scholarly journals Genetic Structure of Populations of the Wheat Sharp Eyespot Pathogen Rhizoctonia cerealis Anastomosis Group D Subgroup I in China

2017 ◽  
Vol 107 (2) ◽  
pp. 224-230 ◽  
Author(s):  
Wei Li ◽  
Yingpeng Guo ◽  
Aixiang Zhang ◽  
Huaigu Chen
Keyword(s):  
Genetic Structure ◽  
Anastomosis Group ◽  
Gene Pools ◽  
Evolutionary Potential ◽  
Long Distance ◽  
Genetic Characteristics ◽  
Nonrandom Mating ◽  
Sharp Eyespot ◽  
Group D ◽  
Rhizoctonia Cerealis

Sharp eyespot on wheat is caused by Rhizoctonia cerealis anastomosis group D subgroup I (AG-DI) and is an economically important stem-base disease of wheat in temperate regions worldwide. However, the understanding about the field population structure of R. cerealis is limited. In this study, the genetic structure of four wheat-infecting populations in China was investigated using six microsatellite markers characterized from the transcriptome data of R. cerealis AG-DI. A total of 173 unique genotypes were identified among 235 fungal isolates. Departure from Hardy-Weinberg equilibrium, a significant degree of inbreeding, and a significant deficit in heterozygotes indicated a nonrandom mating pattern. Combining the low to intermediate degrees of gametic disequilibrium, although with high genotypic diversity and low to moderate clonal fractions, sexual reproduction probably existed, but the asexual reproduction should be the predominant reproductive mode. Structural analysis showed three gene pools among the four populations, which indicated the existence of three evolutionary origins of R. cerealis AG-DI. The long-distance movement of contaminated material, especially the infected seed, might have caused the moderate gene flow among these populations, which was consistent with the high differentiation among these populations. Overall, the genetic characteristics of the populations suggested a moderate evolutionary potential for R. cerealis AG-DI in China.

scholarly journals Rhizoctonia cerealis anastomosis group GAG-1, the common pathogen of wheat, barley and sugar beet

2014 ◽  
Vol 32 (1) ◽  
pp. 107-117
Author(s):  
Helena Furgał-Węgrzycka ◽  
Jan Adamiak ◽  
Ewa Adamiak
Keyword(s):  
Growth Rate ◽  
Sugar Beet ◽  
Crop Rotation ◽  
Root Rot ◽  
Anastomosis Group ◽  
Sharp Eyespot ◽  
Pathogenicity Tests ◽  
The Common ◽  
Hyphal Diameter ◽  
Rhizoctonia Cerealis

Isuluies of <i>Rhizoctonia cerealis</i> anastomosis group GAG-1 were obtained from sharp eyespot lesions on wheat and on barley culms and from diseased sugar beet seedlings. Isolates of <i>R. cerealis</i> were collected from a fields with crop rotation experiments: sugar beet-spring wheat-winter barley. In pathogenicity tests isolates of <i>R. cerealis</i> from sugar beet seedlings and from sharp eyespot lesions on wheat and barley were pathogenic to these crops. Isolates of <i>R. cerealis</i> from sharp eyespot lesions on wheat and barley caused severe damping-ofTof sugar beet. Isolates of <i>R. cerealis</i> from sugar beet seedlings also caused symptoms of sharp eyespot on wheat and barley. None of the wheat and barley isolates of <i>R. cerealis</i> tested caused root-rot on wheat or barley seedlings. Isolates of <i>R. cerealis</i> obtained from diseased plants of wheat, barley and sugar beet were similar in morphology of cultures and anastomosed with GAG-1 tester isolate. The relatinoship between anastomosis. colony characters, growth rate, hyphal diameter and pathogenicity of AG-4. AG-2-2 and AG-5 isolates obtained together with <i>R. cerealis</i> from diseased plants were also investigated.

scholarly journals First report of Rhizoctonia cerealis causing sharp eyespot in Panicum virgatum in the UK

2001 ◽  
Vol 50 (6) ◽  
pp. 807-807 ◽  
Author(s):  
J. V. Etheridge ◽  
L. Davey ◽  
D. G. Christian
Keyword(s):  
Panicum Virgatum ◽  
First Report ◽  
Sharp Eyespot ◽  
The Uk ◽  
Rhizoctonia Cerealis

scholarly journals Genetic structure and dispersal patterns of the invasive psocid Liposcelis decolor (Pearman) in Australian grain storage systems

