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PubMed2002

Fine mapping of a quantitative trait locus for twinning rate using combined linkage and linkage disequilibrium mapping.

A novel and robust method for the fine-scale mapping of genes affecting complex traits, which combines linkage and linkage-disequilibrium information, is proposed. Linkage information refers to recombinations within the marker-genotyped generations and linkage disequilibrium to historical recombinations before genotyping started. The identity-by-descent (IBD) probabilities at the quantitative trait locus (QTL) between first generation haplotypes were obtained from the similarity of the marker alleles surrounding the QTL, whereas IBD probabilities at the QTL between later generation haplotypes were obtained by using the markers to trace the inheritance of the QTL. The variance explained by the QTL is estimated by residual maximum likelihood using the correlation structure defined by the IBD probabilities. Unlinked background genes were accounted for by fitting a polygenic variance component. The method was used to fine map a QTL for twinning rate in cattle, previously mapped on chromosome 5 by linkage analysis. The data consisted of large half-sib families, but the method could also handle more complex pedigrees. The likelihood of the putative QTL was very small along most of the chromosome, except for a sharp likelihood peak in the ninth marker bracket, which positioned the QTL within a region <1 cM in the middle part of bovine chromosome 5. The method was expected to be robust against multiple genes affecting the trait, multiple mutations at the QTL, and relatively low marker density.

Animals↗
PubMedDate not supplied

Genetic basis of diabetic nephropathy.

Diabetes mellitus is the leading cause of end-stage renal disease. Development and progression of diabetic nephropathy result from a combination of genetic susceptibility and metabolic and hemodynamic abnormalities. In America, some racial and ethnic minorities have a significant burden of diabetic nephropathy, and, although genetic studies suggest that inherited factors play a major role in the pathogenesis of diabetic nephropathy, little information has been gained on the genes and molecular mechanisms involved. The genetic background of diabetic nephropathy is believed to be polygenic, and the genes predisposing to the development and progression of diabetic nephropathy are actively being investigated. New knowledge in identifying and understanding the role of susceptibility gene(s) will provide valuable information that could help develop new preventive and therapeutic strategies.

Albuminuria↗
PubMed1996

Family study and segregation analysis of Tourette syndrome: evidence for a mixed model of inheritance.

To investigate the transmission of Tourette syndrome (TS) and associated disorders within families, complex segregation analysis was performed on family study data obtained from 53 independently ascertained children and adolescents with TS and their 154 first-degree relatives. The results suggest that the susceptibility for TS is conveyed by a major locus in combination with a multifactorial background. Other models of inheritance were definitively rejected, including strictly polygenic models, all single major locus models, and mixed models with dominant and recessive major loci. The frequency of the TS susceptibility allele was estimated to be .01. The major locus accounts for over half of the phenotypic variance for TS, whereas the multifactorial background accounts for approximately 40% of phenotypic variance. Penetrance estimates suggest that all individuals homozygous for the susceptibility allele at the major locus are affected, whereas only 2.2% of males and 0.3% of females heterozygous at the major locus are affected. Of individuals affected with TS, approximately 62% are heterozygous and approximately 38% are homozygous at the major locus. While none of the families had two parents affected with TS, 19% of families had two parents affected with the broader, phenotype, which includes TS, chronic tic disorder, or obsessive-compulsive disorder.

Adolescent↗
PubMed2026

Polygenic Risk Identifies Older Adults Who May Benefit From Aspirin for the Primary Prevention of Ischemic Stroke.

