelerated senescence along with enhanced breakdown of protein and starch in flag leaves was correlated with higher grain yield, NUE for grain yield, and NUE for grain protein under N limitation. The more dramatic reductions in flag leaf N compounds and carbohydrate reserves in VA08MAS-369 were linked with significantly elevated expression of genes and enzymes associated with these metabolic pathways in this high NUE genotype. Consistent with the gene expression data, nitrate reductase, glutamine synthetase, and NAD-dependent glutamate dehydrogenase activities were highly induced under limited N in VA08MAS-369. It was previously reported that accelerated senescence contributes to increased grain protein content in wheat under regular N supply. This study provides molecular and physiological evidence that vigorous senescence and N remobilization also benefit grain yield under N deprivation.
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    The Accuracy of Genomic Prediction between Environments and Populations for Soft Wheat Traits
    Huang, Mao; Ward, Brian P.; Griffey, Carl A.; Van Sanford, David A.; McKendry, Anne; Brown-Guedira, Gina L.; Tyagi, Priyanka; Sneller, Clay H. (2018-12)
    Genomic selection (GS) uses training population (TP) data to estimate the value of lines in a selection population. In breeding, the TP and selection population are often grown in different environments, which can cause low prediction accuracy when the correlation of genetic effects between the environments is low. Subsets of TP data may be more predictive than using all TP data. Our objectives were (i) to evaluate the effect of using subsets of TP data on GS accuracy between environments, and (ii) to assess the accuracy of models incorporating marker x environment interaction (MEI). Two wheat (Triticum aestivum L.) populations were phenotyped for 11 traits in independent environments and genotyped with single-nucleotide polymorphism markers. Within each population trait combination, environments were clustered. Data from one duster were used as the TP to predict the value of the same lines in the other cluster(s) of environments. Models were built using all TP data or subsets of markers selected for their effect and stability. The GS accuracy using all TP data was >0.25 for 9 of 11 traits. The between-environment accuracy was generally greatest using a subset of stable and significant markers; accuracy increased up to 48% relative to using all TP data. We also assessed accuracy using each population as the TP and the other as the selection population. Using subsets of TP data or the MEI models did not improve accuracy between populations. Using optimized subsets of markers within a population can improve GS accuracy by reducing noise in the prediction data set.
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    Assessing Genetic and Environmental Influence on Traits Associated with Natto Quality
    Cook, David E. (Virginia Tech, 2008-05-08)
    Food grade soybean production is a high value alternative to conventional soybean use. The production of natto, a fermented soyfood, requires soybean cultivars that consistently express specific quality traits over a range of growing environments. Therefore, it is necessary to evaluate genetic and environmental influence for natto quality traits to ensure consistent performance. A multi location experiment was conducted in 2006 and 2007 to address the influence of soybean cropping system (double crop vs. full season) and environmental factors on traits associated with natto quality. Two statistical models were used to analyze the effects of planting system and environment on agronomic traits such as yield, maturity, and seed size and natto quality traits such as water absorption, water loss after steaming, seed coat deficiency, and rate of water absorption. Genotype variation was significant for all traits, but genetic differences for water loss after steaming were minimal. Planting system significantly influenced all natto quality traits. Seed coat deficiency and rate of water absorption displayed the most differential response and double crop plantings produced superior characteristics. Genotype à environment interactions were significant for all traits, but they did not confound selecting superior natto cultivars. Significant environment and year effects indicate environmental sensitivity, but genotype rankings rarely changed. The results indicate that genotype was the most important factor controlling the natto quality traits tested. These results suggest breeding for superior natto cultivars is possible but environmental influence must be accounted for and multi environment testing is necessary for genotype natto quality evaluation.
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    Assessment and Reaction of Triticum aestivum Genotypes to Fusarium graminearum and effects on Traits Related to Grain Yield and Seed Quality
    Chappell, Matthew (Virginia Tech, 2001-12-14)
    Fusarium graminearum (Schwabe), causal organism of fusarium head blight (FHB), has become a major pathogen of wheat (Triticum aestivum L.) throughout North America. Since its discovery in the United States, the disease has spread south and east until at present it is an annual threat for growers of winter wheat in the Mid-Atlantic region. Yield losses for soft red winter (SRW) wheat averaged 908 kg ha-1 in the FHB outbreak of 1998 (Griffey et al., 1999). The economic loss from this single FHB epidemic was an estimated 8.5 million dollars. Environmental conditions favorable for FHB development, including above average rainfall and temperatures during anthesis, have become more common in the Upper-Midwestern wheat-growing region over the past decade, leading to substantial losses in wheat and barley crops. This, coupled with low prices being paid for wheat, has prompted research toward solving the problem of FHB across the nation. The majority of labor and financial resources devoted to FHB research are dedicated to incorporating FHB resistance into adapted wheat lines. While this is a prudent method of combating this disease, this process will take many years to complete. We have examined all FHB assessment parameters, which include FHB incidence, FHB severity, FHB index, percentage fusarium damaged kernels (percentage FDK), and 15-acetyl deoxynivalenol toxin (DON toxin) accumulation, to ascertain which assessment parameters best quantify FHB resistance levels in addition to grain yield and grain volume weight (GVW) losses. FHB index provides the most reliable in-field assessment of a genotype's resistance level, whereas percentage FDK provides a reliable measure of a genotype's resistance level post-harvest. FHB index and percentage FDK are also the most predictive assessment parameters with regard to grain yield and GVW loss. A wide range in both level and type of resistance was observed among genotypes examined in this study. The cultivars Agripro Patton, Ernie, INW9824, Roane, and the experimental line NY87048W-7388 consistently had lower scores for FHB assessment parameters and lower losses of grain yield and GVW.
