共查询到20条相似文献,搜索用时 15 毫秒
1.
Gene flow between cultivated and wild sunflowers 总被引:6,自引:0,他引:6
D. M. Arias L. H. Rieseberg 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1994,89(6):655-660
With the development of transgenic crops, concern has been expressed regarding the possible escape of genetically-engineered genes via hybridization with wild relatives. This is a potential hazard for sunflowers because wild sunflowers occur as weeds in fields where cultivated sunflowers are grown and hybridization between them has been reported. In order to quantify the potential for gene escape, two experimental stands of sunflower cultivars were planted at two sites with different rainfall and altitude profiles. Populations of wild plants were planted at different distances from each cultivar stand. An allele homozygous in the cultivar (6Pgd-3-a), but absent in the wild populations, was used as a molecular marker to document the incidence and rate of gene escape from the cultivar into the wild populations of sunflowers. Three-thousand achenes were surveyed to determine the amount of gene flow from the cultivated to the wild populations. The marginal wild populations (3 m from the cultivar) showed the highest percentage (27%) of gene flow. Gene flow was found to decrease with distance; however, gene flow occurred up to distances of 1000 m from the source population. These data suggest that physical distance alone will be unlikely to prevent gene flow between cultivated and wild populations of sunflowers. 相似文献
2.
Premise
Cultivated species and their wild relatives often hybridize in the wild, and the hybrids can survive and reproduce in some environments. However, it is unclear whether cultivar alleles are permanently incorporated into the wild genomes or whether they are purged by natural selection. This question is key to accurately assessing the risk of escape and spread of cultivar genes into wild populations.Methods
We used genomic data and population genomic methods to study hybridization and introgression between cultivated and wild carrot (Daucus carota) in the United States. We used single nucleotide polymorphisms (SNPs) obtained via genotyping by sequencing for 450 wild individuals from 29 wild georeferenced populations in seven states and 144 cultivars from the United States, Europe, and Asia.Results
Cultivated and wild carrot formed two genetically differentiated groups, and evidence of crop–wild admixture was detected in several but not all wild carrot populations in the United States. Two regions were identified where cultivar alleles were present in wild carrots: California and Nantucket Island (Massachusetts). Surprisingly, there was no evidence of introgression in some populations with a long-known history of sympatry with the crop, suggesting that post-hybridization barriers might prevent introgression in some areas.Conclusions
Our results provide support for the introgression and long-term persistence of cultivar alleles in wild carrots populations. We thus anticipate that the release of genetically engineered (GE) cultivars would lead to the introduction and spread of GE alleles in wild carrot populations. 相似文献3.
Assessment of interspecific hybridization between transgenic oilseed rape and wild radish under normal agronomic conditions 总被引:5,自引:0,他引:5
A. M. Chèvre F. Eber H. Darmency A. Fleury H. Picault J. C. Letanneur M. Renard 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,100(8):1233-1239
In order to assess the hybridization rate between oilseed rape and wild radish under normal agronomic conditions, three 1-ha
field experiments were performed. In each case, wild radish plants were transplanted at different densities in the middle,
the border, or the margin of the herbicide-tolerant oilseed rape field. Among the 189084 seedlings obtained from seeds harvested
on wild radish plants, only one herbicide-tolerant interspecific hybrid (RrRrAC, 2n = 37) was characterized from seeds harvested
on an isolated plant growing in the margin of the field. Thus, for the wild radish total harvest, with a 95% confidence limit,
the frequency of interspecific hybrids was assessed to range from 10–7 to 3.10–5. Interspecific hybrids were detected in all cases among the smallest seeds with a diameter less than 1.6 mm harvested on
oilseed rape, but the highest frequency was obtained from oilseed rape close to wild radish plants growing as clusters in
the border or the margin of the field. Most hybrids had the expected triploid genomic structure (ACRr, 2n = 28) except for
four amphidiploids (AACCRrRr, 2n = 56) and one hybrid from a wild radish unreduced gamete (ACRrRr, 2n = 37). Among the 73847
seedlings observed on the oilseed rape total harvest, the frequency of interspecific hybrids was assessed to range from 2.10–5to 5.10–4, with a 95% confidence limit. The results are discussed with regard to the type of oilseed rape variety used and the characteristics
of the interspecific hybrids.
Received: 5 October 1999 / Accepted: 11 November 1999 相似文献
4.
