bluuebunny/crossref_metadata_2025 huggingface dataset:
MEG-1 and MEG-2 Are Embryo-Specific P-Granule Components Required for Germline Development in Caenorhabditis elegans
Authors: Leacock Stefanie W , Reinke Valerie
Published: January 2008

In Caenorhabditis elegans, germ granules called P granules are directly inherited from mother to daughter and segregate with the germ lineage as it separates from the soma during initial embryonic cell divisions. Here we define meg-1 and meg-2 (maternal-effect germ-cell defective), which are expressed in the maternal germline and encode proteins that localize exclusively to P granules during embryonic germline segregation. Localization of MEG-1 to P granules depends upon the membrane-bound protein MES-1. meg-1 mutants exhibit multiple germline defects: P-granule mis-segregation in embryos, underproliferation and aberrant P-granule morphology in larval germ cells, and ultimately, sterility as adults. The penetrance of meg-1 phenotypes increases when meg-2 is also absent. Loss of the P-granule component pgl-1 in meg-1 mutants increases germ-cell proliferation, while loss of glh-1 decreases proliferation. Because meg-1 is provided maternally but its action is required in the embryonic germ lineage during segregation from somatic lineages, it provides a critical link for ensuring the continuity of germline development from one generation to the next.
Loss of LINE-1 Activity in the Megabats
Authors: Cantrell Michael A , Scott LuAnn , Brown Celeste J , Martinez Armando R , Wichman Holly A
Published: January 2008

LINE-1 (L1) retrotransposons are the most abundant type of mammalian retroelement. They have profound effects on genome plasticity and have been proposed to fulfill essential host functions, yet it remains unclear where they lie on the spectrum from parasitism to mutualism. Their ubiquity makes it difficult to determine the extent of their effects on genome evolution and gene expression because of the relative dearth of animal models lacking L1 activity. We have isolated L1 sequences from 11 megabat species by a method that enriches for recently inserted L1s and have done a bioinformatic examination of L1 sequences from a 12th species whose genome was recently shotgun sequenced. An L1 extinction event appears to have occurred at least 24 million years ago (MYA) in an ancestor of the megabats. The ancestor was unusual in having maintained two highly divergent long-term L1 lineages with different levels of activity, which appear, on an evolutionary scale, to have simultaneously lost that activity. These megabat species can serve as new animal models to ask what effect loss of L1 activity has on mammalian genome evolution and gene expression.
Role of RAD51 in the Repair ofMuDR-Induced Double-Strand Breaks in Maize (Zea maysL.)
Authors: Li Jin , Wen Tsui-Jung , Schnable Patrick S
Published: January 2008

Rates of Mu transposon insertions and excisions are both high in late somatic cells of maize. In contrast, although high rates of insertions are observed in germinal cells, germinal excisions are recovered only rarely. Plants doubly homozygous for deletion alleles of rad51A1 and rad51A2 do not encode functional RAD51 protein (RAD51−). Approximately 1% of the gametes from RAD51+ plants that carry the MuDR-insertion allele a1-m5216 include at least partial deletions of MuDR and the a1 gene. The structures of these deletions suggest they arise via the repair of MuDR-induced double-strand breaks via nonhomologous end joining. In RAD51− plants these germinal deletions are recovered at rates that are at least 40-fold higher. These rates are not substantially affected by the presence or absence of an a1-containing homolog. Together, these findings indicate that in RAD51+ germinal cells MuDR-induced double-strand breaks (DSBs) are efficiently repaired via RAD51-directed homologous recombination with the sister chromatid. This suggests that RAD51− plants may offer an efficient means to generate deletion alleles for functional genomic studies. Additionally, the high proportion of Mu-active, RAD51− plants that exhibit severe developmental defects suggest that RAD51 plays a critical role in the repair of MuDR-induced DSBs early in vegetative development.
Cytonuclear Genic Incompatibilities Cause Increased Mortality in Male F2 Hybrids ofNasonia giraultiandN. vitripennis
Authors: Niehuis Oliver , Judson Andrea K , Gadau Jürgen
Published: January 2008

The haplodiploid wasp genus Nasonia is a promising model for studying the evolution of genic incompatibilities due to the existence of interfertile species and haploid males. The latter allows for significantly reducing the sample size required to detect and map recessive dysfunctional genic interactions. We exploited these features to study the genetics of intrinsic hybrid inviability in male F2 hybrids of Nasonia giraulti and N. vitripennis. Analyzing marker segregation in 225 hybrid embryos, we inferred a linkage map with 38 framework markers. The markers were tested for marker transmission ratio distortion (MTRD) and interchromosomal linkage disequilibrium in populations of embryonic and adult hybrids. We found evidence for four transmission ratio distorting loci (TRDL). Three TRDL showed a deficit of the N. giraulti allele in hybrids with N. vitripennis cytoplasm. A separate TRDL exhibited a deficiency of the N. vitripennis allele in hybrids with N. giraulti cytoplasm. We ascribe the observed MTRD in adult hybrids to cytonuclear genic incompatibilities causing differential mortality during development since hybrid embryos did not show MTRD. The identified cytonuclear genic incompatibilities in F2 hybrids with N. vitripennis cytoplasm account for most of the intrinsic hybrid inviability in this cross. The high mortality rate in F2 hybrids with N. giraulti cytoplasm cannot be explained by the single identified TRDL alone, however.
Cypress Surrogate Mother Produces Haploid Progeny From Alien Pollen
Authors: Pichot Christian , Liens Benjamin , Nava Juana L Rivera , Bachelier Julien B , El Maâtaoui Mohamed
Published: January 2008