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    Association Analysis of Baking and Milling Quality Traits in an Elite Soft Red Winter Wheat Population
    Gaire, Rupesh; Huang, Mao; Sneller, Clay H.; Griffey, Carl A.; Brown-Guedira, Gina L.; Mohammadi, Mohsen (2019-05)
    Although grain yield is the most important trait for growers, milling and baking industries demand high-quality and scab-free grains for various end products. To accelerate breeding of wheat (Triticum aestivum L.) cultivars with high grain quality, genetic dissection of quality traits is necessary. Genome-wide association studies (GWAS) were conducted to identify genomic regions responsible for milling and baking quality traits in soft red winter wheat (SRWW). Seven quality traits were evaluated in two locations and 2 yr for 270 elite SRWW lines. These traits include flour yield, softness equivalent, flour protein, and four solvent (lactose, sodium carbonate, sucrose, and water) retention capacity measurements. In this study, 27,449 single nucleotide polymorphism (SNP) markers were developed by using both genotyping-by-sequencing and 90K SNP array technologies. A linear mixed model in GWAS, accounting for population structure and kinship, was fitted to identify 18 [-log(P) >= 4.0] genomic regions on 12 different chromosomes associated with the quality traits. Only one of these associations seems to be a previously identified quantitative trait locus, whereas others are novel associations. The most significant associations for quality traits were identified on chromosomes 1B, 2A, 2B, 4B, 5A, 7A, and 7D. Candidate gene searches, facilitated by the wheat genome assembly, led us to the identification of putative genes related to SRWW quality traits including fasciclin-like arabinogalactan. The results of this study can be used in developing high-quality SRWW varieties for the eastern region of the United States.
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    Bulk segregant analysis for anther culture response and leptine content in backcross families of diploid potato
    Boluarte, Tatiana (Virginia Tech, 1999-09-15)
    Diploid potato populations between a primitive cultivated species, Solanum phureja, and a weedy species, S. chacoense, were used to examine the segregation of microsatellite markers and three traits in backcrosses. Two of the traits, anther culture competence and 2n pollen production, originated from S. phureja whereas the third, leptine production (a specific glycoalkaloid known to convey resistance to the Colorado potato beetle) originated from S. chacoense. Using CP2, a self-incompatible F₁ hybrid originating from a cross between S. chacoense clone 80-1 and S. phureja clone 1-3, three populations were developed: 1-3 x CP2 (PBCp), CP2 x 1-3 (PBCc), and CP2 x 80-1 (CBC). For the microsatellite study, four simple sequence repeat (SSR) primer pairs that amplified fragments within potato sequences found in the GenBank were used to look at segregation ratios in our backcross populations and to eliminate possible spurious genotypes bearing non-parental alleles in these populations. Seventeen spurious genotypes were discarded from PBCp; none was found in PBCc or CBC. Two SSR loci showed skewed segregation in PBCp (favoring transmissnion of the allele originally found in 80-1), PBCc showed normal segregation at all loci, and CBC showed distorted segregation at one locus (revealing a deficiency of homozygotes). In the study of anther culture, three components of ACR were investigated in a preliminary study: 1) embryos produced per anther (EPA), 2) embryo regeneration rate and 3) percentage of monoploids (2n=1x=12) among regenerants. CP2 was intermediate, 80-1 was low, and 1-3 was high for ACR. Only EPA was selected for further characterization in our populations. PBCp (78 genotypes) and CBC (57 genotypes), were characterized for anther culture response ACR/EPA in a series of studies. Nine high and ten low selections were identified in CBC, and ten high and ten low selections were identified in PBCp. EPA selections were used for bulk segregant analysis (BSA) using 214 RAPD primers. Two bands, one amplified by OPQ-10 and another by OPZ-4 were linked in coupling and in repulsion, respectively, to ACR in PBCp. One band amplified by OPW-14 primer was linked in coupling to ACR in CBC. One-way ANOVAs for data from remaining genotypes of the populations verified linkage of the markers to ACR/EPA. For 2n pollen production, a total of 77 PBCp genotypes was characterized; 80-1 produces low % 2n pollen, and 1-3 produces high % 2n pollen. Pollen samples were stained with propidium iodide and examined by flow cytometry. The frequency of 2n pollen varied continuously from 1.7 % to 40.6 % among the 41 genotypes that flowered sufficiently to allow three separate pollen collections. Variation due to the environment was observed where the frequency of 2n pollen appeared greater over a range of genotypes on single collection days. BSA could not be used due to limited population size and a low number of selections at the extremes of the distribution of phenotypes. The continuous variation for 2n pollen production suggests multigenic control of the trait. In the study of leptine content in reciprocal backcross populations, 87 genotypes within PBCp, and 42 genotypes within PBCc were characterized using gas chromatography of leaf samples. CP2 was intermediate, 1-3 had zero, and 80-1 was high for leptine content in the foliage. Leptines were present in low levels in 43 of 87 genotypes in PBCp, indicating simple genetic control. In PBCc, only 7 of 42 genotypes expressed leptines, generally at a higher level than in PBCp, indicating cytoplasmic inheritance. Ten high and ten nil selections within PBCp, and seven high and eight nil selections within PBCc were used for BSA using 214 RAPD primers. Three primers OPQ-2, OPT-16 and OPT-20 amplified bands segregating with high bulks in both populations. These markers were linked in coupling to leptine content in PBCp. Linkage was verified by ANOVAs for leptine content in the entire population.
