共查询到20条相似文献,搜索用时 15 毫秒
1.
C. Lexer B. Heinze H. Steinkellner S. Kampfer B. Ziegenhagen J. Glössl 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,99(1-2):185-191
Microsatellites were used for genetic analysis of maternal half-sib families of Quercus robur, pedunculate oak, a highly outcrossing tree species. A model half-sib family including the mother tree and 28 offspring individuals
as well as samples from six single tree harvests from a forestry company, 4–8 individuals each, were genotyped at 9 microsatellite
loci. No prior information about the genotypes of the mother trees were available for these six seedlot samples. Analysis
of the model half-sib family revealed that the maternal genotypes can be inferred from the offspring genotypes due to codominant
Mendelian inheritance of the microsatellites. Analysis of the single tree harvests, supplied as six maternal half-sib families,
revealed contaminations with unrelated seedlings in four out of six cases. Average relatedness between the remaining individuals
indicated that they were indeed half-sibs, probably with a proportion of full-sibs among them. For five samples the genotypes
of the mother trees were partially inferred from the offspring genotypes. The supposed number of five different mother trees
was confirmed by direct comparison of the maternal genotypes and by pairwise FST calculations between families. We show that correct genotype reconstruction can be confirmed by monitoring recombination
events between linked markers. Our results demonstrate that microsatellite analysis is a suitable means to approach two key
problems of legal regulations on the marketing of seed material from pedunculate oak: the number of trees included in seed
harvests and the detection of seed contaminations.
Received: 4 November 1998 / Accepted: 28 November 1998 相似文献
2.
Doriane Pican?o-Rodrigues Spartaco Astolfi-Filho Maristerra R. Lemes Rogerio Gribel Alexandre M. Sebbenn Charles R. Clement 《Genetics and molecular biology》2015,38(1):59-66
Peach palm (Bactris gasipaes) is cultivated by many indigenous and
traditional communities from Amazonia to Central America for its edible fruits, and
is currently important for its heart-of-palm. The objective of this study was to
investigate the mating system of peach palm, as this is important for conservation
and breeding. Eight microsatellite loci were used to genotype 24 open-pollinated
progenies from three populations of the Pampa Hermosa landrace maintained in a
progeny trial for genetic improvement. Both the multi-locus outcrossing rates (0.95
to 0.99) and the progeny level multi-locus outcrossing rates (0.9 to 1.0) were high,
indicating that peach palm is predominantly allogamous. The outcrossing rates among
relatives were significantly different from zero (0.101 to 0.202), providing evidence
for considerable biparental inbreeding within populations, probably due to farmers
planting seeds of a small number of open-pollinated progenies in the same plot. The
correlations of paternity estimates were low (0.051 to 0.112), suggesting a large
number of pollen sources (9 to 20) participating in pollination of individual fruit
bunches. Effective population size estimates suggest that current germplasm
collections are insufficient for long-term ex situ conservation. As
with most underutilized crops, on farm conservation is the most important component
of an integrated conservation strategy. 相似文献
3.
Estimation of outcrossing rate in a breeding population of Eucalyptus urophylla with dominant RAPD and AFLP markers 总被引:7,自引:0,他引:7
F. A. Gaiotto M. Bramucci D. Grattapaglia 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(5-6):842-849
Eucalyptus breeding is typically conducted by selection in open-pollinated progenies. As mating is controlled only on the female side
of the cross, knowledge of outcrossing versus selfing rates is essential for maintaining adequate levels of genetic variability
for continuous gains. Outcrossing rate in an open-pollinated breeding population of Eucalyptus urophylla was estimated by two PCR-based dominant marker technologies, RAPD and AFLP, using 11 open-pollinated progeny arrays of 24
individuals. Estimated outcrossing rates indicate predominant outcrossing and suggest maintenance of adequate genetic variability
within families. The multilcous outcrossing rate (tm) estimated from RAPD markers (0.93±0.027), although in the same range, was higher (α>0.01) than the estimate based on AFLP
(0.89±0.033). Both estimates were of similar magnitude to those estimated for natural populations using isozymes. The estimated
Wright’s fixation index was lower than expected based on tm possibly resulting from selection against selfed seedlings when sampling plants for the study. An empirical analysis suggests
that 18 is the minimum number of dominant marker loci necessary to achieve robust estimates of tm. This study demonstrates the usefulness of dominant markers, both RAPD and AFLP, for estimating the outcrossing rate in breeding
and natural populations of forest trees. We anticipate an increasing use of such PCR-based technologies in mating-system studies,
in view of their high throughput and universality of the reagents, particularly for species where isozyme systems have not
yet been optimized.
