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1.
Combining genetic gain and diversity by considering average coancestry in clonal selection of Norway spruce 总被引:3,自引:0,他引:3
Y. Q. Zheng D. Lindgren O. Rosvall J. Westin 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(8):1312-1319
Genetic relationship within a population can be measured by average coancestry. This can also be expressed as an effective
number which represents the relative genetic diversity of the population. The goal of breeding can be formulated to maximise
genetic value minus average coancestry times a constant (the “penalty constant”). An iterative search algorithm can then be
used to find the best selections for meeting this goal. Two such algorithms, one for a fixed number of selections and the
other for a variable optimum number, were applied to select a mixture of field-tested Norway spruce clones with known parents.
The results were compared with those from the conventional method of restricting parental contributions to the selected population
as a means to control diversity. Coancestry-adjusted selection always yielded more gain than restricted selection at a given
effective population size (except under circumstances where the methods were equivalent). Expressed another way, at any given
level of gain, coancestry-adjusted selection maintained a larger effective population size than did restricted selection.
The relative superiority of coancestry-adjusted selection declined when the effective population size approached the lowest
value, that at which no penalty or restriction was applied. The method was extended by the second search algorithm to optimise
the selected number of clones. The optimal number of clones can be rather large when diversity is heavily valued, but the
reduction in genetic gain becomes large.
Received: 7 April 1997 / Accepted: 9 June 1997 相似文献
2.
Polymorphism, distribution, and segregation of AFLP markers in a doubled haploid rice population 总被引:18,自引:0,他引:18
M. Maheswaran P. K. Subudhi S. Nandi J. C. Xu A. Parco D. C. Yang N. Huang 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(1):39-45
We exploited the newly developed amplified fragment length polymorphism (AFLP) technique to study the polymorphism, distribution
and inheritance of AFLP markers with a doubled haploid rice population derived from ‘IR64’/‘Azucena’. Using only 20 pairs
of primer combinations, we detected 945 AFLP bands of which 208 were polymorphic. All 208 AFLP markers were mapped and distributed
over all 12 chromosomes. When these were compared with RFLP markers already mapped in the population, we found the AFLP markers
to be highly polymorphic in rice and to follow Mendelian segregation. As linkage map of rice can be generated rapidly with
AFLP markers they will be very useful for marker-assisted backcrossing.
Received: 11 April 1996 / Accepted: 14 June 1996 相似文献
3.
RAPD markers on seed bulks efficiently assess the genetic diversity of a Brassica oleracea L. collection 总被引:6,自引:0,他引:6
I. Divaret E. Margalé G. Thomas 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(6-7):1029-1035
The concept of a core collection was elaborated to fit the necessity of optimizing the management, for both conservation
and use, of genetic resources in sizeable collections. This approach requires an analysis of how the genetic variability is
structured among the accessions. The large number of heterogeneous populations in our collection of Brassica oleracea makes genetic diversity studies based on plant-to-plant analysis impracticable. To overcome this limitation, the variability
analysis by RAPD on seed bulks was investigated for its efficiency in assessing the structure of the genetic diversity of
this collection. The optimal bulk size and the bulking or sampling variation were evaluated with bulks of different size and
with replicated samples. A mixture of known genotypes was also used to characterise the band detection in bulks, and to compare
the plant-to-plant and the bulk methods. Forty seeds were chosen to represent each population. In such a bulk, the detection
of bands depended on the proportion of the genotype they were derived from in the mixture. Intense and frequent bands were
detected in the bulk with a 15% detection limit. The observed bulking or sampling variation within populations was smaller
than the variation between populations, leading to an efficient separation of populations with a clustering of all samples
of the same population. The distances calculated from bulk data were highly correlated with the distances based on the plant-to-plant
analysis. We demonstrated that RAPD on seed bulks can be used to describe the genetic diversity between populations.
Received: 27 August 1998 / Accepted: 29 September 1998 相似文献
4.
A. Singh M. S. Negi J. Rajagopal S. Bhatia U. K. Tomar P. S. Srivastava M. Lakshmikumaran 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,99(1-2):272-279
Genetic diversity was estimated in 37 neem accessions from different eco-geographic regions of India and four exotic lines
from Thailand using AFLP markers. Seven AFLP selective primer combinations generated a total of 422 amplification products.
