Quantitative Trait Loci Differentiating the Outbreeding Mimulus Guttatus from the Inbreeding M. Platycalyx

Theoretical predictions about the evolution of selfing depend on the genetic architecture of loci controlling selfing (monogenic vs. polygenic determination, large vs. small effect of alleles, dominance vs. recessiveness), and studies of such architecture are lacking. We inferred the genetic basis of mating system differences between the outbreeding Mimulus guttatus and the inbreeding M. platycalyx by quantitative trait locus (QTL) mapping using random amplified polymorphic DNA and isozyme markers. One to three QTL were detected for each of five mating system characters, and each QTL explained 7.6-28.6% of the phenotypic variance. Taken together, QTL accounted for up to 38% of the variation in mating system characters, and a large proportion of variation was unaccounted for. Inferred QTL often affected more than one trait, contributing to the genetic correlation between those traits. These results are consistent with the hypothesis that quantitative variation in plant mating system characters is primarily controlled by loci with small effect.     

Multiple genes for essential-hypertension susceptibility on chromosome 1q

Essential hypertension, defined as elevated levels of blood pressure (BP) without any obvious cause, is a major risk factor for coronary heart disease, stroke, and renal disease. BP levels and susceptibility to development of essential hypertension are partially determined by genetic factors that are poorly understood. Similar to other efforts to understand complex, non-Mendelian phenotypes, genetic dissection of hypertension-related traits employs genomewide linkage analyses of families and association studies of patient cohorts, to uncover rare and common disease alleles, respectively. Family-based mapping studies of elevated BP cover the large intermediate ground for identification of genes with common variants of significant effect. Our genomewide linkage and candidate-gene-based association studies demonstrate that a replicated linkage peak for BP regulation on human chromosome 1q, homologous to mouse and rat quantitative trait loci for BP, contains at least three genes associated with BP levels in multiple samples: ATP1B1, RGS5, and SELE. Individual variants in these three genes account for 2-5-mm Hg differences in mean systolic BP levels, and the cumulative effect reaches 8-10 mm Hg. Because the associated alleles in these genes are relatively common (frequency >5%), these three genes are important contributors to elevated BP in the population at large.     

Multiple Alleles for Tuber Shape in Diploid Potato Detected by Qualitative and Quantitative Genetic Analysis Using Rflps

Tuber shape in potato is commonly regarded as displaying continuous variation, yet at the diploid level phenotypes can be discerned visually, having round or long tubers. Inheritance of qualitative tuber shape can be explained by a single locus Ro, round being dominant to long. With restriction fragment length polymorphisms (RFLPs) the Ro locus was mapped on chromosome 10. Tuber shape was also studied as a quantitative trait, using the length/width ratio as trait value. The estimated broad sense heritability was h(2) = 0.80. The morphologically mapped Ro locus explained 75% of the genetic variation, indicating the presence of a major quantitative trait locus (QTL) at the Ro locus and minor genetic factors. RFLP alleles linked with Ro alleles were used to divide the progeny into four genotypic classes: Ro( &) Ro( &) : Ro( &) ro : roRo( &) : roro = 1 : 1 : 1 : 1. The recessive ro allele is identical by descent in both parents. The significantly different effects (P = 0.0157) of the non-identical alleles Ro( &) and Ro( &) provided evidence for multiallelism at the Ro locus. Linkage mapping of the Ro locus was compared with QTL mapping. Only those markers which are polymorphic in both parents allow accurate QTL mapping when genetic factors segregate from both parents. This finding applies to QTL mapping in all outbreeders without homozygous inbred strains.     

High-resolution mapping of the blood pressure QTL on chromosome 7 using Dahl rat congenic strains

It was previously shown using Dahl salt-sensitive (S) and salt-resistant (R) rats that a blood pressure quantitative trait locus (QTL) was present on rat chromosome 7. In the present work, this QTL was localized to a region less than 0.54 cM in size on the linkage map using a series of congenic strains. This region was contained in a single yeast artificial chromosome that was 220 kb long. This small segment still contained the primary candidate locus Cyp11b1 (11beta-hydroxylase), but the adjacent candidate genes Cyp11b2 (aldosterone synthase) and Cyp11b3 were ruled out. It is concluded that 11beta-hydroxylase, through its known genetic variants altering the production of 18-hydroxy-11-deoxy corticosterone, is very likely to account for the blood pressure QTL on chromosome 7 in the Dahl rat model of hypertension. This QTL accounts for about 23 mm Hg under the condition of 2% NaCl diet for 24 days.     

