Enhanced East Pacific Rise hydrothermal activity during the last two glacial terminations.

Mid-ocean ridge magmatism is driven by seafloor spreading and decompression melting of the upper mantle. Melt production is apparently modulated by glacial-interglacial changes in sea level, raising the possibility that magmatic flux acts as a negative feedback on ice-sheet size. The timing of melt variability is poorly constrained, however, precluding a clear link between ridge magmatism and Pleistocene climate transitions. Here we present well-dated sedimentary records from the East Pacific Rise that show evidence of enhanced hydrothermal activity during the last two glacial terminations. We suggest that glacial maxima and lowering of sea level caused anomalous melting in the upper mantle and that the subsequent magmatic anomalies promoted deglaciation through the release of mantle heat and carbon at mid-ocean ridges.

Field Resistance to the Ug99 Race Group of the Stem Rust Pathogen in Spring Wheat Landraces.

Wheat landraces provide a source of genetic variability for breeding. The emergence and spread of highly virulent races of the stem rust pathogen (Ug99 race group of Puccinia graminis f. sp. tritici) threaten wheat production globally. Spring wheat landraces were screened for resistance in eight field seasons at the Kenya Agricultural Research Institute, Njoro, where the Ug99 race group has become endemic. Accessions showing resistance in one season were retested and screened with molecular markers associated with resistance genes Sr2, Sr24, Sr36, and Lr34/Yr18; two height-reducing genes; and a photoperiod insensitivity allele. Of 2,509 accessions tested, 278 were categorized as resistant based on results from at least two seasons. Of these resistant accessions, 32 were positive for one or more markers for Sr2, Sr36, Rht-B1b, or Rht-D1b, indicating that they do not fit the definition of "landrace" because these genes were likely introduced via modern breeding practices. Thus, 246 resistant "landrace" accessions were identified. Of countries with more than five tested accessions, Afghanistan, Iran, Portugal, Ethiopia, Uzbekistan, Greece, Tajikistan, Bosnia and Herzegovina, and Serbia had at least 10% of tested accessions that were resistant to the Ug99 race group. Future research will characterize the resistance to determine its novelty and incorporate novel genes into improved lines.

New Diversity Arrays Technology (DArT) markers for tetraploid oat (Avena magna Murphy et Terrell) provide the first complete oat linkage map and markers linked to domestication genes from hexaploid A. sativa L.

Nutritional benefits of cultivated oat (Avena sativa L., 2n = 6x = 42, AACCDD) are well recognized; however, seed protein levels are modest and resources for genetic improvement are scarce. The wild tetraploid, A. magna Murphy et Terrell (syn A. maroccana Gdgr., 2n = 4x = 28, CCDD), which contains approximately 31% seed protein, was hybridized with cultivated oat to produce a domesticated A. magna. Wild and cultivated accessions were crossed to generate a recombinant inbred line (RIL) population. Although these materials could be used to develop domesticated, high-protein oat, mapping and quantitative trait loci introgression is hindered by a near absence of genetic markers. Objectives of this study were to develop high-throughput, A. magna-specific markers; generate a genetic linkage map based on the A. magna RIL population; and map genes controlling oat domestication. A Diversity Arrays Technology (DArT) array derived from 10 A. magna genotypes was used to generate 2,688 genome-specific probes. These, with 12,672 additional oat clones, produced 2,349 polymorphic markers, including 498 (21.2%) from A. magna arrays and 1,851 (78.8%) from other Avena libraries. Linkage analysis included 974 DArT markers, 26 microsatellites, 13 SNPs, and 4 phenotypic markers, and resulted in a 14-linkage-group map. Marker-to-marker correlation coefficient analysis allowed classification of shared markers as unique or redundant, and putative linkage-group-to-genome anchoring. Results of this study provide for the first time a collection of high-throughput tetraploid oat markers and a comprehensive map of the genome, providing insights to the genome ancestry of oat and affording a resource for study of oat domestication, gene transfer, and comparative genomics.

Identification of novel genomic regions associated with resistance to Pyrenophora tritici-repentis races 1 and 5 in spring wheat landraces using association analysis.

