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PubMed2000

High-density molecular map of chromosome region harboring stripe-rust resistance genes YrH52 and Yr15 derived from wild emmer wheat, Triticum dicoccoides.

Two stripe-rust resistance genes, YrH52 and Yr15, derived from the Israeli wild emmer wheat, Triticum dicoccoides, have been located on chromosome 1B. The main objectives of the present study were to increase marker density in the vicinity of YrH52 gene by means of AFLP, RAPD and microsatellite markers, to improve the map of another T dicoccoides-derived stripe-rust resistance gene Yr15 using microsatellite markers, and to preliminarily discriminate these two genes. Additional 26 marker loci comprising 20 AFLPs, three RAPDs, and three microsatellites were found to be linked to YrH52 gene. An updated genetic map consisting of 45 marker loci, in the region of YrH52 gene, was constructed with a total map length of 107.7 cm. The mean interval length was 0.96 cm in the region Xgwm359b-P55M53b carrying YrH52 gene. YrH52 was bracketed by Xgwm413 (Nor1 and UBC212a) and Xgwm273a (Xgwm273d) with map distance of 1.3 and 2.7 cm from either side, respectively. Eight additional microsatellite markers were found to be linked with Yr15, and the linkage map of Yr15 gene was thus obviously improved. In the YrH52-mapping population, no crossover was detected in the interval UBC212a (Xgwm413)-Yr15-Nor1, and YrH52 was located distally outside this interval. It may suggest that YrH52 is different from Yr15 even though both of them are derived from T. dicoccoides and are mapped on chromosome 1BS. The large number of molecular makers revealed in the present study would be helpful for the marker-assisted introgression of the T. dicoccoides-derived YrH52 and Yr15 stripe-rust resistance genes into elite cultivars of wheat, and the high-density map would accelerate the map-based cloning of the two genes.

Basidiomycota↗

PubMed2003

Synthesis of intergeneric hybrids and establishment of genomic affinity between Diplotaxis catholica and crop Brassica species.

Intergeneric hybrids of the wild crucifer Diplotaxis catholica (2n = 18, D(C)D(C)) as female with two crop Brassica species, namely Brassica rapa (2n = 20; AA) and Brassica juncea (2n = 36; AABB) as male, were developed, using ovary and sequential culture. Reciprocal crosses were not successful, suggesting unilateral cross incompatibility. Morphologically, the hybrid plants resembled the crop brassica parents, but were nearly male- as well as female-sterile. Induction of amphiploidy helped to improve pollen fertility for the D. catholica x B. rapa cross (73%), but less so for the D. catholica x B. juncea cross (35-40%). Female fertility was also higher in both the amphiploids. Cytological analysis of the F(1) hybrids revealed aberrant meiosis with predominant occurrence of the univalents. Partial genomic homoeology between the A genome of B. rapa and the D(C) genome of D. catholica was indicated by the presence of up to five bivalents in 14.7% of the PMCs in the D. catholica x B. rapa hybrid, and 1-2 trivalents or a quadrivalent in nearly 44% of the PMCs in the derived amphiploid. In the second cross, D. catholica x B. juncea, up to six bivalents and one trivalent were observed indicating homoeology between the A/B genomes of B. juncea and the D(C) genome of D. catholica. The possibility of introgression of desirable genes from D. catholica into crop Brassica species exists in view of significant affinity between the D(C) and A/B genomes.

Brassica↗

PubMed2006

CAPs markers to assist selection for low vicine and convicine contents in faba bean (Vicia faba L.).