QTL mapping of inbreeding-related cold sensitivity and conditional lethality in Drosophila melanogaster

Inbreeding depression is a central theme within genetics, and is of specific interest for researchers within evolutionary and conservation genetics and animal and plant breeding. Inbreeding effects are thought to be caused by the joint expression of conditional and unconditional deleterious alleles. Whenever the expression of deleterious alleles is conditional, this can result in extreme environmental sensitivity in certain inbred lineages. Analysis of conditional lethal effects can reveal some of the loci that are sensitive to inbreeding. We performed a QTL (quantitative trait locus) mapping study of inbreeding-related and conditionally expressed lethality in Drosophila melanogaster. The lethal effect was triggered by exposure to a cold shock. We used a North Carolina crossing Design 3 to establish the mapping population, as well as to estimate the average dominance ratio and heritability. We found two QTL on the major autosomes carrying recessive lethals that caused male mortality, one of which also affected female mortality. More detailed study of these loci will provide information on the mechanistic basis and environmental sensitivity of inbreeding depression.     

Recent approaches into the genetic basis of inbreeding depression in plants

Predictions for the evolution of mating systems and genetic load vary, depending on the genetic basis of inbreeding depression (dominance versus overdominance, epistasis and the relative frequencies of genes of large and small effect). A distinction between the dominance and overdominance hypotheses is that deleterious recessive mutations should be purged in inbreeding populations. Comparative studies of populations differing in their level of inbreeding and experimental approaches that allow selection among inbred lines support this prediction. More direct biometric approaches provide strong support for the importance of partly recessive deleterious alleles. Investigators using molecular markers to study quantitative trait loci (QTL) often find support for overdominance, though pseudo-overdominance (deleterious alleles linked in repulsion) may bias this perception. QTL and biometric studies of inbred lines often find evidence for epistasis, which may also contribute to the perception of overdominance, though this may be because of the divergent lines initially crossed in QTL studies. Studies of marker segregation distortion commonly uncover genes of major effect on viability, but these have only minor contributions to inbreeding depression. Although considerable progress has been made in understanding the genetic basis of inbreeding depression, we feel that all three aspects merit more study in natural plant populations.     

Quantitative trait locus analysis of stage-specific inbreeding depression in the Pacific oyster Crassostrea gigas

Inbreeding depression and genetic load have been widely observed, but their genetic basis and effects on fitness during the life cycle remain poorly understood, especially for marine animals with high fecundity and high, early mortality (type-III survivorship). A high load of recessive mutations was previously inferred for the Pacific oyster Crassostrea gigas, from massive distortions of zygotic, marker segregation ratios in F(2) families. However, the number, genomic location, and stage-specific onset of mutations affecting viability have not been thoroughly investigated. Here, we again report massive distortions of microsatellite-marker segregation ratios in two F(2) hybrid families, but we now locate the causative deleterious mutations, using a quantitative trait locus (QTL) interval-mapping model, and we characterize their mode of gene action. We find 14-15 viability QTL (vQTL) in the two families. Genotypic frequencies at vQTL generally suggest selection against recessive or partially recessive alleles, supporting the dominance theory of inbreeding depression. No epistasis was detected among vQTL, so unlinked vQTL presumably have independent effects on survival. For the first time, we track segregation ratios of vQTL-linked markers through the life cycle, to determine their stage-specific expression. Almost all vQTL are absent in the earliest life stages examined, confirming zygotic viability selection; vQTL are predominantly expressed before the juvenile stage (90%), mostly at metamorphosis (50%). We estimate that, altogether, selection on vQTL caused 96% mortality in these families, accounting for nearly all of the actual mortality. Thus, genetic load causes substantial mortality in inbred Pacific oysters, particularly during metamorphosis, a critical developmental transition warranting further investigation.     