The average number of scorable fragments was 60 per experiment, and a high degree (69.8%) of polymorphism was obtained per
assay with values ranging from 58% to 83.8%. Several rare and accession-specific bands were identified which could be effectively
used to distinguish the different genotypes. Genetic relationships within the accessions were evaluated by generating a similarity
matrix based on the Jaccard index. The phenetic dendrogram generated by UPGMA as well as principal correspondence analysis
separated the 37 Indian genotypes from the four Thai lines. The cluster analysis indicated that neem germplasm within India
constitutes a broad genetic base with the values of genetic similarity coefficient ranging from 0.74 to 0.93. Also, the Indian
genotypes were more dispersed on the principal correspondence plot, indicating a wide genetic base. The four lines from Thailand,
on the other hand, formed a narrow genetic base with similarity coefficients ranging from 0.88 to 0.92. The lowest genetic
similarity coefficient value (0.47) was observed between an Indian and an exotic genotype. The level of genetic variation
detected within the neem accessions with AFLP analysis suggests that it is an efficient marker technology for delineating
genetic relationships amongst genotypes and estimating genetic diversity, thereby enabling the formulation of appropriate
strategies for conservation and tree improvement programs.
Received: 20 October 1998 / Accepted: 28 November 1998 相似文献
5.
Characteristics of genetic variation in the progenies of protoplast-derived plants of rice, Oryza sativa cv Nipponbare 总被引:3,自引:0,他引:3
M. Yamagishi T. Koba T. Shimada K. Itoh Y. Sukekiyo K. Shimamoto 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(1):1-7
Genetic variation in protoplast-derived rice (Oryza sativa L.) plants was characterized using first and second generation selfed progenies. A total of 133 regenerated plants were obtained
from ten protoplasts of the japonica rice cultivar Nipponbare. Sixty two regenerated plants which set enough seeds for the subsequent field tests at the next
generation and were derived from five protoplasts were selected, and their selfed seeds were used as the first selfed-seed
progeny generation). Fifteen plants were selected from each of the 15 lines, and their selfed seeds were used for tests at the generation. Thirty seven lines (60%) segregated plants with detrimental mutant characters of yellow-green phenotype, dwarf stature, dense and short
panicle, or low seed fertility. According to the segregation patterns in the lines having mutated plants among those originated
from the same protoplasts, the stages of mutation induction were estimated. Additionally, five quantitative traits were changed
in almost all and lines. Varied quantitative traits of heading date, number of spikelets per panicle, and seed fertility, were in a heterozygous
state. However, culm and panicle lengths showed high uniformity, whereas reduced culm and panicle lengths were caused by mutational
changes in polygenes and/or multiple genes.
Received: 20 March 1996 / Accepted: 21 June 1996 相似文献
6.
A. H. del Rio J. B. Bamberg Z. Huaman 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(1-2):191-198
Effects of gene bank seed-increases on the genetic integrity of potato germ plasm is a major concern of gene bank managers.
Thus the Association of Potato Inter-gene-bank Collaborators (APIC), a consortium of world potato gene bank leaders, initiated
this joint research project using RAPD markers to determine genetic relationships between increased generations within accessions.
Solanum jamesii (2n=2x=24) and S. fendleri (2n=4x=48), two wild potato species native to North America, were used as plant material. These species represented two major breeding
systems found among Solanum species: outcrossing diploids and inbreeding disomic tetraploids, respectively. Comparisons were made between populations
one generation apart and between sister populations generated from a common source. Fourteen such comparisons within S. jamesii accessions had an average similarity of 96.3%, and 21 such comparisons within S. fendleri accessions had an average similarity of 96.0%. No pairs of populations were significantly different, despite the fact that
RAPD markers easily separated all of these very similar accessions within their respective species. Only one of six S. jamesii accessions analyzed showed a significant change in gene frequencies among generations. These findings indicate that there
has been minimal loss or change of genetic diversity in ex situ germplasm using the gene bank techniques standard at NRSP-6 and other world potato gene banks.