BACKGROUND: Low-dose aspirin is no longer recommended for routine primary prevention in older adults due to bleeding risks outweighing vascular benefits. We hypothesized that an integrative polygenic score (iPGS) could identify a subgroup of older individuals who derive net benefit from aspirin for the primary prevention of ischemic stroke. METHODS: We performed post hoc analysis of the ASPREE randomized, placebo-controlled trial (Aspirin in Reducing Events in the Elderly) of daily 100-mg aspirin, in 12&#x2009;031 genotyped participants of European ancestry aged >70 years without prior cardiovascular disease. The iPGS was derived from >1.2 million variants and evaluated both continuously and by quintiles. Cox models assessed associations between polygenic risk, ischemic stroke, and major bleeding events, and tested the interaction between the iPGS and treatment allocation, with adjustment for baseline lifestyle and clinical covariates. RESULTS: The mean age of participants was 75.1 years, and 54.9% were women. Over a median of 4.6 years, 187 ischemic strokes and 373 major bleeds occurred, including 101 intracranial bleeds (46 hemorrhagic strokes). Each 1-SD increase in the iPGS was associated with higher incident ischemic stroke risk (hazard ratio, 1.39 [95% CI, 1.20-1.62]). An interaction between the continuous iPGS and aspirin allocation was observed for ischemic stroke (P=0.04) but not major bleeding. In the highest iPGS quintile, aspirin reduced ischemic stroke by 51% (hazard ratio, 0.49 [95% CI, 0.28-0.85]) without significantly increasing major bleeding (hazard ratio, 1.15 [95% CI, 0.71-1.88]). No benefit was observed in the overall cohort or in lower-risk quintiles. CONCLUSIONS: Among older adults, high polygenic risk identifies individuals who may experience substantial stroke reduction with aspirin, with no excess bleeding. These findings raise the possibility that genomic risk stratification may enable targeted aspirin use for the primary prevention of ischemic stroke. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01038583.

Humans↗
PubMed1997

Assessment of learning by the Morris water task and fear conditioning in inbred mouse strains and F1 hybrids: implications of genetic background for single gene mutations and quantitative trait loci analyses.

Genetic methods including the creation of transgenic or null mutant models and mapping studies using quantitative trait loci strategies can be used to identify candidate genes in mice that regulate learning processes. Interpretations as to the impact of single gene mutations for polygenic behaviours like learning will depend in part on the genetic background of the animals used for these manipulations. To address the issue of genetic variability, 12 inbred strains and seven different F1 hybrids were tested on multiple behavioural tasks, including two complex learning paradigms: the Morris water task and fear conditioning. Strain differences were found for all variables measured. In the hidden platform version of the Morris task, the albino animals performed poorly while overall the F1 hybrids showed the best selectivity for the trained quadrant as measured in a probe trial. In contrast, almost all genotypes performed well on the contextual fear conditioning task and learned to associate the test context with the pairing of a foot shock and auditory stimulus as demonstrated 24 h after training by increased freezing in the test environment compared to an altered context. Significant genetic correlations were obtained for behavioural measures suggesting that the same genes regulate various aspects of performance on behavioural tasks. Scores from these multiple inbred strains and F1 hybrids provide a baseline level of learning ability for fear conditioning and the Morris water task. The results of the present study confirm the importance of genetic background in the performance of various learning tasks. This variability should be considered when developing new transgenic or null mutant animal models.

Acoustic Stimulation↗
PubMed2006

[Candidate genes and polymorphism analysis in type 2 diabetes mellitus].

BACKGROUND AND PURPOSE: Diabetes mellitus type 2 is a polygenic disease. Up to now, numerous candidate genes have been examined and tested for their association to metabolic parameters and late complications of diabetes. Between 2000 to 2004, polymorphisms of the following genes and their association to metabolic parameters and late complications of diabetes were examined in the authors' laboratory: PAI-1 (plasminogen activator inhibitor-1), PPARgamma2 (peroxisome proliferator-activated receptor gamma2), UCP-1 (uncoupling protein-1), and adiponectin. Based on this, the question was examined whether the combination of the respective rarely occurring genotypes results in an increased atherogenic risk and a higher prevalence of micro- and macrovascular late complications of diabetes. MATERIAL AND METHODS: Subjects were enrolled from a cohort of 570 type 2 diabetic patients (246 female and 324 male, mean age 66.9+/-9.2 years) who had participated in a population-based study on diabetes and its complications in a mobile survey unit in 23 towns and villages in Bavaria (Germany). Retinopathy was diagnosed by nonmydriatic fundus photography (Canon CR4-45 NM). Photographs of the retina of both eyes (one photo per eye) were taken. Data on macrovascular complications of diabetes were obtained using a standardized questionnaire. RESULTS: A significant association between the number of rarely occurring genotype combinations and the following parameters could be described: diastolic blood pressure, total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, and grade of retinopathy. CONCLUSION: An accumulation of certain genotypes of candidate genes for diabetes mellitus type 2 is associated with the severity of dyslipidemia and microvascular late complications, e.g., grade of retinopathy. Therefore, screening for genotype combinations of these metabolic target genes might offer the opportunity to identify diabetic patients at a high risk for macro- and microvascular complications.

Adult↗
PubMed2001

Investigation of HLA-DPA1 genotypes as predictors of inflammatory bowel disease in the German, South African, and South Korean populations.