2010 ◽  
Vol 100 (5) ◽  
pp. 521-527 ◽  
Author(s):  
K.M. Mikac ◽  
N.N. FitzSimmons
Keyword(s):  
Genetic Structure ◽  
Isolation By Distance ◽  
Geographic Distance ◽  
Allelic Diversity ◽  
Mantel Test ◽  
Null Alleles ◽  
Dispersal Patterns ◽  
Long Distance ◽  
Population Comparisons ◽  
Low Levels

AbstractMicrosatellite markers were used to investigate the genetic structure among invasive L. decolor populations from Australia and a single international population from Kansas, USA to determine patterns of dispersal. Six variable microsatellites displayed an average of 2.5–4.2 alleles per locus per population. Observed (HO) heterozygosity ranged from 0.12–0.65 per locus within populations; but, in 13 of 36 tests, HO was less than expected. Despite low levels of allelic diversity, genetic structure estimated as θ was significant for all pairwise comparisons between populations (θ=0.05–0.23). Due to suspected null alleles at four loci, ENA (excluding null alleles) corrected FST estimates were calculated overall and for pairwise population comparisons. The ENA-corrected FST values (0.02–0.10) revealed significant overall genetic structure, but none of the pairwise values were significantly different from zero. A Mantel test of isolation by distance indicated no relationship between genetic structure and geographic distance among all populations (r2=0.12, P=0.18) and for Australian populations only (r2=0.19, P=0.44), suggesting that IBD does not describe the pattern of gene flow among populations. This study supports a hypothesis of long distance dispersal by L. decolor at moderate to potentially high levels.

scholarly journals Susceptibility of winter Triticale Cultivars to Rhizoctonia Cerealis (sharp eyespot) and R. Solani

2012 ◽  
Vol 52 (4) ◽  
pp. 421-434 ◽  
Author(s):  
Grzegorz Lemańczyk
Keyword(s):  
Field Study ◽  
Growth Stage ◽  
Disease Index ◽  
High Susceptibility ◽  
North Central ◽  
Winter Triticale ◽  
Sharp Eyespot ◽  
The Mean ◽  
Rhizoctonia Cerealis ◽  
Seedling Infection

AbstractIn the field study period from 2006 to 2010, the incidence and severity of sharp eyespot caused byRhizoctoniawere recorded on 36 cultivars of triticale at the milk ripe growth stage. Four localities in north-central Poland were included: Chrząstowo, Dębina, Kończewice and Minikowo. The susceptibility of the seedlings of 30 cultivars of triticale toR. cerealis(AG-D subgroup I) andR. solani(AG-5) was studied in the laboratory. There was much variation in incidence and severity of sharp eyespot between years and locations. The disease was most intense at Chrząstowo. At this location, the mean percentage of diseased stems on 28 cultivars was 2.6-35.7 (-55.0), and the mean disease index was 0.7-15.6 (-24.5), with the lowest and highest values in 2008 and 2009, respectively. At Minikowo, the disease was least intense. At this location, the mean percentage of diseased stems on 23 cultivars was 1.0-4.6 (-18.0), and the mean disease index was 0.3-1.4 (-6.3), with the lowest and highest values in 2006 and 2007, respectively. The cultivars with least intense disease were Tulus and Atletico (Chrząstowo), Grenado and Zorro (Dębina), Krakowiak and Tornado (Kończewice), and Woltario and Constans (Minikowo). The cultivars with most intense disease were Alekto (Chrząstowo), Baltiko (Dębina), Pawo (Kończewice) and Borwo (Minikowo). MostlyR. cerealiswas isolated from the diseased stems;R. solaniwas isolated only sporadically. There was a wide variation in the susceptibility of triticale cultivars toRhizoctonia. Most triticale seedlings inoculated withR. cerealisproduced symptoms typical of sharp eyespot. Seedlings inoculated withR. solaniformed extended lesions with no defined borders. Most symptoms developed on coleoptiles, with less symptoms on the leaves and the least on the roots. There was much variation in susceptibility of triticale cultivars to bothRhizoctoniaspecies. Cultivars were grouped into six categories according to the intensity of seedling infection. Categories 1, 2 and 3, representing low, moderate and high susceptibility toR. cerealis, included 17, 10 and 3 cultivars, respectively.Categories 4, 5 and 6, representing low, moderate and high susceptibility toR. solani, included 3, 12 and 15 cultivars, respectively.Cultivars Baltiko and Zorro had low, and cv. Cultivo had high susceptibility to bothRhizoctoniaspecies. No cultivar was resistant toRhizoctonia. There was a positive correlation between infection byR. cerealisandR. solani.Infection of coleoptiles byR. cerealisorR. solaniwas significantly correlated with infection of leaves. No correlation between intensity of sharp eyespot on triticale plants in the field and on seedlings in controlled conditions was found.