Received: 28 October 1996 / Accepted: 7 March 1997 相似文献
7.
Use of microsatellites to evaluate genetic diversity and species relationships in the genus Lycopersicon 总被引:1,自引:0,他引:1
A. E. Alvarez C.C.M. van de Wiel M.J.M. Smulders B. Vosman 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(8):1283-1292
In order to determine how informative a set of microsatellites from tomato is across the genus Lycopersicon, 17 microsatellite loci, derived from regions in and around genes, were tested on 31 accessions comprising the nine species
of the genus. The microsatellite polymorphisms were used to estimate the distribution of diversity throughout the genus and
to evaluate the efficacy of microsatellites for establishing species relationships in comparison with existing phylogeny reconstructions.
Gene diversity and genetic distances were calculated. A high level of polymorphism was found, as well as a large number of
alleles unique for species. The level of polymorphism detected with the microsatellite loci within and among species was highly
correlated with the respective mating systems, cross-pollinating species having a significantly higher gene diversity compared
to self-pollinating species. In general, microsatellite-based trees were consistent with a published RFLP-based dendrogram
as well as with a published classification based on morphology and the mating system. A tree constructed with low-polymorphic
loci (gene diversity <0.245) was shown to represent a more-reliable topology than a tree constructed with more-highly polymorphic
loci.
Received: 19 February 2001 / Accepted: 26 March 2001 相似文献
8.
Genetic biodiversity impacts of silvicultural practices and phenotypic selection in white spruce 总被引:5,自引:0,他引:5
O. P. Rajora 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,99(6):954-961
Forest-management practices relying on natural and/or artificial regeneration and domestication can significantly affect genetic
diversity. The aim of the present study was to determine and compare the genetic diversity of the pristine old-growth, naturally
and artificially regenerated and phenotypically selected white spruce, and to determine the genetic-diversity impacts of silvicultural
practices. Genetic diversity was determined and compared for 51 random amplified polymorphic DNA (RAPD) loci for the adjacent
natural old-growth, naturally regenerated and planted white spruce stands at each of four sites, one oldest plantation and
open-pollinated progeny of 30 phenotypic tree-improvement selections of white spruce from Saskatchewan. Each of the 420 white
spruce individuals sampled was genetically unique. The old-growth stands had the highest, and the phenotypic selections the
lowest, genetic diversity. The genetic diversity of the natural regeneration was comparable to that of the old-growth, whereas
the genetic diversity of the plantations was comparable to that of the selections. On average, the genetic diversity of the
old-growth and natural regeneration was significantly higher than that of the plantations and selections. The mean percent
of loci polymorphic, the number of alleles per locus, the effective number of alleles per locus, heterozygosity, and Shannon’s
index was 88.7, 83.8, 72.2 and 66.7; 1.89, 1.84, 1.72 and 1.67; 1.69, 1.62, 1.53 and 1.46; 0.381, 0.349, 0.297 and 0.259;
and 0.548, 0.506, 0.431 and 0.381 for the old-growth stands; natural regeneration; plantations; and open-pollinated progeny
of selections; respectively. Reduced genetic diversity in the plantations and selections suggest that their genetic base is
relatively narrow, and should therefore be broadened in order to maintain genetic diversity, and sustainably manage and conserve
white spruce genetic resources.
Received: 12 March 1999 / Accepted: 17 March 1999 相似文献
9.
M. Pillay E. Ogundiwin D. C. Nwakanma G. Ude A. Tenkouano 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,102(6-7):965-970
The genetic diversity and phylogenetic relationships of 29 East African highland banana (Musa spp.) cultivars and two outgroup taxa, M. acuminata Calcutta 4 and Agbagba were surveyed by RAPD analysis. A genetic similarity matrix was established based on the presence
or absence of polymorphic amplified fragments. Phylogenetic relationships were determined by UPGMA cluster analysis. RAPDs
showed that the highland bananas are closely related with a narrow genetic base. Nevertheless, there were sufficient RAPD
polymorphisms that were collectively useful in distinguishing the cultivars. The dendrogram was divisible into a major cluster
composed of all the AAA highland banana cultivars and Agbagba (AAB) and a minor cluster consisting of Kisubi (AB), Kamaramasenge
(AB) and Calcutta 4 (AA). Several subgroups are recognized within the major cluster. RAPD data did not separate beer and cooking
banana cultivars. Our study showed that RAPD markers can readily dissect genetic differences between the closely related highland
bananas and provide a basis for the selection of parents for improvement of this germplasm.