The antinutritional factors (ANFs) present in Vicia spp. seeds are a major constraint to the wider utilization of these crops as grain legumes. In the case of faba bean (Vicia faba L.), a breeding priority is the absence vicine and convicine (v-c); responsible for favism in humans and for the reduced animal performance or low egg production in laying hens. The discovery of a spontaneous mutant allele named vc-, which induces a 10-20 fold reduction of v-c contents, may facilitate the process. However, the high cost and difficulty of the chemical detection of v-c seriously restricts the advances in breeding-selection. To identify random amplified polymorphic DNA (RAPD) markers linked to this gene, we have analysed an F(2 )population derived from a cross between a line with high v-c content (Vf6) and the vc- genotype (line 1268). Quantification of v-c was done by spectrophotometry on the parents and the F(2 )population (n = 136). By using bulked segregant analysis (BSA), two RAPD markers linked in coupling and repulsion phase to the allele vc- were identified and further converted into sequence characterized amplified regions (SCARs). Amplification of SCARS was more consistent, although the initial polymorphism between pools was lost. To recover the polymorphisms several approaches were explored. Restriction digestion with HhaI (for SCAR SCH01(620)) and RsaI (for SCAR SCAB12(850)) revealed clear differences between the parental lines. The simultaneous use of the two cleavage amplified polymorphism (CAP) markers will allow the correct fingerprinting of faba bean plants and can be efficiently used in breeding selection to track the introgression of the vc- allele to develop cultivars with low v-c content and improved nutritional value.

Animals↗

PubMed2003

Molecules and morphology: evidence for cryptic hybridization in African Hyalomma (Acari: Ixodidae).

The role of natural hybridization and introgression as part of the evolutionary process is of increasing interest to zoologists, particularly as more examples of gene exchange among species are identified. We present mitochondrial and nuclear sequence data for Hyalomma dromedarii, Hyalomma truncatum, and Hyalomma marginatum rufipes (Acari: Ixodidae) collected from one-humped camels in Ethiopia. These species are well differentiated morphologically and genetically; sequence data from the mitochondrial DNA (mtDNA) cytochrome oxidase I gene indicates 10-14% divergence between the species. However, incongruence between morphology and the mtDNA phylogeny was observed, with multiple individuals of H. dromedarii and H. truncatum present on the same mtDNA lineage as H. marginatum rufipes. Thus, individuals with morphology of H. dromedarii and H. truncatum are indistinguishable from H. marginatum rufipes on the basis of mtDNA. Multiple copies of ITS-2 were subsequently cloned and sequenced for a subset of individuals from the mtDNA phylogeny, representing both 'normal' and 'putative hybrid' individuals. Very low sequence divergence (0.3%) was observed within 'normal' individuals of both H. dromedarii and H. truncatum relative to the 'putative hybrid' individuals (6 and 2.7%, respectively). The pattern of intra-individual variation in ITS-2 within 'putative hybrid' individuals, particularly in H. dromedarii, strongly suggests that gene flow has occurred among these Hyalomma species, but no indication of this is given by the morphology of the individuals.

Africa↗

PubMed2005

The origins of Iberian horses assessed via mitochondrial DNA.

Despite a number of recent studies that have focused on the origin of domestic horses, genetic relationships between major geographical clusters still remain poorly understood. In this study we analyzed a 296 bp mtDNA fragment from the HVI region of 171 horses representing 11 native Iberian, Barb, and Exmoor breeds to assess the maternal phylogeography of Iberian horses. The mtDNA haplogroup with a CCG motif (nucleotide position 15,494 to 15,496) was the most frequent in Iberian and Barb breeds (0.42 and 0.57, respectively), regardless of geographic location or group of breeds. This finding supports the close genetic relationship between the ancestral mare populations of the Iberian Peninsula and Northern Africa. Phenotypic differences among the Northern and Southern Iberian groups of breeds are not explained by population subdivision based on maternal lineages. Our results also suggest that Northern Iberian ponies--which are phenotypically close to British ponies, especially Exmoor--are the result of an introgression rather than population replacement.

Animals↗

PubMed2005

Multilocus analysis of introgression between two sympatric sister species of Drosophila: Drosophila yakuba and D. santomea.

Drosophila yakuba is widely distributed in sub-Saharan Africa, while D. santomea is endemic to the volcanic island of São Tomé in the Atlantic Ocean, 280 km west of Gabon. On São Tomé, D. yakuba is found mainly in open lowland forests, and D. santomea is restricted to the wet misty forests at higher elevations. At intermediate elevations, the species form a hybrid zone where hybrids occur at a frequency of approximately 1%. To determine the extent of gene flow between these species we studied polymorphism and divergence patterns in 29 regions distributed throughout the genome, including mtDNA and three genes on the Y chromosome. This multilocus approach, together with the comparison to the two allopatric species D. mauritiana and D. sechellia, allowed us to distinguish between forces that should affect all genes and forces that should act on some genes (e.g., introgression). Our results show that D. yakuba mtDNA has replaced that of D. santomea and that there is also significant introgression for two nuclear genes, yellow and salr. The majority of genes, however, has remained distinct. These two species therefore do not form a "hybrid swarm" in which much of the genome shows substantial introgression while disruptive selection maintains distinctness for only a few traits (e.g., pigmentation and male genitalia).