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    Characterization of Hulled and Hulless Winter Barley, Hordeum vulgare L., Through Traditional Breeding and Molecular Techniques
    Berger, Gregory Lawrence (Virginia Tech, 2012-11-28)
    Phenotypic and genotypic characterization of hulled and hulless winter barley (Hordeum vulgare L.) is necessary for improvement using traditional and molecular breeding techniques.  Identification of genomic regions conferring resistance to Fusarium head blight (caused by Fusarium graminearum), leaf rust (caused by Puccinia hordei G. Otth), powdery mildew [caused by Blumeria graminis (DC.) E.O. Speer f. sp. hordei Em. Marchal], net blotch (caused by Pyrenophora teres) and spot blotch [caused by Cochliobolus sativus (Ito & Kuribayashi) Drechsler ex Dastur] will greatly aid in breeding for improved resistance.  Determining factors that contribute to yield differences between hulled and hulless genotypes, and identification of markers associated with yield and yield related traits will greatly aid in improvement of hulled and hulless genotypes.  The hulled cultivar Nomini, hulless cultivar Eve, and hulless line VA06H-48 were consistently resistant to Fusarium head blight (FHB) and had low deoxynivalenol (DON) accumulation.  Screening with molecular markers on chromosomes 2H and 6H for FHB and DON identified quantitative trait loci (QTL) which may confer resistance in Virginia Tech germplasm.  Evaluation of hulled and hulless full-sibs from four populations indicated  that  grain volume weight and protein concentration were significantly (P d 0.05) higher for hulless genotypes, while seedling emergence and grain ash concentration were significantly (P d 0.05) higher for hulled genotypes.  In linear regression analysis, none of the assessed traits explained yield variation in all populations and environments.  Identification of hulless genotypes having yield potentials similar to those of their hulled sibs should be possible after adjusting for hull weight.  A genome wide association study was used to identify chromosome regions governing traits of importance in six-rowed winter barley germplasm and to identify single nucleotide polymorphisms (SNPs) markers for use in a marker-assisted breeding program. Significant SNPs associated with previously described QTL or genes were identified for heading date, test weight, yield, grain protein, polyphenol oxidase activity, and resistance to leaf rust, powdery mildew, net blotch, and spot blotch.  Novel QTL also were identified for agronomic, quality, and disease resistance traits.  These SNP-trait associations provide the opportunity to directly select for QTL contributing to multiple traits in breeding programs.
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    Characterization of Soybean Germplasm with Modified Phosphorus and Sugar Composition
    Maupin, Laura Marie (Virginia Tech, 2010-09-20)
    The development of soybean [Glycine max (L.) Merr.] cultivars with modified phosphorus (P) composition has nutritional and environmental benefits, but poor seed germination and emergence presents challenges for commercial production. Different genetic mutations in two sources of germplasm, CX1834 and V99-5089, decrease the phytate and increase the inorganic phosphorus (Pi) content of seed. In V99-5089, a mutation in the D-myo-inositol 3-phosphate synthase 1 gene (MIPS1) also results in elevated sucrose content with a concomitant decrease in raffinose and stachyose content, further improving the nutritional value of soybean meal. Prior to the release of V99-5089-derived germplasm, germplasm with the MIPS1 mutation was characterized and compared to CX1834-derived germplasm to determine the effects of this mutation on agronomic and seed composition traits in multiple environments. The correlations between P and sugar seed composition traits were favorable for improving the nutritional composition of soybean. Lack of genotype à environment interaction for sugar traits allows for selection in one growing environment. Despite the significant genotype à environment interaction for phytate and Pi, lines with the MIPS1 gene could readily be distinguished from normal phytate lines, even in unfavorable environments. Phenotypic selection for seed Pi content was more effective than marker assisted selection with the Satt453 marker. The CX1834-derived lines were lower for phytate and higher for Pi content compared to the V99-5089-derived lines. The use of subtropical winter nursery environments for population development resulted in significant reductions in emergence of low phytate genotypes, skewing segregation ratios and prohibiting the analysis of agronomic traits. Emergence was significantly affected by genotype, environment, and the genotype à environment interaction in three emergence tests of advanced low phytate lines. Emergence of modified lines was reduced but some were in a range that would not prohibit commercialization of P modified cultivars. Yields of the best emerging lines were not significantly different from the control cultivars. The results of this study indicate that the development of commercial cultivars with the V99-5089-derived MIPS1 mutation is possible but breeders and producers must focus attention on emergence during population development and seed production to emphasize selection of lines with high emergence potential.
