Allozyme genetic diversity among Fagus grandifolia trees resistant or susceptible to beech bark disease in natural populations

2000 ◽  
Vol 30 (5) ◽  
pp. 778-789 ◽  
Author(s):  
Daniel B Houston ◽  
David R Houston
Keyword(s):  
Prince Edward Island ◽  
Natural Populations ◽  
Fagus Grandifolia ◽  
Population Diversity ◽  
Beech Bark Disease ◽  
Polymorphic Loci ◽  
Expected Heterozygosity ◽  
Disease Occurrence ◽  
Dormant Bud ◽  
Natural Stands

American beech (Fagus grandifolia Ehrh.) trees resistant (R = 760) and susceptible (S = 681) to beech bark disease were located and mapped in nine natural stands in West Virginia (WV), Massachusetts (MA), Maine (ME), Nova Scotia (NS), and Prince Edward Island (PEI). Dormant bud tissue collected from each tree was examined by isozyme analysis to characterize the population genetic structure of R and S subpopulations mapped in each of four intensively sampled (R/S) stands, and five additional populations in which only R trees were sampled. Seventeen enzymes (with 9 polymorphic and 14 monomorphic loci) were analyzed to estimate variation across the spatial range of disease occurrence. All populations possessed significant levels of inter- and intra-population diversity; several parameters appeared to increase in magnitude from southwest to northeast across the range. In the R/S stands, percent polymorphic loci averaged 38%, average number of alleles/locus was 1.8 (3.0 for polymorphic loci), and mean expected heterozygosity was 0.165. Most genetic variation resided within populations (97%; GST = 0.03). Analyses of pooled R and S subpopulations demonstrated that observed heterozygosities were up to 26% higher in S trees, i.e., R tree populations exhibited consistent heterozygote deficits.

Incidence of beech bark disease resistance in the eastern Acadian forest of North America

2013 ◽  
Vol 89 (05) ◽  
pp. 690-695 ◽  
Author(s):  
Anthony R. Taylor ◽  
Donnie A. McPhee ◽  
Judy A. Loo
Keyword(s):  
North America ◽  
Prince Edward Island ◽  
Geographical Area ◽  
Fagus Grandifolia ◽  
Natural Resistance ◽  
Beech Bark Disease ◽  
Eastern Canada ◽  
Average Percentage ◽  
Acadian Forest ◽  
Disease Free

Beech bark disease (BBD) is a fatal affliction of American beech (Fagus grandifolia Ehrh.) in North America. Although natural resistance to BBD has been observed, reports vary with respect to incidence of resistance, with 1% being most commonly acknowledged. In this paper, we provide the first formal, empirical estimate of BBD resistance over a wide geographical area where BBD has been prevalent for longest in North America. We conducted our study in the Acadian Forest region of eastern Canada. Thirty-five beech-dominated stands (>5 ha each) were surveyed across the provinces of New Brunswick, Nova Scotia, and Prince Edward Island, spanning a time since infection (TSI) period between 1890 and 1975. Stands were surveyed for incidence of disease-free beech trees, which was used as a proxy for BBD resistance. Across our study area, the average percentage of disease-free trees observed was 3.3%; however, the occurrence of disease-free trees varied significantly geographically, with the oldest, most southerly TSI zone indicating 2.2% and the youngest, most northerly TSI zone showing 5.7%. Although geographic variation of disease-free beech trees may reflect disease exposure time, we speculate that lower minimum winter temperatures, combined with less intensive land-use history are the underlying mechanisms that explain the higher observed percentage of disease-free trees in the most northerly TSI zones.

