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PubMed2002

Participants' ratings of male physicians who vary in race and communication style.

Research has shown minorities receive lower quality health care than White persons even with socioeconomic conditions controlled. This difference may partially be related to racially biased attitudes and impaired communication in interracial relationships between physicians and patients. This study investigated the effect of physicians' race and nonverbal communication style on participants' evaluations. Patients at a local health clinic were participants (N = 116: 84% Black, 16% White). Each participant viewed one of four videotapes showing varied race of a physician (Black or White) and the physician's nonverbal behavior (expressing concern or distance), and then completed a questionnaire evaluating the depicted physician. Overall, participants did not give significantly different preferences for physicians of the same race. However, participants' evaluations were significantly associated with physicians' nonverbal style. Nonverbal concern was associated with highest satisfaction, trust, self-disclosure, recall of information, likelihood of recommending the physician, and intent to comply with the physician's recommendations. When male and female participants were compared, preference for a physician of the same race was found only among male participants who viewed verbally distant physicians. Results suggest that social skills are more important than race in shaping patients' perceptions of physicians.

Black or African American↗
PubMed2005

The influence of health status, age, and race on screening mammography in elderly women.

BACKGROUND: Screening mammography is controversial for elderly women because of an absence of efficacy data. Decisions to screen are based on individualized assessment of risks and benefits. Our objective was to determine how screening mammography varies by age and race when adjusted for propensity to die. METHODS: In a retrospective cohort study, rates of screening mammogram performed in 2000-2001 based on claims, adjusted for propensity to die in 2000, were determined for a nationally representative 5% random sample of female fee-for-service Medicare beneficiaries 65 years and older in (N = 722,310). RESULTS: The overall rate of screening was 39%. When stratified into quintiles by propensity to die, 2-year rates ranged from 61% in the lowest-risk group to 5% in the highest-risk group. In analyses stratified by age and adjusted for propensity to die, 42% of women aged 65 to 69 years were screened, declining to 26% of women 85 years and older (P<.001). Adjusted screening rates for white women, black women, and women of other races were 40%, 30%, and 25%, respectively (P<.001). Thus, among women with similar health status, the youngest women were 1.61 times more likely to be screened compared with the oldest; compared with black women and women of other races, white women were 1.38 and 1.60 times, respectively, more likely to be screened. CONCLUSIONS: Decisions to screen for breast cancer are related not only to health status but also to age and race. Underuse and overuse of screening mammography likely occurs owing to age- and race-associated decision making. Assessment of life expectancy may more accurately identify women who could benefit from screening.

Age Factors↗
PubMed2005

Race, education, and weight change in a biracial sample of women at midlife.

BACKGROUND: Overall rates of obesity have increased dramatically in the United States, yet African American women remain disproportionately represented among the overweight and obese. The excess weight observed in African American women is primarily considered a result of low socioeconomic status, but recent cross-sectional findings suggest otherwise. METHODS: We examined the interactive effects of race and 3 levels of education (low [high school or less]; moderate [some college]; and high [college degree or more]) on body mass index (BMI) (calculated as weight in kilograms divided by the square of height in meters) and changes in BMI over 4 years in 2019 middle-aged African American and white women from the Study of Women's Health Across the Nation (SWAN). Data were analyzed with mixed effects regression models. RESULTS: At baseline, we observed a significant race x education interaction (estimate, -3.7; 95% confidence interval, -5.3 to -2.1; P<.001) on BMI. Compared with whites, African Americans had higher BMIs, but only at the moderate (means, 32.1 and 29.2) and highest (means, 31.5 and 27.8) level of education. At the lowest level of education, African American and white women were similar in BMI (means, 31.1 [African American] and 31.2 [white]). Body mass index increased significantly for all women over follow-up (estimate, 0.22; 95% confidence interval, 0.17 to 0.26; P<.001), but increases did not differ by race, education, or race x education. Results were unchanged after adjustment for potential confounding variables. CONCLUSIONS: For middle-aged women, racial disparities in BMI are largely patterned by education, with the greatest disparities observed at higher levels of education. The absence of significant longitudinal effects suggests that these race-education patterns are set in place and well established before midlife.