Although most living organisms reproduce sexually, some have developed a uniparental reproduction where the embryo usually derives from the female parent. A unique case of paternal apomixis in plants has been recently reported in Cupressus dupreziana, an endangered Mediterranean conifer. This species produces unreduced pollen that develop into all-paternal embryos within the seed tissues. We analyzed seedlings produced by open-pollinated C. dupreziana seed trees using morphological descriptors, ploidy levels assessed through flow cytometry, and AFLP genetic diversity. In situ C. dupreziana seed trees (from Algeria) produced only diploid C. dupreziana progeny. In contrast, only one-third of the progeny produced by ex situ C. dupreziana seed trees planted in French collections were similar to C. dupreziana seedlings; the other progeny were haploid or diploid C. sempervirens seedlings. These results demonstrate that C. dupreziana ovules allow for the development of all-paternal embryos from pollen produced by another species, C. sempervirens. Thus, the in planta androgenesis is achieved through the combination of the embryogenic behavior of pollen grains and the ability of seed tree ovules to act as a surrogate mother. This phenomenon offers a unique opportunity to produce, by natural means, highly valuable material for genetic studies and selection of sterile cultivars.
rosy Function Is Required for Juvenile Hormone Effects in Drosophila melanogaster
Authors: Zhou Xiaofeng , Riddiford Lynn M
Published: January 2008

Application of a high dose of juvenile hormone (JH) III or its mimics (JHM) to Drosophila at the white puparium stage causes the formation of a pupal-like abdomen with few or no short bristles. We report here that the rosy (ry) gene encoding the enzyme xanthine dehydrogenase (XDH), which catalyzes the final two-step oxidation in purine catabolism, is required for this effect of JH on the epidermis. In ry506 (null allele) homozygotes or hemizygotes, JH III or pyriproxifen (a JHM) had little effect on abdominal bristle or cuticle formation, but disrupted the development of the central nervous system as in wild-type flies. Wild-type ry rescued the JH sensitivity of the abdominal epidermis in ry506 mutants. Inhibition of XDH activity phenocopied the ry null mutant's insensitivity to JH. Larvae fed on hypoxanthine or xanthine showed a decreased JH sensitivity. ry506 clones were sensitive to JH, indicating that ry is required non-cell autonomously for the JH effects. Normally JH applied at pupariation causes the aberrant reexpression of the transcription factor broad in the abdominal epidermis during adult development, but in the ry506 mutant most of the cells in the dorsal tergite showed no broad reexpression, indicating that ry is upstream of broad in the JH signaling pathway.
Accuracy of Genomic Selection Using Different Methods to Define Haplotypes
Authors: Calus M P L , Meuwissen T H E , de Roos A P W , Veerkamp R F
Published: January 2008

Genomic selection uses total breeding values for juvenile animals, predicted from a large number of estimated marker haplotype effects across the whole genome. In this study the accuracy of predicting breeding values is compared for four different models including a large number of markers, at different marker densities for traits with heritabilities of 50 and 10%. The models estimated the effect of (1) each single-marker allele [single-nucleotide polymorphism (SNP)1], (2) haplotypes constructed from two adjacent marker alleles (SNP2), and (3) haplotypes constructed from 2 or 10 markers, including the covariance between haplotypes by combining linkage disequilibrium and linkage analysis (HAP_IBD2 and HAP_IBD10). Between 119 and 2343 polymorphic SNPs were simulated on a 3-M genome. For the trait with a heritability of 10%, the differences between models were small and none of them yielded the highest accuracies across all marker densities. For the trait with a heritability of 50%, the HAP_IBD10 model yielded the highest accuracies of estimated total breeding values for juvenile and phenotyped animals at all marker densities. It was concluded that genomic selection is considerably more accurate than traditional selection, especially for a low-heritability trait.
Parental Effect of DNA (Cytosine-5) Methyltransferase 1 on Grandparental-Origin-Dependent Transmission Ratio Distortion in Mouse Crosses and Human Families
Authors: Yang Lanjian , Andrade Moises Freitas , Labialle Stephane , Moussette Sanny , Geneau Geneviève , Sinnett Donna , Belisle Alexandre , Greenwood Celia M T , Naumova Anna K
Published: January 2008

Transmission ratio distortion (TRD) is a deviation from the expected Mendelian 1:1 ratio of alleles transmitted from parents to offspring and may arise by different mechanisms. Earlier we described a grandparental-origin-dependent sex-of-offspring-specific TRD of maternal chromosome 12 alleles closely linked to an imprinted region and hypothesized that it resulted from imprint resetting errors in the maternal germline. Here, we report that the genotype of the parents for loss-of-function mutations in the Dnmt1 gene influences the transmission of grandparental chromosome 12 alleles. More specifically, maternal Dnmt1 mutations restore Mendelian transmission ratios of chromosome 12 alleles. Transmission of maternal alleles depends upon the presence of the Dnmt1 mutation in the mother rather than upon the Dnmt1 genotype of the offspring. Paternal transmission mirrors the maternal one: live-born offspring of wild-type fathers display 1:1 transmission ratios, whereas offspring of heterozygous Dnmt1 mutant fathers tend to inherit grandpaternal alleles. Analysis of allelic transmission in the homologous region of human chromosome 14q32 detected preferential transmission of alleles from the paternal grandfather to grandsons. Thus, parental Dnmt1 is a modifier of transmission of alleles at an unlinked chromosomal region and perhaps has a role in the genesis of TRD.
Genetic Linkage Map of the Nucleolus Organizer Region in the Soybean
Authors: Yang Kiwoung , Jeong Soon-Chun
Published: January 2008