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    Combining ability, protein, heterosis, and prediction of F₁ performance with RFLPs in a diallel of maize
    Ball, Dale Warren (Virginia Tech, 1994-07-06)
    Improving protein quality and identifying superior inbreds and hybrids are significant challenges in commercial maize breeding programs. These two problems were addressed in separate studies on inbreds and hybrids from a complete diallel cross of 12 elite proprietary inbred lines of maize evaluated in field trials in two locations for two years. One of the inbreds (WI) was a novel source of high quality protein obtained from Wilson Seeds, Inc. in Harlan, Iowa. In the first study, diallel analyses were used to study combining ability and types of gene action important in the inheritance of protein content, grain yield, grain moisture at harvest, time to silk, kernel hardness, and density. General combining ability (GCA) and specific combining ability (SCA) effects were highly significant for all traits indicating presence of both additive and non-additive effects, respectively. Reciprocal effects (REe), often assumed to be absent in maize diallel studies, were significant for grain yield and protein concentration, suggesting that choice of female parent may be important for these traits. Ratios expressing the relative importance of GCA and SCA indicated that protein concentration is controlled primarily by additive gene action. In the second study, restriction fragment length polymorphism (RFLP) data were obtained for the 12 inbreds using 42 genomic clones each with four restriction enzymes. Modified Roger's distances were calculated and used in cluster analyses for heterotic grouping of the inbreds. Two measures of level of heterozygosity and hybrid value were evaluated as means of predicting Fl performance of hybrids in the complete diallel set of hybrids and in groups of hybrids representing crosses between and within heterotic groups. Results from this study confirm those of previous investigations with respect to prediction of hybrid performance when comparable groupings of crosses between related and unrelated lines were evaluated. This study further indicates that RFLPs may also be useful for prediction of hybrid performance in situations typical of early generations of many maize breeding programs where recombinant inbreds are testcrossed to a common tester inbred.
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    Conversion of deoxynivalenol to 3-acetyldeoxynivalenol in barley derived fuel ethanol co-products with yeast expressing trichothecene 3-O-acetyltransferases
    Khatibi, Piyum A.; Montanti, Justin; Nghiem, Nhuan P.; Hicks, Kevin B.; Berger, Gregory L.; Brooks, Wynse S.; Griffey, Carl A.; Schmale, David G. III (2011-09-02)
    Background The trichothecene mycotoxin deoxynivalenol (DON) may be concentrated in distillers dried grains with solubles (DDGS; a co-product of fuel ethanol fermentation) when grain containing DON is used to produce fuel ethanol. Even low levels of DON (≤ 5 ppm) in DDGS sold as feed pose a significant threat to the health of monogastric animals. New and improved strategies to reduce DON in DDGS need to be developed and implemented to address this problem. Enzymes known as trichothecene 3-O-acetyltransferases convert DON to 3-acetyldeoxynivalenol (3ADON), and may reduce its toxicity in plants and animals. Results Two Fusarium trichothecene 3-O-acetyltransferases (FgTRI101 and FfTRI201) were cloned and expressed in yeast (Saccharomyces cerevisiae) during a series of small-scale ethanol fermentations using barley (Hordeum vulgare). DON was concentrated 1.6 to 8.2 times in DDGS compared with the starting ground grain. During the fermentation process, FgTRI101 converted 9.2% to 55.3% of the DON to 3ADON, resulting in DDGS with reductions in DON and increases in 3ADON in the Virginia winter barley cultivars Eve, Thoroughbred and Price, and the experimental line VA06H-25. Analysis of barley mashes prepared from the barley line VA04B-125 showed that yeast expressing FfTRI201 were more effective at acetylating DON than those expressing FgTRI101; DON conversion for FfTRI201 ranged from 26.1% to 28.3%, whereas DON conversion for FgTRI101 ranged from 18.3% to 21.8% in VA04B-125 mashes. Ethanol yields were highest with the industrial yeast strain Ethanol Red®, which also consumed galactose when present in the mash. Conclusions This study demonstrates the potential of using yeast expressing a trichothecene 3-O-acetyltransferase to modify DON during commercial fuel ethanol fermentation.
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    Derivation and Comparison of Androgenic and Gynogenic Monoploid Potato Families
    Cutright, Rebecca J. (Virginia Tech, 1998-07-16)
    Monopoloid potato (2n = 1x = 12) can be derived either paternally through anther/microspore culture or maternally through crossing with a haploid-inducing pollinator. Evidence from other genera suggests that androgenic and gynogenic haploid populations derived from the same parent may differ due to gametic selection and/or epigenetic factors. Our objectives were to derive androgenic and gynogenic monoploid populations from each of two diploid (2n = 2x = 24) Solanum phureja clones and compare their phenotypic characteristics in a greenhouse study. A haploid-inducing pollinator, S. phureja IVP101, was crossed to two selections of S. phureja (PP5 and BARD1-3). A total of 185 fruit was obtained from PP5 and 398 from BARD1-3, resulting from 85% and 65% fruit set, respectively. Seed lacking the dominant embryo spot marker carried by IVP101 were selected and germinated in vitro. From 29,300 PP5 x IVP101 seeds, 278 were spotless, resulting in 27 monoploids. Approximately 37 monoploids were obtained from the 99,500 BARD1-3 x IVP101 seeds of which 500 were spotless. In anther culture, PP5 and BARD1-3 yielded 0.16 and 1.67 embryos per anther respectively of which 51% and 44% of the regenerants were monoploid. A total of 32 anther-derived monoploids has been obtained from PP5 and 130 from BARD1-3. Rooted cuttings of 21 androgenic and 21 gynogenic PP5 monoploids were established in a greenhouse in each of three randomized complete blocks. Although the anther-derived monoploids appeared more vigorous, none of the differences between the two populations were significant. Flow cytometry revealed that anther derived progeny of PP5 and BARD1-3 had 3-8% greater nuclear DNA content than gynogenic monoploids derived from the same parental clones.