Black or African American↗
PubMed1999

Childhood passive smoking, race, and coronary artery disease risk: the MCV Twin Study. Medical College of Virginia.

BACKGROUND: Children with long-term exposure to passive cigarette smoke may be at elevated risk for the development of premature coronary artery disease (CAD). OBJECTIVE: To examine how CAD risk factors, exposure to passive smoking, sex, and race are related in pubertal children and to determine if there is an identifiable childhood risk profile (i.e., does passive smoking interact with other coronary risk factors to increase the risk of developing premature CAD). DESIGN: Cohort analytic study. SETTING: The Medical College of Virginia (MCV) Twin Study, Richmond, Va. SUBJECTS: Randomly selected twins from 408 11-year-old twin pairs recruited from nearby schools. METHODS: Data collection occurred at 18-month intervals on family and health histories, smoking and alcohol consumption, blood pressure, anthropometrics, and biochemical assays. Data from cohorts of 11-year-olds studied through age 15 years were analyzed by repeated-measures analyses of variance using a mixed modeling approach. Models for high-density lipoprotein cholesterol (HDL-C) included race, sex, passive smoking status, weight, systolic and diastolic blood pressures, and all interactions. RESULTS: Passive smoke exposure was greater in white families than in black families. Levels of HDL-C and HDL2-C (HDL subfraction 2 cholesterol) were lower in white children than in black children (visit 1: HDL-C, mean +/- SD, 1.21+/-0.26 vs. 1.31+/-0.26 mmol/L [47.0+/-10.1 vs. 50.6+/-10.1 mg/dL], P< or =.01; HDL2, mean +/- SD, 0.31+/-0.18 vs. 0.41+/-0.19 mmol/L [12.3+/-7.0 vs. 15.9+/-7.4 mg/dL], P< or =.001). Children with a family history of cardiovascular disease had differences in HDL-C levels related to race that were worsened by exposure to cigarette smoke. In these children, HDL-C level was lower in those exposed to passive smoking (visit 1: 1.18+/-0.23 vs. 1.25+/-0.23 mmol/L [45.6+/-9 vs. 48.2+/-9 mg/dL] and visit 4: 0.98+/-0.10 vs. 1.19+/-0.18 mmol/L [37.8+/-4 vs. 46.0+/-7 mg/dL]; P<.001), with white children having lower HDL-C levels than black children (visit 1: 1.12+/-0.21 vs. 1.36+/-0.23 mmol/L [43.2+/-8 vs. 52.7+/-9 mg/ dL] and visit 4: 0.97+/-0.31 vs. 1.01+/-0.31 mmol/L [37.6+/-12 vs. 39.0+/-12 mg/dL]; P = .004). In white families, as weight increased, boys exposed to passive smoking showed the greatest decrease in HDL-C level (P<.01 for weight by sex and passive smoking interaction). Risk factors for CAD, such as blood pressure, interacted with HDL-C and these relationships varied by race and sex. CONCLUSIONS: Pubertal children with long-term passive cigarette smoke exposure have lower HDL-C levels. Racial differences in HDL-C levels are related to passive smoke exposure. In children with a family history of cardiovascular disease, interactions exist between passive smoking, HDL-C level, and blood pressure that differ by sex and race. White males exposed to passive smoking who have a family history of cardiovascular disease and higher weights and diastolic blood pressures may be at special risk for premature CAD.

Adolescent↗
PubMed1999

Race, gender, and partnership in the patient-physician relationship.