Simple polymorphisms in ribosomal DNA repeats in the nucleolus organizer region (NOR) permitted the development of markers for the genetic mapping of the soybean NOR. The markers map to the top end of soybean linkage group F, one of either telomeric end predicted in the cytogenetic and primary trisomic studies.
A Gain-of-Function Suppressor Screen for Genes Involved in Dorsal–Ventral Boundary Formation in the Drosophila Wing
Authors: Bejarano Fernando , Luque Carlos M , Herranz Héctor , Sorrosal Georgina , Rafel Neus , Pham Thu Thuy , Milán Marco
Published: January 2008

The Drosophila wing primordium is subdivided into a dorsal (D) and a ventral (V) compartment by the activity of the LIM-homeodomain protein Apterous in D cells. Cell interactions between D and V cells induce the activation of Notch at the DV boundary. Notch is required for the maintenance of the compartment boundary and the growth of the wing primordium. Beadex, a gain-of-function allele of dLMO, results in increased levels of dLMO protein, which interferes with the activity of Apterous and results in defects in DV axis formation. We performed a gain-of-function enhancer-promoter (EP) screen to search for suppressors of Beadex when overexpressed in D cells. We identified 53 lines corresponding to 35 genes. Loci encoding for micro-RNAs and proteins involved in chromatin organization, transcriptional control, and vesicle trafficking were characterized in the context of dLMO activity and DV boundary formation. Our results indicate that a gain-of-function genetic screen in a sensitized background, as opposed to classical loss-of-function-based screenings, is a very efficient way to identify redundant genes involved in a developmental process.
An Unstable Targeted Allele of the Mouse Mitf Gene With a High Somatic and Germline Reversion Rate
Authors: Bismuth Keren , Skuntz Susan , Hallsson Jón H , Pak Evgenia , Dutra Amalia S , Steingrímsson Eiríkur , Arnheiter Heinz
Published: January 2008

The mouse Mitf gene encodes a transcription factor that is regulated by serine phosphorylation and is critical for the development of melanin-containing pigment cells. To test the role of phosphorylation at a particular serine, S73 in exon 2 of Mitf, we used a standard targeting strategy in mouse embryonic stem cells to change the corresponding codon into one encoding an alanine. By chance, we generated an allele in which 85,222 bp of wild-type Mitf sequence are duplicated and inserted into an otherwise correctly targeted Mitf gene. Depending on the presence or absence of a neomycin resistance cassette, this genomic rearrangement leads to animals with a white coat with or without pigmented spots or a gray coat with obligatory white and black spots. Several independent, genetically stable germline revertants that lacked the duplicated wild-type sequence but retained the targeted codon were then derived. These animals were normally pigmented, indicating that the serine-to-alanine mutation is not deleterious to melanocyte development. The fact that mosaic coat reversions occur in all mice lacking the neo-cassette and that ∼1% of these transmit a reverted allele to their offspring places this mutation among those with the highest spontaneous reversion rates in mammals.
Spatial and Temporal Control of Gene Expression in Drosophila Using the Inducible GeneSwitch GAL4 System. I. Screen for Larval Nervous System Drivers
Authors: Nicholson Louise , Singh Gunisha K , Osterwalder Thomas , Roman Gregg W , Davis Ronald L , Keshishian Haig
Published: January 2008

There is a critical need for genetic methods for the inducible expression of transgenes in specific cells during development. A promising approach for this is the GeneSwitch GAL4 system of Drosophila. With GeneSwitch GAL4 the expression of upstream activating sequence (UAS) effector lines is controlled by a chimeric GAL4 protein that becomes active in the presence of the steroid RU486 (mifepristone). To improve the utility of this expression system, we performed a large-scale enhancer-trap screen for insertions that yielded nervous system expression. A total of 204 GeneSwitch GAL4 lines with various larval expression patterns in neurons, glia, and/or muscle fibers were identified for chromosomes I–III. All of the retained lines show increased activity when induced with RU486. Many of the lines reveal novel patterns of sensory neurons, interneurons, and glia. There were some tissue-specific differences in background expression, with muscles and glia being more likely to show activity in the absence of the inducing agent. However, >90% of the neuron-specific driver lines showed little or no background activity, making them particularly useful for inducible expression studies.
Role of the Saccharomyces cerevisiae Rad51 Paralogs in Sister Chromatid Recombination
Authors: Mozlin Amy M , Fung Cindy W , Symington Lorraine S
Published: January 2008

Rad51 requires a number of other proteins, including the Rad51 paralogs, for efficient recombination in vivo. Current evidence suggests that the yeast Rad51 paralogs, Rad55 and Rad57, are important in formation or stabilization of the Rad51 nucleoprotein filament. To gain further insights into the function of the Rad51 paralogs, reporters were designed to measure spontaneous or double-strand break (DSB)-induced sister or nonsister recombination. Spontaneous sister chromatid recombination (SCR) was reduced 6000-fold in the rad57 mutant, significantly more than in the rad51 mutant. Although the DSB-induced recombination defect of rad57 was suppressed by overexpression of Rad51, elevated temperature, or expression of both mating-type alleles, the rad57 defect in spontaneous SCR was not strongly suppressed by these same factors. In addition, the UV sensitivity of the rad57 mutant was not strongly suppressed by MAT heterozygosity, even though Rad51 foci were restored under these conditions. This lack of suppression suggests that Rad55 and Rad57 have different roles in the recombinational repair of stalled replication forks compared with DSB repair. Furthermore, these data suggest that most spontaneous SCR initiates from single-stranded gaps formed at stalled replication forks rather than DSBs.
Examination of Interchromosomal Interactions in Vegetatively Growing DiploidSchizosaccharomyces pombeCells by Cre/loxP Site-Specific Recombination
Authors: Molnar Monika , Kleckner Nancy
Published: January 2008

