bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent Molecular and Genomic Studies on Stress Tolerance of Forage and Turf Grasses
Authors: Zhang Y. , Mian M. A. R. , Bouton J. H.
Published: February 2006

Improvement in stress tolerance of forage and turf grasses is a major breeding goal. Most forage and some turf grasses are grown on marginal lands under stressful environments with minimal inputs. In contrast, current high‐input turf grass production systems such as golf courses and lawns are expensive and often environmentally unfriendly. Cultivars with improved stress tolerance are necessary for the development of sustainable and environmentally friendly production systems. Until recently, decades of breeding and selection have resulted in limited improvements of stress tolerance of forage and turf grass species. Recent developments in molecular and genomic sciences suggest new methods to improve stress tolerance in many plants, but compared to major crop plants (e.g., rice [Oryza sativa L.], wheat [Triticum spp.], and maize [Zea mays L.]), the development of molecular and genomic resources for forage and turf grasses has been limited. In this review, we present an overview of recent molecular and genomic studies aimed at improving stress tolerance of forage and turf grasses, including endophyte grass interactions. Important molecular and genomic resources are now available for some forage and turf grasses, including ryegrasses (Lolium spp.) and fescues (Festuca spp.). Noteworthy progress is being made in improvements of both biotic and abiotic stress tolerances of these grasses, but the challenge is to simplify and streamline the molecular tools and new discoveries for cost‐effective and efficient application in forage and turf grass breeding. Stress tolerances of many forage and turf grasses are influenced by their mutualistic association with Neotyphodium spp. endophytes, and this area of research is discussed.
Breeding Effects on Nitrogen Use Efficiency of Spring Cereals under Northern Conditions
Authors: Muurinen S. , Slafer G. A. , Peltonen‐Sainio P.
Published: February 2006

Spring cultivars of barley (Hordeum vulgare L.), oat (Avena sativa L.), and wheat (Triticum aestivum L.) are the most important crops in Finnish agricultural systems. The increasing need to reduce pollution from N fertilizer is concomitantly strengthening the importance of improving the understanding of nitrogen use efficiency (NUE) of these crops. The aim of this work was to study the differences in NUE, defined as the crop's ability to produce yield with one available N unit, among spring cereal cultivars, and to determine the achievements of plant breeding in NUE under northern European growing conditions. Field experiments were conducted in Finland during 2003 and 2004. Samples from matured plants of 17 to 18 cultivars of each of the three cereal species released between 1909 and 2002 were studied. There were no clear differences in NUE among modern spring cultivars. However, there were cultivar differences within species and significant NUE improvements on wheat and particularly for oat across time. There was no clear trend of NUE and year of release of cultivars in two‐row spring barley, probably because breeding for malting barley involves consistent selection for low‐protein cultivars. The study revealed that most breeding effects on NUE were associated with changes in nitrogen uptake efficiency (UPE).
Characterization of Amphiploid Hybrids between Bluebunch and Thickspike Wheatgrasses
Authors: Jensen Kevin B. , Maughan Kory W. , Asay Kay H.
Published: February 2006

An amphiploid derivative from hybrids between bluebunch wheatgrass (2n = 2x = 14) [Pseudoroegneria spicata (Pursh) A. Love] and thickspike wheatgrass (2n = 4x = 28) [Elymus lanceolatus (Scribner and Smith) Gould] was developed to compare cytological, morphological, anatomical, and seed characteristics between the triploid F1 hybrids (2n = 3x = 21) and their colchicine induced hexaploid (2n = 6x = 42) derivative (C0). The amphiploid population produced an average of 3.1 seeds spikelet−1 and pollen stainability averaged 85.5%. Seed set under self‐pollination in the amphiploids ranged from <1% to >99% with an average of 50%. Fifty‐eight of the 103 plants studied were hexaploid (2n = 6x = 42). The remaining plants had chromosomes ranging from 2n = 39 to 2n = 44 and were less fertile than the euploids. Meiosis in the euploid plants was regular and typical of a segmental autoallohexaploid St1St1St2St2HH. The most common meiotic chromosome configuration was 21 bivalents. A high frequency of bivalents and a low frequency of quadrivalents indicate that the St genomes of the two parental species have diverged. The amphiploids had thicker culms, more leaves per culm, and longer and wider leaves than either parental species. Multivariate analysis demonstrated that the amphiploids, though morphologically similar to the parental species, was distinct. In general, C0 hybrids were less vigorous than the F1 from which they were derived. Through amphiploidy, genetic introgression between the two species is possible.
Spectral Reflectance Indices as a Potential Indirect Selection Criteria for Wheat Yield under Irrigation
Authors: Babar M. A. , Reynolds M. P. , van Ginkel M. , Klatt A. R. , Raun W. R. , Stone M. L.
Published: February 2006