Size and shape of sampling units for estimating incidence of sharp eyespot, Rhizoctonia cerealis, in plots of wheat

1982 ◽  
Vol 99 (2) ◽  
pp. 461-464 ◽  
Author(s):  
C. A. Gilligan
Keyword(s):  
Crop Yield ◽  
Stem Canker ◽  
Perfect State ◽  
Size And Shape ◽  
Oil Seed ◽  
Oil Seed Rape ◽  
Sharp Eyespot ◽  
Similar Area ◽  
Rhizoctonia Cerealis

It has long been known that the size and shape of sampling units used to assess crop yield may have significant effects upon the precision of the estimates (Smith, 1938; Hudson, 1939) but little is known about the effects when estimating incidence of disease. Gilligan (1980) showed that estimates of the incidence (i.e. presence or absence of disease) of stem canker (Phomx, lingam, perfect state Lepto sphaeria maculans)of oil-seed rape were more precise when large square sampling units rather than long rectangular units of similar area or small square sampling units were used. Moreover, estimates derived from the frequently used method of sampling by removal of 25 stems, supposedly at random from each plot, were shown to be biased.

scholarly journals Molecular genetic diversity and differentiation of Nile tilapia (Oreochromis niloticus, L. 1758) in East African natural and stocked populations

2019 ◽  
Author(s):  
Papius Dias Tibihika ◽  
Manuel Curto ◽  
Esayas Alemayehu ◽  
Herwig Waidbacher ◽  
Charles Masembe ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Genetic Structure ◽  
East Africa ◽  
Oreochromis Niloticus ◽  
Nile Tilapia ◽  
Anthropogenic Activities ◽  
Genetic Erosion ◽  
Gene Pools ◽  
East African ◽  
Nile Tilapia Oreochromis Niloticus

Abstract Background The need for enhancing the productivity of fisheries in Africa triggered the introduction of non-native fish, causing dramatic changes to local species. In East Africa, the extensive translocation of Nile tilapia (Oreochromis niloticus) is one of the major factors in this respect. Using 40 microsatellite loci with SSR-GBS techniques, we amplified a total of 664 individuals to investigate the genetic structure of O. niloticus from East Africa in comparison to Ethiopian and Burkina Faso populations. Results All three African regions were characterized by independent gene-pools, however, the Ethiopian population from lake Tana showed to be more divergent than expected suggesting that it might be a different species. In East Africa, the genetic structure was congruent with both geographical location and anthropogenic activities. O. niloticus from Lake Turkana (Kenya) was isolated, while in Uganda, despite populations being rather similar to each other, two main natural catchments were able to be defined. We show that these two groups contributed to the gene-pool of different non-native populations. Moreover, admixture and possible hybridization with other tilapiine species may have contributed to the genetic divergence found in some populations such as Lake Victoria. We detected other factors that might be affecting Nile tilapia genetic variation. For example, most of the populations have gone through a reduction of genetic diversity, which can be a consequence of bottleneck caused by overfishing, genetic erosion due to fragmentation or founder effect resulting from stoking activities. Conclusions The anthropogenic activities particularly in the East African O. niloticus translocations, promoted admixture and contact with the native congenerics which may contribute to outbreeding depression and hence compromising the sustainability of the species in the region.

scholarly journals Whole-Genome Analysis of Coxsackievirus B3 Reflects Its Genetic Diversity in China and Worldwide