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    Development of genetic transformation systems in creeping bentgrass (Agrostis palustris Huds.)
    Xiao, Lian (Virginia Tech, 1994)
    As a first step toward improving creeping bentgrass (Agrostis palustris Huds.) via genetic engineering, this study was conducted to develop genetic transformation systems in creeping bentgrass. Establishment of embryogenic cell cultures is a prerequisite for crop improvement via genetic engineering. A protocol for initiating and maintaining embryogenic callus and suspension cultures in creeping bentgrass was developed by substantially modifying and combining a few existing protocols. A high frequency of plant regeneration was obtained following this protocol. Several factors affecting electroporation efficiency were studied using transient expression assay of the reporter uuid gene encoding B-glucuronidase (GUS). Increases in plasmid DNA resulted in increases in GUS activity. Maximal GUS activity was observed at field strength of 950 V/cm, protoplast density of 2 x 10⁶/ml, and KCl concentration of 125 mM in the electroporation buffer. Information obtained from this study facilitated optimization of electroporation conditions. To identify a 5’ regulatory sequence conferring a high level of transgene expression in creeping bentgrass, the effect of six different 5’ regulatory sequences on transient gene expression was studied in electroporated creeping bentgrass protoplasts. The cauliflower mosaic virus (CaMV) 35S promoter was least active; whereas the rice actin 1 gene 5’ sequence was most active among the six sequences tested. Ranked in order of activity (high to low), the other four 5’ sequences were: 1) the CaMV 35S promoter plus the maize alcohol dehydrogenase 1 gene (Adh1) intron 6; 2) the 5’ sequence of the maize ubiquitin gene (Ubi-1), 3) the maize Adh1 promoter and its intron 1, and 4) the 35S promoter plus the Adh1 intron 1. Stable transformation of creeping bentgrass was conducted via particle bombardment and electroporation using a plasmid, pZO1052, containing the reporter B-glucuronidase (uidA) gene and the selectable marker hygromycin phosphotransferase (hph) gene under the control of CaMV 35S promoter plus the maize Adh1 intron 6. Putative transformants were selected by culturing cells on medium containing hygromycin. Transgenic plants and calli were obtained following particle bombardment. The frequency of putative transformants was 4.6 hygromycin-resistant colonies per bombardment. Integration of the transgenes was confirmed by Southern blot hybridization. A high frequency of escapes, however, occurred in the transformant selection following electroporation, which resulted in inefficient transformant recovery. In this study, efficient genetic transformation systems using particle bombardment were established. Use of these systems will facilitate the improvement of creeping bentgrass.
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    Differential responses of grain yield, grain protein content and their associated traits to nitrogen supply in soft red winter wheat
    Tamang, Bishal Gole; Brasier, Kyle G.; Thomason, Wade E.; Griffey, Carl A.; Fukao, Takeshi (2017)
    Increased application of nitrogen fertilizers has significantly raised grain yield and protein concentration in wheat. However, only 30–50% of applied fertilizer nitrogen are usually utilized by the plant. In this study, four soft red winter wheat genotypes (Triticum aestivum L., IL07-4415, MD05W10208-11-8, OH06-150-57 and Sisson) were grown under three different nitrogen regimes (high, medium, and low) in a greenhouse, and grain yield, grain protein concentration, nitrogen use efficiency (NUE) and their associated traits were evaluated. Among the four genotypes, a high-yielding cultivar, Sisson, exhibited superior performance in terms of grain weight plant–1 and NUE for yield (NUEY) at low nitrogen due to maintained grain number spike–1 and harvest index. Significant yield losses due to nitrogen limitation were attributable to reduced spike number plant–1 and grain number spike–1 in the other genotypes. Interestingly, a linear relationship between NUEY and NUE for grain protein (NUEP) was detected at high (R2 = 0.67) and low (R2 = 0.42) nitrogen; both of these traits were positively correlated with grain number spike–1, 1000-seed weight, and harvest index under nitrogen-limited conditions (R2 = 0.35–0.48). These results suggest that simultaneous improvement of NUEY and NUEP could be achieved through the selection of the three yield components (grain number spike–1, 1000-seed weight, and harvest index) at low nitrogen.