Animals↗

PubMed2000

Identification and characterization of wheat-wheatgrass translocation lines and localization of barley yellow dwarf virus resistance.

Stable introgression of agronomically important traits into crop plants through wide crossing often requires the generation and identification of translocation lines. However, the low efficiency of identifying lines containing translocations is a significant limitation in utilizing valuable alien chromatin-derived traits. Selection of putative wheatgrass-wheat translocation lines based on segregation ratios of progeny from gamma-irradiated seed using a standard phenotypic analysis resulted in a low 4% success rate of identifying barley yellow dwarf virus (BYDV) resistant and susceptible translocation lines. However, 58% of the susceptible progeny of this irradiated seed contained a Thinopyrum intermedium chromosome-specific repetitive sequence, which indicated that gamma-irradiation-induced translocations occurred at high rate. Restriction fragment length polymorphism (RFLP) analysis of susceptible lines containing alien chromatin, their resistant sister lines and other resistant lines showed that more than one third of the progeny of gamma-irradiated double monosomic seeds contained wheatgrass-wheat translocations. Genomic in situ hybridization (GISH) analysis of selected lines confirmed that these were wheatgrass-wheat translocation lines. This approach of initially identifying BYDV susceptible deletion lines using an alien chromosome-specific repetitive sequence followed by RFLP analysis of their resistant sister lines efficiently identified resistant translocation lines and localized the BYDV resistance to the distal end of the introgressed Th. intermedium chromosome.

Chromatin↗

PubMed1993

[Arguments for the modification of the genome (introgression) of the human parasite Schistosoma haematobium by genes from S. bovis, in Niger].

Characterization of schistosome populations from human in eastern Niger, through intra-uterine egg morphology of female parasites and phenotopic analyses of worms observed for acid phosphatase using electrophoretic separation, renders results that suggest an intogression of S. haematobium from man by genes of S. bovis, a parasite of domestic livestock. The origin of this introgression, that could implicate S. curassoni as well, another livestock parasite that hybridize with S. bovis, is discussed.

Animals↗

PubMed2000

Characterization and mapping of resistance to Oidium lycopersicum in two Lycopersicon hirsutum accessions: evidence for close linkage of two Ol-genes on chromosome 6 of tomato.

The cultivated tomato is susceptible to powdery mildew (Oidium lycopersicum). Several accessions of wild species are resistant. In this study we describe (i) the genetics and mapping of resistance to O. lycopersicum in G1.1290, one of the resistant accessions in Lycopersicon hirsutum, (ii) fine mapping of Ol-1 originated from L. hirsutum G1.1560, another resistant accession of L. hirsutum, and (iii) tests of allelism for resistance in G1.1290 and G1.1560. Initially, it is demonstrated that the resistance in G1.1290 to O. lycopersicum is controlled by an incompletely dominant gene, designated Ol-3. By using an advanced breeding line (ABL) containing introgression fragment(s) from G1.1290, Ol-3 was found to be associated with several RFLP and SCAR markers on chromosome 6. By using these markers, Ol-3 was mapped between markers TG25/SCAF10 and H9A11 on chromosome 6. Secondly, after testing some F3 lines and their progenies from the cross between L. esculentum cv Moneymaker and L. hirsutum G1.1560, we provided more evidence for the map position of Ol-1 to lie between SCAF10 and H9A11, indicating that Ol-1 and Ol-3 are in the same chromosome region. Thirdly, although allelism tests could not discriminate between Ol-1 and Ol-3, (indirect) evidence suggested that these two genes are not identical. They might instead represent functional genes of a cluster of Ol-homologues.