Genetic analysis of traits distinguishing outcrossing and self-pollinating forms of currant tomato,Lycopersicon pimpinellifolium (Jusl.) Mill

The evolution of inbreeding is common throughout the angiosperms, although little is known about the developmental and genetic processes involved. Lycopersicon pimpinellifolium (currant tomato) is a self-compatible species with variation in outcrossing rate correlated with floral morphology. Mature flowers from inbreeding and outcrossing populations differ greatly in characters affecting mating behavior (petal, anther, and style lengths); other flower parts (sepals, ovaries) show minimal differences. Analysis of genetic behavior, including quantitative trait locus (QTL) mapping, was performed on representative selfing and outcrossing plants derived from two contrasting natural populations. Six morphological traits were analyzed: flowers per inflorescence; petal, anther, and style lengths; and lengths of the fertile and sterile portions of anthers. All traits were smaller in the selfing parent and had continuous patterns of segregation in the F(2). Phenotypic correlations among traits were all positive, but varied in strength. Quantitative trait locus mapping was done using 48 RFLP markers. Five QTL total were found involving four of the six traits: total anther length, anther sterile length, style length, and flowers per inflorescence. Each of these four traits had a QTL of major (>25%) effect on phenotypic variance.     

Genetic basis of adaptation in Arabidopsis thaliana: local adaptation at the seed dormancy QTL DOG1

Local adaptation provides an opportunity to study the genetic basis of adaptation and investigate the allelic architecture of adaptive genes. We study delay of germination 1 (DOG1), a gene controlling natural variation in seed dormancy in Arabidopsis thaliana and investigate evolution of dormancy in 41 populations distributed in four regions separated by natural barriers. Using F(ST) and Q(ST) comparisons, we compare variation at DOG1 with neutral markers and quantitative variation in seed dormancy. Patterns of genetic differentiation among populations suggest that the gene DOG1 contributes to local adaptation. Although Q(ST) for seed dormancy is not different from F(ST) for neutral markers, a correlation with variation in summer precipitation supports that seed dormancy is adaptive. We characterize dormancy variation in several F(2) -populations and show that a series of functionally distinct alleles segregate at the DOG1 locus. Theoretical models have shown that the number and effect of alleles segregatin at quantitative trait loci (QTL) have important consequences for adaptation. Our results provide support to models postulating a large number of alleles at quantitative trait loci involved in adaptation.     

Prevalence,control and awareness of high blood pressure among Canadian adults. Canadian Heart Health Surveys Research Group.

OBJECTIVE: To estimate the prevalence and distribution of elevated blood pressure (BP) among Canadian adults and to determine the level of control, treatment, awareness and prevalence of other risk factors among adults with high BP. DESIGN: Population-based cross-sectional surveys. SETTING: Nine Canadian provinces, from 1986 to 1990. PARTICIPANTS: A probability sample of 26,293 men and women aged 18 to 74 years was selected from the health insurance registers in each province. For 20,582 subjects, BP was measured at least twice. Nurses administered a standard questionnaire and recorded two BP measurements using a standardized technique. Two further BP readings, anthropometric measurements and a blood specimen for lipid analysis were obtained from those subjects who attended a clinic. OUTCOME MEASURES: Mean values of systolic and diastolic BP, prevalence of elevated BP using different criteria, and prevalence of smoking, elevated blood cholesterol, body mass index, physical activity and presence of diabetes by high BP status are reported. MAIN RESULTS: Sixteen percent of men and 13% of women had diastolic BP of 90 mm Hg or greater or were on treatment (or both). About 26% of these subjects were unaware of their hypertension, 42% were being treated and their condition controlled, 16% were treated and not controlled, and 16% were neither treated nor controlled. Use of non-pharmacologic treatment of high BP with or without medication was low (22%). Hypertensive subjects showed a higher prevalence of elevated total cholesterol, high body mass index, diabetes and sedentary lifestyle than normotensive subjects. Most people with elevated BP were in the 90 to 95 mm Hg range for diastolic pressure and 140 to 160 mm Hg range for systolic pressure. Prevalence of high isolated systolic BP sharply increased in men (40%) and women (49%) 65 to 74 years old. CONCLUSIONS: The relatively low level of control of elevated BP calls for population and individual strategies, stressing a non-pharmacologic approach and addressing isolated systolic hypertension in the elderly.     