Received: 28 June 2000 / Accepted: 1 August 2000 相似文献
10.
The genetic diversity of annual wild soybeans grown in China 总被引:13,自引:0,他引:13
Y. S. Dong B. C. Zhuang L. M. Zhao H. Sun M. Y. He 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(1):98-103
Annual wild soybeans (Glycine soja), the ancestors of cultivated soybeans (G. max), are important sources of major genes for resistance to pests, diseases and environmental stresses. The study of their genetic
diversity is invaluable for efficient utilization, conservation and management of germplasm collections. In this paper, the
number of accessions, the variation of traits, the genetic diversity indexes (Shannon index) and the coefficient of variation
were employed to study the geographical distribution of accessions, genetic diversity of characters and genetic diversity
centers of annual wild soybean by statistical analysis of the database from the National Germplasm Evaluation Program of China.
Most annual wild soybeans are distributed in Northeast China, and the number of accessions decreases from the Northeast to
other directions in China. The genetic diversity indexes (Shannon index) were 0.49, 0.74, 0.02, 0.55, 1.45, 2.41, 1.27 and
1.89 for flower color, sootiness of seed coat, cotyledon color, pubescence color, hilum color, leaf shape, stem type and seed
color, respectively. Coefficients of variation were 7.1%, 28.7%, 76.43% and 18.2% for protein content, oil content, 100-seed
weight and days to maturity, respectively. Three genetic diversity centers, the Northeast, the Yellow River Valley and the
Southeast Coasts of China, are proposed based on the geographical distribution of the number of accessions, genetic diversity
and the multivariate variation coefficient. Based on these results and Vavilov’s theory of crop origination, two opposing
possible models for the formation of the three centers are proposed, either these centers are independent of each other and
the annual wild soybeans in these centers originated separately, or the Northeast center was the primary center for annual
wild soybeans in China, while the Yellow River Valley center was derived from this primary center and served as the origin
for the Southeast Coast center.
Received: 25 June 2000 / Accepted: 18 October 2000 相似文献
11.
Assessment of genetic diversity in a Morus germplasm collection using fluorescence-based AFLP markers 总被引:6,自引:0,他引:6
A. Sharma R. Sharma H. Machii 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,101(7):1049-1055
To meet various breeding objectives and to conserve the existing genetic resources of mulberry for future use, the present
study was undertaken to investigate the amount of genetic diversity and to establish the relationships between mulberry genotypes
using fluorescence-based AFLP markers. Genetic diversity was estimated in 45 mulberry accessions from different eco-geographic
regions of Japan and other parts of the world. Five primer combinations amplified an average of 110 AFLP markers per primer
combination, ranging in size from 35 to 500 bp. A high degree of polymorphism was revealed by these combinations that ranged
from 69.7 to 82.3% across all the genotypes studied. Several rare genotype-specific bands were also identified which could
be effectively utilized to distinguish different genotypes. The wide range in genetic similarity coefficients (0.58–0.99)
indicated that the mulberry germplasm collection represents a genetically diverse popu-lation. The phenetic dendrogram generated
by the UPGMA method grouped 45 accessions into four major clusters, which was in agreement with the results from conventional
methods. Clustering of some genotypes into strictly separate groups was not readily apparent and no clear interrelationships
could be depicted, in spite of their different geographic origin. In addition, AFLP analysis provided sufficient polymorphism
for DNA typing and contributed additional insights into the genetic structure of the mulberry germplasm. These results will
help in the formulation of appropriate strategies for conservation and variety improvement in mulberry, for which little or
no knowledge of genetic diversity is currently available.
Received: 30 December 1999 / Accepted: 14 March 2000 相似文献
12.