This study examines sporophytic and gametophytic vigor in wild and cultivated varieties of Cucurbita pepo L. and their hybrids in order to determine whether hybrid vigor extends to the microgametophyte generation. It also examines
the variation in sporophytic and gametophytic vigor to discern the non-genetic influences of pollen provisioning by the sporophyte
on pollen performance from the genetic influences of the microgametophyte’s own genotype on pollen performance. A cultivated
and a wild C. pepo and their F1 and the F2 generations were grown under field conditions and flower and fruit production were monitored over
one summer. We found that the four types of plants differed significantly in the number of male and female flowers and the
number of fruits they produced. The F1 plants produced significantly more male flowers and marginally more female flowers
and fruits than the parental lines. To estimate gametophytic vigor pollen was germinated in vitro and pollen tube length measured
after 30 min. We found that pollen tubes from the F1 plants had significantly greater growth than tubes from the parental
lines or the F2 generation, indicating that hybrid vigor extends to the microgametophytic generation. By partitioning the
variance of pollen tube growth into ’within’ and ’among’ plant components of variation, we were able to show that the genotype
of the microgametophyte influences pollen performance in vitro, but that expression of hybrid vigor in the microgametophyte
is likely to be due to an environmental effect related to provisioning of the pollen grains during development.
Received: 16 April 1998 / Revision accepted: 18 August 1998 相似文献
5.
Gliadin polymorphism in wild and cultivated einkorn wheats 总被引:4,自引:0,他引:4
M. Ciaffi L. Dominici D. Lafiandra 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(1):68-74
To study the relationships between different species of the Einkorn group, 408 accessions of Triticum monococcum, T. boeoticum, T. boeoticum ssp. thauodar and T. urartu were analyzed electrophoretically for their protein composition at the Gli-1 and Gli-2 loci. In all the species the range of allelic variation at the loci examined is remarkable. The gliadin patterns of T. monococcum and T. boeoticum were very similar to one another but differed substantially from those of T. urartu. Several accessions of T. boeoticum and T. monococcum were shown to share the same alleles at the Gli-1 and Gli-2 loci, confirming the recent nomenclature that considers these wheats as different subspecies of the same species, T. monococcum. The gliadin composition of T. urartu resembled that of the A genome of polyploid wheats more than did T. boeoticum or T. monococcum, supporting the hypothesis that T. urartu, rather than T. boeoticum, is the donor of the A genome in cultivated wheats. Because of their high degree of polymorphism the gliadin markers may
help in selecting breeding parents from diploid wheat germ plasm collections and can be used both to search for valuable genes
linked to the gliadin-coding loci and to monitor the transfer of alien genes into cultivated polyploid wheats.
Received: 8 July 1996 / Accepted: 12 July 1996 相似文献
6.
S. Mariette M. Lefranc P. Legrand D. Taneyhill N. Frascaria-Lacoste N. Machon 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(6-7):904-908
Isoenzymes were used to evaluate gene diversity and genetic differentiation among six populations of wild cherry (Prunus avium L.) in France. We contrast the genetic characteristics of a population resulting from a recent colonization with those of
a much older population of the same species. No significant genetic structure was observed among populations; in this respect
wild cherry does not differ from other forest trees. No founder effects could be detected in the newly colonized population.
To explain the results, we discuss classic explanations for the lack of genetic differentiation among populations, including
balancing selection and neutral drift/migration. In order to account for the absence of founder effects, we propose a hypothesis
based on the life cycle of forest trees, namely that the length of the juvenile phase reduces the impact of small numbers
of initial founders.
Received : 26 November 1996 / Accepted : 20 December 1996 相似文献
7.