Mapping of quantitative trait loci for canopy-wilting trait in soybean (Glycine max L. Merr)

Drought stress adversely affects [Glycine max (L.) Merr] soybean at most developmental stages, which collectively results in yield reduction. Little information is available on relative contribution and chromosomal locations of quantitative trait loci (QTL) conditioning drought tolerance in soybean. A Japanese germplasm accession, PI 416937, was found to possess drought resistance. Under moisture-deficit conditions, PI 416937 wilted more slowly in the field than elite cultivars and has been used as a parent in breeding programs to improve soybean productivity. A recombinant inbred line (RIL) population was derived from a cross between PI 416937 and Benning, and the population was phenotyped for canopy wilting under rain-fed field conditions in five distinct environments to identify the QTL associated with the canopy-wilting trait. In a combined analysis over environments, seven QTL that explained 75?% of the variation in canopy-wilting trait were identified on different chromosomes, implying the complexity of this trait. Five QTL inherited their positive alleles from PI 416937. Surprisingly, the other two QTL inherited their positive alleles from Benning. These putative QTL were co-localized with other QTL previously identified as related to plant abiotic stresses in soybean, suggesting that canopy-wilting QTL may be associated with additional morpho-physiological traits in soybean. A locus on chromosome 12 (Gm12) from PI 416937 was detected in the combined analysis as well as in each individual environment, and explained 27?% of the variation in canopy-wilting. QTL identified in PI 416937 could provide an efficient means to augment field-oriented development of drought-tolerant soybean cultivars.     

Does fructan have a functional role in physiological traits? Investigation by quantitative trait locus mapping

* The role of fructan in growth and drought-stress responses of perennial ryegrass (Lolium perenne) was investigated in an F(2) mapping family that segregates for carbohydrate metabolism. * A quantitative trait locus approach was used to compare the genetic control of traits. * Growth and drought-stress traits were extremely variable within the family. Most traits had high broad-sense heritability. Quantitative trait loci (QTL) were identified for most traits; the maximum number of QTL per trait was four. Between 11% and 75% of total phenotypic variation was explained. Few growth-trait QTL coincided with previously identified fructan QTL. A cluster of drought-trait QTL was close to two previously identified regions of the genome with tiller base fructan QTL in repulsion. * The high sugar parent contributed few alleles that increased 'reserve-driven' growth or performance during drought-stress. Correlation of growth and drought-stress traits with fructan content was low and increasing fructan content per se would not appear to improve drought resistance. Complex patterns of carbohydrate partitioning and metabolism within the cell may explain contradictory relationships between carbohydrate content and growth/stress-resistance traits.     

Selective genotyping with epistasis can be utilized for a major quantitative trait locus mapping in hypertension in rats

Epistasis used to be considered an obstacle in mapping quantitative trait loci (QTL) despite its significance. Numerous epistases have proved to be involved in quantitative genetics. We established a backcross model that demonstrates a major QTL for hypertension (Ht). Seventy-eight backcrossed rats (BC), derived from spontaneously hypertensive rats (SHR) and normotensive Fischer 344 rats, showed bimodal distribution of systolic blood pressure (BP) values and a phenotypic segregation ratio consistent with 1:1. In this backcross analysis, sarco(endo)plasmic reticulum Ca(2+)-dependent ATPase (Serca) II heterozygotes showed widespread bimodality in frequency distribution of BP values and obviously demonstrated Ht. First, in genome-wide screening, Mapmaker/QTL analysis mapped Ht at a locus between D1Mgh8 and D1Mit4 near Sa in all 78 BC. The peak logarithm of the odds (LOD) score reached 5.3. Second, Serca II heterozygous and homozygous BC were analyzed separately using Mapmaker/QTL. In the 35 Serca II heterozygous BC, the peak LOD score was 3.8 at the same locus whereas it did not reach statistical significance in the 43 Serca II homozygotes. Third, to map Ht efficiently, we selected 18 Serca II heterozygous BC with 9 highest and 9 lowest BP values. In these 18 BC, the peak LOD score reached 8.1. In 17 of the 18, D1Mgh8 genotypes (homo or hetero) qualitatively cosegregated with BP phenotypes (high or low) (P < 0.0001, by chi-square analysis). In conclusion, selective genotyping with epistasis can be utilized for a major QTL mapping near Sa on chromosome 1 in SHR.     