Distribution of allozymic alleles and genetic diversity in the American Barley Core Collection 总被引:4,自引:0,他引:4
F. Liu G.-L. Sun B. Salomon R. von Bothmer 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,102(4):606-615
A survey of allozymic alleles and genetic diversity was made for 151 accessions of the American Barley Core Collection. A
total of 25 alleles at ten loci were observed. Two loci were monomorphic. The average diversity index for individual loci
ranged between 0.026 and 0.649. Most significant differences in allelic frequency and genetic diversity value were found between
spring and winter barley. Spring barley showed a greatly higher average diversity than winter barley (t=2.124, P=0.071). The smallest differences in allelic frequencies and diversity values were observed between the two geographical regions,
North and South America. Rare alleles were detected only in a few accessions. Seven rare alleles were associated with spring
barley. The genetic similarities among the 151 accessions ranged from 0.20 to 1.00, which showed that a high level of genetic
variability exists in this set of core accessions. Cluster analysis and principal coordinate analysis did not give clear-cut
separation of different types of barley, but most of the winter barley accessions were closely associated.
Received: 7 April 2000 / Accepted: 13 June 2000 相似文献
13.
Geographic patterns of intraspecific variations in traits related to photosynthesis and biomass were examined in two separate
common garden experiments using seed collected from 26 Sitka alder (Alnus sinuata Rydb.) and 18 paper birch (Betula papyrifera Marsh.) populations from climatically diverse locations in British Columbia, Canada. Exchange rates of carbon dioxide and
water vapour were measured on 2-year-old seedlings to determine the maximum net instantaneous photosynthetic rate, mesophyll
conductance, stomatal conductance, and photosynthetic water use efficiency. Height, stem diameter, root and shoot dry mass
and fall frost hardiness data were also obtained. Mean population maximum photosynthetic rate ranged from 10.35 to 14.57 μmol
CO2 m–2 s–1 in Sitka alder and from 14.76 to 17.55 μmol CO2 m–2 s–1 in paper birch. Based on canonical correlation analyses, populations from locations with colder winters and shorter (but
not necessarily cooler) summers had higher maximum photosynthetic rates implying the existence of an inverse relationship
between leaf longevity and photosynthetic capacity. Significant canonical variates based on climatic variables derived for
the seed collection sites explained 58% and 41% of variation in the rate of photosynthesis in Sitka alder and paper birch,
respectively. Since growing season length is reflected in date of frost hardiness development, an intrinsic relationship was
found between photosynthetic capacity and the level of fall frost hardiness. The correlation was particularly strong for paper
birch (r=–0.77) and less strong for Sitka alder (r=–0.60). Mean population biomass accumulation decreased with increased climate coldness. These patterns may be consequential
for evaluation of the impact of climate change and extension of the growing season on plant communities.
Received: 12 July 1999 / Accepted: 24 November 1999 相似文献
14.
Arne Sellin 《Trees - Structure and Function》2000,14(4):215-222
Different calculation methods, based on needle geometry, for estimating both projected area (PLA) and total surface area (TLA)
of foliage in Norway spruce [Picea abies (L.) Karst.] were compared. Seventy-eight shoots of four age classes were sampled from both the basal and top thirds of crowns.
Three dimensions (the length, minor and major diameters) of needles were taken, and the needle shape was approximated to a
parallelepiped or ellipsoid. There was a perfect coincidence of the measured and estimated values of PLA calculated as the
width of the needle projection multiplied by needle length, and corrected for needle taper (method III), or when the needle
projection was treated as a rectangle joined with half-ellipses at both ends (method IV). The most reliable estimations of
TLA resulted from treating the needle sides as faces of the parallelepiped tapering at their ends in the form of half-ellipses.
The ratio of TLA to PLA ranged from 2.2 to 4.0 depending on the needle morphology. Needle minor diameter (anatomical width;
D
1) was found to be a better morphological index of the spruce foliage than needle flatness, i.e. the ratio of major to minor
diameter. Expressing the factor for converting PLA to TLA as a function of D
1 considerably improved the precision of the estimates. Close relationships were established between specific leaf area, expressed
on both a projected area (SLAP) and total surface area basis (SLAT), needle dry weight (R
2 was 0.799 and 0.852, respectively) and minor diameter of needles (R
2 was 0.701 and 0.554, respectively).