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    Effect of 1B/1R Chromosomal Translocation on Dough Rheology of Soft Red Winter Wheat Flour
    Uriyo, Maria Jr. (Virginia Tech, 1997-01-29)
    Nine 1B/1R translocated soft red winter wheat (SRWW) varieties and six non-1B/1R varieties from two crop years (1995-1996 and 1996-1997), grown in two Virginia locations (Warsaw and Blacksburg), were studied to evaluate the effects of the 1R rye chromosome on soft wheat flour quality and baking performance. The presence of the 1B/1R chromosomal translocation in wheat has been reported to provide disease resistance, but produce sticky doughs. The 1995-1996 and 1996-1997 SRWW flours were subjected to farinograph analysis and dough stickiness testing. Dough stickiness was determined by the Schwarzlaff-Shepherd Dough Stripping Method. Wheat samples from 1995-1996 were also analyzed for protein, ash, and moisture content, alkaline water retention capacity (AWRC), cookie diameter, tensile stress and strain, and by ¹³C nuclear magnetic resonance (¹³C-NMR) spectroscopy techniques. Significant (p = 0.0001) negative correlations were found between AWRC and cookie diameter of SRWWs grown in Warsaw and Blacksburg. Location was found to exert a significant effect on AWRC, cookie diameter and stickiness (p < 0.05). Farinograph data revealed that mixing characteristics of SRWW were affected significantly by variety, crop year and location (p < 0.05). In some cases the 1B/1R varieties had lower breakdown rates, longer departure times (DT) and lower mixing tolerance index (MTI), than their non-1B/1R counterparts. There was a significant difference (p = 0.0133) in the stickiness of 1B/1R and non-1B/1R samples from Blacksburg. However no such difference was found in the corresponding Warsaw samples (p = 0.9826), indicating that location exerted a significant effect on stickiness. Two flour samples exhibiting stickiness (one with and one without 1B/1R) and two non-sticky samples (one with and one without the 1B/1R) were fractionated into gluten, starch and water-solubles (WS) in order to determine if the sticky dough factor resided in the 1B/1R and / or non-1B/1R WS. The peel time of the interchanged samples, as in the case of 'Massey' flour combined with the WS from VA52-22, increased to 79 seconds from the 30 seconds originally observed in the Massey flour. However when gluten and starch fractions from a non-sticky, non-1B/1R sample,VA54-21, were mixed with WS from VA54-211 (sticky, 1B/1R), the peel time went from 18 in the original flour to 8 seconds. Tensile measurements showed dough stress was not significantly affected by the presence or absence of 1B/1R (p = 0.7057). However, dough strain was lower in 1B/1R translocated SRWWs (p = 0.0048). A ¹³C-NMR spectra failed to show differences amongst selected 1B/1R and non-1B/1R dough samples. Proton relaxation time (T1-rho-[H]) - a ¹³C-NMR technique, indicated that water did not exert a significant influence on the molecular dynamics within the dough samples of Massey (non-1B/1R), VA54-211 (1B/1R) and VA52-22 (1B/1R). However, the non-sticky, non-1B/1R sample (VA54-21) had a higher proton relaxation time at 62 ppm which may indicate the size of starch-protein particles in VA54-21 doughs were larger and less flexible than in the other three doughs.
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    Evaluating an Advanced Intensive Management Strategy for Virginia Wheat
    Childress, Michael Blanton (Virginia Tech, 2011-04-29)
    Current Virginia soft red winter wheat (Triticum aestivum L.) management strategies have been in place for over 20 years. A new advanced intensive management (AIM) system has been evaluated in order to improve Virginia wheat yields and attempt to bring state average wheat yields of 4288 kg ha⁻¹ more closely in-line with the maximum yield achieved in the Virginia Tech Official Soft Red Winter Wheat Trials of 7400 kg ha⁻¹. Increases in nitrogen (N) fertilizer application rates and splits, a chelated micronutrient blend, increased seeding rates, and a "no tolerance" pest control methodology were compared to current intensive management practices in this study. Additional fall N application and an increased seeding rate resulted in an increased number of tillers m-2 at growth stage (GS) 25 and biomass at GS 30. This increased number of tillers may lead to a greater amount of viable grain head production and increased wheat yields. Higher seeding and N application rate resulted in dramatically increased lodging in 2009 with resultant yield loss. Grain yield was significantly affected by management type in three of six instances. The number of heads m-2 was the yield component factor most influenced by factors tested in these studies.