BACKGROUND AND AIMS: Inflammatory bowel disease (IBD) is a polygenic disorder, as demonstrated by epidemiological evidence, genetic linkage, and the identification of the first susceptibility gene, NOD2. Genetic linkage analysis has identified and replicated several genomic regions as locations for susceptibility genes, including chromosome 6p (termed IBD3). The HLA-DP genes play an important role in antigen presentation and are located within the chromosome 6p linkage region. PATIENTS AND METHODS: We investigated HLA-DPA1 as a positional and functional candidate gene for IBD using 249 German multiplex IBD families, 174 unrelated German controls, 48 monoplex families from a mixed South African population, 87 IBD patients, and 71 controls from a South Korean sample. Polymorphisms in exon 2 at amino acid positions 31, 37-38 and 50 were genotyped using direct sequencing. Analyses were performed using chi(2) statistics, multipoint transmission disequilibrium test and nonparametric linkage analysis. RESULTS: A marginally significant association for Crohn's disease was detected in the German family cohort for DPA1*02021. This finding was not replicated in ulcerative colitis or any of the other populations. CONCLUSION: HLA-DPA1 is not a major determinant of IBD risk in any of the three populations. The transmission distortion observed in the German cohort may indicate an extended haplotype, suggesting another disease relevant gene in the vicinity of HLA-DPA.

Case-Control Studies↗
PubMed2003

The 4G/4G genotype of the 4G/5G polymorphism of the type-1 plasminogen activator inhibitor (PAI-1) gene is a determinant of penetrating behaviour in patients with Crohn's disease.

BACKGROUND: Crohn's disease is a heterogeneous disorder with polygenic inheritance. AIM: To assess the effect of the 4G/5G polymorphism of the type-1 plasminogen activator inhibitor (PAI-1) gene, the major inhibitor of fibrinolysis, on Crohn's disease susceptibility and phenotype. METHODS: One hundred and fifty-seven patients with Crohn's disease and 350 controls were included prospectively. Medical records were reviewed to determine changes in the Crohn's disease phenotype. The 4G/5G polymorphism was assessed by polymerase chain reaction techniques. RESULTS: The frequencies of the 4G/4G, 4G/5G and 5G/5G genotypes were similar in patients with Crohn's disease and controls. The 4G/4G genotype (P < 0.0001; odds ratio, 4.84) and male sex (P = 0.009; odds ratio, 2.63) were independent risk factors for penetrating behaviour in Crohn's disease. Most Crohn's disease patients had a non-penetrating phenotype at diagnosis. The probability of development of a penetrating phenotype within 5 years of diagnosis was higher in patients with the 4G/4G genotype (72% vs. 19%, P < 0.0001). CONCLUSIONS: The 4G/4G genotype of the PAI-1 gene does not influence Crohn's disease susceptibility, but increases by five-fold the probability of penetrating behaviour. Most patients with the 4G/4G genotype have a non-penetrating phenotype at diagnosis, but develop a penetrating behaviour within 5 years. Genotyping the 4G/5G polymorphism may be useful for the identification of a sub-group of patients with aggressive Crohn's disease, who might benefit from specific therapy.

Adult↗
PubMed2001

Polymorphisms in the TNF-alpha and TNF-receptor genes in patients with coronary artery disease.

BACKGROUND: Coronary artery disease (CAD) is both multifactorial and polygenic in nature. Atheroma formation, the pathological hallmark of CAD, is an inflammatory process, with pro-inflammatory cytokines, such as tumour necrosis factor-alpha (TNF-alpha), having a major role in its pathogenesis. We have therefore investigated whether polymorphisms in the TNF-alpha (- 238 and - 308), TNF receptor 1 (position - 609 and + 10, intron 6) and TNF receptor 2 (position + 422, codon 198) genes show an association with CAD. MATERIALS AND METHODS: Patients with angiographically proven single vessel (n = 58) and multivessel (n = 122) CAD were compared to patients with angiographically proven normal coronary arteries (n = 79) and volunteers without clinical evidence of CAD (n = 250). Genotyping was performed by PCR-RFLP analysis. For the TNF-alpha polymorphisms, a meta-analysis of all published studies was also undertaken. RESULTS: No significant differences in allele or genotype frequencies were found between the normal coronary artery group or healthy volunteers and patients with CAD for any of the polymorphisms. There was also no difference in allele frequency between patients with single- and multivessel disease. For the - 308 and - 238 TNRalpha gene polymorphisms, a meta-analysis of our data and previously published studies failed to demonstrate any significant association with CAD. CONCLUSIONS: Polymorphisms in the TNF-alpha promoter region and TNF-receptor genes are not associated with the development of CAD.

