The effect of an oak wilt epidemic on the genetic structure of a Texas live oak population

1998 ◽  
Vol 76 (11) ◽  
pp. 1900-1907 ◽  
Author(s):  
Bruce A McDonald ◽  
Brenda K Bellamy ◽  
Jiasui Zhan ◽  
David N Appel
Keyword(s):  
Genetic Structure ◽  
Gene Diversity ◽  
Host Population ◽  
Oak Wilt ◽  
Tree Disease ◽  
Live Oak ◽  
Genotype Frequencies ◽  
Central Texas ◽  
Multilocus Associations ◽  
Allozyme Loci

Oak wilt is a fungal tree disease that has killed millions of live oaks (Quercus fusiformis Small) in the oak woodlands of central Texas. Allozymes were used to characterize the genetic structure of live oak populations prior to infection (pre-epidemic) and following passage of an epidemic wave (post-epidemic). Pre-epidemic trees (N = 112) were sampled along transects in front of an expanding disease front. Post-epidemic trees (N = 109) were survivors of an epidemic that swept through an area of approximately 28 ha over a period of 20 years. Significant differences in allele and genotype frequencies existed between pre- and post-epidemic populations. Gene diversity was lower for two of the four allozyme loci in the post-epidemic population. Departures from Hardy-Weinberg equilibria occurred for two loci and multilocus associations developed in the post-epidemic population. These results demonstrate that disease can have a significant impact on the genetic structure of a natural host population. We hypothesize that selection for increasing disease resistance was the dominant evolutionary force leading to genetic change in this plant pathosystem.Key words: host-pathogen interactions, population genetics, Ceratocystis fagacearum, coevolution.

scholarly journals Studies on Pruning Cuts and Wound Dressings for Oak Wilt Control

2007 ◽  
Vol 33 (2) ◽  
pp. 132-139
Author(s):  
Kim Camilli ◽  
David Appel ◽  
W. Todd Watson
Keyword(s):  
Positive Control ◽  
Negative Control ◽  
Wound Dressings ◽  
Infection Rates ◽  
Oak Wilt ◽  
Tree Disease ◽  
Central Texas ◽  
High Hazard ◽  
Negative Controls ◽  
Positive Controls

Ceratocystis fagacearum causes the destructive tree disease called oak wilt. One means of pathogen spread is by insect vectors (Nitidulidae) that transmit spores into fresh wounds on healthy trees. Experiments were conducted in central Texas on native live oaks (Quercus fusiformis) to test pruning methods and paints on disease development. Three treatment combinations were tested on 30 trees (10 trees/treatment): flush cut unpainted, flush cut painted, and unpainted pruning cuts made according to the Shigo method. Unpainted puncture wounds were made on the lower trunks of an additional 20 trees as controls. C. fagacearum spores were applied to the pruning cuts and half of the puncture wounds (positive controls) after treatment, whereas the other half of the punctures received distilled water as negative controls. Oak wilt symptoms first appeared in the flush cut unpainted treatment 31 days after inoculation. Infection rates, in decreasing order, were; positive control (70%), flush cut unpainted (60%), Shigo pruning method (40%), flush cut painted (20%), and negative control (10%). Pruning wounds, regardless of method, were effective infection courts for the oak wilt pathogen. Fewer trees became infected when pruning cuts were painted, but differences among infection rates for pruning cuts were not statistically significant. Tree diameters and stem aspect ratio had no bearing on infection rates. The Shigo method is recognized as a superior method for pruning, but there is no reason to change current recommendations to paint fresh wounds on susceptible oaks in high-hazard oak wilt areas.

scholarly journals Using Airborne Digital Imagery for Detecting Oak Wilt Disease

Plant Disease ◽  
1999 ◽  
Vol 83 (6) ◽  
pp. 502-505 ◽  
Author(s):  
J. H. Everitt ◽  
D. E. Escobar ◽  
D. N. Appel ◽  
W. G. Riggs ◽  
M. R. Davis
Keyword(s):  
Near Infrared ◽  
Wilt Disease ◽  
Digital Imagery ◽  
Near Infrared Reflectance ◽  
Oak Wilt ◽  
South Central ◽  
Live Oak ◽  
Oak Trees ◽  
Light Reflectance ◽  
Central Texas

Color-infrared (CIR) digital imagery was evaluated as a remote sensing tool for detecting oak wilt disease in live oak (Quercus fusiformis). Aerial CIR digital imagery and CIR photography were obtained concurrently of a live oak forested area in south-central Texas affected by oak wilt. Dead, diseased, and healthy live oak trees could generally be delineated as well in the digital imagery as in the CIR photography. Light reflectance measurements obtained in the field showed that dead, diseased, and healthy trees had different visible and near-infrared reflectance values.