The probability with which different regions of a genome come in contact with one another is a question of general interest. The current study addresses this subject for vegetatively growing diploid cells of fission yeast Schizosaccharomyces pombe by application of the Cre/loxP site-specific recombination assay. High levels of allelic interactions imply a tendency for chromosomes to be colocalized along their lengths. Significant homology-dependent pairing at telomere proximal loci and robust nonspecific clustering of centromeres appear to be the primary determinants of this feature. Preference for direct homolog-directed interactions at interstitial chromosomal regions was ambiguous, perhaps as a consequence of chromosome flexibility and the constraints and dynamic nature of the nucleus. Additional features of the data provide evidence for chromosome territories and reveal an intriguing phenomenon in which interaction frequencies are favored for nonhomologous loci that are located at corresponding relative (rather than absolute) positions within their respective chromosome arms. The latter feature, and others, can be understood as manifestations of transient, variable, and/or occasional nonspecific telomeric associations. We discuss the factors whose interplay sets the probabilities of chromosomal interactions in this organism and implications of the inferred organization for ectopic recombination.
Distinct Activities of the Germline and Somatic Reproductive Tissues in the Regulation of Caenorhabditis elegans' Longevity
Authors: Yamawaki Tracy M , Arantes-Oliveira Nuno , Berman Jennifer R , Zhang Peichuan , Kenyon Cynthia
Published: January 2008

The two parts of the Caenorhabditis elegans reproductive system, the germ cells and the somatic reproductive tissues, each influence the life span of the animal. Removing the germ cells increases longevity, and this life span extension requires the somatic gonad. Here we show that the somatic gonad and the germ cells make distinct contributions to life span determination. The life span increase produced by loss of the germ cells requires the DAF-16/FOXO transcription factor. In response to germ-cell removal, DAF-16 accumulates in nuclei. We find that the somatic gonad is not required for DAF-16 nuclear accumulation or for the increased stress resistance that is produced by germ-cell removal. The somatic gonad is required, however, for expression of specific DAF-16 target genes. DAF-16 is known to be activated by reduced insulin/IGF-1 signaling in C. elegans. In certain insulin/IGF-1-pathway mutants, the somatic gonad is not required for germ-cell removal to extend life span. Our genetic experiments suggest that these mutations reduce insulin/IGF-1 signaling below a critical threshold level. At these low levels of insulin/IGF-1 signaling, factors normally provided by the somatic gonad are no longer needed for germ-cell removal to increase the expression of DAF-16 target genes.
Differential Regulation of Anaphase Promoting Complex/Cyclosome Substrates by the Spindle Assembly Checkpoint in Saccharomyces cerevisiae
Authors: Keyes Brice E , Yellman Christopher M , Burke Daniel J
Published: January 2008

The anaphase promoting complex (APC) targets proteins for degradation to promote progression through the cell cycle. Here we show that Clb5, an APCCdc20 substrate, is degraded when the spindle checkpoint is active, while other APCCdc20 substrates are stabilized, suggesting that APCCdc20 inhibition by the spindle checkpoint is substrate specific.
Alice O. Howell, The Heavens Declare: Astrological Ages and the Evolution of Consciousness, Gordon Strachan, The Return of Merlin: Star Lore and the Patterns of History and Milan Spurek, Praga Mysteriosa
Authors: Thorley Anthony
Published: January 2008

Alice O. Howell, The Heavens Declare: Astrological Ages and the Evolution of Consciousness (Wheaton, IL: Quest Books, Theosophical Publishing House, 2006). IBSN 10: 0-8356-0835-2. Gordon Strachan, The Return of Merlin: Star Lore and the Patterns of History (Edinburgh: Floris Books, 2006). IBSN 10: 0-86315-553-7.
Milan Spurek, Praga Mysteriosa (Prague: Krasna Pani, 2002). IBSN 80-903076-4-7.
Patrick Curry, Ecological Ethics: A Critical Introduction
Authors: Judd Steve
Published: January 2008

Patrick Curry, Ecological Ethics: A Critical Introduction (Cambridge, UK: Polity Press; Malden, MA: Blackwell, 2006). ISBN/SKU 0745629083.
Bernadette Brady, Astrology: A Place in Chaos
Authors: York Michael
Published: January 2008

Bernadette Brady, Astrology: A Place in Chaos (Bournemouth: Wessex Astrologer, 2006), 178pp. ISBN 1902405218.
Where East Meets West – Dual Hybridity in the E-Discourse of Hong Kong Bilinguals
Authors: Carter Ronald , Fung Loretta
Published: January 2008