Adult↗
PubMed2002

Association of a novel single nucleotide polymorphism of the prostacyclin synthase gene with myocardial infarction.

BACKGROUND: Myocardial infarction (MI) is a complex multifactorial and polygenic disorder that is thought to result from an interaction between an individual's genetic makeup and various environmental factors. The purpose of this study was to investigate the association between a novel single nucleotide polymorphism in the prostacyclin synthase gene and MI. METHODS AND RESULTS: By the use of polymerase chain reaction-single-strand conformation polymorphism analysis, we identified a single nucleotide polymorphism, C1117A, in exon 8. This nucleotide change did not cause an amino acid change in codon 373. We performed an association study of the polymorphism in 138 patients and 130 healthy control subjects. Multiple logistic linear regression analysis showed the genotype distributions were significantly different between the control group and the MI group (odds ratio, 2.12; 95% CI, 1.47-3.05, P =.04). The C/C genotype was found more frequently in the MI group than in the control group. CONCLUSIONS: We conclude that the C1117A polymorphism in exon 8 is associated with risk for MI and may be a genetic marker of MI in Japanese persons.

Case-Control Studies↗
PubMedDate not supplied

Cohort effects in a genetically determined trait: eye colour among US whites.

BACKGROUND: While the inheritance of eye colour is likely polygenic, blue eye colour is thought to follow an inheritance pattern similar to that of a recessive trait. Consequently, age-related differences in the prevalence of blue eye colour would be unanticipated. AIM: This study explores the finding and explanation for birth cohort differences in the prevalence of blue eye colour in the US white population. SUBJECTS AND METHODS: Data from the first (1971-1975) and third (1988-1994) US National Health and Nutrition Examination Surveys (NHANES-I and NHANES-III), nationally representative surveys of the US population, were analysed. Trends in eye colour prevalence by birth cohort were analysed together with mortality rates according to eye colour. US census data (1980) were examined to explore cohort differences in ancestry and assortative mating by ancestry. RESULTS: The prevalence of blue eye colour among non-Hispanic whites in NHANES-III was 57.4% (95% CI: 50.1-64.7) for individuals born between 1899 and 1905 compared to 33.8% (95% CI: 31.3-36.5) for those born between 1936 and 1951. No association was found between survival and eye colour, nor was a cohort effect evident for primary ancestry. However, proportions reporting only one ancestry in census data declined with successive birth cohorts. CONCLUSIONS: A cohort effect in blue eye colour prevalence was found for the US white population. A secular trend of decreasing assortative mating by ancestry is the likely explanation.

Adult↗
PubMed2005

Chromosomal mapping of a quantitative trait locus for the development of albuminuria in diabetic KK/Ta mice.

BACKGROUND: The KK/Ta mouse strain serves as a suitable polygenic model for human type 2 diabetes. We previously reported a genome-wide linkage analysis of KK/Ta alleles contributing to type 2 diabetes and related phenotypes such as fasting hyperglycaemia, glucose intolerance, hyperinsulinaemia, obesity and dyslipidaemia. METHODS: Since KK/Ta mice spontaneously develop renal lesions closely resembling those in human diabetic nephropathy, we investigated the susceptibility loci using the KK/Ta x (BALB/c x KK/Ta) F1 backcross progeny in the present study. RESULTS: A genome-wide analysis of susceptibility loci for albuminuria with microsatellite-based chromosomal maps showed a contributing KK/Ta locus, provisionally designated UA-1, with a significant linkage with the interval on chromosome 2 at 83.0 cM close to the microsatellite marker D2Mit311 with a maximum LOD of 3.5 (chi(2) = 13.2, P = 0.0003). UA-1 was different from the susceptibility loci contributing to type 2 diabetes, which we earlier identified. The mode of inheritance differed from that of hypertension. The progeny homozygous for UA-1 showed significantly higher urinary albumin levels. CONCLUSIONS: Although there were no significant correlations between urinary albumin levels and other diabetic phenotypes, the group of progeny homozygous for both UA-1 and alleles for fasting hyperglycaemia showed the highest urinary albumin levels. Thus, UA-1 appears to increase the risk of diabetic nephropathy, particularly in individuals susceptible to fasting hyperglycaemia, in a gene dosage-dependent manner. There are potentially important candidate genes that may be relevant to diabetic nephropathy.

