大白菜-结球甘蓝5号和8号单体异附加系的筛选和鉴定

为建立成套的大白菜-结球甘蓝异附加系,以大白菜-结球甘蓝异源三倍体（AAC,2n=3x=29）与二倍体大白菜（AA,2n=2x=20）回交世代BC1为材料,对其进行细胞学观察并从中筛选单体异附加系。结果表明,BC1群体植株发生了染色体数目变异,变异范围为2n=20～29,其中以2n=23～24的非整倍体植株居多,占总观察株数的51．44％;对2个2n=21的植株进行核型分析,初步鉴定为大白菜-结球甘蓝5号和8号单体异附加系,分别命名为CO-5—1和CO-8—2。     

Genome‐wide association study identifies loci associated with liability to alcohol and drug dependence that is associated with variability in reward‐related ventral striatum activity in African‐ and European‐Americans

Genetic influences on alcohol and drug dependence partially overlap, however, specific loci underlying this overlap remain unclear. We conducted a genome‐wide association study (GWAS) of a phenotype representing alcohol or illicit drug dependence (ANYDEP) among 7291 European‐Americans (EA; 2927 cases) and 3132 African‐Americans (AA: 1315 cases) participating in the family‐based Collaborative Study on the Genetics of Alcoholism. ANYDEP was heritable (h ² in EA = 0.60, AA = 0.37). The AA GWAS identified three regions with genome‐wide significant (GWS; P < 5E‐08) single nucleotide polymorphisms (SNPs) on chromosomes 3 (rs34066662, rs58801820) and 13 (rs75168521, rs78886294), and an insertion‐deletion on chromosome 5 (chr5:141988181). No polymorphisms reached GWS in the EA. One GWS region (chromosome 1: rs1890881) emerged from a trans‐ancestral meta‐analysis (EA + AA) of ANYDEP, and was attributable to alcohol dependence in both samples. Four genes (AA: CRKL, DZIP3, SBK3; EA: P2RX6) and four sets of genes were significantly enriched within biological pathways for hemostasis and signal transduction. GWS signals did not replicate in two independent samples but there was weak evidence for association between rs1890881 and alcohol intake in the UK Biobank. Among 118 AA and 481 EA individuals from the Duke Neurogenetics Study, rs75168521 and rs1890881 genotypes were associated with variability in reward‐related ventral striatum activation. This study identified novel loci for substance dependence and provides preliminary evidence that these variants are also associated with individual differences in neural reward reactivity. Gene discovery efforts in non‐European samples with distinct patterns of substance use may lead to the identification of novel ancestry‐specific genetic markers of risk.     

Identifying host genetic risk factors in the context of public health surveillance for invasive pneumococcal disease

Host genetic factors that modify risk of pneumococcal disease may help target future public health interventions to individuals at highest risk of disease. We linked data from population-based surveillance for invasive pneumococcal disease (IPD) with state-based newborn dried bloodspot repositories to identify biological samples from individuals who developed invasive pneumococcal disease. Genomic DNA was extracted from 366 case and 732 anonymous control samples. TagSNPs were selected in 34 candidate genes thought to be associated with host response to invasive pneumococcal disease, and a total of 326 variants were successfully genotyped. Among 543 European Americans (EA) (182 cases and 361 controls), and 166 African Americans (AA) (53 cases and 113 controls), common variants in surfactant protein D (SFTPD) are consistently underrepresented in IPD. SFTPD variants with the strongest association for IPD are intronic rs17886286 (allelic OR 0.45, 95% confidence interval (CI) [0.25, 0.82], with p = 0.007) in EA and 5′ flanking rs12219080 (allelic OR 0.32, 95%CI [0.13, 0.78], with p = 0.009) in AA. Variants in CD46 and IL1R1 are also associated with IPD in both EA and AA, but with effects in different directions; FAS, IL1B, IL4, IL10, IL12B, SFTPA1, SFTPB, and PTAFR variants are associated (p≤0.05) with IPD in EA or AA. We conclude that variants in SFTPD may protect against IPD in EA and AA and genetic variation in other host response pathways may also contribute to risk of IPD. While our associations are not corrected for multiple comparisons and therefore must be replicated in additional cohorts, this pilot study underscores the feasibility of integrating public health surveillance with existing, prospectively collected, newborn dried blood spot repositories to identify host genetic factors associated with infectious diseases.     