Alleles↗

PubMed2003

Congenic strains confirm the presence of salt-sensitivity QTLs on chromosome 1 in the Sabra rat model of hypertension.

We previously detected by linkage analysis in segregating populations derived from crosses between the Sabra hypertension-prone rat (SBH/y) and the hypertension-resistant strain (SBN/y) two QTLs for salt susceptibility on chromosome 1, with sex specificity: in males SS1a and SS1b, and in females SS1b only. To provide support for a functional role of these QTLs in relation to hypertension, we constructed congenic strains by replacing most of or selected segments from chromosome 1 from SBN/y with the homologous chromosomal regions of SBH/y, or reciprocally from SBH/y with segments of SBN/y, leaving the other chromosomes unperturbed. Genetic screening with over 150 microsatellite markers confirmed the homozygosity of the targeted genomic inserts and of the remainder of the genomic background. The phenotype of the congenic strains was tested by salt loading with DOCA-salt over a 4-wk period and measuring blood pressure by tail-cuff (in all animals) or radiotelemetry (in select groups) at baseline and during salt loading. In the congenic strains in which a chromosomal segment incorporating QTL SS1a from SBN/y was introgressed onto the genomic background of SBH/y, the blood pressure response to salt loading, as measured by tail-cuff, was decreased by 16 mmHg in both males and females compared with the parental SBH/y; replacing the QTL SS1b reduced the blood pressure response by 30 and 21 mmHg, respectively. In the congenic strains in which both SS1a and SS1b were introgressed from SBN/y onto the genomic background of SBH/y, the reduction in blood pressure was 34 mmHg in males and 38 mmHg in females; these latter results were confirmed by radiotelemetry. When either one or both QTLs together were introgressed from SBH/y onto the SBN/y genomic background, tail-cuff measurements failed to detect an increase in blood pressure above baseline; telemetric measurements in the congenic strains introgressing both QTLs together, however, detected a significant rise in blood pressure after 3 and 4 wk of salt loading. Neither the origin of the Y chromosome nor the sex of the parental strain had any significant impact on the magnitude of the blood pressure response to salt loading. We conclude that the congenic rat strains that we constructed for the chromosome 1 QTLs provide functional evidence for the role of gene systems within QTLs SS1a and SS1b in the blood pressure response to salt loading. The unexpected finding was that QTL SS1a contributes to the hypertensive response also in females. The data indicate the lack of a Y chromosomal effect or of parental imprinting.

Animals↗

PubMed2000

Hybrid origins of honeybees from italy (Apis mellifera ligustica) and sicily (A. m. sicula).

The genetic variability of honeybee populations Apis mellifera ligustica, in continental Italy, and of A. m. sicula, in Sicily, was investigated using nuclear (microsatellite) and mitochondrial markers. Six populations (236 individual bees) and 17 populations (664 colonies) were, respectively, analysed using eight microsatellite loci and DraI restriction fragment length polymorphism (RFLP) of the cytochrome oxidase I (COI)-cytochrome oxidase II (COII) region. Microsatellite loci globally confirmed the southeastern European heritage of both subspecies (evolutionary branch C). However, A. m. ligustica mitochondrial DNA (mtDNA) appeared to be a composite of the two European (M and C) lineages over most of the Italian peninsula, and only mitotypes from the African (A) lineage were found in A. m. sicula samples. This demonstrates a hybrid origin for both subspecies. For A. m. ligustica, the most widely exported subspecies, this hybrid origin has long been obscured by the fact that in the main area of queen production (from which most of the previous ligustica bee samples originated) the M mitochondrial lineage is absent, whereas it is present almost everywhere else in Italy. This presents a new view of the evolutionary history of European honeybees. For instance, the Iberian peninsula was considered as the unique refuge for the M branch during the quaternary ice periods. Our results show that the Apennine peninsula played a similar role. The differential distribution of nuclear and mitochondrial markers observed in Italy seems to be a general feature of introgressed honeybee populations. Presumably, it stems from the social nature of the species in which both genome compartments are differentially affected by the two (individual and colonial) reproduction levels.

Alleles↗

PubMed2004

Genetic complexity of an obesity QTL ( Fob3) revealed by detailed genetic mapping.