CONTEXT: Many studies have documented race and gender differences in health care received by patients. However, few studies have related differences in the quality of interpersonal care to patient and physician race and gender. OBJECTIVE: To describe how the race/ethnicity and gender of patients and physicians are associated with physicians' participatory decision-making (PDM) styles. DESIGN, SETTING, AND PARTICIPANTS: Telephone survey conducted between November 1996 and June 1998 of 1816 adults aged 18 to 65 years (mean age, 41 years) who had recently attended 1 of 32 primary care practices associated with a large mixed-model managed care organization in an urban setting. Sixty-six percent of patients surveyed were female, 43% were white, and 45% were African American. The physician sample (n = 64) was 63% male, with 56% white, and 25% African American. MAIN OUTCOME MEASURE: Patients' ratings of their physicians' PDM style on a 100-point scale. RESULTS: African American patients rated their visits as significantly less participatory than whites in models adjusting for patient age, gender, education, marital status, health status, and length of the patient-physician relationship (mean [SE] PDM score, 58.0 [1.2] vs 60.6 [3.3]; P = .03). Ratings of minority and white physicians did not differ with respect to PDM style (adjusted mean [SE] PDM score for African Americans, 59.2 [1.7] vs whites, 61.7 [3.1]; P = .13). Patients in race-concordant relationships with their physicians rated their visits as significantly more participatory than patients in race-discordant relationships (difference [SE], 2.6 [1.1]; P = .02). Patients of female physicians had more participatory visits (adjusted mean [SE] PDM score for female, 62.4 [1.3] vs male, 59.5 [3.1]; P = .03), but gender concordance between physicians and patients was not significantly related to PDM score (unadjusted mean [SE] PDM score, 76.0 [1.0] for concordant vs 74.5 [0.9] for discordant; P = .12). Patient satisfaction was highly associated with PDM score within all race/ethnicity groups. CONCLUSIONS: Our data suggest that African American patients rate their visits with physicians as less participatory than whites. However, patients seeing physicians of their own race rate their physicians' decision-making styles as more participatory. Improving cross-cultural communication between primary care physicians and patients and providing patients with access to a diverse group of physicians may lead to more patient involvement in care, higher levels of patient satisfaction, and better health outcomes.

Adult↗
PubMed1996

"Race" specificity and the femur/stature ratio.

This inquiry explores a series of problems related to the femur/stature ratio first raised by Feldesman et al. (1990). In particular, we used a revised data set and a more elaborate research protocol to address questions pertaining to: (1) whether the femur/stature ratios of three quasigeographic "races" ("Blacks," "Whites," "Asians") are statistically significantly different; (2) whether these are statistically (as opposed to biologically) coherent groups; and (3) whether the "race"-specific ratios are more accurate than the simple generic femur/stature ratio. We used ANOVA, ANOCOVA, post hoc analysis, k-means cluster analysis, linear discriminant functions, and approximate randomization to determine whether the group differences in the ratio were significant, and to assess the coherence of the "racial" groups themselves. We used validation procedures including mean absolute deviation, mean squared error, and Pitman's measure of closeness of a known sample of 798 femur/stature pairs to compare the accuracy of the generic ratio and the group-specific ratios. The results confirmed that the "Black" femur/stature ratio is significantly different from those of "Whites" and "Asians"; however, group coherence was poor, with results barely better than chance. We found that "race"-specific ratios slightly outperform the generic ratio when "race" is certain, but the gains are small for the assumptions required. More significantly, however, we found that when "race" attribution is uncertain or unknown, as in paleoanthropology, the wrong ratio (or the wrong regression equation) performs poorer than the generic femur/stature ratio. As a result, we recommend that researchers continue using the generic femur/ stature ratio to estimate stature in pre- and protohistoric populations. An alternative equation, a generic regression, yields even better stature estimates; however, we urge further study before recommending that researchers use this instead of the more thoroughly tested generic femur/stature ratio.

Analysis of Variance↗
PubMed1999

Exploratory analysis on the effect of race on clinical outcome in patients with advanced prostate cancer receiving bicalutamide or flutamide, each in combination with LHRH analogues. The Casodex Combination Study Group.