The Nucleolus Organizer Region of Maize (ZEA MAYS L.): Tests for Ribosomal Gene Compensation or Magnification

Ribosomal gene compensation and magnification that might be detected on a whole-plant basis was not found in maize. Plants monosomic for chromosome 6 (the NOR chromosome) were compared with monosomic-8 and monosomic-10 plants, disomic sibs, and parental lines. Assuming no rDNA compensation, monosomic-6 plants showed approximately the decrease expected in rRNA cistron number. Monosomic-8 had a normal ribosomal gene number, while monosomic-10 showed a decrease; but further documentation is needed. Besides demonstrating the absence of gene compensation, the results document our previous conclusion that maize chromosome 6 carries DNA complementary to ribosomal RNA. Further documentation was provided from studies with trisomic chromosome 6 plants showing proportional increases in ribosomal gene number. Progeny of the monosomic plants crossed as males to a standard singlecross hybrid possessed expected ribosomal gene numbers suggesting the lack of ribosomal gene magnification.—The ragged (rgd) mutant of maize, suspected of being deficient in rRNA cistrons, had a normal number.     

Significant associations of CHRNA2 and CHRNA6 with nicotine dependence in European American and African American populations

The direct physiological effects that promote nicotine dependence (ND) are mediated by nicotinic acetylcholine receptors (nAChRs). In line with the genetic and pharmacological basis of addiction, many previous studies have revealed significant associations between variants in the nAChR subunit genes and various measures of ND in different ethnic samples. In this study, we first examined the association of variants in nAChR subunits α2 (CHRNA2) and α6 (CHRNA6) genes on chromosome 8 with ND using a family sample consisting of 1,730 European Americans (EAs) from 495 families and 1,892 African Americans (AAs) from 424 families (defined as the discovery family sample). ND was assessed by two standard quantitative measures: smoking quantity (SQ) and the Fagerström Test for ND (FTND). We found nominal associations for all seven tested SNPs of the genes with at least one ND measure in the EA sample and for two SNPs in CHRNA2 in the AA sample. Of these, associations of SNPs rs3735757 with FTND (P = 0.0068) and rs2472553 with both ND measures (with a P value of 0.0043 and 0.00086 for SQ and FTND, respectively) continued to be significant in the EA sample even after correction for multiple tests. Further, we found several haplotypes that were significantly associated with ND in the EA sample in CHRNA6 and in the both EA and AA samples in CHRNA2. To confirm the associations of the two genes with ND, we conducted a replication study with an independent case–control sample from the SAGE study, which showed a significant association of the two genes with ND, although the significantly associated SNPs were not always the same in the two samples. Together, these findings indicate that both CHRNA2 and CHRNA6 play a significant role in the etiology of ND in AA and EA smokers. Further replication in additional independent samples is warranted.     

Gene-Based Sequencing Identifies Lipid-Influencing Variants with Ethnicity-Specific Effects in African Americans

Although a considerable proportion of serum lipids loci identified in European ancestry individuals (EA) replicate in African Americans (AA), interethnic differences in the distribution of serum lipids suggest that some genetic determinants differ by ethnicity. We conducted a comprehensive evaluation of five lipid candidate genes to identify variants with ethnicity-specific effects. We sequenced ABCA1, LCAT, LPL, PON1, and SERPINE1 in 48 AA individuals with extreme serum lipid concentrations (high HDLC/low TG or low HDLC/high TG). Identified variants were genotyped in the full population-based sample of AA (n = 1694) and tested for an association with serum lipids. rs328 (LPL) and correlated variants were associated with higher HDLC and lower TG. Interestingly, a stronger effect was observed on a “European” vs. “African” genetic background at this locus. To investigate this effect, we evaluated the region among West Africans (WA). For TG, the effect size among WA was the same in AA with only African local ancestry (2–3% lower TG), while the larger association among AA with local European ancestry matched previous reports in EA (10%). For HDLC, there was no association with rs328 in AA with only African local ancestry or in WA, while the association among AA with European local ancestry was much greater than what has been observed for EA (15 vs. ∼5 mg/dl), suggesting an interaction with an environmental or genetic factor that differs by ethnicity. Beyond this ancestry effect, the importance of African ancestry-focused, sequence-based work was also highlighted by serum lipid associations of variants that were in higher frequency (or present only) among those of African ancestry. By beginning our study with the sequence variation present in AA individuals, investigating local ancestry effects, and seeking replication in WA, we were able to comprehensively evaluate the role of a set of candidate genes in serum lipids in AA.     