Tan spot, caused by Pyrenophora tritici-repentis, is a major foliar disease of wheat worldwide. Host plant resistance is the best strategy to manage this disease. Traditionally, bi-parental mapping populations have been used to identify and map quantitative trait loci (QTL) affecting tan spot resistance in wheat. The association mapping (AM) could be an alternative approach to identify QTL based on linkage disequilibrium (LD) within a diverse germplasm set. In this study, we assessed resistance to P. tritici-repentis races 1 and 5 in 567 spring wheat landraces from the USDA-ARS National Small Grains Collection (NSGC). Using 832 diversity array technology (DArT) markers, QTL for resistance to P. tritici-repentis races 1 and 5 were identified. A linear model with principal components suggests that at least seven and three DArT markers were significantly associated with resistance to P. tritici-repentis races 1 and 5, respectively. The DArT markers associated with resistance to race 1 were detected on chromosomes 1D, 2A, 2B, 2D, 4A, 5B, and 7D and explained 1.3-3.1% of the phenotypic variance, while markers associated with resistance to race 5 were distributed on 2D, 6A and 7D, and explained 2.2-5.9% of the phenotypic variance. Some of the genomic regions identified in this study correspond to previously identified loci responsible for resistance to P. tritici-repentis, offering validation for our AM approach. Other regions identified were novel and could possess genes useful for resistance breeding. Some DArT markers associated with resistance to race 1 also were localized in the same regions of wheat chromosomes where QTL for resistance to yellow rust, leaf rust and powdery mildew, have been mapped previously. This study demonstrates that AM can be a useful approach to identify and map novel genomic regions involved in resistance to P. tritici-repentis.

Development of oat-based markers from barley and wheat microsatellites.

Although microsatellites are an efficient and reliable genetic marker system, availability is limited in cultivated oat (Avena sativa L.). Previous research has suggested that microsatellites from related species may be adapted to oat. This study investigated the stability of existing oat microsatellites, sequenced polymorphic oat amplicons derived from wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) primers, and redesigned primers to develop oat-based markers. We evaluated 161 published oat microsatellites and identified 9 with polymorphism between mapping parents Ogle1040 and TAM O-301 (OT). We also studied 30 wheat, 1 Aegilops tauschii Coss., and 9 barley primers with reported oat polymorphism. Sixteen primers (1 A. tauschii, 10 wheat, 5 barley) amplified random oat sequences and were used to generate 28 new oat STS markers. Eight primers, 4 each from wheat and barley, amplified oat repetitive motifs, generating 10 new oat SSRs. Four additional SSRs were developed from characterization of thaumatin-like pathogenesis-related protein sequences formerly utilized as the Rast1-4 oat marker. These new markers, along with 9 existing oat SSRs and 6 previously identified disease resistance loci, were mapped in the OT population, joining 3 pairs of linkage groups. Map locations of multiallelic SSRs and disease-resistance QTL interactions suggested possible homoeologous relationships among the oat chromosomes.

Quantitative trait loci in the Ogle/TAM O-301 oat mapping population controlling resistance to Puccinia coronata in the field.

Crown rust is the most damaging disease of cultivated oat (Avena sativa) and genetic resistance is the primary means of controlling the disease. Quantitative trait loci (QTL) with major and minor effects have been identified in Ogle1040 and TAM O-301 (most notably, Pc58 and PcNQMG/LGCG from TAM O-301 and OT-27 from Ogle1040) through single-isolate greenhouse and field tests. To map loci and determine the effectiveness of previously identified QTL against naturally occurring pathogen populations in highly disease-conducive environments, the Ogle/TAM O-301 (OT) recombinant inbred line (RIL) population was grown in Texas and Louisiana over 2 years and in Manitoba, Canada. The genetic region characterized by the Pc58 resistance gene complex, particularly Pc58a, accounted for most of the diseased leaf area (DLA) and infection type (IT) variance in all five experiments. Additionally, the genetic region characterized by PcNQMG/LGCG accounted for a portion of the IT variance in three experiments. Although no QTL was detected on OT-27 in this study, all the markers on this linkage group were associated (P < 0.0001) with reducing both IT and DLA using single-marker analysis. Screening with 25 Puccinia coronata isolates from six different states indicated that Pc58abc and Pc58a were highly effective, while characterization using F(2) populations derived from OT RILs containing the two main genetic regions responsible for crown rust resistance in TAM O-301 (Pc58 and PcNQMG/LGCG) and a minor QTL in Ogle (OT-27) indicated that Pc58a, in combination with a locus in Ogle1040, provided high levels of resistance to natural races in Texas. This study provides new information and key loci in OT mapping population and may be useful for effective control of crown rust in North America.

Identification and validation of quantitative trait loci for partial resistance to crown rust in oat.