Allozyme variability in natural populations of green alder (Alnus crispa) in Quebec

Genome ◽  
1987 ◽  
Vol 29 (2) ◽  
pp. 345-352 ◽  
Author(s):  
J. Bousquet ◽  
W. M. Cheliak ◽  
M. Lalonde
Keyword(s):  
Natural Populations ◽  
Outcrossing Rate ◽  
Polymorphic Loci ◽  
Alnus Crispa ◽  
Model Average ◽  
Expected Heterozygosity ◽  
Green Alder ◽  
Hardy Weinberg Equilibrium ◽  
Fixation Indices ◽  
Sexually Mature

Vegetative and sexual tissues from 22 populations of Alnus crispa (Ait.) Pursh (green alder, Betulaceae) in Quebec were analyzed for electrophoretically demonstrable diversity of 11 enzymes encoded by 16 structural loci in sexually mature populations. Of these 16 loci, 9 were found polymorphic. A total of 28 different alleles were detected with no more than three alleles per locus. No two-locus linkage disequilibrium was observed between eight polymorphic loci analyzed. Assuming a diploid model, average level of expected heterozygosity was 0.14 in the mature generation, with nearly all populations in Hardy–Weinberg equilibrium for the set of polymorphic loci investigated. Mean outcrossing rate was 0.95. Fixation indices revealed low inbreeding with no specific subpopulation structure. Hence, an important level of gene flow would exist within the populations. Without any strong evidence for polyploidy, and in the light of results obtained, the species could be classified equally well as a diploid or a diploidized allotetraploid. Key words: actinorhizal plant, alder, allozymes, Alnus, fixation indices, heterozygosity, outcrossing rate, polyploidy.

scholarly journals Genetic analysis of silver-fir populations in the Beskids

2011 ◽  
Vol 72 (2) ◽  
pp. 115-119 ◽  
Author(s):  
Leon Mejnartowicz
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Genetic Analysis ◽  
Abies Alba ◽  
Genetic Distances ◽  
Silver Fir ◽  
Geographical Distance ◽  
Polymorphic Loci ◽  
Expected Heterozygosity ◽  
Rare Alleles

Twenty-eight isozymic loci were studied in the Beskid Mts., in four populations of common silver-fir (<em>Abies alba</em>): one in Beskid Makowski (BM) and three populations in Beskid Sądecki (BS). Their genetic variation and diversity were analyzed, and Nei's genetic distances between the populations were calculated. The results show that the geographical distance between the BM population and the three BS populations is reflected in genetic distances. The BM population is clearly distinct from the others. It has the lowest genetic diversity (<em>I</em> = <em>0.42</em>), percentage of polymorphic loci <em>(%PoL </em>= <em>64.29</em>) and number of rare alleles (<em>NoRa </em>= <em>5</em>). Besides, the BM population has the highest observed heterozygosity (<em>Ho </em>= <em>0.291</em>), which exceeds the expected heterozygosity (<em>He </em>= <em>0.254</em>), estimated on the basis of the Hardy-Weinberg Principle. On the contrary, BS populations are in the state of equilibrium, which is manifested, in similar values of <em>He </em>= <em>0.262 </em>and <em>Ho </em>= <em>0.264</em>.

STUDIES OF NATURAL POPULATIONS OF MUS. V. A SURVEY OF NINE LOCI FOR POLYMORPHISMS

1969 ◽  
Vol 11 (3) ◽  
pp. 497-513 ◽  
Author(s):  
M. L. Petras ◽  
J. D. Reimer ◽  
F. G. Biddle ◽  
J. E. Martin ◽  
R. S. Linton
Keyword(s):  
Geographic Distribution ◽  
Mus Musculus ◽  
Additional Data ◽  
Natural Populations ◽  
House Mice ◽  
Polymorphic Loci

An examination of house mice (Mus musculus) from a number of sites in southwestern Ontario revealed six loci (Hbb, Es-2, Es-3, Es-5, Ldr-1 and A) to be polymorphic and three (Es-1, Pro-1 and Trf-1) to be monomorphic. A comparison of the Ontario samples with samples from southeastern Michigan suggests that the polymorphisms detected are common to Mus populations in both regions and are relatively stable. Data reported by other investigators suggest that some of these polymorphisms have a broad geographic distribution. Also discussed are findings of loci described elsewhere. Two of these T and Ea-1, are polymorphic in some of the populations under consideration. General conclusions include: (1) that polymorphic loci are probably as frequent in mouse populations as in Drosophila and man; (2) that the polymorphisms observed are relatively stable and widespread; (3) that some of the alleles responsible for the polymorphisms observed are not neutral; and (4) that additional data are necessary to elucidate the mechanisms responsible for the polymorphisms observed.

scholarly journals Genetic diversity in natural populations of Buriti (Mauritia flexuosa L. f.)