The objectives of this study were to assess the potential of using spectral reflectance indices (SRI) as an indirect selection tool to differentiate spring wheat (Triticum aestivum L.) genotypes for grain yield under irrigated conditions. This paper demonstrates only the first step in using the SRI as indirect selection criteria by reporting genetic variation for SRI among genotypes, the effect of phenology and year on SRI and their interaction with genotypes, and the correlations between SRI and grain yield and yield components of wheat. Three field experiments—15 CIMMYT globally adapted genotypes (GHIST), 25 random F3–derived lines (RLs1), and 36 random F3–derived lines (RLs2)—were conducted under irrigated conditions at the CIMMYT research station in northwest Mexico in three different years. Five previously developed SRI (photochemical reflectance index [PRI], water index [WI], red normalized difference vegetation index [RNDVI], green normalized difference vegetation index [GNDVI], simple ratio [SR]) and two newly calculated SRI (normalized water index‐1 [NWI‐1] and normalized water index‐2 [NWI‐2]) were evaluated in the experiments. In general, genotypic variation for all the indices was significant. Near infrared radiation (NIR)–based indices (WI, NWI‐1, NWI‐2) gave the highest levels of association with grain yield during the 3 yr of the study. A clear trend for higher association between grain yield and the NIR‐based indices was observed at heading and grainfilling than at booting. Overall, NIR‐based indices were more consistent and differentiated grain yield more effectively compared to the other indices. The results demonstrated the potential of using SRI as a tool in breeding programs for selecting for increased genetic gains for yield.
Adaptedness and Heterosis in Corn and Mule Hybrids
Authors: Troyer A. Forrest
Published: February 2006

The origin of U.S. Corn Belt corn (Zea mays L.), heterotic groups, and heterotic patterns becomes less obvious with more cycles of breeding. Heterosis is poorly understood; simple curiosity cries out for more information. I endeavor to shed light on the effect of adaptedness and heterosis on U.S. Corn Belt corn. I relate pertinent happenings in the phenomenal increase in U.S. corn production. I briefly review the origins of Northern Flint and Southern Dent races of corn and two major, persistent open‐pollinated cultivars; and how corn hybridization was preceded and eased by hybrid species of the horse (Equus spp.). I discuss heterotic groups and patterns. The objective of U.S. corn breeding has been to adapt a tropical crop to a temperate climate. Adaptedness is important. Open‐pollinated cultivars emphasized local adaptation, but some cultivars were more popular, widely grown, and better adapted over a broad geographic region. Hybrid seed corn companies grew larger by selling more widely adapted hybrids that favored germplasm from the more popular, widely grown, better adapted open‐pollinated cultivars containing more genes for adaptedness. I examine morphological differences between inbred parents of a widely adapted hybrid. Relatively constant percentage of heterosis of well‐adapted hybrids over years is due to seasonal climate affecting hybrids and their parent inbreds in a like manner because of their selection for adaptedness. Adaptedness has been more important than heterosis in the U.S. corn yield and production increases. Adaptedness in analogous heterotic species hybrids of the genus Equus, where body size is female dominant, apparently discriminates for body size between mules and hinnies that have virtually identical genotypes—adaptedness determines superiority over and above heterosis.
Marker‐Assisted Selection for the Broad‐Spectrum Potato Late Blight Resistance Conferred by Gene RB Derived from a Wild Potato Species
Authors: Colton Lara M. , Groza Horia I. , Wielgus Susan M. , Jiang Jiming
Published: February 2006

Potato (Solanum tuberosum L.) late blight, caused by Phytophthora infestans (Mont.) de Bary, is one of the most damaging diseases in any crop. Deployment of resistant varieties is the most effective way to control this disease. However, breeding for late blight resistance has been a challenge because the race‐specific resistance genes introgressed from wild potato S. demissum Lindl. have been short lived and breeding for “horizontal” or durable resistance has achieved only moderate successes. We previously demonstrated that the high‐level late blight resistance in a wild potato relative, S. bulbocastanum Dunal subsp. bulbocastanum, is mainly controlled by a single resistance gene RB Transgenic potato lines containing the RB gene have showed strong late blight resistance, comparable to the backcrossed progenies derived from the somatic hybrids between potato and S. bulbocastanum Here we report the development of a polymerase chain reaction‐based DNA marker for tracking the RB gene in breeding populations derived from the potato × S. bulbocastanum somatic hybrids. Several marker‐positive breeding lines showed the expected late blight resistance in greenhouse evaluations. Our results demonstrate that marker‐based selection will allow us to effectively transfer the RB gene into potato using traditional breeding methods, an alternative to deploying the RB gene through genetic transformation.
Cytogenetic and Nuclear DNA Content Characterization of Diploid Bromus erectus and Bromus variegatus
Authors: Tuna Metin , Vogel Kenneth P. , Arumuganathan K.
Published: February 2006

Bromus erectus Huds. (erect brome) and B. variegatus M. Bieb. are Eurasian Bromus species that have been tentatively identified as potential progenitors of smooth bromegrass (B. inermis Leyss) which is the principal cultivated bromegrass in North America. The objective of this study was to characterize the genome of diploid accessions of B. erectus (2n = 2x = 14) and B. variegatus (2n = 2x = 14) using nuclear DNA content and cytogenetic analysis using Giemsa C‐banding. The nuclear DNA content for B. erectus (6.19 ± 0.08 pg 2C−1) was less than that of B. variegatus (6.76 ± 0.05 pg 2C−1). These two species can be distinguished cytogenetically with the karyotypes that were developed. Complete karyotypes were not developed for both species because within species, multiple chromosomes were similar in size and C‐banding. Both species had two pairs of chromosomes with satellites but the size of the satellites and the number and position of C‐bands on these chromosomes differed between species. Bromus variegatus had five pairs of chromosomes with telomeric C‐bands on both arms, while B. erectus had four pairs of chromosomes with a single telomeric band on the long arm and a single pair with telomeric bands on both arms. Comparison with the previously reported karyotypes and nuclear DNA contents for tetraploid and octaploid B. inermis suggest that if the diploid species B. erectus and B. variegatus were the donor species for these polyploids, significant evolutionary changes have occurred since the initial formation of these species including chromosome loss and re‐arrangement.
Forage Preservation Method Influences Alfalfa Nutritive Value and Feeding Characteristics
Authors: Hancock D.W. , Collins M.
Published: February 2006