BACKGROUND: Black race has been associated with a significantly increased risk of prostate cancer mortality. This exploratory analysis investigated the effect of race on the clinical outcome of combined androgen blockade (CAB). METHODS: Data for analysis were obtained from a double-blind, randomized, multicenter trial comparing CAB in the form of bicalutamide (50 mg once daily) or flutamide (250 mg three times daily) plus luteinizing hormone-releasing hormone analogs (LHRHa; goserelin acetate 3.6 mg, or leuprolide acetate 7.5 mg) in 813 patients with stage D(2) prostate cancer (median follow-up, 160 weeks). Patients were analyzed according to race (African American [AA], white, or other). The primary clinical events were disease progression and survival. RESULTS: Four hundred and four patients received bicalutamide/LHRHa and 409 received flutamide/LHRHa. Although treatment with bicalutamide/LHRHa resulted in slightly longer time to progression and survival time in white and AA males than treatment with flutamide/LHRHa, the differences between the treatment groups were not statistically significant. CONCLUSIONS: No marked effect of race on clinical outcome was observed regardless of antiandrogen, suggesting that similar treatment benefits are to be expected in either race.

Adenocarcinoma↗
PubMed2026

Survival by Race and Ethnicity in Children and Adolescents/Young Adults With Relapsed/Refractory Hodgkin Lymphoma: A Pooled Analysis of Children's Oncology Group Trials.

PURPOSE: Despite 5-year survival rates of over 90% among children and adolescents/young adults (CAYAs) with classic Hodgkin lymphoma (cHL), 15%-20% relapse after frontline therapy. Prior analysis of frontline Children's Oncology Group (COG) clinical trials demonstrated that, despite similar rates of relapse, non-Hispanic Black (NHB) and Hispanic (vs. non-Hispanic White [NHW]) patients experienced higher post-relapse mortality. It is unknown whether post-relapse disparities persist when second-line treatment is delivered in a cooperative group trial setting. We examined overall survival (OS) by race and ethnicity in CAYAs enrolled in COG trials for relapsed/refractory (r/r) cHL. METHODS: A pooled analysis of individual-level data from CAYAs (&#x2264; 29 years) receiving therapy for r/r cHL on COG clinical trials (2001-2016) was conducted. The Kaplan-Meier method estimated 3-year OS by racial and ethnic groups. Cox regression models examined associations of race and ethnicity and OS, adjusted for age, insurance, first versus &#x2265;2 relapse, and time from initial diagnosis to relapse trial enrollment. RESULTS: Among 175 CAYAs treated on COG trials for r/r cHL (5.7% Asian or Pacific Islander, 14.9% Hispanic, 14.3% NHB, 61.7% NHW, 3.4% other), at median follow-up of 4.9 years, 3-year OS was 82.1% (95% confidence interval [CI], 75.3%-87.1%) and did not differ by race and ethnicity (p = 0.36). In multivariable analyses, shorter time from diagnosis to relapse trial enrollment (p = 0.01) and &#x2265;2 relapses (vs. first, p = 0.004) conferred worse OS, with no significant effect of race and ethnicity (p = 0.43). CONCLUSION: Post-relapse survival did not differ by race and ethnicity among CAYAs enrolled in COG trials for r/r cHL, suggesting access to clinical trials may mitigate OS disparities.

Humans↗
PubMedDate not supplied

Race and sex differences and contribution of height: a study on bone size in healthy Caucasians and Chinese.

Osteoporosis is characterized by a loss of bone strength, of which bone size (BS) is an important determinant. However, studies on the factors determining BS are relatively few. The present study evaluated the independent effects of height, age, weight, sex, and race on areal BS at the hip and spine, measured by dual-energy X-ray absorptiometry, while focusing on the differential contributions of height to BS across sex, race, and skeletal site. The subjects were aged 40 years or older, including 763 Chinese (384 males and 379 females) from Shanghai, People's Republic of China, and 424 Caucasians (188 males and 236 females) from Omaha, Nebraska. Basically, Caucasians had significantly larger BS than Chinese. After adjusting for height, age, and weight, the Chinese had similar spine BS, but significantly larger intertrochanter BS in both sexes and larger total hip BS in females compared with Caucasians. Males had significantly larger BS than females before and after adjustment in both ethnic groups. The effects of age, weight, and race varied, depending on skeletal site. As expected, height had major effects on BS variation in both sexes and races. Height tended to account for larger BS variation at the spine than at the hip (except for Chinese females), and larger BS variation in Caucasians than in Chinese of the same sex (except for the trochanter in females). We conclude that height is a major predictor for BS, and its contributions vary across sex, race, and skeletal site.