2011 ◽  
Vol 11 (3) ◽  
pp. 216-223 ◽  
Author(s):  
Liene Rocha Picanço Gomes ◽  
Maria Teresa Gomes Lopes ◽  
Jania Lilia da Silva Bentes ◽  
Willian Silva Barros ◽  
Pedro de Queiroz Costa Neto ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Length Polymorphism ◽  
Fragment Length Polymorphism ◽  
Natural Populations ◽  
Analysis Of Molecular Variance ◽  
Molecular Variance ◽  
Polymorphic Loci ◽  
Mauritia Flexuosa ◽  
Geographical Distances ◽  
Traditional Communities

This study aimed to characterize the genetic diversity of buriti populations by AFLP (Amplified Fragment Length Polymorphism) markers. The analysis was performed in four populations used by traditional communities in the state of Amazonia (Bom Jesus do Anamã, Lauro Sodré, Santa Luzia do Buiçuzinho, and Esperança II). From each population 30 plants were randomly selected. To obtain the markers four primer combinations were used. The percentage of polymorphic loci was estimated, the molecular variance among and within populations analyzed and a dendrogram constructed. The primers detected 339 polymorphic loci ranging from 81.1 % to 91.1 % among populations. Analysis of molecular variance attributed 77.18 % to variation within and 22.8 % to variation between populations. The dendrogram indicated the formation of two groups, showing that the populations of Bom Jesus do Anamã and Lauro Sodré are genetically most similar and thet the genetic and geographical distances are not correlated.

scholarly journals Inter- and intra-population variation of local maize (Zea mays L.) populations from Slovakia and Czech Republic

2008 ◽  
Vol 43 (No. 1) ◽  
pp. 7-15 ◽  
Author(s):  
P. Múdry ◽  
J. Kraic
Keyword(s):  
Zea Mays ◽  
Genetic Variation ◽  
Czech Republic ◽  
Population Variation ◽  
Polymorphic Loci ◽  
Maize Populations ◽  
Expected Heterozygosity ◽  
Isoenzyme Polymorphism ◽  
New Alleles

Evaluation of genetic variation was performed within 62 local maize populations originating from Slovakia and Czech Republic. In total 48 alleles at 22 analyzed isoenzyme loci with an average of 2.2 alleles per locus were revealed. The percentage of polymorphic loci ranged from 14% to 59% and the frequencies of detected alleles varied from null to four per locus. No polymorphism was detected at the loci <i>Dia2</i>, <i>Got3</i>, <i>Mdh4</i>, <i>Mmm</i>, and <i>Pgm1</i>. The highest number of alleles (four) was detected at loci <i>Acp1</i>, <i>Cat3</i>, <i>Pgm2</i>. No new alleles were identified, nevertheless the frequency of seven alleles was only about 1%. The expected heterozygosity ranged from null to 0.492 with an average of 0.197. The revealed isoenzyme polymorphism confirmed that all analyzed populations were heterogeneous and as many as 17 of them were completely heterogeneous. None of the analyzed populations was identical in the frequency of alleles at all 22 analyzed loci.

scholarly journals Post-settlement viability in the American oyster (Crassostrea virginica): an overdominant phenotype

1983 ◽  
Vol 41 (3) ◽  
pp. 259-270 ◽  
Author(s):  
E. Zouros ◽  
Shiva M. Singh ◽  
David W. Foltz ◽  
André L. Mallet
Keyword(s):  
Crassostrea Virginica ◽  
Age Groups ◽  
Natural Populations ◽  
Electrophoretic Analysis ◽  
American Oyster ◽  
Marine Molluscs ◽  
Direct Involvement ◽  
Polymorphic Loci ◽  
Enzyme Polymorphisms ◽  
Genetic Interpretation

SUMMARYThe degree of heterozygosity as determined by electrophoretic analysis of three or four polymorphic loci correlates positively with survival in age groups of the American oyster (Crassostrea virginica) collected as spat from two different natural populations. The phenomenon is shown to operate in ages from 2 weeks (post-settlement) to 3 years and appears to be general in populations of marine molluscs. The most likely explanation for this result is that heterozygosity improves survival through its effect on growth (heterozygotes grow faster). The effects of individual loci on viability are independent of each other. A direct involvement of the enzyme polymorphisms is the most probable genetic interpretation of the data, but associative overdominance cannot be excluded.