Forage preserved as baled silage can reduce dry matter and quality losses compared with hay systems if sufficient stretch wrap is layered to adequately exclude oxygen. The objectives of this study were to determine the optimum film amount for alfalfa (Medicago sativa L.) preserved as round bale silage and to compare the forage quality and losses to that of dry hay. Two field trials compared alfalfa silages wrapped in two, four, or six layers of plastic film and hay controls. Bales wrapped with four or six layers had significantly lower temperatures than two layer treatments. In Trial 1 (July harvest), silage with two layers had higher post‐storage neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) concentrations than did silage prepared with either four or six layers. No consistent differences in forage quality parameters were observed among silage treatments in Trial 2 (September harvest). After 5 mo, concentrations of ADF, NDF, and ADL in the silages with four or six layers of film were lower than hay in both trials; however, crude protein (CP) did not differ across preservation treatments. In a preference trial, cows (Bos taurus) offered all treatments from Trial 2 preferred silages preserved with four or six layers of film to the two‐layer treatment and hay control. We conclude that more than two layers of film are needed for consistent preservation of alfalfa round bale silage. The results demonstrated the potential advantage in quality for alfalfa baled silage compared with conventionally harvested and stored hay.
Estimating Genotypic Correlations and Their Standard Errors Using Multivariate Restricted Maximum Likelihood Estimation with SAS Proc MIXED
Authors: Holland James B.
Published: February 2006

Plant breeders traditionally have estimated genotypic and phenotypic correlations between traits using the method of moments on the basis of a multivariate analysis of variance (MANOVA). Drawbacks of using the method of moments to estimate variance and covariance components include the possibility of obtaining estimates outside of parameter bounds, reduced estimation efficiency, and ignorance of the estimators' distributional properties when data are missing. An alternative approach that does not suffer these problems, but depends on the assumption of normally distributed random effects and large sample sizes, is restricted maximum likelihood (REML). This paper illustrates the use of Proc MIXED of the SAS system to implement REML estimation of genotypic and phenotypic correlations. Additionally, a method to obtain approximate parametric estimates of the sampling variances of the correlation estimates is presented. MANOVA and REML methods were compared with a real data set and with simulated data. The simulation study examined the effects of different correlation parameter values, genotypic and environmental sample sizes, and proportion of missing data on Type I and Type II error rates and on accuracy of confidence intervals. The two methods provided similar results when data were balanced or only 5% of data were missing. However, when 15 or 25% data were missing, the REML method generally performed better, resulting in higher power of detection of correlations and more accurate 95% confidence intervals. Samples of at least 75 genotypes and two environments are recommended to obtain accurate confidence intervals using the proposed method.
Management of Switchgrass‐Dominated Conservation Reserve Program Lands for Biomass Production in South Dakota
Authors: Mulkey V. R. , Owens V. N. , Lee D. K.
Published: February 2006

Switchgrass (Panicum virgatum L.) has been planted on land enrolled in the Conservation Reserve Program (CRP). Management strategies for conversion of this land from CRP to biomass energy require evaluation. Objectives of this study were to: (i) determine the effect of harvest timing and N rate on biomass production and characteristics of switchgrass land enrolled in or managed similarly to CRP and (ii) evaluate the impact of harvest management on species composition and persistence. Five N rates (spring applications of 0, 56, 112, and 224 kg ha−1 and 224 kg ha−1 split between spring and postharvest) and two harvest timings (anthesis and post‐killing frost) were applied to plots from 2001 to 2003 at three South Dakota locations. Harvesting after a killing frost produced higher total yields and improved switchgrass persistence compared with anthesis harvests. The concentration of neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) increased between anthesis and killing‐frost harvests, while total nitrogen (TN) and ash decreased. Nitrogen applied at 56 kg ha−1 increased total biomass without affecting switchgrass persistence, but there was no additional benefit with N above 56 kg ha−1 Harvesting long‐established switchgrass stands once per year after a killing frost and applying N at 56 kg ha−1 was an effective system for switchgrass biomass production and persistence on land enrolled in or managed similarly to CRP in South Dakota.
Resistance to Tobacco Black Shank in Nicotiana Species
Authors: Li B.‐C. , Bass W. T. , Cornelius P. L.
Published: February 2006