T. Sota 《Population Ecology》2002,44(3):0145-0156
In the evolutionary process of an animal lineage, interactions in secondary contacts of differentiated populations and introgressive
hybridization may play an important role. In the Japanese islands, the carabid subgenus Ohomopterus (genus Carabus) exhibits a marked differentiation in body size and genital morphology. Although geographical differentiation is apparent,
two or three species usually coexist at many localities. Their reproductive isolation relies on body size differences, chemical
cues for mate recognition, and a species-specific genital lock-and-key system. However, these isolation mechanisms are not
always effective enough to prevent interspecific hybridization. An initial assessment of the species-level phylogeny with
mitochondrial gene sequences revealed that the gene genealogy is highly inconsistent with the morphology-based taxonomy. A
comparison of mitochondrial and nuclear gene genealogies showed that these are strongly incongruent with each other, while
the nuclear gene genealogy is more consistent with traditional taxonomy, indicating the repeated occurrence of introgression
of mitochondria across species. Here, two different cases of mitochondrial introgression among Ohomopterus species are described in detail, one for parapatric species and the other for sympatric species. First, mitochondrial haplotypes
and sequences were studied in Carabus insulicola and three taxa parapatric with C. insulicola, at least two of which hybridize with C. insulicola naturally. Among the four species studied, directional introgressions of mitochondria across boundary zones were detected.
Second, in the Mt. Kongo area in central Honshu, which harbors five species, introgression of mitochondria among four out
of the five species was detected, despite the apparent absence of on-going natural hybridization. These inferred cases of
mitochondrial introgression indicate that species interactions through hybridization could have played an important role at
various stages in the evolution of Ohomopterus.
Received: April 12, 2002 / Accepted: October 17, 2002
Acknowledgments I am grateful to Alfried P. Vogler for a long-lasting collaboration in the molecular phylogenetic study of Ohomopterus. R. Ishikawa, K. Kubota, M. Ujiie, Y. Takami, and F. Kusumoto have also collaborated at various stages of this study. Thanks
are also due to K. Miyashita, T. Funakoshi, H. Fujimoto, T. Dejima, Y. Nagahata, T. Miyagawa, K. Yodoe, H. Kadowaki, S. Nakamine,
Y. Oka, H. Tanaka, T. Tanabe, K. Kusakari, and T. Okumura for their care of specimens. Supported by grants-in-aid from the
Japan Society for the Promotion of Science (Nos. 09640748, 11304056). 相似文献
8.
M. Le Thierry d’Ennequin O. Panaud B. Toupance A. Sarr 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,100(7):1061-1066
AFLP markers were used to assess genetic diversity and patterns of geographic variation among 39 accessions of foxtail millet
(Setaria italica) and 22 accessions of green foxtail millet (S. viridis), its putative wild progenitor. A high level of polymorphism was revealed. Dendrograms based on Nei and Li distances from
a neighbour joining procedure were constructed using 160 polymorphic bands. Bootstrap values revealed that no specific geographic
structure can be extracted from these data. The high level of diversity among Chinese accessions was consistent with the hypothesis
of a centre of domestication in China. The results also showed that accessions from Eastern Europe and Africa form two distinct
clusters. The narrow genetic basis of these two gene pools may be the result of local-adaptation.
Received: 1 June 1999 / Accepted: 16 September 1999 相似文献
9.
The use of microsatellite markers for detection of genetic diversity in barley populations 总被引:41,自引:0,他引:41
D. Struss J. Plieske 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(1-2):308-315
A barley lambda-phage library was screened with (GA)n and (GT)n probes for developing microsatellite markers. The number of repeats ranged from 2 to 58 for GA and from 2 to 24 for GT. Fifteen
selected microsatellite markers were highly polymorphic for barley. These microsatellite markers were used to estimate the
genetic diversity among 163 barley genotypes chosen from the collection of the IPK Genebank, Germany. A total of 130 alleles
were detected by 15 barley microsatellite markers. The number of alleles per microsatellite marker varied from 5 to 15. On
average 8.6 alleles per locus were observed. Except for GMS004 all other barley microsatellite markers showed on average a
high value of gene diversity ranging from 0.64 to 0.88. The mean value of gene diversity in the wild forms and landraces was
0.74, and even among the cultivars the gene diversity ranged from 0.30 to 0.86 with a mean of 0.72. No significant differences
in polymorphism were detected by the GA and GT microsatellite markers. The estimated genetic distances revealed by the microsatellite
markers were, on average , 0.75 for the wild forms, 0.72 for landraces and 0.70 among cultivars. The microsatellite markers
were able to distinguish between different barley genotypes. The high degree of polymorphisms of microsatellite markers allows
a rapid and efficient identification of barley genotypes.
Received: 26 November 1997 / Accepted: 19 January 1998 相似文献
10.