Seasonal variation and clonal selection in cyclically parthenogenetic rose aphids (Macrosiphum rosae)

1985 ◽  
Vol 27 (2) ◽  
pp. 224-232 ◽  
Author(s):  
L. R. Rhomberg ◽  
S. Joseph ◽  
R. S. Singh
Keyword(s):  
Genetic Variation ◽  
Seasonal Variation ◽  
Clonal Selection ◽  
Natural Populations ◽  
Allozyme Variation ◽  
Polymorphic Loci ◽  
Esterase Loci ◽  
Allozyme Loci ◽  
Macrosiphum Rosae ◽  
Asexual Cycle

Patterns of geographic and seasonal genetic variation were assessed in natural populations of cyclically parthenogenetic rose aphids Macrosiphum rosae (L.). Nine populations were studied for a red–green colour morph and 30 allozyme loci (20 coding for enzymes and 10 for abundant proteins). Genetic variation was found at 5 of 20 enzyme loci (20%); all 10 abundant proteins proved monomorphic. The average heterozygosity was 4.3%. At some polymorphic loci genotypic frequencies showed significant deviations from Hardy–Weinberg proportions. Six local populations from Hamilton, Ontario, were studied for seasonal variation at the colour locus and at two polymorphic esterase loci (Est-2 and Est-4). All three loci showed large changes in genotypic frequencies over the season during the asexual cycle, but only for Est-4 were changes consistent among populations. This locus undergoes a regular seasonal cycle, the directional changes during the asexual phase presumably being balanced by changes during the sexual phase. The frequencies of three-locus genotypes within each locality fluctuated dramatically over the course of a season, reflecting the domination of local infestations by a few particularly successful clones. We speculate that because of such clonal competition followed by extensive migration, much of the selectively neutral variation is purged from aphid populations. The remaining polymorphic loci, which are mostly di- or tri-allelic, are subject to balancing natural selection at the gene or at closely linked loci. The Est-4 in rose aphids is an example of such a selectively maintained polymorphism.Key words: aphids, allozyme variation, seasonal variation, parthenogenesis, clonal selection, population structure.

Segregation of allozyme loci in megagametophytes of Engelmann spruce and subalpine fir

Genome ◽  
1988 ◽  
Vol 30 (2) ◽  
pp. 103-107 ◽  
Author(s):  
Kathleen L. Shea
Keyword(s):  
Natural Populations ◽  
Segregation Ratio ◽  
Colorado Front Range ◽  
Abies Lasiocarpa ◽  
Front Range ◽  
Subalpine Fir ◽  
Polymorphic Loci ◽  
Engelmann Spruce ◽  
Low Levels ◽  
Allozyme Loci

Segregation ratios and linkage of 10 allozyme loci were examined in haploid megagametophytes obtained from natural populations of Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) in the Colorado Front Range. For data pooled over trees, the 1:1 segregation ratio expected at Mendelian loci was obtained for five polymorphic loci in 32 Engelmann spruce trees and for seven polymorphic loci in 40 subalpine fir trees. The Gdh and Idh loci in spruce were very tightly linked: no recombinants were detected among 60 megagametophytes of trees heterozygous for both loci. In fir only the Aco and Pgm-1 loci were linked, with an estimated recombination rate of 0.317 ± 0.073. The low levels of among-tree heterogeneity and of segregation distortion found in these populations suggest that reliable estimates of both genetic variation and outcrossing rates can be obtained using allozyme data from these wind-pollinated species.Key words: segregation, linkage, allozymes, Engelmann spruce, subalpine fir.

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