Black shank [caused by Phytophthora parasitica (Dast.) var. nicotianae (B. de Haan) Tucker] is one of the most devastating diseases in tobacco (Nicotiana tabacum L.). Phytophthora parasitica var. nicotianae race 1 is the most damaging race of this fungus. The objective of this study was to identify the Nicotiana species that are resistant to P. parasitica var. nicotianae race 1 as part of the effort to develop Nicotiana‐based plant varieties for applications in the production of plant‐made pharmaceuticals (PMPs). The roots of approximately 26‐d‐old growth room–grown plants were inoculated with zoospores of an isolate of P. parasitica var. nicotianae race 1 by a dipping procedure. The percentage of plants that were free of symptoms 10 to 14 d after inoculation was taken as a measure of resistance to the fungus. We evaluated a total of 97 Nicotiana accessions from 37 species from the USDA collection and other sources. Among the 97 accessions, three from N. debneyi Domin, two from N. repanda Willd. ex Lehm., and one each from N. megalosiphon Van Heurck & Mull. Arg., N. plumbaginifolia Viv., N. suaveolens Lehm., and N. sylvestris Speg. & Comes were found to be resistant. Their resistances were further confirmed after they were evaluated for an additional three times. These nine accessions were then challenged by another isolate of race 1. All accessions except for the N. sylvestris accession were found to be resistant. Nicotiana debneyi, N. megalosiphon, and N. suaveolens were not previously reported to be resistant to P. parasitica var. nicotianae race 1. Our study indicated that the undomesticated Nicotiana species constitute a rich genetic source for resistance to the tobacco disease black shank.
QTLs Associated with Resistance to Soybean Cyst Nematode in Soybean: Meta‐Analysis of QTL Locations
Authors: Guo B. , Sleper D. A. , Lu P. , Shannon J. G. , Nguyen H. T. , Arelli P. R.
Published: February 2006

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is the most important pest of soybean [Glycine max (L.) Merr.] in the world. A total of 17 quantitative trait locus (QTL) mapping papers and 62 marker–QTL associations have been reported for resistance to soybean cyst nematode in soybean. Conflicting results often occurred. The objectives of this study were to: (i) evaluate evidence for reported marker–QTL associations for resistance to SCN in soybean and (ii) extract relatively reliable and useful information from the reported marker–QTL associations in soybean. A meta‐analysis was conducted for QTL locations by comparing the 95% confidence intervals of the reported QTLs. QTLs for different races or different studies were classified into one cluster if their confidence intervals had a region in common. The QTLs of the same cluster may have a shared locus. QTLs for different races or different studies were classified into different clusters if their confidence regions had no region in common and were ≥ 20 cM away from each other. Different clusters may represent different loci. Reported SCN resistant QTLs were classified into three categories: suggestive, significant, and confirmed. Confirmed QTLs are credible and can be candidates for fine mapping and gene cloning. QTLs on linkage groups (LGs) G, A2, B1, E, and J were classified as confirmed. Two clusters of QTLs were identified on LG G. One of them is rhg1 One cluster of QTLs was identified near the end of LG B1, but one QTL may exist around the middle of LG B1. One cluster of QTLs was identified on LGs A2, E, and J, respectively. QTLs on LGs B2, C1, C2, D1a, D2, L, M, and N were classified into suggestive or significant. Confirmation studies are needed to lend credibility for these QTLs. A relationship between soybean QTLs and SCN races is discussed.
Relationships between Emergence and Soil Water Content for Perennial Cool‐Season Grasses Native to Iran
Authors: Gazanchian Ali , Khosh Kholgh Sima Nayer A. , Malboobi Mohamad A. , Majidi Heravan Eslam
Published: February 2006

Native cool‐season grasses are important for improvement of arid and semiarid rangelands in Iran. However, germination and seedling emergence of these species is a critical phase in these areas and are not well understood. The objective of this study was to evaluate the effect of low soil moisture on emergence of 36 populations of native cool‐season grasses from 15 species of seven genera including Elymus, Agropyron, Secale, Hordeum, Bromus, Festuca, and Dactylis that were collected from different locations of Iran. A pot experiment was conducted in a greenhouse using a completely randomized design with three replicates. The populations were evaluated under field capacity (FC, −0.33 MPa), 75, 50, and 25% FC. Decreasing soil water content from FC to 25% FC reduced overall mean emergence from 69.3% to zero. Significant differences occurred among species and soil moisture levels for all characters except root/shoot dry weight ratio. Seedling emergence rate and root and shoot growth were decreased by limiting soil water content, while root‐to‐shoot length ratio (43%) was increased. Minimum water requirement for seedling emergence of all species except Dactylis glomerata L. was 50% FC (−0.6 MPa). Cluster analysis and canonical discriminant analysis separated the populations into five clusters. Populations in Clusters I and III had intermediate, Cluster II the greatest, and Clusters IV and V the least tolerance to low soil moisture. Cluster I and III had greater root and shoot biomass and rapid emergence, whereas decreasing soil moisture caused a severe reduction of root growth of 60% compared with the control. In response to low soil moisture, Cluster II showed high final emergence and the greatest stability (low sensitivity index) of root growth. Clusters IV and V had delayed emergence, low growth potential, and high sensitivity index for shoot and root growth under low soil moisture. In response to low soil moisture, there were differences among species and accessions of the same species collected from different ecological regions. These results suggest that the genetic diversity of Cluster II could be used for plant breeding programs and renovation of pastures in arid and semiarid regions of Iran.
Global Adaptation of Spring Bread and Durum Wheat Lines Near‐Isogenic for Major Reduced Height Genes
Authors: Mathews Ky L. , Chapman Scott C. , Trethowan Richard , Singh Ravi P. , Crossa Jose , Pfeiffer Wolfgang , van Ginkel Maarten , DeLacy Ian
Published: February 2006