The effect of an oak wilt epidemic on the genetic structure of a Texas live oak population

1998 ◽  
Vol 76 (11) ◽  
pp. 1900-1907 ◽  
Author(s):  
Bruce A. McDonald ◽  
Brenda K. Bellamy ◽  
Jiasui Zhan ◽  
David N. Appel
Keyword(s):  
Genetic Structure ◽  
Oak Wilt ◽  
Live Oak

scholarly journals Genetic Structure of Rhynchosporium secalis in Australia

1999 ◽  
Vol 89 (8) ◽  
pp. 639-645 ◽  
Author(s):  
B. A. McDonald ◽  
J. Zhan ◽  
J. J. Burdon
Keyword(s):  
Genetic Structure ◽  
Gene Diversity ◽  
Sampling Site ◽  
Geographic Distance ◽  
South Australia ◽  
Rflp Markers ◽  
Rhynchosporium Secalis ◽  
Fungal Isolates ◽  
Fungal Populations ◽  
Average Gene

Restriction fragment length polymorphism (RFLP) markers were used to determine the genetic structure of Australian field populations of the barley scald pathogen Rhynchosporium secalis. Fungal isolates were collected by hierarchical sampling from five naturally infected barley fields in different geographic locations during a single growing season. Genetic variation was high in Australian R. secalis populations. Among the 265 fungal isolates analyzed, 214 distinct genotypes were identified. Average genotype diversity within a field population was 65% of its theoretical maximum. Nei's average gene diversity across seven RFLP loci was 0.54. The majority (76%) of gene diversity was distributed within sampling site areas measuring ≈1 m2; 19% of gene diversity was distributed among sampling sites within fields; and 5% of gene diversity was distributed among fields. Fungal populations from different locations differed significantly both in allele frequencies and genotype diversities. The degree of genetic differentiation was significantly correlated with geographic distance between populations. Our results suggest that the R. secalis population in Western Australia has a different genetic structure than populations in Victoria and South Australia.

scholarly journals Diverging Genetic Structure of Coexisting Populations of the Black Storm-Petrel and the Least Storm-Petrel in the Gulf of California

2020 ◽  
Vol 13 ◽  
pp. 194008292094917
Author(s):  
Misael D. Mancilla-Morales ◽  
Santiago Romero-Fernández ◽  
Araceli Contreras-Rodríguez ◽  
José J. Flores-Martínez ◽  
Víctor Sánchez-Cordero ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Genetic Structure ◽  
Population Genetic Structure ◽  
Mate Selection ◽  
Gulf Of California ◽  
Population Genetic ◽  
Life Histories ◽  
Gene Diversity ◽  
Isolation By Distance ◽  
Storm Petrel

Estimations on the influence of evolutionary and ecological forces as drivers of population gene diversity and genetic structure have been performed on a growing number of colonial seabirds, but many remain poorly studied. In particular, the population genetic structure of storm-petrels (Hydrobatidae) has been evaluated in only a few of the 24 recognized species. We assessed the genetic diversity and population structure of the Black Storm-Petrel ( Hydrobates melania) and the Least Storm-Petrel ( Hydrobates microsoma) in the Gulf of California. The two species were selected because they are pelagic seabirds with comparable ecological traits and breeding grounds. Recent threats such as introduced species of predators and human disturbance have resulted in a decline of many insular vertebrate populations in this region and affected many different aspects of their life histories (ranging from reproductive success to mate selection), with a concomitant loss of genetic diversity. To elucidate to what extent the population genetic structure occurs in H. melania and H. microsoma, we used 719 base pairs from the mitochondrial cytochrome oxidase c subunit I gene. The evaluation of their molecular diversity, genetic structure, and gene flow were performed through diversity indices, analyses of molecular and spatial variance, and isolation by distance (IBD) across sampling sites, respectively. The population genetic structure (via AMOVA and SAMOVA) and isolation by distance (pairwise p-distances and FST/1– FST (using ΦST) were inferred for H. microsoma. However, for H. melania evidence was inconclusive. We discuss explanations leading to divergent population genetic structure signatures in these species, and the consequences for their conservation.

Genetic homogeneity of weathervane scallops (Patinopecten caurinus) in the northeastern Pacific

2010 ◽  
Vol 67 (11) ◽  
pp. 1827-1839 ◽  
Author(s):  
Patrick M. Gaffney ◽  
Carita M. Pascal ◽  
Jeffery Barnhart ◽  
W. Stewart Grant ◽  
James E. Seeb
Keyword(s):  
Genetic Differentiation ◽  
Gene Diversity ◽  
Isolation By Distance ◽  
Population Expansion ◽  
Gulf Of Alaska ◽  
Nucleotide Sequencing ◽  
Mt Dna ◽  
Northeastern Pacific ◽  
Nuclear Loci ◽  
Allozyme Loci