Selection responses of means and inbreeding depression for female fecundity in Drosophila melanogaster suggest contributions from intermediate-frequency alleles to quantitative trait variation

The extent to which quantitative trait variability is caused by rare alleles maintained by mutation, versus intermediate-frequency alleles maintained by balancing selection, is an unsolved problem of evolutionary genetics. We describe the results of an experiment to examine the effects of selection on the mean and extent of inbreeding depression for early female fecundity in Drosophila melanogaster. Theory predicts that rare, partially recessive deleterious alleles should cause a much larger change in the effect of inbreeding than in the mean of the outbred population, with the change in inbreeding effect having an opposite sign to the change in mean. The present experiment fails to support this prediction, suggesting that intermediate-frequency alleles contribute substantially to genetic variation in early fecundity.     

Individual QTLs controlling quantitative variation in blood pressure inherited in a Mendelian mode

We studied three possible genotypes at 10 well-defined blood pressure (BP) QTLs using congenic rat lines. The central question was whether the hypertensive or normotensive allele is dominant, or whether there is partial dominance. The congenic strains were employed to investigate the BP effects of alleles originating from normotensive rats in the background of hypertensive Dahl salt-sensitive (DSS) rats. The normotensive alleles at eight QTLs were fully dominant over DSS alleles, which we tentatively interpreted as indicating that DSS rats incurred a loss of function at these loci and that the QTLs produced BP-reducing agents. In contrast, the normotensive allele of only one QTL was recessive over its DSS counterpart, implying a gain of function at this QTL or a null allele involved in generating a BP-elevating agent. Only one locus, C17QTL, had alleles exhibiting partial dominance. These estimates of dominance differ considerably from those obtained by QTL analysis in a F2 cross. This disagreement demonstrates the importance of establishing a cause-effect relationship between a QTL and its phenotypic effect via congenic strains. The dominance relationships suggest pertinent strategies for gene identification and pharmaceutical intervention.     

水稻叶片叶绿素和过氧化氢含量的QTL检测及上位性分析

研究水稻叶片叶绿素和过氧化氢含量的遗传规律,对探讨光合代谢产物遗传规律和开展高产育种具有重要指导意义。利用由日本晴／Kasalath∥日本晴的杂交组合衍生的98个回交重组自交家系(BC1F9)所组成的BIL(backcross inbred lines)群体,在第1、2、3和10染色体上分别检测出5个与叶绿素含量相关的QTL和2个影响剑叶过氧化氢含量的QTL,其中位于第1染色体的RFLP标记C86和C813之间的q-Chll对叶绿素含量的影响最为显著,对表型变异的贡献率达22％,其增效基因来自粳稻品种日本晴;同时在该区间检测到1个与剑叶过氧化氢含量相关的QTL:q-H2O2I,对过氧化氢含量的减效基因来自日本晴品种。上位性分析结果显示影响叶绿素含量及过氧化氢含量的非等位QTL之间存在显著的上位性效应。具有上位性效应的QTL分布于第2、6、11和12染色体上,未检测到与q-Chll或q-H2O2I互作的位点。暗示日本晴品种的RFLP标记C86和C813之间存在1个能够提高叶绿素含量,同时又能降低过氧化氢含量的主效QTL,其加性效应显著而不存在上位性效应。     

Overdominant epistatic loci are the primary genetic basis of inbreeding depression and heterosis in rice. II. Grain yield components

The genetic basis underlying inbreeding depression and heterosis for three grain yield components of rice was investigated in five interrelated mapping populations using a complete RFLP linkage map, replicated phenotyping, and the mixed model approach. The populations included 254 F(10) recombinant inbred lines (RILs) derived from a cross between Lemont (japonica) and Teqing (indica), two backcross (BC) and two testcross populations derived from crosses between the RILs and the parents plus two testers (Zhong413 and IR64). For the yield components, the RILs showed significant inbreeding depression and hybrid breakdown, and the BC and testcross populations showed high levels of heterosis. The average performance of the BC or testcross hybrids was largely determined by heterosis. The inbreeding depression values of individual RILs were negatively associated with the heterosis measurements of the BC or testcross hybrids. We identified many epistatic QTL pairs and a few main-effect QTL responsible for >65% of the phenotypic variation of the yield components in each of the populations. Most epistasis occurred between complementary loci, suggesting that grain yield components were associated more with multilocus genotypes than with specific alleles at individual loci. Overdominance was also an important property of most loci associated with heterosis, particularly for panicles per plant and grains per panicle. Two independent groups of genes appeared to affect grain weight: one showing primarily nonadditive gene action explained 62.1% of the heterotic variation of the trait, and the other exhibiting only additive gene action accounted for 28.1% of the total trait variation of the F(1) mean values. We found no evidence suggesting that pseudo-overdominance from the repulsive linkage of completely or partially dominant QTL for yield components resulted in the overdominant QTL for grain yield. Pronounced overdominance resulting from epistasis expressed by multilocus genotypes appeared to explain the long-standing dilemma of how inbreeding depression could arise from overdominant genes.     