Obesity is proving to be a serious health concern in the developed world as well as an unwanted component of growth in livestock production. While recent advances in genetics have identified a number of monogenic causes of obesity, these are responsible for only a small proportion of human cases of obesity. By divergent selection for high and low fat content over 60 generations, we have created Fat (F) and Lean (L) lines of mice that represent a model of polygenic obesity similar to the situation in human populations. From previous crosses of these lines, four body fat quantitative trait loci (QTL) were identified. We have created congenic lines (F(chr15L)), by recurrent marker-assisted backcrossing, to introgress the QTL region with the highest LOD score, Fob3 on Chr 15, from the L-Iine into the F-line background. We have further mapped this QTL by progeny testing of recombinants, produced from crosses between the F-line and congenic F(chrl5L) mice, showing that the Fob3 QTL region is a composite of at least two smaller effect QTL-the proximal QTL Fob3a is a late-onset obesity QTL, whereas the distal Fob3b is an early-onset obesity QTL.

Analysis of Variance↗

PubMed2006

Inheritance of gynandromorphism in the parasitic wasp Nasonia vitripennis.

The parasitic wasp Nasonia vitripennis has haplo-diploid sex determination. Males develop from unfertilized eggs and are haploid, whereas females develop from fertilized eggs and are diploid. Females and males can be easily distinguished by their morphology. A strain that produces individuals with both male and female features (gynandromorphs) is studied. We provide data on female/male patterning within and between individuals, on environmental effects influencing the occurrence of gynandromorphism, and on its pattern of inheritance. A clear anterior/posterior pattern of feminization is evident in gynandromorphic individuals that developed from unfertilized haploid eggs. The proportion of gynandromorphic individuals can be increased by exposing the mothers to high temperature and also by exposing embryos at early stages of development. Selection for increased gynandromorph frequency was successful. Backcross and introgression experiments showed that a combination of a nuclear and a heritable cytoplasmic component causes gynandromorphism. Analyses of reciprocal F(2) and F(3) progeny indicate a maternal effect locus (gyn1) that maps to chromosome IV. Coupled with previous studies, our results are consistent with a N. vitripennis sex determination involving a maternal/zygotic balance system and/or maternal imprinting. Genetics and temperature effects suggest a temperature-sensitive mutation of a maternally produced masculinizing product that acts during a critical period in early embryogenesis.

Analysis of Variance↗

PubMedDate not supplied

T-cell and chemokine receptor variation in south Amerindian populations.

The immune response of relatively small, endogamous populations is of special interest, because they may differ from those of large, ethnically diverse, urban groups. As a contribution to this area of investigation, we tested 99 individuals from two Brazilian native populations for two T-cell receptor gene segments (TCRBV3S1 and TCRBV18) and 241 subjects from eight tribes of this ethnic group in relation to the chemokine receptor CCR5delta32 allele. Differences in TCRBV3S1 and TCRBV18 prevalences of the Amerindians in relation to European- and African-derived individuals were not marked. We confirmed the absence of the CCR5delta32 allele in most groups, its presence in the Mura and Kaingang, probably because of European gene introgression.

Aged↗

PubMed1997

The salmon SmaI family of short interspersed repetitive elements (SINEs): interspecific and intraspecific variation of the insertion of SINEs in the genomes of chum and pink salmon.

The genomes of chum salmon and pink salmon contain a family of short interspersed repetitive elements (SINEs), designated the salmon SmaI family. It is restricted to these two species, a distribution that suggests that this SINE family might have been generated in their common ancestor. When insertions of the SmaI SINEs at 10 orthologous loci of these species were analyzed, however, it was found that there were no shared insertion sites between chum and pink salmon. Furthermore, at six loci where SmaI SINEs have been species-specifically inserted in chum salmon, insertions of SINEs were polymorphic among populations of chum salmon. By contrast, at four loci where SmaI SINEs had been species-specifically inserted in pink salmon, the SINEs were fixed among all populations of pink salmon. The interspecific and intraspecific variation of the SmaI SINEs cannot be explained by the assumption that the SmaI family was amplified in a common ancestor of these two species. To interpret these observations, we propose several possible models, including introgression and the horizontal transfer of SINEs from pink salmon to chum salmon during evolution.