Computer-mediated communication (CMC) is a growing topic in linguistic research. Based on an 80,000-word corpus of MSN messaging data of twenty English-Cantonese bilingual interlocutors, this paper investigates cross-linguistic and cross-cultural features of e-discourse in relation to spoken and written language. Where East meets West, the new register demonstrates a dual form of hybridity: a hybridity of an amalgam of spoken and written language with a largely oral orientation and a hybridity of transcreative language, as a construct of modality, technology, linguistic and cultural diversity.1 Four central forms of language, namely, compressed language, personalised language, transcreative language and visual language are identified for expressing interpersonal solidarity and cultural identity. Against this background sounds, letters, words, typography, spellings and graphics are manipulated and played with under parameters such as modality as well as temporality, synchronicity and spatiality in computer-mediated communication.2 It is speculated that some generic forms of text features and interactional strategies are common in non-English Internet users but this emerging form of online writing is challenging and reshaping the conventional literacy practices that formal education promotes.
The “Unseen Engineer”
Authors: Lukin Annabelle
Published: January 2008

A number of linguistic studies in recent decades have sought to explain the nature of war discourses, and a number of recurring features have been identified (van Leeuwen, in press). Taking a corpus of press briefings by Coalition military spokesman from the beginning of the Iraq invasion, this paper combines detailed grammatical analysis (based on four days of briefings), with an excursus into prosodic motifs created through certain lexical tendencies (based on seven days of briefings), in order to explore the kind of ‘existential fabric’ (Butt, 1988) this discourse creates in its particular representation of the phenomenal realm of war. The grammatical method involves the analysis of the experiential function of language, using systemic functional grammar. An additional resource drawn on is Roget’s Thesaurus, against which particular elements of the discourse – such as the lexical verbs which construe material action – are mapped. The analysis reveals the lexical and grammatical patterns which function as resources for muting the intensely violent nature of war.
Protolanguage, Mirror Neurons, and the “Front-Heavy” Brain: Explorations in the Evolution and Functional Organization of Language
Authors: Melrose Robin
Published: January 2008

In recent years, linguistic research into protolanguage and interpersonal semantics, and neuroscientific research into mirror neurons and the central role of the prefrontal cortex in language processing have provided new insights into how language may have evolved and how it may be functionally organized. This paper attempts to draw together these two strands of research by linking (1) studies of the neural processing of attitude, evaluation and theory of mind to the evolution of interpersonal semantics, and (2) research into mirror neurons and the processing of verbs and nouns to the evolution of ideational semantics. The paper then goes on to investigate the role of the prefrontal cortex in the functional organization of language, concluding that although language is widely distributed in the brain, there is some evidence for distinct ideational and interpersonal pathways in the brain controlled by the prefrontal cortex.
Reproductive Characteristics of Weakfish in Delaware Bay: Implications for Management
Authors: Nye Janet A. , Targett Timothy E. , Helser Thomas E.
Published: January 2008

We quantified size and age at maturity, batch fecundity, spawning frequency, and annual fecundity for weakfish Cynoscion regalis in Delaware Bay in 1999 and 2000. Information about these critical characteristics are needed for stock assessment models, which have never been assessed in Delaware Bay nor anywhere in the range of the weakfish since 1991–1992, when abundance was very low. Stock size increased from 1991–1992 to 1999–2000, but size at maturity was 168 ± 4.1 mm (mean ± SE) and did not appear to increase with stock size. Ninety-seven percent of age-1 fish were mature, but they arrived later to the estuary, had lower batch fecundity, and spawned less frequently than did older fish. The annual fecundity of fish age 2–6 was at least 30 times as great as that of age-1 fish. Batch fecundity was similar between Chesapeake Bay and Delaware Bay in the same year once corrected for fish size. The relationships of batch fecundity to both female weight and length were statistically equal between the two time periods in which batch fecundity has been quantified (1991–1992 and 1999–2000). However, we did detect differences in batch fecundity at age and the length–weight relationship over time. The difference in the length–weight relationship is due to the absence of large (>400 mm) and old (>4 years) females and indicates that the population has not recovered to its former stock structure. The absence of large females could lead to lower egg production than expected and may help explain the slow recovery of this species. We suggest decreasing the proportion of mature fish at age 1 to account for the low egg production of this age-class and to continue efforts to enhance the size and age structure of the population.
Retrospective Evaluation of Preseason Forecasting Models for Sockeye and Chum Salmon
Authors: Haeseker Steven L. , Peterman Randall M. , Su Zhenming , Wood Chris C.
Published: January 2008

Using comprehensive data sets for chum salmon Oncorhynchus keta (40 stocks) and sockeye salmon O. nerka (37 stocks) throughout their North American ranges, we compared the retrospective performance of 11 models in preseason forecasting of adult abundance. Chum and sockeye salmon have more complicated age structures than pink salmon O. gorbuscha, which we investigated previously (Haeseker et al. 2005), and this complexity presents new challenges as well as opportunities for forecasting. We extended our previous work to include two new forecasting models that make use of leading indicators: either the survival rate of earlier-maturing pink salmon from the same brood year (Ricker pink salmon index model) or the abundance of earlier-maturing siblings (hybrid sibling model, a new version of the standard sibling model). No single forecasting model was consistently the best for either chum or sockeye salmon, but the hybrid sibling model frequently performed best based on mean absolute error, mean percent error, and root mean square error. As was observed for pink salmon, several naïve models (i.e., simple time series models without explicitly modeled mechanisms) also performed well, as did forecast averaging models composed of two models with the least-correlated forecasting errors. In general, model ranking depended on the particular stock and performance measure used. However, even the top-ranked model for each stock explained on average only 21% of the observed interannual variation in chum salmon recruitment and only 36% of the variation in sockeye salmon recruitment. Although improvements may be possible for some stocks in specific circumstances, a major breakthrough in general forecasting ability seems unlikely given the breadth of stocks and models examined to date. Therefore, better in-season updates and adjustments to fishing regulations and a cautious approach to opening and closing fisheries should remain high priorities.
Influence of River Level on Temperature and Hydraulic Gradients in Chum and Fall Chinook Salmon Spawning Areas Downstream of Bonneville Dam, Columbia River
Authors: Geist David R. , Arntzen Evan V. , Murray Christopher J. , McGrath Kathleen E. , Bott Yi-Ju , Hanrahan Timothy P.
Published: January 2008