Differential gene expression between African American and European American colorectal cancer patients

The incidence and mortality of colorectal cancer (CRC) is higher in African Americans (AAs) than other ethnic groups in the U. S., but reasons for the disparities are unknown. We performed gene expression profiling of sporadic CRCs from AAs vs. European Americans (EAs) to assess the contribution to CRC disparities. We evaluated the gene expression of 43 AA and 43 EA CRC tumors matched by stage and 40 matching normal colorectal tissues using the Agilent human whole genome 4x44K cDNA arrays. Gene and pathway analyses were performed using Significance Analysis of Microarrays (SAM), Ten-fold cross validation, and Ingenuity Pathway Analysis (IPA). SAM revealed that 95 genes were differentially expressed between AA and EA patients at a false discovery rate of ≤5%. Using IPA we determined that most prominent disease and pathway associations of differentially expressed genes were related to inflammation and immune response. Ten-fold cross validation demonstrated that following 10 genes can predict ethnicity with an accuracy of 94%: CRYBB2, PSPH, ADAL, VSIG10L, C17orf81, ANKRD36B, ZNF835, ARHGAP6, TRNT1 and WDR8. Expression of these 10 genes was validated by qRT-PCR in an independent test set of 28 patients (10 AA, 18 EA). Our results are the first to implicate differential gene expression in CRC racial disparities and indicate prominent difference in CRC inflammation between AA and EA patients. Differences in susceptibility to inflammation support the existence of distinct tumor microenvironments in these two patient populations.     

Characterization of an Alien Chromosome of <Emphasis Type="Italic">Oryza officinalis</Emphasis> Transferred the Genomic and Cytological Environment of <Emphasis Type="Italic">Oryza sativa</Emphasis>

Distant hybridization between rice species and their genome interactions have become the hot points of genetic research. The new formed hybrid was unstable and many of the alien chromosomes would be excluded out in the meiosis procedure. In this study, we investigated the phenomenon that the monosomic alien addition lines (MAALs) of Oryza officinalis (CC)–Oryza sativa (AA) inherited in the genomic and cytoplasmic environments of cultivated rice. In a series of backcross programs, every time the MAALs were backcrossed with the recurrent parent Hejiang19, we get a portion of the backcross progenies that were similar to the female parent MAALs in morphological characters (with rolled leaves) and chromosome constitutions (2n + 1). The monosomic alien chromosome exhibited stable inheritance in the genomic and cytoplasmic environments of cultivated rice. Molecular biology and fluorescence in situ hybridization (FISH) analyses on mitotic cells showed that the alien chromosomes in MAALs were inclined to be transferred integrated into the backcross progenies with rolled leaves and no big fragments of alien chromosomes introgressing into the chromosomes of cultivated rice. By FISH analysis on the meiotic cells, we proved that the single alien chromosome performing nonstandard meiosis and behaving like a dispensable genetic factor, which would be the cytological reasons for the stable inheritance of alien chromosomes.     

Phenotypic effects of the Y chromosome are variable and structured in hybrids among house mouse recombinant lines

Hybrid zones between divergent populations sieve genomes into blocks that introgress across the zone, and blocks that do not, depending on selection between interacting genes. Consistent with Haldane's rule, the Y chromosome has been considered counterselected and hence not to introgress across the European house mouse hybrid zone. However, recent studies detected massive invasion of M. m. musculus Y chromosomes into M. m. domesticus territory. To understand mechanisms facilitating Y spread, we created 31 recombinant lines from eight wild‐derived strains representing four localities within the two mouse subspecies. These lines were reciprocally crossed and resulting F1 hybrid males scored for five phenotypic traits associated with male fitness. Molecular analyses of 51 Y‐linked SNPs attributed ~50% of genetic variation to differences between the subspecies and 8% to differentiation within both taxa. A striking proportion, 21% (frequencies of sperm head abnormalities) and 42% (frequencies of sperm tail dissociations), of phenotypic variation was explained by geographic Y chromosome variants. Our crossing design allowed this explanatory power to be examined across a hierarchical scale from subspecific to local intrastrain effects. We found that divergence and variation were expressed diversely in different phenotypic traits and varied across the whole hierarchical scale. This finding adds another dimension of complexity to studies of Y introgression not only across the house mouse hybrid zone but potentially also in other contact zones.     