Albuminuria↗
PubMed2003

Missense mutation of exon 3 in the type A human natriuretic peptide receptor gene is associated with myocardial infarction.

BACKGROUND: Myocardial infarction (MI) is a complex multifactorial and polygenic disorder that is thought to result from interaction between genetic make-up and various environmental factors. We previously identified a missense mutation, methionine (ATG) to isoleucine (ATC) at nucleotide 1023 (M341I), in exon 3 of the human natriuretic peptide receptor A type (hNPRA) gene. This mutation is associated with increased risk for essential hypertension (EH). The purpose of this study was to investigate association between MI and the M341I mutation in the hNPRA gene. MATERIAL/METHODS: The study population included 305 healthy control subjects and 230 patients with MI, all of whom were below the age of 70 years. To assess the identified mutation in the target exon using Taq I restriction fragment length polymorphism (RFLP), specific primers were utilized. Based on the results of the PCR-RFLP, we developed a convenient and automatic method for genotyping by allelic discrimination using TaqMan PCR chemistry. RESULTS: Multiple logistic linear regression analysis showed significant difference in genotype distribution between the control and MI groups. Overall distribution of alleles also differed significantly between the MI and control groups (p=0.028). The C allele was found more frequently in the MI group than in the control group. CONCLUSIONS: We conclude that the M341I missense mutation is associated with risk for MI and may be a genetic marker of MI in Japanese people.

Aged↗
PubMedDate not supplied

Detection of oncogenic HPV and identification of 72Arg polymorphic p53 by in situ PCR for clinical routine purposes.

BACKGROUND: Ano-genital carcinoma is a polyfactorial and polygenic disease. Certain strains of human papillomavirus (HPV) have been detected in a high percentage of patients. It has been suggested that p53 polymorphisms may be relevant for the interaction with viral proteins that inactivates p53. MATERIALS AND METHODS: Patients were selected on the basis of HPV infection, clinical history, positive PAP test and type of lesion. In situ PCR was performed on smear samples, in four steps: a) preparation on clean biobond-treated slides, b) permeabilisation and digestion; c) in situ PCR amplification; d) in situ hybridisation with a fluorescent probe. RESULTS: In situ PCR analysis of the smears confirmed the results obtained by classic PCR and by in situ PCR of frozen sections. CONCLUSION: In situ PCR on smears could be used in targeted-screening for young and post-menopausal women, as well as in the development of large scale studies to establish the connection among the presence of HPV, p53 polymorphisms and the risk of cervical cancer. ABBREVIATIONS: PCR, polymerase chain reaction; OsO4, osmium tetroxide; HPV, human papilloma virus; PBS, phosphate-buffered saline; SDS, sodium dodecyl sulphate.

Female↗
PubMed2006

The contribution of endogenous opioids to food reward is dependent on sex and background strain.

Complex behaviors such as those associated with reward to unconditioned positive reinforcers are polygenic processes. In studies using genetically modified mice specific for the endogenous opioid systems an observed phenotype in a complex behavior is likely to be dependent on interacting genes which, in inbred mouse lines, influence that phenotype. To address this issue we examined operant responding for palatable food reinforcers in mice lacking the expression of beta-endorphin, enkephalin or both peptides congenic to two different genetic backgrounds; C57BL/6J and DBA/2J. These two inbred strains were chosen because their endogenous opioid states differ and they respond differently to exogenous opioids in many behavioral assays. We found that wildtype and mutant C57BL/6J mice acquired operant responding for food reinforcers faster than DBA/2J mice, regardless of their opioid genotype. Although wildtype DBA/2J mice had a significant deficit in acquisition of bar-pressing behavior to reach a pre-established performance criterion, no subsequent deficit was observed under two different schedules of reinforcement. Additionally, we found that mice lacking enkephalin had decreased motivation to bar press for palatable food reinforcers under a progressive ratio regardless of sex or background strain. In contrast, the only subset of beta-endorphin-deficient mice that had decreased motivation to bar press under a progressive ratio was males on the C57BL/6J background. Of the two classical endogenous opioid peptides with preferential activation of the mu opioid receptor, the knockout models would suggest that enkephalins play a more consistent role than beta-endorphin in mediating the motivation for food reward when tested under a progressive ratio.