The effect of major dwarfing genes, Rht‐B1 and Rht‐D1, in bread (Triticum aestivum L.) and durum (Triticum turgidum L. var. durum) wheats varies with environment. Six reduced‐height near‐isogenic spring wheat lines, included in the International Adaptation Trial (IAT), were grown in 81 trials around the world. of the 56 IAT trials yielding >3 Mg ha−1, the mean yield of semidwarfs was significantly greater than talls in 54% of trials; in the 27 trials yielding <3 Mg ha−1, semidwarfs were superior in only 24%. Sixteen pairs of semidwarf–tall near‐isolines were grown in six managed drought environment trials (DETs) in northwestern Mexico. In these trials, semidwarfs outyielded talls in all but the most droughted environment (2.5 Mg ha−1). The effect of the height alleles varied with genetic background and environment. For both yield and height, variance components for allele and environment by allele interaction were larger than those for genetic background and genetic background by environment. Pattern analysis showed that tall and semidwarf lines had similar adaptation to stressed environments (<2.8 Mg ha−1, low rainfall), while semidwarfs yielded more in less stressed environments (>4.3 Mg ha−1, high rainfall). The best adapted near‐isogenic pair had a Kauz background, where the tall was only 16% taller than the dwarf. In the Kauz‐derived pair, the semidwarf outyielded the tall in only 13% of trials with no differences in low yielding trials. This supports the idea that “short talls” may be useful in marginal environments (yield <3 Mg ha−1).
Usefulness of Gene Information in Marker‐Assisted Recurrent Selection: A Simulation Appraisal
Authors: Bernardo Rex , Charcosset Alain
Published: February 2006

Genomics and post‐genomics sciences are expected to uncover most, if not all, of the quantitative trait loci (QTL) in plants. Prior knowledge of QTL locations can then be exploited in marker‐assisted recurrent selection (MARS). Our objectives were to determine (i) whether prior knowledge of QTL locations is advantageous in MARS, and (ii) whether knowledge of the QTL themselves, as opposed to knowledge of markers linked to QTL, is advantageous in MARS. We simulated MARS in a maize (Zea mays L.) F2 population. We found that when 10 QTL controlled the trait, the percentage of known QTL that maximized the response to MARS was PMax = 100%. In contrast, PMax was often less than 100% when 40 or 100 QTL controlled the trait and QTL effects were estimated with a population size (N = 100) typically used in MARS. This result implied it was advantageous to exploit only the QTL with large effects and ignore those with small effects, even if the locations of all QTL were known. For a trait controlled by 40 QTL, the response was up to 50% greater when PMax = 70% of the QTL were known through markers for the QTL themselves rather than through linked markers. We conclude that having known QTL in MARS is most beneficial for traits controlled by a moderately large number of QTL (e.g., 40). We speculate that a combination of approaches would be needed to exploit information on markers for QTL themselves, markers linked to QTL, and unknown QTL.
Glycine soja PI 468916 SCN Resistance Loci's Associated Effects on Soybean Seed Yield and Other Agronomic Traits
Authors: Kabelka E. A. , Carlson S. R. , Diers B. W.
Published: February 2006

The soybean cyst nematode (SCN, Heterodera glycines Riggs and Niblack) is the most important soybean [Glycine max (L.) Merr.] pathogen in the USA and its control relies on genetic resistance. When resistance genes from exotic sources are transferred into elite cultivars, deleterious alleles are frequently transferred with resistance through genetic linkages. Two SCN resistance loci have been identified in G. soja Sieb. and Zucc. PI 468916, and the effect these loci have on yield and other agronomic traits is not known. The objective of this study was to determine the effect of each G. soja SCN resistance gene on yield and other agronomic traits in elite soybean backgrounds. These effects were tested in two populations each segregating for SCN resistance derived from G. soja, with one population also segregating for the SCN resistance loci, rhg1, derived from G. max PI 88788. Each population was analyzed for genetic markers linked to the SCN resistance loci and field tested in multiple environments with low to high SCN infestations. The G. soja and rhg1 SCN resistance alleles either had no effect or significantly (P < 0.05) enhanced yield compared with the susceptible alleles. The SCN resistance alleles were also associated with increasing days to maturity, plant height, and lodging scores. Deployment of the G. soja SCN resistance loci will increase the genetic diversity for SCN resistance and will provide breeders with an alternative source of SCN resistance that is not associated with reduced yield.
Polyphenol Oxidase and o‐Diphenols Inhibit Postharvest Proteolysis in Red Clover and Alfalfa
Authors: Sullivan Michael L. , Hatfield Ronald D.
Published: February 2006

Many forages experience significant proteolytic losses when preserved by ensiling. Such losses in alfalfa (Medicago sativa L.) are especially high, with degradation of 44 to 87% of the forage protein to nonprotein N (NPN). In contrast, red clover (Trifolium pratense L.) has up to 90% less proteolysis during ensiling. Here we demonstrate that the combination of polyphenol oxidase (PPO) and o‐diphenol PPO substrates, both abundantly present in red clover, is responsible for postharvest proteolytic inhibition in this forage crop. Proteolysis in red clover leaf extracts increased nearly fivefold when endogenous o‐diphenols were removed by gel filtration but returned to starting levels by adding back an exogenous o‐diphenol. Proteolysis in leaf extracts of red clover plants silenced for PPO expression was dramatically increased compared to control plants. Leaf extracts of transgenic alfalfa expressing a red clover PPO gene showed a nearly fivefold o‐diphenol–dependent decrease in proteolysis compared to those of control alfalfa. We also demonstrate that PPO levels 10‐ to 20‐fold lower than those typically found in red clover are sufficient for proteolytic inhibition, that as little as 0.25 μmol o‐diphenol mg−1 protein has a substantial impact on proteolysis, that a wide variety of o‐diphenols are functional substrates in proteolytic inhibition, and that proteolysis is reduced for PPO‐expressing alfalfa in small‐scale ensiling experiments. Together, these results indicate that PPO and o‐diphenols can be an effective treatment to prevent protein loss in ensiled forage crops.
Anion Exchange Membrane Soil Nitrate Predicts Turfgrass Color and Yield
Authors: Mangiafico Salvatore S. , Guillard Karl
Published: February 2006