Association of amyloid precursor protein-binding protein,family B,member 1 with nicotine dependence in African and European American smokers

Although epidemiological studies reveal that cigarette smoking is inversely associated with Alzheimer’s disease (AD) and Parkinson’s disease (PD), the underlying mechanism remains largely unknown. Considering the facts that amyloid precursor protein-binding protein, family B, member 1 (APBB1) is mapped to a suggestive linkage region on chromosome 11 for nicotine dependence (ND), and has been implicated in the pathogenesis of AD and PD, it represents a plausible candidate for genetic study of ND. Five single nucleotide polymorphisms (SNPs) within APBB1 were genotyped in a sample consisting of 2,037 participants of either African-American (AA) or European-American (EA) origin, and examined their associations with ND assessed by three commonly used measures: Smoking Quantity (SQ), the Heaviness of Smoking Index (HSI), and the Fagerström Test for ND (FTND). Individual SNP-based association analysis showed that all five SNPs are associated with at least one ND measure in one of the three samples; however, only the association of SNP rs4758416 with SQ and HSI remained significant after correction for multiple testing in the pooled sample. Haplotype analysis demonstrated three major haplotypes significantly associated with ND after Bonferroni correction. Formed by rs4758416-rs10839562-rs1079199, haplotype C-C-T showed positive association with FTND in the AA and pooled samples, and conversely, haplotype G-C-T showed negative association with SQ and HSI in AA and EA samples. Another haplotype, C-T-G, formed by rs10839562-rs1079199-rs8164, was significantly associated with HSI in the EA sample. Based on these findings, we conclude that APBB1 represents an important candidate gene in the genetic study on ND and neurodegenerative diseases and warrants further investigation in future.     

Conditional Hitchhiking of Mitochondrial DNA: Frequency Shifts of Drosophila Melanogaster Mtdna Variants Depend on Nuclear Genetic Background

Tests were performed of the selective neutrality of mitochondrial DNA (mtDNA) variants from geographic populations of Drosophila melanogaster in Argentina (ARG) and Central Africa (CAF). The two populations were completely reproductively compatible. The two distinct mtDNA haplotypes from the two populations were competed in replicate experimental populations on three nuclear genetic backgrounds: homozygous ARG, homozygous CAF, or hybrid ARG/CAF. Mitochondrial haplotype frequencies did not change significantly on either of the two homozygous nuclear backgrounds, and there was no change after experimental perturbation of haplotype frequencies. On the hybrid background, the ARG haplotype frequency increased significantly for the first two generations in all replicate populations but then did not change in subsequent generations. After perturbation, the ARG haplotype frequency increased in only one of four replicates. There is no evidence for selective differences among mtDNA variants in homozygous nuclear contexts or for nuclear-mitochondrial coadaptation. While some ``fitness' difference among mtDNA variants is required to account for the observed frequency shifts, it appears that in these hybrid populations, mtDNA is hitchhiking on fitness variation among hybrid segregating nuclear genes. These results have implications for the use of mtDNA in the study of hybrid zones and gene flow.     

Genotypic and Allelic Variability in CYP19A1 among Populations of African and European Ancestry

CYP19A1 facilitates the bioconversion of estrogens from androgens. CYP19A1 intron single nucleotide polymorphisms (SNPs) may alter mRNA splicing, resulting in altered CYP19A1 activity, and potentially influencing disease susceptibility. Genetic studies of CYP19A1 SNPs have been well documented in populations of European ancestry; however, studies in populations of African ancestry are limited. In the present study, ten ‘candidate’ intronic SNPs in CYP19A1 from 125 African Americans (AA) and 277 European Americans (EA) were genotyped and their frequencies compared. Allele frequencies were also compared with HapMap and ASW 1000 Genomes populations. We observed significant differences in the minor allele frequencies between AA and EA in six of the ten SNPs including rs10459592 (p<0.0001), rs12908960 (p<0.0001), rs1902584 (p = 0.016), rs2470144 (p<0.0001), rs1961177 (p<0.0001), and rs6493497 (p = 0.003). While there were no significant differences in allele frequencies between EA and CEU in the HapMap population, a 1.2- to 19-fold difference in allele frequency for rs10459592 (p = 0.004), rs12908960 (p = 0.0006), rs1902584 (p<0.0001), rs2470144 (p = 0.0006), rs1961177 (p<0.0001), and rs6493497 (p = 0.0092) was observed between AA and the Yoruba (YRI) population. Linkage disequilibrium (LD) blocks and haplotype clusters that is unique to the EA population but not AA was also observed. In summary, we demonstrate that differences in the allele frequencies of CYP19A1 intron SNPs are not consistent between populations of African and European ancestry. Thus, investigations into whether CYP19A1 intron SNPs contribute to variations in cancer incidence, outcomes and pharmacological response seen in populations of different ancestry may prove beneficial.     