Animals↗
PubMed1996

Production of congenic mouse strains carrying genomic intervals containing SLE-susceptibility genes derived from the SLE-prone NZM2410 strain.

Systemic lupus erythematosus is inherited as a complex polygenic trait. Four genomic intervals containing major SLE-susceptibility loci were previously identified by interval mapping in the NZM2410 mouse model. In this paper, we utilized a marker-assisted selection protocol to produce four congenic mouse strains, each carrying an NZM2410-derived SLE-susceptibility interval on a C57BL/6-resistant background. Each strain carries only one susceptibility allele derived from this polygenic model and consequently can be used to characterize the specific component phenotypes contributed by individual SLE-susceptibility genes. We illustrate the efficacy of this approach with phenotypic data for one of our congenic strains, B6.NZMH2(z). Our results indicate that this single genomic interval from Chromosome (Chr) 17 of NZM2410 can mediate increased levels of IgG autoantibodies specific for chromatin and that, similar to results obtained in our original genetic cross, B6.NZMH2(z/b) heterozygotes are more prone than B6.NZMH2(z) homozygotes to the development of humoral autoimmunity to nuclear antigens. These results illustrate the feasibility of using congenic strains to dissect the complex pathogenic mechanisms that mediate polygenic SLE. These congenic strains will be valuable tools in the genetic analysis of SLE susceptibility. In future studies, these congenic strains will be interbred to produce bi- and tri-congenic strains in order to assess the role of genetic interactions in the expression of specific components of SLE pathogenesis. They will also be instrumental to the positional cloning and identification of the genes responsible for SLE susceptibility, via the production of congenic recombinants.

Animals↗
PubMed1993

Selective breeding, congenic strains, and other classical genetic approaches to the analysis of alcohol-related polygenic pleiotropisms.

Dimensions of behavioral sensitivities to alcohol in mice are under control of polygenic systems of relatively small size. The mode of inheritance of these phenotypes is frequently additive, with no evidence of dominance, epistasis, or sex linkage. The utility of classical breeding methodologies, such as selection, for assessment of genetic correlations is reviewed. A distinction is drawn between pleiotropisms in these polygenic systems, and the statistical concept of a genetic correlation. Development of congenic strains is argued to be a powerful alternative methodology, heretofore unused in alcohol pharmacogenetics. Using the phenotype of behavioral activation produced by a low dose of ethanol, we describe the production of an activated congenic strain on the non-activated background of the C57BL/6 mouse strain. Through five generations of repeated backcrossing, from a genetically heterogenous stock, "activational" alleles are being successfully transferred to the C57BL/6 background. Theoretical issues in the creation of congenic strains in potentially polygenic systems are covered, including number of effective loci and heritability.

Alcohol Drinking↗
PubMed2002

[Genetics study on photo- and thermo-sensitive genic male sterility of indica rice (O. satival L.)].

The sterility segregation and its genetic patterns of indica P(T)GMS rice were analyzed mainly based on the investigation of bagged seed-set of individuals in reciprocal F2 population from the crosses between P(T)GMS lines of different origin and typical indica conventional varieties of different ecotype under long day-length and high temperature condition by using the software of the maximum likelihood method. The results showed that the sterility of Annong S-1, Hengnong S-1, and W6154S, of which the sterility alteration was mainly induced by temperature fluctuation, was controlled by one major recessive gene. But the sterility of W7415S was controlled by more than two major recessive genes. Apart from the major recessive gene, there was a group of polygenes in controlling of the sterility segregation in F2 population. Moreover, the polygenic variance was different from line to line. It implied that the polygenes of W6154S or W7415S was far more complicated than that of Annong S-1 and Hengnong S-1 according to the maximum likelihood method. All the conventional indica varieties of different ecotypes possessed the major dominant fertility genes. Meanwhile, the genetic background in different ecotype conventional varieties, the essentiality of which lies in the existence of polygenes, was different and influenced the major gene expression deeply. It was also indicated that genetic background of middle-season variety Nanjing 11 was more complicated than that of early-season variety Erjiuqing and late-season variety GER-1 as well. Finally, the differences of drift in critical temperature inducing male sterility of P(T)GMS lines (for short term DCT) and the strategy of breeding practically usable P(T)GMS line with slighter DCT were discussed in the paper.

Crosses, Genetic↗