Individual variation between general practitioners in labelling of hypertension.

Variation in labelling of hypertension by individual general practitioners was studied during a continuous opportunistic screening programme for hypertension in a single general practice with 12 principals. All the general practitioners agreed to label as hypertensive patients with systolic pressures of greater than or equal to 200 mm Hg or diastolic pressures of greater than or equal to 110 mm Hg on three consecutive readings. The overall number of patients labelled hypertensive at the beginning of the screening programme was 505 and this rose to 801 after five years. There was a large variation in the numbers of patients recorded as hypertensive at the start of the screening period, with numbers ranging from eight to 112 for individual practitioners. The variation persisted during the screening period, with the numbers of patients detected by individual general practitioners ranging from four to 46. The average systolic and diastolic pressures recorded among these patients also varied between doctors, and only 24 out of 187 patients had their high pressures recorded on three occasions and so fully met the criteria for diagnosing hypertension. Clearly, general practitioners are following their own individual criteria in defining hypertension and taking into account factors other than just the measured blood pressure.     

Community care compared with hospital outpatient care for hypertensive patients.

Three hundred and seventy-six patients with treated diastolic blood pressures of less than 105 mm Hg and no history of accelerated hypertension or renal failure were selected from among those attending the Hammersmith Hospital hypertension clinic. Their average lying treated blood pressure was 146 mm Hg systolic and 90 mm Hg diastolic and average age 56 years; 18% were black, 6% Asian, and 76% white. The patients were mostly having multiple treatment, 90% receiving a diuretic, 35% methyldopa, 33% propranolol, 18% atenolol, 9% hydrallazine, and 7% bethanidine. They were randomly allocated to either two years of further hospital outpatient care or referred back to their general practitioners. During the two years 19 (10%) of the 187 patients followed up in hospital defaulted and three had their treatment discontinued. Twelve (6%) of the 189 followed up by their general practitioners defaulted from follow-up and nine had their treatment discontinued. At the end of the trial the average lying blood pressure was 148 mm Hg systolic and 88 mm Hg diastolic in the hospital group and 149 mm Hg systolic and 90 mm Hg diastolic in the general practice group. The change in blood pressure was calculated for each individual and showed an average fall of 1.6 mm Hg in standing diastolic pressure in the hospital group and a rise of 1.4 mm Hg in the general practice group (p less than 0.05). The 90% confidence limits for a difference in standing diastolic pressure between the groups were 1 and 5 mm Hg with the pressure lower in the hospital group. General practice care was not quite as effective in controlling blood pressure as continued specialist supervision over two years in this selected group of treated outpatients with mild or moderate hypertension, but these results show that the discharge back to general practitioners of patients who are well controlled after hospital treatment is a sensible policy.     

Stress-Management Training for Essential Hypertension: A Controlled Study

Forty three patients with essential hypertension participated in a study on the effectiveness of stress-management training for essential hypertension. After 6–9 clinic and 48 self-measured readings of systolic and diastolic blood pressures (SBP and DBP), 22 patients were treated with a program based on education, relaxation, and problem-solving training; and another 21 patients were assigned to a waiting list control group. At post-treatment, mean reductions of clinic BP (17/13 mm Hg vs. 6.9/4.7 mm Hg for SBP/DBP), percentages of subjects who achieved at least a 5 mm Hg reduction (86/86% vs. 48/48% for SBP/DBP) and percentages of subjects who in addition achieved a normotensive level (59/68% vs. 29/14% for SBP/DBP) were significantly higher in the treated group than in the control group. Concerning self-measured BP, the effectiveness of the stress-management training was not so considerable (mean reductions of 3.6/2.4 mm Hg and percentages of subjects who achieved a 5 mm Hg reduction of 52/38% for SBP/DBP), but it was significant and maintained in a 4-month follow-up assessment (mean reductions of 4/2 mm Hg and percentages of subjects who achieved a 5 mm Hg reduction of 48/33% for SBP/DBP). It is suggested that stress-management training can be beneficial for treatment of essential hypertension.