Received: 14 April 1998 / Accepted: 23 September 1999 相似文献
15.
The use of microsatellites for detecting DNA polymorphism, genotype identification and genetic diversity in wheat 总被引:35,自引:0,他引:35
M. Prasad R. K. Varshney J. K. Roy H. S. Balyan P. K. Gupta 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,100(3-4):584-592
A set of 20 wheat microsatellite markers was used with 55 elite wheat genotypes to examine their utility (1) in detecting
DNA polymorphism, (2)in the identifying genotypes and (3) in estimating genetic diversity among wheat genotypes. The 55 elite
genotypes of wheat used in this study originated in 29 countries representing six continents. A total of 155 alleles were
detected at 21 loci using the above microsatellite primer pairs (only 1 primer amplified 2 loci; all other primers amplified
1 locus each). Of the 20 primers amplifying 21 loci, 17 primers and their corresponding 18 loci were assigned to 13 different
chromosomes (6 chromosomes of the A genome, 5 chromosomes of the B genome and 2 chromosomes of the D genome). The number of
alleles per locus ranged from 1 to 13, with an average of 7.4 alleles per locus. The values of average polymorphic information
content (PIC) and the marker index (MI) for these markers were estimated to be 0.71 and 0.70, respectively. The (GT)n microsatellites were found to be the most polymorphic. The genetic similarity (GS) coefficient for all possible 1485 pairs
of genotypes ranged from 0.05 to 0.88 with an average of 0.23. The dendrogram, prepared on the basis of similarity matrix
using the UPGMA algorithm, delineated the above genotypes into two major clusters (I and II), each with two subclusters (Ia,
Ib and IIa, IIb). One of these subclusters (Ib) consisted of a solitary genotype (E3111) from Portugal, so that it was unique
and diverse with respect to all other genotypes belonging to cluster I and placed in subcluster Ia. Using a set of only 12
primer pairs, we were able to distinguish a maximum of 48 of the above 55 wheat genotypes. The results demonstrate the utility
of microsatellite markers for detecting polymorphism leading to genotype identification and for estimating genetic diversity.
Received: 15 May 1999 / Accepted: 27 July 1999 相似文献
16.
Seed output is determined by two processes: resource acquisition and the allocation of resources to seeds. In order to clarify
how the reaction norm of seed output is controlled by the phenotypic expression of its two components, we examined the genetic
components of plasticity of seed dry mass, plant size, and reproductive allocation under different conditions of soil nutrient
availability and conspecific competition among eight families of Abutilon theophrasti. Without competition, the reaction norm of seed mass of the families crossed between the lowest and other nutrient levels,
although neither of its components, plant size and reproductive allocation, showed such a response. The crossing reaction
norm (i.e., reversal of relative fitnesses of different genotypes along the environmental gradient) of seed mass resulted
from (1) a trade-off between plant size and reproductive allocation, and (2) changes in the relative magnitude of genetic
variances in plant size and reproductive allocation with soil nutrient availability. While allocation was more important in
determining seed mass under limiting nutrient conditions, plant size became more important under high-nutrient conditions.
There were no significant genetic variances in seed mass, plant size, and reproductive allocation in the competition treatment,
except at the highest nutrient level. The results show that plant competition mitigated the effects of genetic differences
in plant performance among the families. We discuss the results in relation to maintenance of genetic variation within a population.
Received: 16 August 1996 / Accepted 26 April 1997 相似文献
17.
The HOX-like gene Cnox2-Pc is expressed at the anterior region in all life cycle stages of the jellyfish Podocoryne carnea 总被引:3,自引:0,他引:3
The marine jellyfish Podocoryne carnea (Cnidaria, Hydrozoa) has a metagenic life cycle consisting of a larva, a colonial polyp and a free-swimming jellyfish (medusa).