Cottonwood hybridization affects tannin and nitrogen content of leaf litter and alters decomposition 总被引:3,自引:0,他引:3
Cottonwoods are dominant riparian trees of the western United States and are known for their propensity to hybridize. We compared
the decomposition of leaf litter from two species (Populus angustifolia and P. fremontii) and their hybrids. Three patterns were found. First, in one terrestrial and two aquatic experiments, decomposition varied
twofold among tree types. Second, backcross hybrid leaves decomposed more slowly than those of either parent. Third, the variation
in decomposition between F1 and backcross hybrids was as great as the variation between species. These results show significant differences in decomposition
in a low-diversity system, where >80% of the leaf litter comes from just two species and their hybrids. Mechanistically, high
concentrations of condensed tannins in leaves appear to inhibit decomposition (r
2=0.63). The initial condensed tannin concentration was high in narrowleaf leaves, low or undetectable in Fremont leaves, and
intermediate in F1 hybrid leaves (additive inheritance). Backcross hybrids were high in condensed tannins and were not different from narrowleaf
(dominant inheritance). Neither nitrogen (N) concentration nor the ratio of ash-free dry weight to N (a surrogate for carbon:nitrogen
ratio) were significantly correlated with decomposition. The N content of leaf material at the end of each year’s experiment
was inversely correlated with rates of litter mass loss and varied 1.6- to 2.1-fold among tree classes. This result suggests
that hybrids and their parental species are used differently by the microbial community.
Received: 7 April 1999 / Accepted: 2 November 1999 相似文献
11.
The relationship between homozygous and hemizygous transgene expression levels over generations in populations of transgenic rice plants 总被引:10,自引:0,他引:10
James VA Avart C Worland B Snape JW Vain P 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2002,104(4):553-561
Segregating T1, T2 and T3 transgenic rice populations, derived from independent particle-bombardment-mediated transformation events were examined in
order to assess the effect of gene dosage on transgene expression levels and stability. The expression level of the unselected
β-glucuronidase (gusA) reporter gene was quantified in plants from these populations. The gusA gene dosage was determined by segregation analysis of progeny seedlings at the structural level (by PCR) and at the expression
level. For some transformation events a gene dosage effect on transgene expression was observed, leading to higher transgene
expression levels in homozygous progeny than in hemizygous progeny or primary transgenic plants. However, in many other transformation
events, the homozygous state appears to be disadvantageous, being associated with lower transgene expression levels, gene
silencing or counter-selection of homozygous plants across generations. Change of gene dosage is probably one of the key factors
influencing transgene expression levels and stability in transgenic rice. This is particularly important when considering
molecular genetic studies and crop improvement programmes. The possible influence of matrix attachment regions (MARs) in increasing
the likelihood of an additive effect on transgene expression level is discussed.
Received: 21 March 2001 / Accepted: 29 June 2001 相似文献
12.
Genetic variance, coefficient of parentage, and genetic distance of six soybean populations 总被引:4,自引:0,他引:4
T. Helms G. Vallad P. McClean J. Orf 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(1):20-26
Plant breeders would like to predict which biparental populations will have the largest genetic variance. If the population
genetic variance could be predicted using coefficient of parentage or genetic distance estimates based on molecular marker
data, breeders could choose parents that produced segregating populations with a large genetic variance. Three biparental
soybean {Glycine max (L.) Merr.} populations were developed by crossing parents that were closely related, based on pedigree relationships. Three
additional biparental populations were developed by crossing parents that were assumed to be unrelated. The genetic variance
of each population was estimated for yield, lodging, physiological maturity, and plant height. Coefficient of parentage was
calculated for each pair of parents used to develop the segregating populations. Genetic distance was determined, based on
the number of random amplified polymorphic markers (RAPD) that were polymorphic for each pair of parents. Genetic distance
was not associated with the coefficient of parentage or the magnitude of the genetic variance. The genetic variance pooled
across the three closely related populations was smaller than the genetic variance pooled across the three populations derived
from crossing unrelated parents for all four traits that were evaluated.
Received: 24 April 1996 / Accepted: 17 May 1996 相似文献
13.