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    Evaluating Methods of Screening for Pre-Harvest Sprouting in Soft Red Winter Wheat and the Effect of Delayed Harvest on Flour Properties
    Burt, Kelly R. (Virginia Tech, 2008-12-09)
    High pre-harvest rainfall in 2006 caused significant pre-harvest sprouting (PHS) and weathering throughout the mid-Atlantic soft red winter wheat (SRWW) (Triticum aestivum L.) growing region. Sprouting and weathering caused decreased flour quality due to lowered dough viscosity and decreased ability to withstand mixing and processing for baked goods. Due to its decreased quality, severely sprouted grain is sold for feed, at a lower price per bushel. Pre-harvest sprouting negatively affects the chain of production from the field to baking operations. The purpose of this research was to evaluate the inherent dormancy and PHS resistance, of current SRWW cultivars and to assess the relationship between falling number and flour quality after grain weathering. Employing a weighted germination index (WGI), a large range in dormancy was observed across SRWW cultivars and seed production. Artificial weathering tests confirmed the use of WGI as a tool for screening for dormancy of SRWW cultivars. The WGI consistently identified cultivars with significantly higher or lower inherent dormancy. "Coker 9553" was highly dormant and resistant to PHS. This cultivar maintained an average falling number of 300 seconds even after receiving an average of 215 mm of rainfall, while the mean falling number for all SRWW cultivars after this amount of weathering was 131 seconds. After only moderate weathering, nine of 15 SRWW cultivars in the study exhibited severe sprouting, demonstrating the need for increased PHS resistance in SRWW wheat. Pre-harvest sprouting resistance groupings, based on average 2008 cultivar falling number were accurately predicted by WGI at both 10 (R2=0.79) and 30°C (R2=0.72) No consistent relationship was observed between head angle, glume tenacity or awn length and PHS resistance. Water absorption, dough stability, farinograph arrival and departure times, peak, and 20-minute drop were measured from grain samples with varying degrees of weathering. All parameters were negatively affected by weathering in 2008. Flour quality parameters were more affected by genotype than falling number suggesting that falling number should not be used as the sole indicator of flour quality after grain weathering. It is clear that there are vast differences in dormancy levels and PHS resistance among SRWW cultivars and stronger dormancy and higher resistance to PHS does not automatically ensure higher quality flour.
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    Evaluation of Methods for Measuring Fusarium-Damaged Kernels of Wheat
    Ackerman, Arlyn J.; Holmes, Ryan; Gaskins, Ezekiel; Jordan, Kathleen E.; Hicks, Dawn S.; Fitzgerald, Joshua; Griffey, Carl A.; Mason, Richard Esten; Harrison, Stephen A.; Murphy, Joseph Paul; Cowger, Christina; Boyles, Richard E. (MDPI, 2022-02-21)
    Fusarium head blight (FHB) is one of the most economically destructive diseases of wheat (Triticum aestivum L.), causing substantial yield and quality loss worldwide. Fusarium graminearum is the predominant causal pathogen of FHB in the U.S., and produces deoxynivalenol (DON), a mycotoxin that accumulates in the grain throughout infection. FHB results in kernel damage, a visual symptom that is quantified by a human observer enumerating or estimating the percentage of Fusarium-damaged kernels (FDK) in a sample of grain. To date, FDK estimation is the most efficient and accurate method of predicting DON content without measuring presence in a laboratory. For this experiment, 1266 entries collectively representing elite varieties and SunGrains advanced breeding lines encompassing four inoculated FHB nurseries were represented in the analysis. All plots were subjected to a manual FDK count, both exact and estimated, near-infrared spectroscopy (NIR) analysis, DON laboratory analysis, and digital imaging seed phenotyping using the Vibe QM3 instrument developed by Vibe imaging analytics. Among the FDK analytical platforms used to establish percentage FDK within grain samples, Vibe QM3 showed the strongest prediction capabilities of DON content in experimental samples, R2 = 0.63, and higher yet when deployed as FDK GEBVs, R2 = 0.76. Additionally, Vibe QM3 was shown to detect a significant SNP association at locus S3B_9439629 within major FHB resistance quantitative trait locus (QTL) Fhb1. Visual estimates of FDK showed higher prediction capabilities of DON content in grain subsamples than previously expected when deployed as genomic estimated breeding values (GEBVs) (R2 = 0.71), and the highest accuracy in genomic prediction, followed by Vibe QM3 digital imaging, with average Pearson’s correlations of r = 0.594 and r = 0.588 between observed and predicted values, respectively. These results demonstrate that seed phenotyping using traditional or automated platforms to determine FDK boast various throughput and efficacy that must be weighed appropriately when determining application in breeding programs to screen for and develop resistance to FHB and DON accumulation in wheat germplasms.
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    Exploration of Physiological and Molecular Responses to Precipitation Extremes in Soybean and Nitrogen Fertility in Wheat
    Gole Tamang, Bishal (Virginia Tech, 2016-09-27)
    Soybean and wheat are important crop species due to their significance for human consumption, animal feed, and industrial use. However, increasing global population and worsening climate change have put a major strain on the production system of these crops. Natural disasters such as flooding and drought can severely impact growth and productivity of these crops. In addition, increased application of synthetic nitrogenous fertilizers to meet the global food demand has led to environment related issues. Therefore, with a goal of understanding mechanisms of flooding and drought tolerance in soybean and nitrogen-use-efficiency in wheat, we explored their physiological and transcriptomic regulation. We characterized the fundamental acclimation responses of soybean to flooding and drought and compared the metabolic and transcriptomic regulation during the stresses in a tissue-specific manner. We demonstrated the dynamic reconfiguration of gene expression and metabolism during flooding, drought, and recovery from these stresses. Our study displayed that flooding triggers more dramatic adjustments than drought at the transcriptional level. We also identified that the soybean genome encodes nine members of group VII ERF genes and characterized their responses in leaves and roots under flooding and drought. Based on the expression patterns, it is estimated that two of the nine genes are promising candidate genes regulating tolerance to submergence and drought. In addition, our genome-scale expression analysis discovered commonly induced ERFs and MAPKs across both stresses (flooding and drought) and tissues (leaves and roots), which might play key roles in soybean survival of flooding and drought. In wheat, we evaluated the effect of three different nitrogen rates on yield and its components across four diverse soft red winter wheat genotypes. The cultivar Sisson displayed superior performance in grain yield and nitrogen use efficiency at low nitrogen levels. Our results suggested that improvement of nitrogen use efficiency in low nitrogen environments can be achieved through the selection of three components: grain number/spike, 1000-seed weight, and harvest index. Overall, this study has advanced our understanding of how plants respond to abiotic stresses such as flooding, drought, and nutrient limitation conditions.