Received: 25 March 1997 / Accepted: 13 May 1997 相似文献
4.
Francimary da Silva Carneiro Alexandre Magno Sebbenn Milton Kanashiro Bernd Degen 《Biotropica》2007,39(5):628-636
Six microsatellite loci were used to compare the mating system and gene flow in two consecutive years of a natural, unlogged population of Symphonia globulifera in a 500 ha experimental plot in the Brazilian Amazon (Flona Tapajós). The species had a low density of reproductive trees per hectare ( d = 0.46 trees/ha). We analyzed 205 trees and 261 and 487 open-pollinated seeds from 26 and 30 mother-trees in the years 2002 and 2003, respectively. A significant spatial genetic structure was detected for the adult trees for distances up to 100 m. We observed only small interannual differences in multilocus outcrossing rate ( , ), biparental inbreeding ( , ), and paternity correlation ( , ). The number of pollen donors contributing to mating of each tree in both years was estimated to be low ( ). Using TwoGener analysis to calculate the density of reproductive trees and the distance of pollen dispersal for normal and exponential models, the lowest error was detected for exponential model. For this model, the estimated density of reproductive trees was lower in 2002 ( trees/ha) than 2003 ( trees/ha), resulting in a higher distance of pollen dispersal in 2002 ( m) than 2003 ( m), although these changes did not affect the outcrossing and correlated mating rates. 相似文献
5.
S. E. Surles J. Arnold A. Schnabel J. L. Hamrick B. C. Bongarten 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1990,80(1):49-56
Summary When conducting tree breeding experiments, geneticists often assume that individuals from open-pollinated families are halfsibs. The reliability of this assumption was tested using data from enzyme electrophoresis to estimate the genetic relatedness among progeny within 22 open-pollinated families of Robinia pseudoacacia L. (black locust) and 34 open-pollinated families of Gleditsia triacanthos L. (honey locust) from natural stands. An algorithm employing population estimates of fixation indices, pollen allele frequencies, and selfing rates was used to calculate the mean expected number of alleles in common across loci under assumptions of either full-sib (i.e., a single pollen parent) or half-sib (i.e., random mating) relationships. For each open-pollinated family, the average coefficient of relationship among progeny was calculated by linear interpolation from the observed number of alleles in common. For most families of both species, coefficients were significantly higher than 0.25 (half-sib relation), but were significantly lower than 0.50 (full-sib relation). These results suggest that the assumption of a half-sib relationship among progeny of open-pollinated families is violated for these tree species. More critical to the estimation of heritabilities and the prediction of genetic gains was the observation that estimates of the coefficient of relationship varied widely among open-pollinated families (for R. pseudoacacia r
0=0.20–0.43, mean=0.34; for G. triacanthos r
0=0.29–0.55, mean=0.36). 相似文献
6.