Absorptiometry, Photon↗
PubMed1977

[Behavior of certain parameters of lipid and energy metabolism. IV. Regulation of lipid and energy metabolism in livers and race and mini pigs].

To characterize the lipid and the energy metabolism in the livers of genetically different types of pigs (land race pig and mini pig), the authors determined the activities of enzymes typical of and limiting these metabolic pathways. Furthermore, they measured the concentrations of typical metabolites and ascertained parameters that are of importance in energy metabolism. The concentrations of acetyl CoA and free fatty acids in the livers of mini pigs were significantly greater than those in the livers of land race pigs, whereas the cholesterol, glycerol, triglyceride and acetoacetate concentrations were reduced. The activities of glucose-6-phosphate dehydrogenase (E.C.1.1.1.49.), citrate synthase (E.C.4.1.3.7.) and ATP citrate lyase (E.C.4.1.3.8.) were lower in the livers of mini pigs than in the livers of land race pigs, whereas the activity of fatty acid synthase was higher. The concentrations of cyclic 3',5'-adenosine monophosphate (AMP) and adenosine diphosphate (ADP) were lower in the livers of mini pigs than in those of land race pigs. In land race pigs, the metabolic process seems, therefore, to be determined in favour of the degradation of free fatty acids and of the generation of energy. In mini pigs, lipogenesis in the liver appears to be the decisive metabolic pathway. The possibility of a higher coordinating control mechanism of the lipid and the energy metabolism is discussed.

ATP Citrate (pro-S)-Lyase↗
PubMed1992

Epidemiology of congenital heart disease in Louisiana: an association between race and sex and the prevalence of specific cardiac malformations.

We hypothesized that susceptibility to the genetic and environmental factors that disrupt cardiac development is associated with race and sex. To evaluate this hypothesis, we asked whether the prevalence of specific cardiac malformations differs by race and sex. We attempted to include all infants born alive in the State of Louisiana from January 1, 1988, through December 31, 1989, and diagnosed by echocardiography, catheterization and/or autopsy within a year of birth as having one of ten specific cardiac malformations. The prevalence of atrioventricular canal defects (AVCD) per 1,000 live births was significantly higher for black females (.744) compared to black males (.198) and for white females (.414) compared to white males (.116). Complete transposition of the great arteries (TGA) was significantly higher for white males (.559) compared to white females (.122); in contrast, TGA was not significantly different for black males (.198) and black females (.169). Obstructive left heart syndrome (OLHS)--aortic stenosis and/or coarctation of the aorta--was significantly higher for white males (.652) compared to white females (.317); in contrast, OLHS was not significantly different for black males (.264) and black females (.169). Single ventricle (SV) was significantly higher for whites (.202) compared to blacks (.067). We did not find that race and sex were associated with differences in the prevalence of tetralogy of Fallot and hypoplastic left heart syndrome. The numbers of infants with anomalous pulmonary venous return, tricuspid atresia, double outlet right ventricle, or truncus arteriosus were too small to measure an association with race and sex. These results demonstrate that the prevalence of a subset of cardiac malformations differs by race and sex.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1982

The chromosomes of two Drosophila races: D. nasuta nasuta and D. n. albomicana. I. Distribution and differentiation of heterochromatin.

Heterochromatin distribution and differentiation in metaphase chromosomes of two morphologically identical Drosophila races, D. nasuta nasuta and D. n. albomicana, have been studied by C- and N-banding methods. -- The total heterochromatin values differ only slightly between these races. However, homologous chromosomes of the two Drosophila forms show striking differences in the size of heterochromatin regions and there is an alternating pattern in D. n. nasuta and D. n. albomicana of chromosomes which contain more, or respectively less heterochromatin than their counterparts in the other race. -- Three different N-banding patterns could be obtained depending on the conditions of the method employed: One banding pattern occurs which corresponds to the C-banding pattern. Another pattern is the reverse of the C-band pattern; the euchromatic chromosome regions and the centromeres are stained whereas the pericentric heterochromatin regions remain unstained. In the Y chromosomes of both races and in chromosome 4 of D. n. albomicana, however, the heterochromatin is further differentiated. In the third N-banding pattern only the centromeres are deeply stained. Furthermore, between the races, subtle staining differences in the pericentric heterochromatin regions can be observed as verified in F1 hybrids. On the basis of C- and N-banding results specific aspects of chromosomal differences between D. n. nasuta and D. n. albomicana are discussed.