Genetic control of amylose content in wheat endosperm starch and differential effects of three Wx genes

The endosperm starch of the wheat grain is composed of amylose and amylopectin. Genetic manipulation of the ratio of amylose to amylopectin or the amylose content could bring about improved texture and quality of wheat flour. The chromosomal locations of genes affecting amylose content were investigated using a monosomic series of Chinese Spring (CS) and a set of Cheyenne (CNN) chromosome substitution lines in the CS genetic background. Trials over three seasons revealed that a decrease in amylose content occurred in monosomic 4A and an increase in monosomic 7B. Allelic variation between CS and CNN was suggested for the genes on chromosomes 4A and 7B. To examine the effects of three Waxy (Wx) genes which encode a granule-bound starch synthase (Wx protein), the Wx proteins from CS monosomics of interest were analyzed using SDS-PAGE. The amount of the Wx protein coded by the Wx-B1 gene on chromosome arm 4AL was reduced in monosomic 4A, and thus accounted for its decreased amylose content. The amounts of two other Wx proteins coded by the Wx-A1 and Wx-D1 genes on chromosome arms 7AS and 7DS, respectively, showed low levels of protein in the monosomics but no effect on amylose content. The effect of chromosome 7B on the level of amylose suggested the presence of a regulator gene which suppresses the activities of the Wx genes.     

一种小麦蓝粒标记单体代换系4E（3D）的创制

以中国春3D单体和小麦-长穗偃麦草4E二体异附加系为材料,通过杂交、回交结合染色体鉴定等方法,培育出了一种具有蓝粒标记的小麦4E(3D)单体代换系.该小麦4E(3D)单体代换系籽粒为浅蓝色,能够正常生长,自交结实率为36.1%,其自交后代可分离出深蓝籽粒小麦4E(3D)二体代换系、浅蓝籽粒小麦4E(3D)单体代换系和白粒小麦3D缺体.结果表明,长穗偃麦草4E染色体对小麦3D染色体缺失有一定的补偿功能,对以染色体定向代换方式快速创制蓝粒标记小麦单体系统具有一定的参考价值.     

八倍体小黑麦耐盐细胞系产生的遗传机制

实验选用来源于八倍体小黑麦（×ＴｒｉｔｉｃｏｓｅｃａｌｅＷｉｔｍａｃｋ）杂种一代Ｂ、Ｃ和原种Ｆ三个品系的成对单倍体和双倍体细胞系,在１％、１．５％和２％ＮａＣｌ水平进行耐盐变异体筛选及其发生机制研究。实验和分析结果表明,未经筛选的细胞系由三类细胞组成,第一类是占大多数没有任何适盐性的细胞,第二类是具有一定适盐性的非变异体细胞,可在继代筛选中被淘汰,第三类细胞是变异体细胞;第二类细胞在杂种材料细胞系中所占比例少于原种细胞系,故杂种细胞较易筛选到耐盐变异体;比较三个级别筛选的变异体频率发现,后一级筛选的变异必须以前一级筛选的变异为基础,即耐盐变异体发生的遗传机制是基因扩增;双倍体细胞中正常同源染色体对基因扩增变异的表达有干扰作用,这种干扰因材料不同在各级筛选中呈现不稳定状态。     

A Genome-Wide Search for Linkage of Estimated Glomerular Filtration Rate (eGFR) in the Family Investigation of Nephropathy and Diabetes (FIND)

Objective

Estimated glomerular filtration rate (eGFR), a measure of kidney function, is heritable, suggesting that genes influence renal function. Genes that influence eGFR have been identified through genome-wide association studies. However, family-based linkage approaches may identify loci that explain a larger proportion of the heritability. This study used genome-wide linkage and association scans to identify quantitative trait loci (QTL) that influence eGFR.

Methods

Genome-wide linkage and sparse association scans of eGFR were performed in families ascertained by probands with advanced diabetic nephropathy (DN) from the multi-ethnic Family Investigation of Nephropathy and Diabetes (FIND) study. This study included 954 African Americans (AA), 781 American Indians (AI), 614 European Americans (EA) and 1,611 Mexican Americans (MA). A total of 3,960 FIND participants were genotyped for 6,000 single nucleotide polymorphisms (SNPs) using the Illumina Linkage IVb panel. GFR was estimated by the Modification of Diet in Renal Disease (MDRD) formula.