Desirable nitrogen (N) management practices for turfgrass supply sufficient N for high quality turf while limiting excess soil N. Previous studies suggested the potential of anion exchange membranes (AEMs) for predicting turfgrass color, quality, or yield. However, these studies suggested a wide range of critical soil nitrate‐nitrogen (NO3–N) values across sample dates. A field experiment, in randomized complete block design with treatments consisting of nine N application rates, was conducted on a mixed species cool‐season turfgrass lawn across two growing seasons. Every 2 wk from May to October, turfgrass color was assessed with three different reflectance meters, and soil NO3–N was measured with in situ AEMs. Cate‐Nelson models were developed comparing relative reflectance value and yield to AEM desorbed soil NO3–N pooled across all sample dates. These models predicted critical AEM soil NO3–N values from 0.45 to 1.4 μg cm−2d−1Turf had a low probability of further positive response to AEM soil NO3–N greater than these critical values. These results suggest that soil NO3–N critical values from AEMs may be applicable across sample dates and years and may serve to guide N fertilization to limit excess soil NO3–N.
Use of Chlorophyll Fluorescence Assessments to Differentiate Corn Hybrid Response To Variable Water Conditions
Authors: O'Neill Patrick M. , Shanahan John F. , Schepers James S.
Published: February 2006

Development of corn (Zea mays L.) germplasm tolerant to water stress will be vital to sustaining corn‐based farming in the U.S. Great Plains. In a companion 4‐yr field study near Shelton, NE, we found that 12 hybrids displayed differential agronomic responses to varying water levels, with tolerant hybrids yielding from 27 to 42% more than susceptible hybrids under stress while yielding similarly under no stress. The objective of this study was to determine if chlorophyll fluorescence (CF) measurements could be used to distinguish tolerant from susceptible hybrids. Leaf temperature (LT) and two CF parameters (ΦPSII, photosystem II quantum efficiency, and ETR, electron transport rate) were measured on three postflowering dates in 2001 using a fluorometer on a subset of original treatments involving two tolerant and susceptible hybrids grown under deficit and adequate water. Water effects were observed on only one date; LT was 2.5°C warmer and ΦPSII and ETR values were 25% lower for deficit vs. adequate water just after silking, signifying increased water stress and decreased photosynthesis during reproductive growth. Under stress, LTs were 2.8°C cooler and ΦPSII and ETR values 50% higher for tolerant vs. susceptible hybrids, while all hybrids produced similar CF values under no stress. Thus, grain yield and photosynthetic responses of hybrids to stress were similar, indicating that CF measurements can be used to distinguish tolerant from susceptible hybrids.
Variation in Nutritional Value of Sorghum Hybrids with Contrasting Seed Weight Characteristics and Comparisons with Maize in Broiler Chicks
Authors: Kriegshauser Travis D. , Tuinstra Mitchell R. , Hancock Joe D.
Published: February 2006

Sorghum [Sorghum bicolor (L.) Moench] hybrids with high seed weight often have higher protein and fat contents. Experiments were conducted to compare the feeding value of grain sorghum hybrids contrasting in seed weight and composition with conventional hybrid maize (Zea mays L.). Feeding assays were conducted using broiler chicks to determine the metabolizable energy (ME) content of the various cereal grains. Eight sorghum hybrids were produced from crosses of two seed parents with two normal‐seeded and two large‐seeded male parent lines. The seed parent lines were ASA3042 and AWheatland. The normal‐seeded male parents were RTx2737 and RTx435, and the large‐seeded parents were KS115 and Eastin‐1. The eight sorghum hybrids and a hybrid maize check were produced under dryland conditions at Manhattan and Ottawa, KS, in 2000 and at Manhattan and Belleville, KS, in 2001. Feeding trials were conducted in the spring of 2001 and 2002. Each trial consisted of a reference diet and the hybrid maize and sorghum entries with six pens per treatment. A combined analysis across environments indicated that hybrid maize had an ME value of 3.51 Mcal kg−1 and the large‐seeded male parent, KS115, produced hybrids with ME values that averaged 3.48 Mcal kg−1 Normal‐seeded hybrids averaged 3.36 Mcal kg−1 These studies indicate that use of KS115 as a means of increasing seed weight and fat content of grain sorghum may also contribute to increased nutritional value of the grain.
Efficient Deletion of Transgenic DNA from Complex Integration Locus of Rice Mediated by Cre/lox Recombination System
Authors: Moore Sarah K. , Srivastava Vibha
Published: February 2006