Animals↗
PubMed1982

Relationships of the anaerobic threshold with the 5 km, 10 km, and 10 mile races.

The purpose of present study was to assess the relationship between anaerobic threshold (AT) and performances in three different distance races (i.e., 5 km, 10 km, and 10 mile). AT, VO2 max, and related parameters for 17 young endurance runners aged 16--18 years tested on a treadmill with a discontinuous method. The determination of AT was based upon both gas exchange and blood lactate methods. Performances in the distance races were measured within nearly the same month as the time of experiment. Mean AT-VO2 was 51.0 ml . kg-1 . min-1 (2.837 l . min-1), while VO2 max averaged 64.1 ml . kg-1 . min-1 (3.568 l . min-1). AT-HR and %AT (AT-VO2/VO2 max) were 174.7 beats . min-1 and 79.6%, respectively. The correlations between VO2 max (ml . kg-1 . min-1) and performances in the three distance races were not high (r = -0.645, r = -0.674, r = -0.574), while those between AT-VO2 and performances was r = -0.945, r = -0.839, and r = -0.835, respectively. The latter results indicate that AT-VO2 alone would account for 83.9%, 70.4%, and 69.7% of the variance in the 5 km, 10 km, and 10 mile performances, respectively. Since r = -0.945 (5 km versus AT-VO2) is significantly different from r = -0.645 (5 km versus VO2 max), the 5 km performance appears to be more related to AT-VO2 than VO2 max. It is concluded that individual variance in the middle and long distance races (particularly the 5 km race) is better accounted for by the variance in AT-VO2 expressed as milliliters of oxygen per kilogram of body weight than by differences in VO2 max.

Adolescent↗
PubMed1995

The physical demands of riding in National Hunt races.

Heart rate (fc) and post-competition blood lactate concentration ([La+]) were studied in seven male professional National Hunt jockeys over 30 races. The fc response for individual races followed a similar pattern for all subjects. The mean peak fc recorded during competition was 184 beats.min-1 (range 162-198 beats.min-1) with average fc during the races ranging from 136 to 188 beats.min-1. During consecutive races the recovery fc did not return to resting values. The mean [La+] was 7.1 mmol.l-1 (range 3.5-15.0 mmol.l-1). The conclusions of this study suggest that riding in National Hunt races is a physically demanding occupation. The muscular activity in this profession requires a high metabolic drive and produces a significant cardiorespiratory response.

Adult↗
PubMed1988

Serum creatine kinase and lactate dehydrogenase changes following an eighty kilometer race. Relationship to lipid peroxidation.

Pre and post race serum malondialdehyde (MDA), creatine kinase (CK) and lactate dehydrogenase (LDH) levels were studied in runners following an 80 km (50 mile) race. MDA is an indicator of lipid peroxidation. Subjects averaged 47.4 years (range 35-60), had a mean maximal oxygen uptake (VO2max) of 48.2 ml/kg, and averaged 121 km (75 miles) per week in training. Throughout the race, runners maintained a pace approximating 72% of VO2max. Previous data from our laboratory indicated a high correlation between resting MDA and total CK and CK-MB. Present resting data confirms prior results (r = 0.84 and 0.69 respectively). In addition, the relationship established at rest persisted following exercise (r = 0.62 and 0.85 respectively). Post race CK, CK-MB, LDH and MDA values for all subjects were significantly greater than resting values (p less than 0.01). Mean post CK and CK-MB levels were nearly 10 and 4 times lower, respectively, than prior values from our laboratory in subjects following a 100 km (62 mile) race. It was concluded that post exercise serum enzyme elevations, universally accepted as a marker of tissue damage, correlate well and may be related to an exercise induced lipid peroxidation.

Creatine Kinase↗
PubMed1997

Effects of race and socioeconomic status on survival of 1,332 black, Hispanic, and white women with breast cancer.