M F Breed K M Ottewell M G Gardner M H K Marklund M G Stead J B C Harris A J Lowe 《Heredity》2015,115(2):100-107
Habitat fragmentation has been shown to disrupt ecosystem processes such as plant-pollinator mutualisms. Consequently, mating patterns in remnant tree populations are expected to shift towards increased inbreeding and reduced pollen diversity, with fitness consequences for future generations. However, mating patterns and phenotypic assessments of open-pollinated progeny have rarely been combined in a single study. Here, we collected seeds from 37 Eucalyptus incrassata trees from contrasting stand densities following recent clearance in a single South Australian population (intact woodland=12.6 trees ha−1; isolated pasture=1.7 trees ha−1; population area=10 km2). 649 progeny from these trees were genotyped at eight microsatellite loci. We estimated genetic diversity, spatial genetic structure, indirect contemporary pollen flow and mating patterns for adults older than the clearance events and open-pollinated progeny sired post-clearance. A proxy of early stage progeny viability was assessed in a common garden experiment. Density had no impact on mating patterns, adult and progeny genetic diversity or progeny growth, but was associated with increased mean pollen dispersal. Weak spatial genetic structure among adults suggests high historical gene flow. We observed preliminary evidence for inbreeding depression related to stress caused by fungal infection, but which was not associated with density. Higher observed heterozygosities in adults compared with progeny may relate to weak selection on progeny and lifetime-accumulated mortality of inbred adults. E. incrassata appears to be resistant to the negative mating pattern and fitness changes expected within fragmented landscapes. This pattern is likely explained by strong outcrossing and regular long-distance pollen flow. 相似文献
7.
Inheritance and diversity of simple sequence repeat (SSR) microsatellite markers in various families of Picea abies 总被引:1,自引:0,他引:1
A large number of sequence-specific SSRs were screened by using electrophoresis on metaphore agarose gels with the bands visualized by ethidium bromide staining. Many SSRs appeared as codominant and many as dominant markers, with presence or absence of bands. A simple Mendelian inheritance pattern for most codominant and dominant SSR loci was found. For many codominant SSR markers, null alleles were detected. The proportion of dominant microsatellites detected in this study (close to 50 %) was much higher than that commonly reported in many other studies. A high proportion of dominant markers together with a high frequency of codominant markers with null alleles may represent two important limitations for the use of microsatellites in different studies. On the other hand, many polymorphic codominant SSR microsatellite markers were found to be highly repeatable, and can be used for population studies, seed certification, quality control of controlled crosses, paternity analysis, pollen contamination, and mapping of QTL in related families. In this paper, we report on the inheritance pattern and diversity of codominant and dominant SSR microsatellites in seven families of Picea abies sharing a common mother. 相似文献
8.
Amplified fragment length polymorphisms (AFLP) were used to study the inheritance of shell color in Argopecten irradians.
Two scallops, one with orange and the other with white shells, were used as parents to produce four F1 families by selfing and outcrossing. Eighty-eight progeny, 37 orange and 51 white, were randomly selected from one of the
families for segregation and mapping analysis with AFLP and microsatellite markers. Twenty-five AFLP primer pairs were screened,
yielding 1138 fragments, among which 148 (13.0%) were polymorphic in two parents and segregated in progeny. Six AFLP markers
showed significant (P < 0.05) association with shell color. All six loci were mapped to one linkage group. One of the markers, F1f335, is completely
linked to the gene for orange shell, which we designated as Orange1, without any recombination in the progeny we sampled.
The marker was amplified in the orange parent and all orange progeny, but absent in the white parent and all the white progeny.
The close linkage between F1f335 and Orange1 was validated using bulk segregation analysis in two natural populations, and
all our data indicate that F1f335 is specific for the shell color gene, Orange1. The genomic mapping of a shell color gene
in bay scallop improves our understanding of shell color inheritance and may contribute to the breeding of molluscs with desired
shell colors. 相似文献
9.
Verdú M González-Martínez SC Montilla AI Mateu I Pannell JR 《Evolution; international journal of organic evolution》2006,60(10):2056-2063
Ovule discounting denotes the reduction in the number of ovules available for cross-fertilization due to the interference of inferior pollen. Traditionally, ovule discounting has been discussed solely from the perspective of compromised outcrossing opportunities as a result of selfing, but the principle is more general. Here, we extend its applicability beyond the simple contrast between selfing and outcrossing by showing that, in the cryptically dioecious tree species Fraxinus ornus, ovule discounting through frequent outcrossing with inferior fathers also constitutes a substantial cost of mating. In F. ornus, hermaphrodites produce pollen capable of siring offspring, but these offspring are less viable than those sired by males and are inferred to produce few, if any, surviving progeny. In this paper, we used microsatellite markers to analyze the mating system and paternity in a wild population of F. ornus. We found that the effective number of sires per mother was low (N(ep) = 2.93 to 4.95), and that paternity was correlated among progeny sampled from the same mother, but not among progeny sampled from neighboring mothers. Despite the existence of a local spatial genetic structure (up to 30 m), we found no evidence of biparental inbreeding. There was negligible selfing by hermaphrodites, but they sired approximately one fourth of the seeds produced by other hermaphrodites. Given that these progeny are not inferred to reach reproductive maturity, this constitutes a substantial cost of ovule discounting in the broad sense. We discuss the possible reasons for why hermaphrodites invest resources into inferior pollen. 相似文献
10.