We assessed genetic differentiation among populations of weathervane scallop ( Patinopecten caurinus ) in the northeastern Pacific, extending over 2500 km in the Gulf of Alaska and southeastern Bering Sea. Variability was surveyed at nuclear loci with allozyme, microsatellite, and single nucleotide polymorphism (SNP) methods, and at mitochondrial (mt)DNA loci with SNPs and nucleotide sequencing. High levels of gene diversity were detected for allozymes (H = 0.080), microsatellites (H = 0.734), and mtDNA (h = 0.781). Genotypes at nuclear loci generally fit Hardy–Weinberg proportions, except for some microsatellite loci, for which null-allele frequencies of 0.02 to 0.34 were estimated. No allele-frequency differences were detected among samples, except for the allozyme loci Gpi and Pep-4. Overall levels of differentiation ranged from FST = 0.0004 for allozymes, FST = 0.0008 for mtDNA to FST = 0.0004 for microsatellites. No isolation by distance was found for any of the markers. A unimodal mtDNA mismatch distribution and significant excesses of low-frequency variants for allozymes, microsatellites, and mtDNA may reflect a post-glacial population expansion. The lack of genetic differentiation measured by neutral markers does not preclude the existence of locally adapted, self-sustaining populations that are important in the harvest management of this species.

scholarly journals  Allele frequency in loci which control coat colours in Hucul horse population

2012 ◽  
Vol 57 (No. 4) ◽  
pp. 178-186 ◽  
Author(s):  
A. Stachurska ◽  
A. Brodacki ◽  
J. Grabowska
Keyword(s):  
Genetic Structure ◽  
Allele Frequency ◽  
Global Strategy ◽  
Recessive Allele ◽  
Genotype Distribution ◽  
Horse Population ◽  
Wahlund Effect ◽  
Animal Genetic Resources ◽  
Genotype Frequencies ◽  
Its Gene

The objective of the study was to determine the frequency of alleles which produce coat colours in Hucul horse population in Poland. The breed is included in the Global Strategy for Management of Farm Animal Genetic Resources, hence its gene pool should remain in unaltered state. Huculs are bay, black, blue dun, yellow dun, tobiano, and chestnut. Grey and chestnut Huculs have always been undesirable. The material consisted of all 1022 matings which resulted in subpopulations recorded in Studbook volumes. The recessive allele frequency was estimated as the square root of recessive genotype frequencies in ASIP (A), MC1R (E), DUN (D), KIT (To region), and STX17 (G) loci. The frequency in A and E loci in total parental generation was also estimated in test matings. Genotype distribution in the population was anticipated according to gamete frequency in sires and dams. Small Wahlund effect, F<sub>ST</sub>and &chi;<sup>2</sup> values for allele distributions show that division into subpopulations did not influence the population genetic structure significantly. Mean recessive allele frequency in A, E, D, To, and G loci amounted to 0.521, 0.115, 0.878, 0.929, and 0.997, respectively, and in A and E loci it was similar to that assessed in test matings. More bay horses and fewer D diluted horses appeared in offspring than expected. A, e, d, and To allele frequency showed a rising tendency. The genetic structure in Hucul population is not constant and does not comply strictly with the preservation aim. Bay, non-diluted, and tobiano horses are preferred. The linkage between MC1R and KIT loci can make the selection against e allele difficult. Breeders&rsquo; preferences may lead to undesired changes in the allele frequency. To avoid such risk, it is recommended to select horses strictly complying with the rules included in the breeding programme and mate the horses randomly from this aspect. &nbsp;

scholarly journals A New Cytosporone Derivative from the Endophytic Fungus Cytospora sp

2014 ◽  
Vol 9 (7) ◽  
pp. 1934578X1400900 ◽  
Author(s):  
Tomoya Takano ◽  
Takuya Koseki ◽  
Hiromasa Koyama ◽  
Yoshihito Shiono
Keyword(s):  
Antimicrobial Activity ◽  
Endophytic Fungus ◽  
2D Nmr ◽  
Ambrosia Beetle ◽  
Oak Wilt ◽  
Tree Disease ◽  
Platypus Quercivorus ◽  
Mass Spectral ◽  
Screening Study ◽  
Raffaelea Quercivora

Japanese oak wilt (JOW) is a tree disease caused by the fungus Raffaelea quercivora, which is vectored by the ambrosia beetle, Platypus quercivorus. In a screening study of the inhibitory active compounds from fungi, a new cytosporone analogue, compound 1, was isolated from the endophytic fungus Cytospora sp. TT-10 isolated from Japanese oak, together with the known compounds, integracin A (2), cytosporones N (3) and A (4). Their structures were determined by extensive 1D– and 2D–NMR spectroscopic and mass spectral analyses. Compound 1 was identified as 4,5-dihydroxy-3-heptylphthalide and named cytosporone E. Compounds 2 and 3 showed antimicrobial activity against Raffaelea quercivora.

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