2021 ◽  
Author(s):  
Qian Yang ◽  
Dongmei Yan ◽  
Yang Song ◽  
Shuangli Zhu ◽  
Yun He ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Phylogenetic Analysis ◽  
Foot And Mouth Disease ◽  
Coxsackievirus B3 ◽  
Whole Genome ◽  
Nucleotide Substitution Rate ◽  
Whole Genome Analysis ◽  
Genetic Characteristics ◽  
Heavy Burden ◽  
Group D

Abstract Background Coxsackievirus B3 (CVB3) has emerged as an active pathogen in myocarditis, aseptic meningitis, hand, foot, and mouth disease (HFMD), and pancreatitis, and is a heavy burden on public health. However, CVB3 has not been systematically analyzed with regard to whole-genome diversity and recombination. Therefore, this study was undertaken to systematically examine the genetic characteristics of CVB3 based on its whole genome. Methods We combined CVB3 isolates from our national HFMD surveillance and global sequences retrieved from GenBank. Phylogenetic analysis was performed to examine the whole genome variety and recombination forms of CVB3 in China and worldwide. Results Phylogenetic analysis showed that CVB3 strains isolated worldwide could be classified into groups A–E based on the sequence of the entire VP1 region. The predominant CVB3 strains in China belonged to group D, whereas group E CVB3 might be circulated globally compared to other groups. The average nucleotide substitution rate in the P1 region of CVB3 was 4.82 × 10−3 substitutions/site/year. Myocarditis was more common with group A. Groups C and D presented more cases of acute flaccid paralysis, and group D may be more likely to cause HFMD. Multiple recombination events were detected among CVB3 variants, and there were twenty-three recombinant lineages of CVB3 circulating worldwide. Conclusions Overall, this study provides full-length genomic sequences of CVB3 isolates with a wide geographic distribution over a long-term time scale in China, which will be helpful for understanding the evolution of this pathogen. Simultaneously, continuous surveillance of CVB3 is indispensable to determine its genetic diversity in China as well as worldwide.

Cryptic Lineages and a Population Dammed to Incipient Extinction? Insights into the Genetic Structure of a Mekong River Catfish

2019 ◽  
Vol 110 (5) ◽  
pp. 535-547 ◽  
Author(s):  
Amanda S Ackiss ◽  
Binh T Dang ◽  
Christopher E Bird ◽  
Ellen E Biesack ◽  
Phen Chheng ◽  
...  
Keyword(s):  
Genetic Structure ◽  
Natural Populations ◽  
Principal Component ◽  
Flood Pulse ◽  
Mekong River ◽  
Effective Population ◽  
Long Distance ◽  
Genetic Lineages ◽  
Low Genetic Diversity ◽  
Population Size Estimates

Abstract An understanding of the genetic composition of populations across management boundaries is vital to developing successful strategies for sustaining biodiversity and food resources. This is especially important in ecosystems where habitat fragmentation has altered baseline patterns of gene flow, dividing natural populations into smaller subpopulations and increasing potential loss of genetic variation through genetic drift. River systems can be highly fragmented by dams built for flow regulation and hydropower. We used reduced-representation sequencing to examine genomic patterns in an exploited catfish, Hemibagrus spilopterus, in a hotspot of biodiversity and hydropower development—the Mekong River basin. Our results revealed the presence of 2 highly divergent coexisting genetic lineages which may be cryptic species. Within the lineage with the greatest sample sizes, pairwise FST values, principal component analysis, and a STRUCTURE analysis all suggest that long-distance migration is not common across the Lower Mekong Basin, even in areas where flood-pulse hydrology has limited genetic divergence. In tributaries, effective population size estimates were at least an order of magnitude lower than in the Mekong mainstream indicating these populations may be more vulnerable to perturbations such as human-induced fragmentation. Fish isolated upstream of several dams in one tributary exhibited particularly low genetic diversity, high amounts of relatedness, and a level of inbreeding (GIS = 0.51) that has been associated with inbreeding depression in other outcrossing species. Our results highlight the importance of assessing genetic structure and diversity in riverine fisheries populations across proposed dam development sites for the preservation of these critically important resources.

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