Aligning male and female linkage maps of apple (Malus pumila Mill.) using multi-allelic markers 总被引:12,自引:0,他引:12
C. Maliepaard F. H. Alston G. van Arkel L. M. Brown E. Chevreau F. Dunemann K. M. Evans S. Gardiner P. Guilford A. W. van Heusden J. Janse F. Laurens J. R. Lynn A. G. Manganaris A. P. M. den Nijs N. Periam E. Rikkerink P. Roche C. Ryder S. Sansavini H. Schmidt S. Tartarini J. J. Verhaegh M. Vrielink-van Ginkel G. J. King 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(1-2):60-73
Linkage maps for the apple cultivars ‘Prima’ and ‘Fiesta’ were constructed using RFLP, RAPD, isozyme, AFLP, SCAR and microsatellite
markers in a ‘Prima’בFiesta’ progeny of 152 individuals. Seventeen linkage groups, putatively corresponding to the seventeen
haploid apple chromosomes, were obtained for each parent. These maps were aligned using 67 multi-allelic markers that were
heterozygous in both parents. A large number of duplicate RFLP loci was observed and, in several instances, linked RFLP markers
in one linkage group showed corresponding linkage in another linkage group. Distorted segregation was observed mainly in two
regions of the genome, especially in the male parent alleles. Map positions were provided for resistance genes to scab and
rosy leaf curling aphid (Vf and Sd
1, respectively) for the fruit acidity gene Ma and for the self-incompatibility locus S. The high marker density and large number of mapped codominant RFLPs and some microsatellite markers make this map an ideal
reference map for use in other progenies also and a valuable tool for the mapping of quantitative trait loci.
Received: 17 November 1997 / Accepted: 9 December 1997 相似文献
11.
Pratima Sinha Md Aminul Islam Madan Singh Negi Shashi Bhushan Tripathi 《Physiology and Molecular Biology of Plants》2015,21(4):605-609
In this paper, we report the estimates of outcrossing rates using open-pollinated progeny arrays of 40 BC1 individuals of Jatropha developed as a result of interspecific hybridization between J. curcas and J. integerrima. For analysis PCR-based dominant AFLP and codominant SSR markers were used. The multilocus outcrossing rate (tm) estimated from AFLP markers (0.892 ± 0.112) are almost in the same range with SSR (0.884 ± 0.293) markers which indicate a high level of heterozygosity. A low value of inbreeding coefficient (F) also points out to the fact that outcrossing was the prevalent mode of reproduction in Jatropha and suggests maintenance of adequate genetic variability within families.
Electronic supplementary material
The online version of this article (doi:10.1007/s12298-015-0318-y) contains supplementary material, which is available to authorized users. 相似文献12.
Mating patterns play a critical role in the maintenance of genetic variation. We analyzed the mating system in a recently fragmented population of the Andean oak (Quercus humboldtii) using four microsatellite loci. Five fragments in northeastern Colombia, South America, were selected consisting of 30.4 trees on average. We sampled about 30 seeds from three target trees in each fragment and genotyped them with four microsatellite loci with a total of 40 alleles across loci. Progenies were analyzed under the mixed mating system model (MLTR program) and the TwoGener pollen pool structure analyses. The number of unshared pollen donors per family (Nu) was estimated using gametotypic counts with the program HAPLOTYPES. Low selfing (3%) is occurring at the population and fragment level. Biparental inbreeding is present (4.9%), but reduced, in the largest fragment. The average pollen neighborhood size (Nep = 5.1 to 6.1) appears comparable to other oak species in sparse landscapes. In contrast, Nu consists of 2 to 4 main donors, although up to 12 are possible, with the mode positively correlated with fragment size. The Andean oak appears to be a resilient species capable of tolerating population subdivision, provided landscapes include large fragments. 相似文献
13.