Transgenic plants may contain several DNA elements, most notably the selectable marker genes, that are not needed after the selection of the transgenic line. Using site‐specific recombination system, such as Cre/lox, targeted deletion of these so‐called unneeded DNA elements can be achieved. To study the efficiency of Cre/lox‐mediated deletion of transgenic DNA from complex locus generated by particle bombardment, we generated two transgenic rice (Oryza sativa L.) lines that contain several copies of lox‐flanked β‐glucuronidase (GUS) gene (gusA) and unmarked hygromycin resistance (hpt) gene and crossed them with a Cre‐expressing line. Excision of both gusA and hpt genes occurred in F1 hybrids. Molecular data demonstrated that Cre/lox recombination was initiated randomly in F1 plants leading to complete excision of all transgene fragments in somatic tissue. F2 analysis suggested that efficient excision also occurred in germline, preventing the transfer of lox‐flanked genes into most of the F2 plants. Further, the excised DNA did not apparently re‐integrate into the genome. Thus, Cre/lox‐mediated DNA recombination in rice is highly suitable for the removal of the unneeded transgenic DNA.
Comparison of an indirect immunofluorescence assay, western blot analysis, and a commercially available ELISA for detection of Ehrlichia canis antibodies in canine sera
Authors: O'Connor Thomas P. , Hanscom Jancy L. , Hegarty Barbara C. , Groat Randall G. , Breitschwerdt Edward B.
Published: February 2006

Objective—To examine the correlation between results for an indirect immunofluorescence assay (IFA) that uses Ehrlichia canis antigen as a substrate (ie, E canis-IFA), 2 western blot (WB) analyses, and a commercially available ELISA in the detection of E canis antibody in dog sera.

Sample Population—54 canine serum samples that were reactive on E canis-IFA and 16 canine serum samples that were E canis-IFA nonreactive.

Procedure—Serum samples were evaluated by use of 2 WB analyses and a commercially available ELISA. Correlation between results of the 3 testing modalities (ie, IFA, WB analyses, and the ELISA) was examined by use of nonreactive (E canis-IFA reciprocal titer, < 20), low-titer (reciprocal titer, 80 to 160), medium-titer (reciprocal titer, 320 to 2,560), and high-titer (reciprocal titer, 5,120 to > 20,480) serum samples.

Results—For all serum samples in the nonreactive (n = 16), medium-titer (17), and high-titer (18) groups, correlation of results among IFA, WB analyses, and the commercially available ELISA was excellent. A poor correlation was found between IFA results and those of WB analyses and the ELISA for serum samples in the low-titer group (19), with only 4 of the 19 serum samples having positive results on both WB analyses and the commercially available ELISA.

Conclusions and Clinical Relevance—The discrepancy between E canis-IFA, WB analyses, and the commercially available ELISA results for the low-titer serum samples may be related to a high IFA sensitivity or, more likely, a lack of specificity associated with cross-reactivity among Ehrlichia spp.
Assessment of the geometry of the cubital (elbow) joint of dogs by use of magnetic resonance imaging
Authors: Janach Katharina J. , Breit Sabine M. , Künzel Wolfgang W. F.
Published: February 2006

Objective—To assess joint geometry and highlight potential evidence of physiologic incongruity in cubital (elbow) joints of large, small, and chondrodystrophic breeds of dogs.

Sample Population—Nonarthritic elbow joints obtained from cadavers of mature dogs of large breeds (n = 19), small breeds (14), or chondrodystrophic breeds (8).

Procedure—Magnetic resonance imaging was used to quantify interosseous gaps at 6 defined positions and 2 sagittal planes of the humeroantebrachial region by use of a fat-suppressed 3-dimensional gradient-echo sequence.

Results—Interosseous gaps in the more medially located sagittal plane were significantly narrower at the level of the anconeal process than at any other position of the joint in large-breed dogs, compared with results for small- or chondrodystrophic-breed dogs. In both sagittal planes, the gaps were significantly wider at the center of the ulnar trochlear notch than at any other position. Significant correlation between body weight and width of the interosseous gaps was found only in large-breed dogs and was found in both sagittal planes at the center of the ulnar trochlear notch (r, 0.834 and r, 0.680, respectively).

Conclusions and Clinical Relevance—In large-breed dogs, the interosseous gap was especially narrow at the level of the anconeal process and its diametric position. This suggests less ability to compensate intra-articular steps in dogs with short ulna syndrome, which predisposes to failure of the union between the anconeal process and olecranon. Geometric incongruity may be regarded as clinically normal in nonarthritic humeroulnar joints. The degree of geometric incongruity increases with body weight.
Effect of body position on cranial migration of epidurally injected methylene blue in recumbent dogs
Authors: Gorgi Alireza A. , Hofmeister Erik H. , Higginbotham Michael J. , Kent Marc
Published: February 2006

Objective—To determine the relationship between different body positions during recumbency on the cranial migration of epidurally injected methylene blue in canine cadavers.

Sample Population—21 fresh cadavers of clinically normal adult female mixed-breed dogs.

Procedure—Dogs were randomly assigned to the following 3 groups: dogs remaining in right lateral recumbency (n = 7), dogs rotated from left to right lateral recumbency (7), and dogs rotated from dorsal to right lateral recumbency (7). Each dog received an epidural injection of 0.05% methylene blue (0.1 mL/kg) at the lumbosacral space. A dorsal laminectomy of the vertebral column was made, and cranial extent of methylene blue in 4 quadrants (right lateral, left lateral, ventral, and dorsal) was determined by examining dura mater staining.

Results—No significant difference was found among groups in regard to body weight or body condition score. Epidural cranial migration of methylene blue in the right lateral quadrant was significantly greater in dogs that remained in right lateral recumbency than in dogs that were rotated from left to right lateral recumbency. No significant difference was found within groups for epidural cranial migration of methylene blue between each quadrant. No significant relationship was found between body weight or body condition score and epidural cranial migration of methylene blue.