Regional structuring of genetic variation in short-lived rock pool populations of Branchipodopsis wolfi (Crustacea: Anostraca) 总被引:3,自引:0,他引:3
The genetic structure of three metapopulations of the southern African anostracan Branchipodopsis wolfi was compared by analysing allozyme variation at four loci (PGM, GPI, APK, AAT). In total, 17 local populations from three
sites (metapopulations) were analysed from rock pools in south-eastern Botswana ranging from 0.2 to 21 m2 in surface area. In three populations we found significant deviations from Hardy-Weinberg (H-W) equilibrium at one or more
loci due to heterozygote deficiencies. Genetic variability at one site was significantly lower than at the other sites, which
may be linked to a greater incidence of extinction and recolonisation, as the basins at this site are shallower and have shorter
hydrocycles. Across all local populations, a significant level of population differentiation was revealed. More than 90% of
this variation was explained by differentiation among sites (metapopulations), although this differentiation did not correlate
with geographic distance, or with environmental variables. Genetic differentiation among populations within metapopulations
was low, but significant at all sites. At only one of the sites was a significantly positive association measured between
genetic and geographic distance among local populations. Our data suggest that persistent stochastic events and limited effective
long-range dispersal appear to dominate genetic differentiation among populations of B. wolfi inhabiting desert rock pools. The lack of association between geographic distance and genetic or ecological differences between
rock pool sites is indicative of historical stochastic events. Low heterozygosity, the significant deviations from H-W equilibrium,
and the large inter- but low intra-site differentiation are suggestive of the importance of short-range dispersal. Gene flow
between metapopulations of B. wolfi appears to be seriously constrained by distances of 2 km or even less.
Received: 28 June 1999 / Accepted: 10 January 2000 相似文献
14.
A. M. Chèvre F. Eber A. Baranger G. Hureau P. Barret H. Picault M. Renard 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(1-2):90-98
Gene flow from glufosinate-resistant transgenic oilseed rape to wild radish was studied over two backcross generations. Under field conditions,?seed production from oilseed rape-wild radish F1 hybrids due to pollination by wild radish was always low: on average 0.12 and 0.78 seeds per 100 flowers and per plant, respectively. The cytogenetics of the resulting «BC1» plants can be explained in the main by three different genomic constitutions: either ACRrRr, 2n=37, ACRr, 2n=28 (the same chromosome number as the mother plant), or by the amphidiploid AACCRrRr, 2n=56. The probability of gene exchange through chromosome pairing was high only in plants with 2n=28 or 37 chromosomes. Due to the viability of unreduced or partially reduced female gametes, most of the «BC1» plants (81.9%) were Basta resistant whereas the analysis of oilseed rape specific loci indicated that their transmission varied with the locus. In spite of low male fertility (8.7%), an improvement of the female fertility over the F1 hybrids was observed with an average production of 1.4 and 11 seeds per 100 flowers and per plant, respectively. At the following «BC2» generation, the bar gene transmission (57.2% of Basta-resistant plants) decreased as did the chromosome number, with a majority of plants having between 24 and 27 chromosomes, with 10.5% similar to wild radish (2n=18). The lower the chromosome number, the better the fertility of the «BC2» plants. On average, 7.9 and 229.3 seeds per 100 flowers and per plant were produced. Gene-flow assessment is discussed based on these data. 相似文献
15.
T. Krugman A. Korol E. Nevo J. W. Snape O. Levy B. Rubin 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(1):46-51
Chlorotoluron is a selective phenylurea herbicide widely used for broad-leaved and annual grass weed control in cereals. Variation in the response to chlorotoluron (CT) was found in both hexaploid bread wheat (Triticum aestivum L.) and wild tetraploid wheat (Triticum dicoccoides KöRN.). Here, we describe the comparative mapping of the CT resistance gene (Su1) on chromosome 6B in bread and wild wheat using RFLP markers. In bread wheat, mapping was based on 58 F4 single-seed descent (SSD) plants of the cross between a genotype sensitive to chlorotoluron, ‘Chinese Spring’ (CS), and a resistant derivative, the single chromosome substitution line, CS (‘Cappele-Desprez’ 6B) [CS (CAP6B). In T dicoccoides, mapping was based on 37 F2 plants obtained from the cross between the CT-susceptible accession B-7 and the resistant accession B-35. Nine RFLP probes spanning the centromere were chosen for mapping. In bread wheat Su1 was found to be linked to α-Amy-1 (9.84 cM) and Xpsr371 (5.2 cM), both on the long arm of 6B, and Nor2 (2.74 cM) on the short arm. In wild wheat the most probable linkage map was Nor2-Xpsr312-Su1-Pgk2, and the genetic distances between the genes were 24.8cM, 5.3cM, and 6.8cM, respectively. These results along with other published map data indicate that the linear order of the genes is similar to that found in T. aestivum. The results of this study also show that the Su1 gene for differential response to chlorotoluron has evolved prior to the domestication of cultivated wheat and not in response to the development and use of chemicals. 相似文献
16.