Management of oat crown rust disease with host resistance is challenging because major gene resistance is generally short lived. Partially resistant oat cultivars could benefit oat growers by providing more durable resistance. The objective of this study was to validate and discover quantitative trait loci (QTL) affecting crown rust resistance in the partially resistant oat line MN841801-1 using conventional and molecular assessments of disease produced in single-race greenhouse inoculations, single-race polycyclic field tests, and under natural infection in disease-conducive environments. Crown rust was assessed on 150 F(6:9) MN841801-1/'Noble-2' recombinant inbred lines. In total, eight QTL associated with MN841801-1 alleles were detected. Of these, seven matched QTL previously identified while a new QTL (Prq8) was detected on linkage group MN13. Four QTL (Prq1a, Prq2, Prq7, and Prq8) were consistently detected and predicative genetic assays for these QTL should be developed for future validation in additional genetic backgrounds.

Qualitative and quantitative trait loci conditioning resistance to Puccinia coronata pathotypes NQMG and LGCG in the oat (Avena sativa L.) cultivars Ogle and TAM O-301.

Mapping disease resistance loci relies on the type and precision of phenotypic measurements. For crown rust of oat, disease severity is commonly assessed based on visual ratings of infection types (IT) and/or diseased leaf area (DLA) of infected plants in the greenhouse or field. These data can be affected by several variables including; (i) non-uniform disease development in the field; (ii) atypical symptom development in the greenhouse; (iii) the presence of multiple pathogenic races or pathotypes in the field, and (iv) rating bias. To overcome these limitations, we mapped crown rust resistance to single isolates in the Ogle/TAM O-301 (OT) recombinant inbred line (RIL) population using detailed measurements of IT, uredinia length (UL) and relative fungal DNA (FDNA) estimates determined by q-PCR. Measurements were taken on OT parents and recombinant inbred lines (RIL) inoculated with Puccinia coronata pathotypes NQMG and LGCG in separate greenhouse and field tests. Qualitative mapping identified an allele conferred by TAM O-301 on linkage group (LG) OT-11, which produced a bleached fleck phenotype to both NQMG and LGCG. Quantitative mapping identified two major quantitative trait loci (QTL) originating from TAM O-301 on LGs OT-11 and OT-32 which reduced UL and FDNA of both isolates in all experiments. Additionally, minor QTLs that reduced UL and FDNA were detected on LGs OT-15 and OT-8, originating from TAM O-301, and on LG OT-27, originating from Ogle. Detailed assessments of the OT population using two pathotypes in both the greenhouse and field provided comprehensive information to effectively map the genes responsible for crown rust resistance in Ogle and TAM O-301 to NQMG and LGCG.

Detached-Leaf Method for Propagating Puccinia coronata and Assessing Crown Rust Resistance in Oat.

The crown rust pathogen Puccinia coronata is an obligate biotroph with wind-disseminated propagules and numerous races. These characteristics make propagation of single-race cultures difficult. Genetic studies using single races in field and greenhouse environments are also problematic because pure cultures can easily become contaminated. In this study, we developed an isolated propagation system for P. coronata and tested its ability to assess host resistance. Oat (Avena sativa) leaf sections (10 cm each) were harvested, disinfested, and suspended in sterile plastic boxes by enclosing 3.5-cm linear sections of each leaf end between 4% agar blocks amended with various chemical constituents. The exposed sections (approximately 3 cm) were inoculated with P. coronata urediniospores suspended in water. Boxes were sealed and incubated in a lighted growth cabinet until the pathogen sporulated. Viable spores were produced on leaves in all treatments, whereas 6-benzylaminopurine (BAP) and kinetin treatments sustained the leaves longer and yielded the most viable spores. Based on these data, the BAP treatment was adopted and used for additional studies. Detached leaves of differential oat cultivars produced the same reactions as whole plants screened under standard conditions in a growth chamber. The proposed detached-leaf system should be useful for the propagation of numerous single-race cultures of P. coronata as well as evaluation of host resistance under highly controlled conditions.

Characterization and mapping of oat crown rust resistance genes using three assessment methods.