Data on multiple paternity within broods has been gathered in several animal species, and comparable data in plants would be of great importance to understand the evolution of reproductive traits in a common framework. In this study, we first isolated and characterized six microsatellite loci from the dioecious plant Silene latifolia (Caryophyllaceae). The polymorphism of the loci was assessed in 60 individual females from four different populations. Two of the investigated loci showed a pattern of inheritance consistent with X-linkage. These microsatellite loci were highly polymorphic and therefore useful tools for parentage analysis. We then used four of the markers to determine paternity within naturally pollinated fruits in four European populations. This study revealed widespread multiple paternity in all populations investigated. The minimum number of fathers per fruit varied from one to nine, with population means ranging from 3.4 to 4.9. The number of fathers per fruit was not significantly correlated with offspring sex ratios. High prevalence of multiple paternity within fruits strongly suggest that pollen competition is likely to occur in this species. This may substantially impact male reproductive success and possibly contribute to increase female and offspring fitness, either through postpollination selection or increased genetic diversity. Wide variation in outcrossing rates may be an overlooked aspect of plant mating systems. 相似文献
14.
Maria João Gaspar Ana I. de-Lucas Ricardo Alía Jorge Almiro Pinto Paiva Elena Hidalgo José Louzada Helena Almeida Santiago C. González-Martínez 《Tree Genetics & Genomes》2009,5(4):609-616
The management of a genetic improvement program is based on the knowledge of the genetic parameters and their relationships
to determine the genetic gains. Knowledge of the coefficient of coancestry (θ) is a requirement for efficient progeny testing scheme and for estimating additive variance components for any quantitative
trait. When using open-pollinated families, most authors assume that the seedlings are related as half-sibs, but this is not
always true. Our aim was to estimate a mean value of the coancestry coefficient of the families present in a maritime pine
Pinus pinaster Ait. (maritime or cluster pine) progeny trial originating from seed collected in a clonal seed orchard and to study how deviations
from the standard assumption of θ = 0.125 affect heritability estimations. Five highly polymorphic microsatellite markers were scored in 125 offspring from
a subsample of five families from the progeny trial. The mean value of the coancestry coefficient of the families present
in this progeny trial was 0.130. Differences between the unadjusted and adjusted heritability estimates were more pronounced
in wood density (0.609 and 0.586, respectively) than in diameter (0.166 and 0.154, respectively). We conclude that in the
trial, the associated error in heritability estimates due to the inclusion of full-sibs, when assuming a standard coefficient
of relationship among open-pollinated sibs of 0.250, was low and that this result is robust with respect to the number of
families sampled, given unbiased estimates of average relationship among offspring within sib families. 相似文献
15.
J. M. Feres A. M. Sebbenn M. C. Guidugli M. A. Mestriner M. L. T. Moraes A. L. Alzate-Marin 《Conservation Genetics》2012,13(2):393-405
For many tree species, mating system analyses have indicated potential variations in the selfing rate and paternity correlation
among fruits within individuals, among individuals within populations, among populations, and from one flowering event to
another. In this study, we used eight microsatellite markers to investigate mating systems at two hierarchical levels (fruits
within individuals and individuals within populations) for the insect pollinated Neotropical tree Tabebuia roseo-alba. We found that T. roseo-alba has a mixed mating system with predominantly outcrossed mating. The outcrossing rates at the population level were similar
across two T. roseo-alba populations; however, the rates varied considerably among individuals within populations. The correlated paternity results
at different hierarchical levels showed that there is a high probability of shared paternal parentage when comparing seeds
within fruits and among fruits within plants and full-sibs occur in much higher proportion within fruits than among fruits.