I. Cattan-Toupance Y. Michalakis C. Neema 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(6-7):844-851
The genetic structure of wild common bean populations was studied in the South-Andean centre of origin of the species. Plants
were collected from 21 populations in Argentina and genetic variability was assessed for molecular and resistance markers.
Polymorphism was weak for phaseolin, the major seed-storage protein, and for RAPD markers, while a high level of polymorphism
was observed for resistance to anthracnose, one of the most important diseases of common bean. For the three traits, within-population
variability was important and represented between 43.6% and 67.5% of the total variation. Although among-population differentiation
was significant for all the traits, no correlation was found between the population distances calculated from RAPDs and resistance.
These results indicate that pathogen selection pressure may be an important factor influencing the distribution of variability
within and among host plant populations.
Received: 28 October 1997 / Accepted: 25 November 1997 相似文献
17.
Microsatellite polymorphism in natural populations of wild emmer wheat,Triticum dicoccoides,in Israel 总被引:5,自引:0,他引:5
Fahima T Röder MS Wendehake K Kirzhner VM Nevo E 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2002,104(1):17-29
Diversity in 20 microsatellite loci of wild emmer wheat, Triticum dicoccoides, was examined in 15 populations (135 genotypes) representing a wide range of ecological conditions of soil, temperature, and
water availability, in Israel and Turkey. An extensive amount of diversity at microsatellite loci was observed despite the
predominantly selfing nature of this plant species. The 20 Gatersleben wheat microsatellites (GWM), representing 13 chromosomes
of genomes A and B of wheat, revealed a total of 364 alleles, with an average of 18 alleles per GWM marker (range: 5–26).
The proportion of polymorphic loci per population averaged 0.90 (range: 0.45– 1.00); genic diversity, He, averaged 0.50 (range 0.094– 0.736); and Shannon’s information index averaged 0.84 (range 0.166–1.307). The coefficients
of genetic distance between populations were high and averaged D=1.862 (range 0.876–3.320), an indication of sharp genetic divergence over short distances. Interpopulation genetic distances
showed no association with geographic distance between the population sites of origin, which ruled out a simple isolation
by distance model. Genetic dissimilarity values between genotypes were used to produce a dendrogram of the relationships among
wild wheat populations by the unweighted pair-group method with arithmetic averages (UPGMA). The results showed that all the
wild emmer wheat populations could be distinguished. Microsatellite analysis was found to be highly effective in distinguishing
genotypes of T. dicoccoides, originating from diverse ecogeographical sites in Israel and Turkey, with 88% of the 135 genotypes correctly classified into
sites of origin by discriminant analysis. Our present microsatellite results are non-random and in agreement with the previously
obtained allozyme and RAPD patterns, although the genetic-diversity values obtained with microsatellites are much higher.
Significant correlates of microsatellite markers with various climatic and soil factors suggest that, as in allozymes and
RAPDs, natural selection causes adaptive microsatellite ecogeographical differentiation, not only in coding, but most importantly
in non-coding genomic regions. Hence, the concept of ”junk DNA” needs to be replaced by at least partly regulatory DNA. The
obtained results suggest that microsatellite markers are useful for the estimation of genetic diversity in natural populations
of T. dicoccoides and for the tagging of agronomically important traits derived from wild emmer wheat.
Received: 27 February 2001 / Accepted: 22 March 2001 相似文献
18.
A. De Bustos C. Casanova C. Soler N. Jouve 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(1):101-111
The genetic variation of 102 natural populations of wild barley growing in Spain was assessed using RAPDs (random amplified
polymorphic DNA). The plant material included the annual species H. marinum subsp. marinum (22 populations) and subsp. gussoneanum (14), H. murinum subsp. murinum (7) and subsp. leporinum (35), and the perennial species H. bulbosum (17) and H. secalinum (7). Ten of the tested 64 arbitrary 10-mer primers amplified polymorphic DNA in all taxonomic units. Analyses was performed
within and between populations, species and subspecies. The primers gave a total of 250 RAPD products. The level of polymorphism
varied between taxonomic units depending on the primers employed and the plant reproductive system. In general, the most variable
were the allogamous species H. secalinum and H. bulbosum and the autogamous H. marinum subsp. marinum. Among the amplified bands, 69 (27%) were shared by at least two different taxonomic units. The remaining bands were specific.