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    Flour quality and dough stickiness of soft red winter wheat lines with and without 1B/1R translocations
    Schwarzlaff, Sabine S. (Virginia Tech, 1995)
    Wheat (Triticum aestivum L.) is one of the major cereals of the world. Farmers must produce wheat with good yield and quality to meet the high demands for wheat flour. To reduce disease and increase wheat yield, cultivars have been developed by replacing the short arm of chromosome 1B of wheat with the short arm of the 1R chromosome from rye (Secale cereale L.). This wheat-rye translocation, 1B/1R, carries linked genes which makes these wheat cultivars more disease resistant and higher yielding. Unfortunately, the 1B/1R translocation in hard wheats has been shown to produce undesirable characteristics such as dough stickiness and reduced mixing tolerance. Many promising wheat lines have been developed by crossbreeding 1B/1R Jines with soft wheat in hopes of producing a 1B/1R soft wheat of good quality for use in soft wheat products. The purpose of this research was to determine the end use quality of flours from soft red winter wheats possessing 1B/ 1R. Fourteen soft wheat varieties (7 without 1 B/1 R and 7 with 1B/lR) grown in two Virginia locations, Warsaw and Blacksburg, were assessed for flour quality and dough stickiness. Four pairs of the experimental wheats were sister lines. Flour quality was evaluated by means of protein content, farinograph analysis, cookie spread and protein analysis. Dough stickiness was measured using the "Schwarzlaff-Shephard Dough Stripping Method", specially designed for this study. It is the first method of its kind to measure dough stickiness quantitatively. Results indicated that the 1B/1R translocation, in general, had no adverse effect on flour quality and dough stickiness of the experimental wheats and even improved mixing tolerance and stability of the wheat flour doughs. The results of the study indicate that flours of 1B/lR wheats can be used in commercial soft wheat bakery formulas.
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    Genetic Analysis of Soybean Mosaic Virus Resistance in Soybean
    Gunduz, Irfan (Virginia Tech, 2000-01-28)
    This research was conducted to analyze the genetics of soybean mosaic virus (SMV) resistance in soybean [Glycine max (L.) Merr.] and to determine allelic relationships of SMV resistance genes and their interactions with SMV strain groups. In the first part of this study, the inheritance of SMV resistance in OX670 and 'Harosoy' was studied to determine the source and identity of the resistance gene/genes in OX670. Other researchers reported that OX670 possesses a single gene at a locus independent of Rsv1 and assigned the gene symbol Rsv2. Rsv2 was presumably derived from the cultivar 'Raiden'. However, later work showed that Raiden contains a single resistance gene at the Rsv1 locus, raising the possibility that the resistance gene in OX670 was not from Raiden. Harosoy and its derivatives make up much of the remaining pedigree of OX670. Results from crosses of OX670 with susceptible cultivars indicate that it contains two independent genes for SMV resistance. One is allelic to the Rsv1 locus, expresses resistance to SMV-G1 and G7 and is derived from Raiden. The other is allelic to the Rsv3 locus, expresses resistance to SMV-G7 but susceptibility to SMV-G1 and is derived from Harosoy. Therefore the Rsv2 locus does not appear to exist in OX670 or its ancestors. The presence of Rsv1 and Rsv3 makes OX670 resistant to all SMV strains from G1 through G7. The second study was conducted to investigate the inheritance and allelomorphic relationships of resistance gene(s) in 'Tousan 140' and 'Hourei', which were reported to carry single independent resistance genes when inoculated with the Japanese SMV strain C. Both of these lines exhibit resistance to strains SMV-G1 through G7. This inheritance study shows that Tousan 140 and Hourei each possess two resistance genes. One of the genes in Hourei confers resistance to SMV-G1 and G7 strains; the other gene confers susceptibility to SMV-G1 but resistance to SMV-G7. Allelism tests indicate that one of the genes in both Hourei and Tousan 140 is allelic to Rsv1, and the other is allelic to Rsv3. The two genes in Tousan 140 were separated into individual lines, R1 and R2. R1, most probably containing Rsv1, exhibited resistance to SMV-G1 through G3 but was susceptible to SMV-G5 through G7. Line R2, most likely possesses Rsv3 gene, was susceptible to SMV-G1 through G3 but resistant to SMV-G5 through G7. Therefore, presence of these two genes makes Tousan 140 resistant to SMV-G1 through G7. The objective of the third study was to investigate inheritance and allelomorphic relationships of SMV resistance in PI88788. PI88788 exhibits resistance to SMV-G1 through G7. Genetic analysis of our data reveals that SMV resistance in PI88788 is conferred by a single gene at a locus tentatively labeled 'Rsv4'. Expression of this gene in the homozygous state decreased accumulation rate and prevented vascular movement of SMV. In the heterozygous state vascular movement of the SMV was delayed but not prevented.