Results

The non-parametric linkage analysis, accounting for the effects of diabetes duration and BMI, identified the strongest evidence for linkage of eGFR on chromosome 20q11 (log of the odds [LOD] = 3.34; P = 4.4×10⁻⁵) in MA and chromosome 15q12 (LOD = 2.84; P = 1.5×10⁻⁴) in EA. In all subjects, the strongest linkage signal for eGFR was detected on chromosome 10p12 (P = 5.5×10⁻⁴) at 44 cM near marker rs1339048. A subsequent association scan in both ancestry-specific groups and the entire population identified several SNPs significantly associated with eGFR across the genome.

Conclusion

The present study describes the localization of QTL influencing eGFR on 20q11 in MA, 15q21 in EA and 10p12 in the combined ethnic groups participating in the FIND study. Identification of causal genes/variants influencing eGFR, within these linkage and association loci, will open new avenues for functional analyses and development of novel diagnostic markers for DN.     

Association of corticotropin-releasing hormone gene variation with performance and meat quality traits in commercial pig lines

The porcine corticotropin-releasing hormone(CRH) gene is a functional-positional candidate for quantitative tract loci on porcine chromosome 4 with major effects on growth and carcass composition. In addition, the central role of CRH in the neuroendocrine response to stress implicates the CRH gene as a functional candidate for meat quality. Association of a single nucleotide polymorphism (SNP) in the promoter region of the porcine CRH gene (g.233C > T) with several growth, carcass and meat quality traits was examined using more than 2000 individuals from four commercial lines: German Landrace (LR), Pietrain (Pi), German Large White x German Landrace (F1) and the German commercial fattening pig cross of Pietrain x F1 (PiF1). Significant association of the CRH SNP was found with feed conversion ratio in the PiF1 line, with carcass length in the LR line and with lean content in the F1, LR and Pi lines. Moreover, significant association with meat colour was found in the Pi and LR lines; however, the effects were in opposite directions. The presented results indicate that sequence variation in the porcine CRH gene has no major effect on growth and carcass composition in commercial pig lines, although it may significantly contribute to variation in meat quality. The g.233C>T SNP may be in incomplete linkage disequilibrium with causal mutations and/or exhibit effects in the context of DNA variation at other interacting loci.     

Possible Race and Gender Divergence in Association of Genetic Variations with Plasma von Willebrand Factor: A Study of ARIC and 1000 Genome Cohorts

The synthesis, secretion and clearance of von Willebrand factor (VWF) are regulated by genetic variations in coding and promoter regions of the VWF gene. We have previously identified 19 single nucleotide polymorphisms (SNPs), primarily in introns that are associated with VWF antigen levels in subjects of European descent. In this study, we conducted race by gender analyses to compare the association of VWF SNPs with VWF antigen among 10,434 healthy Americans of European (EA) or African (AA) descent from the Atherosclerosis Risk in Communities (ARIC) study. Among 75 SNPs analyzed, 13 and 10 SNPs were associated with VWF antigen levels in EA male and EA female subjects, respectively. However, only one SNP (RS1063857) was significantly associated with VWF antigen in AA females and none was in AA males. Haplotype analysis of the ARIC samples and studying racial diversities in the VWF gene from the 1000 genomes database suggest a greater degree of variations in the VWF gene in AA subjects as compared to EA subjects. Together, these data suggest potential race and gender divergence in regulating VWF expression by genetic variations.     

Mitotic karyotypes of Brassica campestris and Brassica alboglabra and identification of the B. alboglabra chromosome in an addition line.

A Brassica campestris-alboglabra monosomic addition line (genome: AA + one chromosome from the C genome, 2n = 21) harbours the Brassica alboglabra (CC, 2n = 18) chromosome with the gene for erucic acid. In order to identify this chromosome, we have studied the mitotic prometaphase chromosomes of Brassica campestris (AA, 2n = 20), B. alboglabra, and the monosomic addition line. More pronounced differential staining and size differences of chromosomes were observed in B. campestris than in B. alboglabra. The karyotype of B. campestris was composed of four median (m), four submedian (sm), and two subterminal (st) chromosome pairs, while that of B. alboglabra was composed of three m, four sm, and two st chromosome pairs, provided that the length of the satellite was excluded when determining the arm ratio of the nucleolar chromosome. The alien chromosome from the C genome in the addition line was easily identified in the background B. campestris genome by its large size, its submedian centromere, and its differential staining pattern. When compared with the karyotype of B. alboglabra, the alien chromosome from the C genome in the monosomic addition line was revealed to be chromosome 4.