Chum salmon Oncorhynchus keta and fall Chinook salmon O. tshawytscha segregate spatially during spawning in the Ives Island side channel of the lower Columbia River downstream from Bonneville Dam. Previous research during one spawning season (2000) suggested that these species selected spawning habitats based on differences in hyporheic temperature and vertical hydraulic gradient (VHG). In this study we confirmed the spatial segregation of spawning based on hyporheic characteristics over 4 years (2001–2004) and examined the effects of load-following operations (power generation to meet short-term electrical demand) at Bonneville Dam on hyporheic function and characteristics. We found that during the study period hyporheic temperature and VHG in chum salmon spawning areas were highly variable during periods of load-following operation, when river levels fluctuated. In contrast, hyporheic water temperature and VHG within chum salmon spawning areas fluctuated less when river levels were not changing owing to load-following operation. Variable temperature and VHG could affect chum and fall Chinook salmon spawning segregation and incubation success by altering the cues each species uses to select redd sites. Additional research will be required to fully assess the effects of load-following operations on the hyporheic environment, spawning site selection, and incubation success of chum and fall Chinook salmon downstream from Bonneville Dam.
Grain Yield Variation in Malting Barley Cultivars in Uruguay and Its Consequences for the Design of a Trials Network
Authors: Ceretta Sergio , van Eeuwijk Fred
Published: January 2008

The efficiency of cultivar trial networks is an important subject in official cultivar testing. We investigated this efficiency for malting barley (Hordeum vulgareL.) in Uruguay, using data on 213 cultivars tested across an eight‐year period at six locations. The variance‐components approach was used to quantify the effects of years, locations, sowing dates and replicates on the precision of cultivar mean comparisons. The relationships among testing environments and genotypic adaptation patterns were explored via biplots. Factorial regression was used to model genotype × environment interaction (GEI) directly in relation to measured environmental variables. Variance components indicated that both the number of locations and sowing dates could be reduced. Biplot analysis identified some repeatable GEI patterns. Factorial regression showed that mean daily temperature during the emergence‐heading period and daily minimum temperature at heading explained 20% of GEI. Still, the majority of the GEI appeared to be highly nonrepeatable. A future network should focus on wide adaptation while enhancing the chances to exploit specific adaptation to the prevalent temperature conditions by sampling contrasting sowing dates at different locations.
Visual and Radiometric Assessments for Yield Losses Caused by Ray Blight in Pyrethrum
Authors: Pethybridge Sarah J. , Hay Frank , Esker Paul , Groom Tim , Wilson Calum , Nutter Forrest W.
Published: January 2008

The potential of remote sensing to nondestructively measure relationships between ray blight disease (caused by Phoma ligulicola), plant measurements and components of pyrethrum [Tanacetum cinerariifolium (Trevir.) Sch. Bip.] biomass and yield using a hand‐held multispectral radiometer was examined. A range of disease intensities were generated using fungicides in three fields over two years. Nondestructive assessments were obtained by measuring the percentage of sunlight reflected from canopies with a radiometer equipped with five wavelength bands. Combinations of wavelength ratios and four vegetation indices were calculated. Relationships between reflectance and biomass were investigated by removing foliage from the canopy and periodically measuring reflectance. Measurements such as stem height and the number of flowers in October consistently had significant linear relationships with relative pyrethrin and flower yield. The best predictors of relative flower and pyrethrin yield were found using either percentage reflectance in the near infrared (830 nm) and the difference vegetative index (DVI). Sev eral measures had significant linear relationships with fresh weight of foliage, including the near infrared bandwidth and the DVI, which explained 95 to 97% of the biomass variation. This study demonstrated that plant measurements and disease intensity are strongly related to pyrethrin yield, and that remote sensing has great potential to nondestructively obtain preharvest yield and biomass estimates.
Quantitative Trait Loci and Epistasis for Crown Freezing Tolerance in the ‘Kanota’ × ‘Ogle’ Hexaploid Oat Mapping Population
Authors: Wooten David R. , Livingston David P. , Holland James B. , Marshall David S. , Murphy J. Paul
Published: January 2008

Crown freezing tolerance is the most important factor conferring oat (Avena spp.) winter hardiness. The objective of this study was to identify quantitative trait loci (QTL) for crown freezing tolerance in the ‘Kanota’ × ‘Ogle’ recombinant inbred line (RIL) mapping population and to examine their relationship with other winter hardiness traits. One hundred thirty‐five RILs were evaluated for crown freezing tolerance in a controlled environment. Previously published molecular marker and linkage map information was used for QTL detection. Seven QTL and four complementary epistatic interactions were identified that accounted for 56% of the phenotypic variation. Ogle contributed alleles for increased crown freezing tolerance at three loci, while Kanota contributed alleles for increased crown freezing tolerance at four loci. All loci where Kanota alleles increased crown freezing tolerance showed complementary epistasis for decreased crown freezing tolerance with the QTL near UMN13. Two of the major QTL identified were in the linkage groups (LG) associated with a reciprocal translocation between chromosomes 7C and 17, which was previously associated with spring growth habit in oat. The results confirm the importance of the chromosomes involved in the reciprocal 7C‐17 translocation in controlling winter hardiness component traits.
Agronomic Traits Improvement and Associations in Hard Red Spring Wheat Cultivars Released in North Dakota from 1968 to 2006
Authors: Underdahl Jesse L. , Mergoum Mohamed , Ransom Joel. K. , Schatz Blaine G.
Published: January 2008