Conclusions and Clinical Relevance—Body positioning and amount of recumbency time influence cranial migration of epidurally injected methylene blue. If greater cranial migration of an epidurally administered drug is desired, placing the patient in lateral recumbency with the surgical site on the dependent side may precede surgery.
Effects of preoperative epidural administration of racemic ketamine for analgesia in sheep undergoing surgery
Authors: Guedes Alonso G. P. , Pluhar G. Elizabeth , Daubs Brian M. , Rudé Elaine P.
Published: February 2006

Objective—To investigate the effects of preoperative epidural administration of racemic ketamine to provide analgesia in sheep undergoing experimental hind limb orthopedic surgery.

Animals—12 adult sheep (weight range, 51.4 to 67.2 kg).

Procedure—Sheep were anesthetized with guaifenesin, thiopental, and isoflurane; after induction of anesthesia, sheep received a lumbosacral epidural injection of ketamine (1 mg/kg; n = 6) or saline (0.9% NaCl) solution (1 mL/7 kg; 6 [control group]). Respiratory and cardiovascular variables were recorded before and at intervals during and for 6 hours after anesthesia. During that 6-hour postoperative period, analgesia was evaluated subjectively with a numeric ranking scale that included assessments of comfort, posture, movement, and response to wound palpation; buprenorphine was administered when a score > 3 (maximum score, 10) was achieved. Rectal temperature, heart and respiratory rates, and lameness were evaluated daily for 2 weeks after surgery.

Results—At all evaluations, cardiovascular and respiratory variables were comparable between the 2 groups. Compared with control sheep, time to first administration of rescue analgesic was significantly longer and total dose of buprenorphine administered during the 6- hour postoperative period was significantly decreased for ketamine-treated sheep. During the second week following surgery, ketamine-treated sheep had significantly less lameness than control sheep.

Conclusions and Clinical Relevance—In sheep undergoing hind limb surgery, preoperative epidural administration of ketamine appears to provide analgesia in the immediate postoperative period and has residual analgesic effects, which may contribute to more rapid return of normal function in surgically treated limbs.
Role of coresistance in the development of resistance to chloramphenicol in Escherichia coli isolated from sick cattle and pigs
Authors: Harada Kazuki , Asai Tetsuo , Kojima Akemi , Ishihara Kanako , Takahashi Toshio
Published: February 2006

Objective—To determine the cause of persistent resistance to chloramphenicol (CP) after the ban on its use in food-producing animals in several countries.

Sample Population—71 CP-resistant and 104 CP-susceptible Escherichia coli strains isolated from sick cattle and pigs in Japan.

Procedure—Susceptibility of all bacterial strains to thiamphenicol (TP) and florfenicol (FFC) was tested by use of an agar dilution method. The CP-resistance genes and variable region within class 1 integrons in CP-resistant strains were identified by use of a PCR assay.

Results—The CP acetyltransferase gene (ie, cat1) was identified as the predominant CP-resistance gene in strains isolated from cattle, and the cat1and nonenzymatic CP-resistance gene (ie, cmlA) were the predominant CP-resistance genes in strains isolated from pigs. Additionally, strains with cat1 isolated from cattle often were resistant to ampicillin, dihydrostreptomycin (DSM), oxytetracycline, and trimethoprim (TMP), whereas strains with cat1 or cmlA isolated from pigs often were resistant to DSM and TMP. Class 1 integrons were significantly more prevalent in strains with CP-resistance genes, compared with prevalence in strains without CP-resistance genes. All gene cassettes within the integrons were involved in resistance to DSM, TMP, or both.

Conclusions and Clinical Relevance—Coresistance that develops because of the use of DSM and TMP in cattle and pigs apparently contributes to the selection of CP-resistant strains of E coli. Thus, it is possible that bacterial resistance to CP in animals would persist despite a ban on the use of CP in cattle and pigs.
Evaluation of gait kinetics in puppies with coxofemoral joint laxity
Authors: Lopez Mandi J. , Quinn Margaret M. , Markel Mark D.
Published: February 2006

Objective—To characterize ground reaction forces (GRFs) and determine whether there were correlations between forces and passive coxofemoral joint laxity in puppies.

Animals—Fifty-one 16-week-old hound-breed dogs.

Procedure—Force-plate gait evaluation and distraction radiographic imaging were performed. Ground reaction forces evaluated included x (mediolateral), y (craniocaudal breaking and propulsion), and z (vertical) peak force and impulse. Z-plane limb loading and unloading rates, loading interval, and weight distribution and y-plane stance time breaking and propulsion percentages were calculated. One-way ANOVA with the Duncan multiple range test was used to evaluate differences in gait variables among limbs. The relationships of left, right, highest, and mean distraction index (DI) with individual limb data of each dog were evaluated with the Spearman rank correlation. Left and right DIs were compared by means of linear regression analysis.

Results—Mean ± SEM DI was 0.67 ± 0.02. Left and right DIs were strongly correlated, but there were no significant relationships between DIs and gait variables. Most fore- and hind limb gait variables differed significantly, whereas paired fore- and hind limb gait variables did not. Asymmetry was most pronounced in the x- and y-planes.

Conclusions and Clinical Relevance—GRFs were consistent with those of clinically normal mature dogs, supporting an absence of association between GRF and DI in young dogs. The GRFs and elucidation of the relationship between GRFs and DI may be useful for future studies in immature dogs.