Significant levels of fixation index were found in both populations and biparental inbreeding is believed to be the main cause
of the observed inbreeding. The number of pollen donors contributing to mating was low. Furthermore, open-pollinated seeds
varied according to relatedness, including half-sibs, full-sibs, self-sibs and self-half-sibs. In both populations, the effective
population size within a family (seed-tree and its offspring) was lower than expected for panmictic populations. Thus, seeds
for ex situ conservation genetics, progeny tests and reforestation must be collected from a large number of seed-trees to
guarantee an adequate effective population in the sample. 相似文献
16.
Although there are many reasons to expect distinct pollinator types to differentially affect a plant's reproductive success, few studies have directly examined this question. Here, we contrast the impact of two kinds of pollinators on reproductive success via male and female functions in the Rocky Mountain columbine, Aquilegia coerulea . We set up pollinator exclusion treatments in each of three patches where Aquilegia plants were visited by either day pollinators (majority bumble bees), by evening pollinators (hawkmoths), or by both (control). Day pollinators collected pollen and groomed, whereas evening pollinators collected nectar but did not groom. Maternal parents, potential fathers and progeny arrays were genotyped at five microsatellite loci. We estimated female outcrossing rate and counted seeds to measure female reproductive success and used paternity analysis to determine male reproductive success. Our results document that bumble bees frequently moved pollen among patches of plants and that, unlike hawkmoths, pollen moved by bumble bees sired more outcrossed seeds when it remained within a patch as opposed to moving between patches. Pollinator type differentially affected the outcrossing rate but not seed set, the number of outcrossed seeds or overall male reproductive success. Multiple visits to a plant and more frequent visits by bumble bees could help to explain the lack of impact of pollinator type on overall reproductive success. The increase in selfing rate with hawkmoths likely resulted from the abundant pollen available in experimental flowers. Our findings highlighted a new type of pollinator interactions that can benefit a plant species. 相似文献
17.
In forests with gap disturbance regimes, pioneer tree regeneration is typically abundant following stand-replacing disturbances, whether natural or anthropogenic. Differences in pioneer tree density linked to disturbance regime can influence pollinator behaviour and impact on mating patterns and genetic diversity of pioneer populations. Such mating pattern shifts can manifest as higher selfing rates and lower pollen diversity in old growth forest populations. In secondary forest, where more closely related pollen donors occur, an increase in biparental inbreeding is a potential problem. Here, we investigate the consequences of secondary forest colonisation on the mating patterns and genetic diversity of open-pollinated progeny arrays for the long-lived, self-compatible pioneer tree, Vochysia ferruginea, at two Costa Rican sites. Five microsatellite loci were screened across adult and seed cohorts from old growth forest with lower density, secondary forest with higher density, and isolated individual trees in pasture. Progeny from both old growth and secondary forest contexts were predominantly outcrossed (tm=1.00) and experienced low levels of biparental inbreeding (tm−ts=0.00–0.04). In contrast to predictions, our results indicated that the mating patterns of V. ferruginea are relatively robust to density differences between old growth and secondary forest stands. In addition, we observed that pollen-mediated gene flow possibly maintained the genetic diversity of open-pollinated progeny arrays in stands of secondary forest adults. As part of a natural resource management strategy, we suggest that primary forest remnants should be prioritised for conservation to promote restoration of genetic diversity during forest regeneration. 相似文献
18.
Rosane G. Collevatti Raquel Estolano Silmara F. Garcia John D. Hay 《Tree Genetics & Genomes》2009,6(4):555-564
We investigated pollen dispersal and breeding structure in the tropical tree species Caryocar brasiliense Camb. (Caryocaraceae), using genetic data from ten microsatellite loci. All adult trees (101) within a patch of 8.3 ha were
sampled, and from these adults 18 open-pollinated maternal progeny arrays were analyzed (280 seeds from 265 fruits). Most
fruits presented only one seed (median equal to 1.000) and mean number of ripened seeds per fruit was 1.053 (SD = 0.828).