ABSTRACT Resistance is the primary means of control for crown rust of oat (Avena sativa L.), caused by Puccinia coronata f. sp. avenae, and better knowledge of the genetics of resistance will enhance resistance breeding. Disease data were generated in the field and greenhouse for parents and recombinant inbred lines of the Ogle/TAM O-301 (OT) oat mapping population using (i) a new quantitative assay that employs quantitative real-time polymerase chain reaction (q-PCR) to estimate fungal growth in the host, (ii) digital image analysis, and (iii) visual ratings. The objectives of this study were to evaluate each assessment method's ability to map a major gene from cv. Ogle and potential quantitative trait loci (QTL) contributed by Ogle and TAM O-301. All three assessment methods identified the major gene in Ogle, which was mapped to linkage group OT6. The resolution produced by q-PCR, however, enabled more precise mapping of the major gene. Quantitative analysis indicated that 64% of the phenotypic variation was accounted for using q-PCR, whereas 41 and 52% were accounted for using visual and digital assessments, respectively. Data generated by q-PCR permitted identification of QTL on linkage groups OT32, accounting for 6% of the phenotypic variation, and OT2, accounting for 4% of the variation. QTL on both OT32 and OT2 were conferred by TAM O-301, one of which (OT2) was indiscernible using data from the visual and digital assessments. The new method of precisely phenotyping crown rust resistance provided a more accurate and thorough means of dissecting resistance in the OT mapping population. Similar methods could be developed and applied to other important cereal rust diseases.

A Quantitative Assay of Puccinia coronata f. sp. avenae DNA in Avena sativa.

Crown rust, caused by Puccinia coronata f. sp. avenae, is the most damaging disease of oat. Quantification of the disease can be done by visual or digital assessments of diseased leaf area, lesion number, lesion size, and latent period. Laborious measurements of sporulation can also be made. As an alternative to these methods, a new quantitative assay was developed. The method employs simple inoculum application, quantitative sampling from inoculated areas, a closed tube DNA extraction method restricting loss of tissue, and real-time polymerase chain reaction (PCR) using a pathogen-specific TaqMan primers/probe set. Image analyses of genotypes with varying levels of crown rust resistance were compared to fungal DNA (FDNA) estimations by the new assay. The moderately resistant genotype IA98822-2 was distinguished from susceptible genotypes at the seedling stage, and the moderately resistant genotype O × T 107 was distinguished from the resistant cultivar TAM-O-301 at seedling and adult plant stages using FDNA. These separations were not evident with digital image analysis. The new assay also detected fungal development earlier and more rapidly in genotypes with lower levels of resistance. The assay can consistently estimate disease and should be useful for studying many aspects of the crown rust host-pathogen interaction where precise assessment of pathogen development is needed.

Women, Co-occurring Disorders, and Violence Study: evaluation design and study population.

The Women, Co-occurring Disorders, and Violence Study (WCDVS) was a multi-site cooperative study to evaluate new service models for women with co-occurring mental health and substance use disorders and a history of physical and/or sexual abuse. Despite common features in the service interventions and evaluation procedures, diversity across the nine sites plus differences introduced by non-random assignment led to numerous methodological challenges. This article describes the design, measurement, and analysis decisions behind the WCDVS and lays the foundation for understanding participant-level outcomes and service costs. This article also describes the study population, as recruited and following attrition at the 6-month follow-up, in order to address the threat of selection bias to inferences drawn from this multi-site study.

Postbaccalaureate Medical/Dental Education Preparatory Program (MEDPREP) at Southern Illinois University School of Medicine.

Between 1972 and 1998, the state and federally funded Medical/Dental Education Preparatory Program (MEDPREP) at Southern Illinois University School of Medicine served approximately 900 qualified minority and disadvantaged students, in an effort to increase the number of underrepresented-minority (URM) students accepted into and retained in health professions schools. To help students improve their application credentials, this post-baccalaureate program establishes high expectations for student progress, designs individual curricula, offers extensive academic and personal counseling, has its own teaching faculty, and operates in a specially equipped, designated facility. This supportive educational environment has demonstrated success. By 1998 over 500 MEDPREP students had been accepted into medical or other health professions schools, and 86% of them had graduated or were scheduled to graduate. And while the number of new URM entrants to medical schools declined nationwide from 1995 to 1997, 70 URM students from MEDPREP matriculated to 28 different allopathic medical schools, eight entered three different osteopathic medical schools, and two entered dental schools. Recent data indicate that the score changes of Medical College Admission Test (MCAT) repeaters who were MEDPREP students were larger than those of all MCAT repeaters reported by the Association of American Medical Colleges (AAMC). In fact, the MEDPREP repeaters' score changes were two to nearly six times greater than the overall changes reported by the AAMC. These gains suggest that a carefully designed, long-term post-baccalaureate intervention such as MEDPREP can increase the pool of qualified URM and disadvantaged students accepted into and retained in health professions schools.

Effect of co-occurrence on the referability of internalizing and externalizing problem behavior in adolescents.