Periodic evaluation of cultivars allows researchers to evaluate genetic variation and progress made in various traits. Determining genetic gain or lack can lead researchers to develop new strategies for trait improvements. A two‐year study was initiated in 2004 to examine the changes in agronomic performance of hard red spring wheat (HRSW) (Triticum aestivum L.) cultivars released by North Dakota State University (NDSU) over the past 40 years. The experiment was conducted in North Dakota at three sites in 2004 and two sites in 2005. The study included 33 HRSW genotypes laid out in a randomized complete‐block design. Cultivars developed since 1968, three advanced lines developed by NDSU, and three cultivars released by other breeding programs were included in the study. The Canadian cultivar Marquis (released in 1911) was included for comparison purposes. Linear regression of cultivar means on year of release showed an annual increase in grain yield of 1.3% yr−1, grain‐volume weight of 0.2% yr−1, and thousand‐kernel weight of 0.3% yr−1 since 1968. There were also significant gains in lodging and disease resistance. Resistance to leaf rust (Puccinia recondita Roberge ex Desmaz. f. sp. tritici) and Fusarium head blight (Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schweinitz) Petch]) was substantially improved in genotypes released since 2002 and 2000, respectively. Therefore, we can conclude from this study that no evidence of a decline has occurred in the improvement of most agronomic traits and that breeders should be able to continue improving these traits by introgressing favorable alleles.
Performance of Early Maize Cultivars Derived from Recurrent Selection for Grain Yield and Striga Resistance
Authors: Badu‐Apraku B. , Lum A. Fontem , Fakorede M.A.B. , Menkir A. , Chabi Y. , The C. , Abdulai M. , Jacob S. , Agbaje S.
Published: January 2008

Maize (Zea mays L.) production in west and central Africa (WCA) is constrained by the parasitic weed Striga hermonthica (Del.) Benth and recurrent drought. Two early maize populations, TZE‐W Pop DT STR C0 (white) and TZE‐Y Pop DT STR C0 (yellow), developed from diverse genetic backgrounds, were subjected to three cycles of S1 recurrent selection under artificial Striga infestation. Inbreds and synthetic cultivars were developed from the different cycles of selection. The populations (C0), derived cultivars, and check cultivars were evaluated in 2002 and 2003 under Striga‐infested and Striga‐free environments in WCA. The objective was to assess the performance of the derived cultivars from the different cycles of selection. Under Striga infestation, ACR 94 TZE Comp5‐Y and ACR 94 TZE Comp5‐W, which were not from the selection program, were the highest‐yielding group (2158 and 2124 kg ha−1, respectively). The second group comprised six products of the selection program, with grain yield ranging from 1806 to 1954 kg ha−1 The third group, with grain yield of 1498 to 1759 kg ha−1 contained mostly Striga‐susceptible cultivars and the C0 of the selection program. Under Striga‐free conditions, the performance of several cultivars from the selection program was equal to or better than ACR 94 TZE Comp5‐Y and ACR 94 TZE Comp5‐W. The genotype plus genotype × environment interaction biplot analysis demonstrated that EV DT‐Y 2000 STR C1 and TZE‐W Pop DT STR C3 from the selection program, along with ACR 94 TZE Comp5‐W, had stable grain yield under Striga‐infested and noninfested conditions.
A PCR‐based Marker for the Rsv1 Locus Conferring Resistance to Soybean Mosaic Virus
Authors: Shi Ainong , Chen Pengyin , Zheng Cuiming , Hou Anfu , Zhang Bo
Published: January 2008

Soybean mosaic virus (SMV) is a highly destructive viral disease. Three loci with 12 alleles conferring SMV resistance have been identified in soybean [Glycine max (L.) Merr.]. The objective of this study was to develop polymerase chain reaction–based markers for detecting the candidate gene 3gG2 at the Rsv1 locus for SMV resistance in diverse soybean germplasm. A pair of DNA primers, Rsv1‐f/r, was developed from the 3gG2 sequence. This primer pair produced a 341‐bp DNA fragment specific for soybean cultivars containing Rsv1 The same fragment was confirmed in genotypes containing Rsv1 alleles including ‘Kwanggyo’ (Rsv1‐k), ‘Marshall’ (Rsv1‐m), ‘Ogden’ (Rsv1‐t), PI 96983 (Rsv1), PI 507389 (Rsv1‐n), ‘Raiden’ (Rsv1‐r), and ‘Suweon 97’ (Rsv1‐s). The Rsv1‐f/r fragment was also amplified in genotypes with two‐gene combinations (Rsv1Rsv3 and Rsv1Rsv4) but not in genotypes containing only Rsv3 or Rsv4 or in the susceptible genotypes. The primer pair was used to screen for Rsv1 alleles in 97 SMV resistant genotypes. Results showed that 55 genotypes contained the 3gG2 gene, while 17 genotypes carrying the Rsv1‐y allele and additional 25 SMV‐resistant genotypes carrying Rsv3 or Rsv4 were not amplified a product using the 3gG2 primer pair. Analysis of an F2 population derived from J05 (Rsv1Rsv3) × ‘Essex’ (rsv1rsv3) showed a cosegregation between the marker Rsv1‐f/r and the Rsv1 allele. Rsv1‐f/r was also shown to be linked to simple sequence repeat marker Satt114 on soybean molecular linkage group F with a distance of 5.42 cM. This marker will give breeders a tool for marker‐assisted selection and gene pyramiding in soybean breeding for SMV resistance.
Direct Response of a Maize Synthetic to Recurrent Selection for Resistance to Stem Borers
Authors: Sandoya G. , Butrón A. , Alvarez A. , Ordás A. , Malvar R. A.
Published: January 2008