Our results showed that C. brasiliense presents a mixed-mating system, with 11.4% of self-pollination, multilocus outcrossing rate of t
m = 0.891 ± 0.025, and high probability of full-sibship within progeny arrays (r
p = 0.135 ± 0.032). Outcrossing rate and self-pollination varied significantly among mother trees. We could detect a maximum
pollen dispersal distance of ∼500 m and a mean pollen dispersal distance of ∼132 m. However, most pollination events (80%)
occurred at distances less than 200 m. Our results also indicated that pollen dispersal is restricted to a neighborhood of
5.4 ha with rare events of immigration (∼1% N
e
m = 0.35). C. brasiliense also presents a significant but weak spatial genetic structure (Sp = 0.0116), and extension of pollen dispersal distance was greater than seed dispersal (N
b = 86.20 m). These results are most likely due to the foraging behavior of pollinators that may have limited flight range.
The highly within-population synchronous flowering, high population density, and clumped distribution reinforce pollinator
behavior and affect residence time leading to a short-distance pollen dispersal. 相似文献
19.
F. C. Yeh K. Morgan 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,73(6):799-808
Summary Arrays of open-pollinated seeds were assayed for allozyme polymorphisms at ten loci (Aat2, Est1, G6pd, Idh, Mdh2, Mdh3, Pgm, Sod, 6Pgd1, 6Pgd2) to obtain estimates of the outcrossing rate and assess multilocus association in a natural population of coastal Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco. The allele frequencies in the samples of adult trees and pollen-gamete pool were similar. Maximum-likelihood estimators of the outcrossing rate for individual loci and two multilocus models were derived using counting methods. The single-locus maximum likelihood estimates (MLEs) of the outcrossing rate were significantly heterogeneous; they varied over a more than two-fold range from 0.404 to 0.935, with an average MLE of 0.741. Both multilocus MLEs of the outcrossing rate were 0.887. The sample of trees was in random mating equilibrium when assessed on a pairwise-locus basis using Burrows' composite measure of gametic disequilibrium, with one exception (Mdh2 Sod) that was attributable to a rare gametic class. In the sample of pollen gametes, 5 of the 45 pairwise-locus associations were nominally significant at the 0.05 level: Idh Est1, Mdh2 Sod, Aat2 Est1, Aat2 Mdh3, and Est1 Mdh3. These apparent associations were attributable in most cases to the relative excess of uncommon or rare paternal gametes of discernibly outcrossed embryos. An additional two-locus association was identified for Mdh2 Pgm which was marginally significant for the major partition of the contingency table that excluded paternal gametes with the rare allele Mdh2
2
. 相似文献
20.
Pollen dispersal and genetic structure of the tropical tree Dipteryx panamensis in a fragmented Costa Rican landscape 总被引:1,自引:1,他引:0
In the face of widespread deforestation, the conservation of rainforest trees relies increasingly on their ability to maintain reproductive processes in fragmented landscapes. Here, we analysed nine microsatellite loci for 218 adults and 325 progeny of the tree Dipteryx panamensis in Costa Rica. Pollen dispersal distances, genetic diversity, genetic structure and spatial autocorrelation were determined for populations in four habitats: continuous forest, forest fragments, pastures adjacent to fragments and isolated pastures. We predicted longer but less frequent pollen movements among increasingly isolated trees. This pattern would lead to lower outcrossing rates for pasture trees, as well as lower genetic diversity and increased structure and spatial autocorrelation among their progeny. Results generally followed these expectations, with the shortest pollen dispersal among continuous forest trees (240 m), moderate distances for fragment (343 m) and adjacent pasture (317 m) populations, and distances of up to 2.3 km in isolated pastures (mean: 557 m). Variance around pollen dispersal estimates also increased with fragmentation, suggesting altered pollination conditions. Outcrossing rates were lower for pasture trees and we found greater spatial autocorrelation and genetic structure among their progeny, as well as a trend towards lower heterozygosity. Paternal reproductive dominance, the pollen contributions from individual fathers, did not vary among habitats, but we did document asymmetric pollen flow between pasture and adjacent fragment populations. We conclude that long-distance pollen dispersal helps maintain gene flow for D. panamensis in this fragmented landscape, but pasture and isolated pasture populations are still at risk of long-term genetic erosion. 相似文献