Assessed the effect of co-occurring versus not co-occurring internalizing and externalizing behavior problems on the reasons parents reported for clinical referral of their adolescent child. Reasons for referral were coded for 181 inpatient adolescents, and parent ratings of internalizing and externalizing behavior were obtained for a general population sample of 500 adolescents. Parents concurrently reported internalizing and externalizing behavior as reasons for referral less frequently (p < .0001) than would be expected given the correlation between these two domains in the general population sample. This suggests that the presence of externalizing problems may decrease parents' concern or awareness of internalizing problems, the presence of internalizing problems may decrease parents' concern or awareness of externalizing problems, or both. Implications for the clinical referral of adolescents and for informal parental efforts at helping their children with externalizing and internalizing problems are discussed.

A multimethod study of problem behavior among Thai and American children in school: teacher reports versus direct observations.

Previous literature describes Thai children as unusually polite, deferent, and behaviorally restrained. Yet, in a recent study employing teacher reports, Thai children were reported to show many more behavior problems than American children. Such a finding may reflect culture-linked differences in the perspective of Thai versus American teachers. To explore this possibility, we used trained observers to conduct direct observations of Thai and American children's school behavior, and we obtained teacher reports on the same children. Observational results were precisely the opposite of previous and present teacher-report findings: Observers reported twice as much problem behavior and off-task behavior in American children as in their Thai age-mates. This pattern may reflect Thai-U.S. differences in teachers' style, societal values and practices, even child temperament. The finding support the value of direct behavior observation in cross-national research on child problems.

Twenty-year follow-up of an enrichment program for students preparing for health professional schools.

BACKGROUND: From 1972 to 1992, the Medical/Dental Education Preparatory Program (MEDPREP) of the Southern Illinois University School of Medicine served 584 underrepresented-minority and educationally disadvantaged students as they prepared for admission to health professional schools. METHOD: For students who had concluded their MEDPREP participation by September 1992, data analysis was performed in terms of gender, race-ethnicity, rates of acceptance and retention, and type of professional school. In addition, a sample of 30 medical school graduates was examined for type of practice and specialty. RESULTS: A total of 350 (60%) of the MEDPREP participants had been accepted to professional schools. Of those accepted, 246 (70%) were members of groups underrepresented in medicine, 301 (86%) had graduated or were in school, and 305 (87%) had been accepted to a total of 47 medical schools. Of the sample of 30 medical school graduates tracked for type of practice and specialty, 28 (93%) were providing direct patient care and 21 (70%) were board certified in the primary care specialties of family practice, pediatrics, obstetrics-gynecology, and internal medicine. CONCLUSION: Because MEDPREP has high rates of acceptance, matriculation, and graduation for its participants, and because such a high percentage of its medical school graduates entered primary care, the program may serve as a model intervention for providing more underrepresented minorities and generalists in medicine.

Adult attitudes toward over- and undercontrolled child problems: urban and rural parents and teachers from Thailand and the United States.

In a study of adult attitudes, urban and rural parents and teachers in Thailand and the U.S. made judgments about two children, one with overcontrolled problems (e.g. shyness, fear), one with undercontrolled problems (e.g. disobedience, fighting). Consistent with previous literature, Thais (vs Americans) rated problems of both types less serious, less worrisome, less likely to reflect personality traits, and more likely to improve with time. Urban-rural differences and parent-teacher differences had negligible impact. The findings suggest that certain cultural differences in adult attitudes toward child problems may be robust across parents and teachers and across urban and rural settings.

Predicting the medical school progress of minority students who participated in a preparatory program.

The grade-point averages (GPAs), Medical College Admission Test (MCAT) scores, and Student Progress Committee (SPC) ratings of 75 minority students who had attended a preparatory program at Southern Illinois University School of Medicine at some period from 1976 through 1986 were analyzed to determine how these variables related to the retention and progress of these students in medical school. Although those retained had higher SPC ratings than those not retained, stepwise regression revealed that none of the variables predicted retention. The MCAT Reading score, however, was significantly higher for students who progressed on schedule; it was the only significant predictor of progress.

The limitations of traditional variables in predicting the progress of nontraditional students.

The traditional preadmissions variables of GPA's, MCAT scores and recommendation decisions of a group of nontraditional medical students who enrolled from 1978-1983 were examined to determine 1) the degree to which a classification model derived from the variables to predict whether they would graduate on schedule, graduate off schedule or not graduate would be applicable to a second group of nontraditional students who enrolled from 1984-1987, and 2) which variables would predict whether the students would graduate on schedule, graduate off schedule or not graduate. The discriminant model correctly classified only 33 percent of the students in the second group; the MCAT Reading score, the only significant predictive variable, accounted for 26 percent of the variance in the progress of the students in the first group.