To study the function of HOX genes in primitive diploblastic animals we screened a library of P. carnea cDNA using PCR primers derived from the most conserved regions in helix 1 and helix 3 of the homeobox. A novel gene, Cnox2-Pc, has been isolated and characterized. Cnox2-Pc is a HOX cluster-like gene, and its homeodomain shows similarity to the Deformed subfamily of HOM-C/HOX genes. In situ hybridization revealed that Cnox2-Pc is expressed in the anterior region of the larva, the polyp head, and the most apical ectoderm of the differentiating bud
during medusa development. In adult medusa expression is restricted to the gastrovascular entoderm. The results suggest that
Cnox2-Pc is involved in establishment of an anterior-posterior axis during development in primitive metazoans.
Received: 23 February 1999 / Accepted: 27 July 1999 相似文献
18.
K. S. Kang D. Lindgren T. J. Mullin 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(6-7):1099-1107
Genetic gain and the gene diversity of seed crops from clonal seed orchards were formulated considering genetic selection,
fertility variation and pollen contamination, and compared for five different management strategies. Genetic response was
studied as a function of orchard management tactics. Management variables included the proportion of clones left after genetic
thinning and/or selective seed harvesting. Formulae were derived to calculate gene diversity (expressed as group coancestry
or status number) based on the sex ratio in an orchard population. The influence of having different sets of clones serving
as seed parents, or pollen parents, or as both, was analysed. In addition, the impact on genetic gain and the gene diversity
of seed crops was studied quantitatively as a function of the quantity and quality of gene flow from outside the orchard.
The negative impact of fertility variation among orchard genotypes on the gene diversity of the seed crop was quantified.
Numerical examples were given to illustrate the impact of orchard management alternatives on genetic gain and gene diversity.
The formulae and results of this study can be used for identifying favourable alternatives for the management of seed orchards.
Received: 16 December 2000 / Accepted: 13 March 2001 相似文献
19.
The morphology and location of crystals encountered in the mature seeds of Norway spruce, Picea abies (L.) Karst., were examined using light and field emission scanning electron microscopy (FESEM). Crystals of various forms
and sizes were discovered in different regions and tissues of seeds, particularly in the testa and the nucellus. Both solitary
crystals and druses were occasionally enveloped by protrusions of the megaspore membranes or the cuticle of the megagametophyte.
Histological studies and acid solubility tests coupled with analysis using energy dispersive X-ray microanalysis and X-ray
diffraction evinced the crystals as calcium oxalate, but were unable to identify different hydration forms. Calcium oxalate
crystals were most abundant in the damaged and infected tissues, and in the structures that desiccate during the development
of the seed. Based on these observations we concluded that the accumulation of calcium oxalate is a regular process belonging
to maturation and defense mechanism in spruce seeds.
Received: 1 July 1998 / Accepted: 20 September 1998 相似文献
20.
Allan J. Baker Annette D. Greenslade Laura M. Darling J. Cam Finlay 《Conservation Genetics》2008,9(3):495-505
To assess genetic diversity in the blue-listed purple martin (Progne subis) population in British Columbia, we analysed mitochondrial control region sequences of 93 individuals from British Columbia
and 121 individuals collected from seven localities of the western and eastern North American subspecies P. s. arboricola and P. s. subis, respectively. Of the 47 haplotypes we detected, 34 were found exclusively in western populations, and 12 were found only
in eastern populations. The most common eastern haplotype (25) was also found in three nestlings in British Columbia and one
in Washington. Another British Columbia nestling had a haplotype (35) that differed by a C to T transition from haplotype
25. Coalescent analysis indicated that these five nestlings are probably descendents of recent immigrants dispersing from
east to the west, because populations were estimated to have diverged about 200,000–400,000 ybp, making ancestral polymorphism
a less likely explanation. Maximum likelihood estimates of gene flow among all populations detected asymmetrical gene flow
into British Columbia not only of rare migrants from the eastern subspecies in Alberta but also a substantial number of migrants
from the adjacent Washington population, and progressively lower numbers from Oregon in an isolation-by distance pattern.
The influx of migrants from different populations is consistent with the migrant-pool model of recolonization which has maintained
high genetic diversity in the small recovering population in British Columbia. Thus, the risk to this population is not from
genetic erosion or inbreeding following a severe population crash, but from demographic stochasticity and extinction in small
populations. 相似文献