Selection against pink stem borer (Sesamia nonagrioides Lef) (PSB) attack was performed in the maize (Zea mays L.) synthetic EPS12. The direct response of the EPS12 population to three cycles of selection to reduce tunnel length damage by PSB while maintaining yield was evaluated. S0 (cycles of selection) and S1 (selfed cycles of selection) generations and testcrosses to three testers were evaluated under artificial infestation with two corn borers, PSB and European corn borer (Ostrinia nubilalis Hubner) (ECB). Genotypes and the genotype × environment interaction were significant for tunnel length and yield. Differences among cycles of selection were significant for tunnel length, and the linear decrease for this trait (−1.80 cm cycle−1) achieved during selection accounted for most of these differences. Yield was not significantly reduced with selection. Inbreeding for yield significantly increased due to selection. EPS12 crossed to EP42 showed a significant increase in yield with selection, while crosses to other testers showed a nonsignificant reduction in yield. Although crosses to EP42 were not significantly different for tunnel length, the high heterosis between EPS12 and EP42 and the increased yield of EPS12 × EP42 during selection suggest that inbred lines developed from advanced cycles of EPS12 could be crossed to EP42 to generate promising hybrids. In general, resistance to PSB and ECB was improved, while yield was maintained, inbreeding was increased, and yield of the cross EP42 × EPS12 was improved.
New Fusarium Head Blight Resistant Spring Wheat Germplasm Identified in the USDA National Small Grains Collection
Authors: Zhang Julia X. , Jin Yue , Rudd Jackie C. , Bockelman Harold E.
Published: January 2008

Fusarium head blight (FHB; caused by Fusarium graminearum Schwabe) is one of the most destructive wheat (Triticum aestivum L.) diseases worldwide. Sources of FHB resistance are limited. The objectives of this study were to screen selected spring wheat accessions in the USDA National Small Grains Collection for FHB reactions using FHB index, visual scabby kernel (VSK), and deoxynivalenol (DON) content. A total of 1035 spring wheat accessions were initially screened in unreplicated field evaluation nurseries in 1998 and 1999. Accessions with low FHB were selected as putative resistant materials and were tested in replicated trials from 1999 to 2002. After three or more years of evaluation, 73 accessions with resistance were identified, including 10 accessions previously reported as resistant to FHB. Selections from Europe had the highest percentage of resistance to VSK, followed by selections from South America and Asia. We concluded that there is diversity for FHB resistance in wheat. Fusarium head blight resistance identified from Europe appeared to be unique in that these accessions normally displayed a moderate level of disease in the field, but a higher level of resistance based on VSK and DON. The discovery of diverse resistant sources will provide diversity so that higher levels of resistance could be developed. The novelty and types of FHB resistance in these selections should be further characterized using molecular markers and different inoculation techniques.
Evaluation of Fusarium Head Blight Resistance in Tetraploid Wheat (Triticum turgidum L.)
Authors: Oliver R. E. , Cai X. , Friesen T. L. , Halley S. , Stack R. W. , Xu S. S.
Published: January 2008

Durum wheat (Triticum turgidum L. subsp. durum) production in North America in recent years has been seriously threatened by epidemics of Fusarium head blight (FHB), caused mainly by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schw.) Petch]. Deployment of FHB‐resistant cultivars has been considered the most effective and cost‐efficient strategy to combat this disease; however, progress in developing FHB‐resistant durum wheat cultivars has been hindered by a lack of effective sources of resistance. The objective of this study is to identify tetraploid wheat germplasm that could be used to enhance FHB resistance in durum wheat. We evaluated FHB reactions in 376 accessions of five cultivated subspecies of T. turgidum, including Persian wheat [T. turgidum subsp. carthlicum (Nevski) Á. Löve and D. Löve], cultivated emmer wheat [T. turgidum subsp. dicoccum (Schrank ex Schübler) Thell.], Polish wheat [T. turgidum subsp. polonicum (L.) Thell.], Oriental wheat [T. turgidum subsp. turanicum (Jakubz.) Á. Löve and D. Löve], and Poulard wheat (T. turgidum L. subsp. turgidum). We used point inoculation to evaluate resistance to the spread of infection over three greenhouse seasons and used the grain inoculum method of inoculation to evaluate putatively resistant accessions in two field locations. Preliminary evaluation data showed that 16 T. turgidum subsp. carthlicum and 4 T. turgidum subsp. dicoccum accessions consistently exhibited resistance or moderate resistance to FHB. These accessions likely carry genetic resistance to FHB and could be used directly in breeding programs to enhance FHB resistance in durum wheat.