Animals↗

PubMed2006

Sequence diversity, reproductive isolation and species concepts in Saccharomyces.

Using the biological species definition, yeasts of the genus Saccharomyces sensu stricto comprise six species and one natural hybrid. Previous work has shown that reproductive isolation between the species is due primarily to sequence divergence acted upon by the mismatch repair system and not due to major gene differences or chromosomal rearrangements. Sequence divergence through mismatch repair has also been shown to cause partial reproductive isolation among populations within a species. We have surveyed sequence variation in populations of Saccharomyces sensu stricto yeasts and measured meiotic sterility in hybrids. This allows us to determine the divergence necessary to produce the reproductive isolation seen among species. Rather than a sharp transition from fertility to sterility, which may have been expected, we find a smooth monotonic relationship between diversity and reproductive isolation, even as far as the well-accepted designations of S. paradoxus and S. cerevisiae as distinct species. Furthermore, we show that one species of Saccharomyces--S. cariocanus--differs from a population of S. paradoxus by four translocations, but not by sequence. There is molecular evidence of recent introgression from S. cerevisiae into the European population of S. paradoxus, supporting the idea that in nature the boundary between these species is fuzzy.

Base Sequence↗

PubMed2004

A genetic map of candidate genes and QTLs involved in tomato fruit size and composition.

In order to screen for putative candidate genes linked to tomato fruit weight and to sugar or acid content, genes and QTLs involved in fruit size and composition were mapped. Genes were selected among EST clones in the TIGR tomato EST database (http://www.tigr.org/tdb/tgi/lgi/) or corresponded to genes preferentially expressed in the early stages of fruit development. These clones were located on the tomato map using a population of introgression lines (ILs) having one segment of Lycopersicon pennellii (LA716) in a L. esculentum (M82) background. The 75 ILs allowed the genome to be segmented into 107 bins. Sixty-three genes involved in carbon metabolism revealed 79 loci. They represented enzymes involved in the Calvin cycle, glycolysis, the TCA cycle, sugar and starch metabolism, transport, and a few other functions. In addition, seven cell-cycle-specific genes mapped into nine loci. Fourteen genes, primarily expressed during the cell division stage, and 23 genes primarily expressed during the cell expansion stage, revealed 24 and 26 loci, respectively. The fruit weight, sugars, and organic acids content of each IL was measured and several QTLs controlling these traits were mapped. Comparison between map location of QTLs and candidate gene loci indicated a few candidate genes that may influence the variation of sugar or acid contents. Furthermore, the gene/QTL locations could be compared with the loci mapped in other tomato populations.

Chromosome Mapping↗

PubMed2004

Genetic structure of korean wild populations of the Medaka Oryzias latipes inferred from allozymic variation.

Previous allozymic studies have revealed that Korean wild populations of Oryzias latipes have differentiated regionally, and are composed of two distinct groups, the East Korean Population and the China-West Korean Population. Recently, mitochondrial DNA (mtDNA) sequencing and restriction fragment length polymorphism (RFLP) analyses have confirmed these two groups, and shown that the distribution ranges of the two groups overlap in western Korea. In order to describe the detailed distributions of the two groups and the gene flow between them, genotypes of 13 allozymic loci were determined in 444 specimens from 96 localities in Korea. The two major groups were supported by remarkable allele frequency differences at six diagnostic loci: ACP*, AMY*, CK-A*, LDH-A*, PGM* and TF*. Individuals with the typical "eastern" genotype were mainly distributed in eastern and southern areas. In contrast, fish with the "western" genotype were predominant in the western area, and were further divided into two subgroups (the Han River and Geum River Subpopulations) by unique alleles at the ADH* locus. In the western coast, two distinct (eastern and western) genotypes were distributed in a mosaic fashion. This distribution pattern was identical to those from mtDNA analyses. Although the distribution patterns of the alleles at three loci (GPI-A*, LDH-C* and SOD*) showed introgressive conditions between the two groups, each population was nearly fixed as either the eastern or western genotype at all six diagnostic loci despite the proximity among samples. Therefore, it is suggested that some reproductive isolation mechanisms exist between the two groups in natural habitats.

Animals↗