BACKGROUND: A survival disadvantage for black women with breast cancer, which persists after controlling for stage of the disease, has been reported. This study investigates the effects of race and socioeconomic status (SES) on breast cancer survival after controlling for age, stage, histology, and type of treatment. METHODS: Kaplan-Meier and Cox proportional hazards models were used to analyze the interaction between race and SES in predicting survival in a sample of 163 black, 205 Hispanic and 964 white women with breast cancer treated at M.D. Anderson Cancer Center a (1987-1991). RESULTS: The results of univariate and multivariate analyses indicate that race was not a significant predictor of survival after adjusting for SES and other confounding factors such as demographic and disease characteristics. SES remained a significant predictor of survival after all adjustments were made. There was no evidence of differences in type of treatment by race or SES if adjustments were made for stage. CONCLUSIONS: These results suggest that institutional factors, such as access to treatment, do not explain survival differences by race or SES. Other factors associated with low SES, such as life-style and behavior, may affect survival.

Black or African American↗
PubMed2002

Microsatellites uncover extraordinary diversity in native American land races and wild populations of cultivated sunflower.

The contemporary oilseed sunflower (Helianthus annuus L.) gene pool is a product of multiple breeding and domestication bottlenecks. Despite substantial phenotypic diversity, modest differences in molecular genetic diversity have been uncovered in anciently and recently domesticated sunflowers. The paucity of molecular marker polymorphisms in early analyses led to the hypothesis of a single domestication origin. Phylogenetic analyses were performed on 47 domesticated and wild germplasm accessions using 122 microsatellite loci distributed throughout the sunflower genome. Extraordinary allelic diversity was found in the Native American land races and wild populations, and progressively less allelic diversity was found in germplasm produced by successive cycles of domestication and breeding. Of 1,341 microsatellite alleles, 489 were unique to land races, exotic domesticates and wild populations, whereas only 15 were unique to elite inbred lines. The number of taxon-specific alleles was 35-fold greater among wild populations (26.27) than elite inbred lines (0.75). Microsatellite genotyping uncovered the possibility of multiple domestication origins. Land races domesticated by Native Americans of the southwestern US (Hopi and Havasupai) formed a clade independent of land races domesticated by Native Americans of the Great Plains and eastern US (Arikara and Seneca). Predictably, domestication and breeding have ratcheted genetic diversity down in sunflower. The contemporary oilseed sunflower gene pool, while not imperiled, could profit from an infusion of novel alleles from the reservoir of latent genetic diversity present in wild populations and Native American land races.

Alleles↗
PubMed2004

Molecular mapping of resistance to Pyrenophora tritici-repentis race 5 and sensitivity to Ptr ToxB in wheat.

Tan spot, caused by Pyrenophora tritici-repentis (Ptr), is an economically important foliar disease in the major wheat growing areas of the world. Multiple races of the pathogen have been characterized based on their ability to cause necrosis and/or chlorosis in differential wheat lines. Isolates of race 5 cause chlorosis only, and they produce a host-selective toxin designated Ptr ToxB that induces chlorosis when infiltrated into sensitive genotypes. The international Triticeae mapping initiative (ITMI) mapping population was used to identify genomic regions harboring QTLs for resistance to fungal inoculations of Ptr race 5 and to determine the chromosomal location of the gene conditioning sensitivity to Ptr ToxB. The toxin-insensitivity gene, which we are designating tsc2, mapped to the distal tip of the short arm of chromosome 2B. This gene was responsible for the effects of a major QTL associated with resistance to the race 5 fungus and accounted for 69% of the phenotypic variation. Additional minor QTLs were identified on the short arm of 2A, the long arm of 4A, and on the long arm of chromosome 2B. Together, the major QTL on 2BS identified by tsc2 and the QTL on 4AL explained 73% of the total phenotypic variation for resistance to Ptr race 5. The results of this research indicate that Ptr ToxB is a major virulence factor, and the markers closely linked to tsc2 and the 4A QTL should be useful for introgression of resistance into adapted germplasm.

Ascomycota↗