The results demonstrate differences in the degree of similarity between taxonomic units. Jaccard’s similarity coefficients
for interval measure within and between populations were used to produce a cluster diagram using the unweighted pair-group
method (UPGMA). The different populations of the species and subspecies of Hordeum fell into three groups. The first group contained the populations belonging to both subspecies of H. marinum, plus those of H. secalinum. The populations of H. marinum subsp. gussoneanum were very closely associated. Those of H. marinum subsp. marinum were grouped in a broad cluster. The second group, occupying the innermost position of the tree, was very closely associated
with the populations of both subspecies of H. murinum. The third branch segregated H. bulbosum. A series of RAPD markers were investigated by cleaving the amplified products of the same size with restriction endonucleases
that recognize targets of 4- or 6-bp. The production of equivalent fragments following cleavage by the same enzyme would seem
to demonstrate their homology in samples from different individuals, populations or taxonomic units.
Received: 18 May 1997 / Accepted: 22 August 1997 相似文献
19.
T. Fahima G. L. Sun A. Beharav T. Krugman A. Beiles E. Nevo 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(3-4):434-447
Genetic diversity in random amplified polymorphic DNAs (RAPDs) was studied in 110 genotypes of the tetraploid wild progenitor
of wheat, Triticum dicoccoides, from 11 populations sampled in Israel and Turkey. Our results show high level of diversity of RAPD markers in wild wheat
populations in Israel. The ten primers used in this study amplified 59 scorable RAPD loci of which 48 (81.4%) were polymorphic
and 11 monomorphic. RAPD analysis was found to be highly effective in distinguishing genotypes of T. dicoccoides originating from diverse ecogeographical sites in Israel and Turkey, with 95.5% of the 100 genotypes correctly classified
into sites of origin by discriminant analysis based on RAPD genotyping. However, interpopulation genetic distances showed
no association with geographic distance between the population sites of origin, negating a simple isolation by distance model.
Spatial autocorrelation of RAPD frequencies suggests that migration is not influential. Our present RAPD results are non-random
and in agreement with the previously obtained allozyme patterns, although the genetic diversity values obtained with RAPDs
are much higher than the allozyme values. Significant correlates of RAPD markers with various climatic and soil factors suggest
that, as in the case of allozymes, natural selection causes adaptive RAPD ecogeographical differentiation. The results obtained
suggest that RAPD markers are useful for the estimation of genetic diversity in wild material of T. dicoccoides and the identification of suitable parents for the development of mapping populations for the tagging of agronomically important
traits derived from T. dicoccoides.
Received: 13 July 1998 / Accepted: 13 August 1998 相似文献
20.
B. Desplanque P. Boudry K. Broomberg P. Saumitou-Laprade J. Cuguen H. Van Dijk 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(8):1194-1201
Beets belonging to the species Beta vulgaris L. can be found in crop, wild and weedy forms, all of which are interfertile. We studied the intra-specific genetic relationships
of about 300 individuals from 54 populations of various French geographic origins using nuclear molecular markers (five single-copy
RFLP loci and one microsatellite locus). The patterns of diversity were congruent for both types of markers. Genetic diversity
in wild beets appeared to be high, both in term of allele number and observed heterozygosity, whereas the narrowness of the
cultivated-beet gene pool was confirmed. Genetic distances between all forms showed that weed beets in northern France are
intermediates between sugar beet and inland wild beets in south-western France. This analysis allowed us to infer the paternal
origin of weed beets and furthermore, is in agreement with a previous study which focused on their maternal origin: weed beet
infesting sugar-beet fields originated from accidental and recurrent hybridization between cultivated lines and ruderal inland
wild beets during the production of commercial seeds in south-western France. Inland wild beets are genetically close to Mediterranean
coastal wild beets, but differ from other coastal forms (from Biscay, Brittany and northern France). The study of gene flow
in the beet complex contributes to the risk assessment of transgenic beets.
Received: 8 June 1998 / Accepted: 8 October 1998 相似文献