Current knowledge on B chromosomes in natural populations of helminth parasites: a review

2004 ◽  
Vol 106 (2-4) ◽  
pp. 222-229 ◽  
Author(s):  
M. Špakulová ◽  
J.C. Casanova
Keyword(s):  
Current Knowledge ◽  
Natural Populations ◽  
B Chromosomes ◽  
Helminth Parasites

Transmission analysis of mitotically unstable B chromosomes in Locusta migratoria

Genome ◽  
1994 ◽  
Vol 37 (6) ◽  
pp. 1027-1034 ◽  
Author(s):  
M. C. Pardo ◽  
M. D. López-León ◽  
J. Cabrero ◽  
J. P. M. Camacho
Keyword(s):  
Germ Line ◽  
Current Knowledge ◽  
Locusta Migratoria ◽  
Sexual Transmission ◽  
Natural Populations ◽  
Meiotic Drive ◽  
B Chromosome ◽  
B Chromosomes ◽  
The Other ◽  
Mitotic Instability

Seventeen controlled crosses in which the mitotically unstable B chromosome of Locusta migratoria was carried by one parent only have provided evidence that B chromosomes are significantly eliminated during sexual transmission in males, at a mean rate that almost counteracts the premeiotic accumulation derived from mitotic instability during germ line development. On the other hand, B chromosomes are significantly accumulated in females, presumably by their preferential migration to the secondary oocyte during the first meiotic division. These results substantially change the current knowledge about this B chromosome system, because the main B accumulation occurs in females and not in males, as was hitherto thought. Furthermore, this case shows that the maintenance of a single B system in natural populations may be the result of many different forces and mechanisms acting for and against B chromosomes.Key words: locust, Locusta migratoria, B chromosomes, accumulation mechanisms, meiotic drive, B elimination, parthenogenesis.

Helminth parasites of wild Mexican mammals: list of species, hosts and geographical distribution

Zootaxa ◽  
2012 ◽  
Vol 3290 (1) ◽  
pp. 1 ◽  
Author(s):  
LUIS GARCÍA-PRIETO ◽  
JORGE FALCÓN-ORDAZ ◽  
CARMEN GUZMÁN-CORNEJO
Keyword(s):  
Geographical Distribution ◽  
Current Knowledge ◽  
Helminth Parasites ◽  
Wild Mammals ◽  
First Time

In the present work, a total of 339 nominal taxa of helminths (53 trematodes, 46 cestodes, 12 acanthocephalans, 227 nem-atodes, and 1 hirudinean), associated with 136 taxa of wild mammals from Mexico, are listed. Information on hosts, hab-itat, distribution, and records is included; these data come from 242 localities, pertaining to 31 of the 32 Mexican states,and represent the current knowledge on helminth parasites of wild mammals in Mexico. Eighteen taxa of helminths are registered for the first time in Mexico, and 46 new locality records are presented.

scholarly journals Genetic Variability of Natural Populations of Grapevine leafroll-associated virus 2 in Pacific Northwest Vineyards

2010 ◽  
Vol 100 (7) ◽  
pp. 698-707 ◽  
Author(s):  
Sridhar Jarugula ◽  
Olufemi J. Alabi ◽  
Robert R. Martin ◽  
Rayapati A. Naidu
Keyword(s):  
Genetic Variability ◽  
Pacific Northwest ◽  
Current Knowledge ◽  
Natural Populations ◽  
Taxonomic Status ◽  
Amino Acid Sequences ◽  
Enzyme Linked Immunosorbent Assay ◽  
Polymorphism Analysis ◽  
Nonsynonymous Site ◽  
Genomic Regions

Genetic variability of field populations of Grapevine leafroll-associated virus 2 (GLRaV-2) in Pacific Northwest (PNW) vineyards was characterized by sequencing the entire coat protein (CP) and a portion of the heat-shock protein-70 homolog (HSP70h) genes. Phylogenetic analysis of CP and HSP70h nucleotide sequences obtained in this study and corresponding sequences from GenBank revealed segregation of GLRaV-2 isolates into six lineages with virus isolates from PNW distributed in ‘PN’, ‘H4’, and ‘RG’ lineages. An estimation of the ratio of nonsynonymous substitutions per nonsynonymous site to synonymous substitutions per synonymous site indicated that different selection pressures may be acting on the two genomic regions encoding proteins with distinct functions. Multiple alignments of CP amino acid sequences showed lineage-specific differences. Enzyme-linked immunosorbent assay results indicated that GLRaV-2-specific antibodies from a commercial source are unable to reliably detect GLRaV-2 isolates in the RG lineage, thereby limiting antibody-based diagnosis of all GLRaV-2 isolates currently found in PNW vineyards. A protocol based on reverse-transcription polymerase chain reaction and restriction fragment length polymorphism analysis was developed for differentiating GLRaV-2 isolates belonging to the three lineages present in the region. The taxonomic status of GLRaV-2 is discussed in light of the current knowledge of global genetic diversity of the virus.

Meiotic stability of B chromosomes and production of macrospermatids in Aiolopus strepens (Orthoptera: Acrididae)

Genome ◽  
1987 ◽  
Vol 29 (1) ◽  
pp. 5-10 ◽  
Author(s):  
J. A. Suja ◽  
C. Garcia de la Vega ◽  
J. S. Rufas
Keyword(s):  
Key Words ◽  
Natural Populations ◽  
B Chromosomes ◽  
Supernumerary Chromosomes ◽  
Mitotic Instability ◽  
Meiotic Stability ◽  
Intercellular Connections

Four males from several Spanish natural populations of Aiolopus strepens were found to carry B chromosomes. These are short and acrocentric and are identical in the different individuals. They show mitotic instability and meiotic stability. When present in odd numbers one unpaired B is generally observed, while in even numbers they usually form bivalents. In no case were lagging B's observed. B chromosomes do not affect nucleolar expression. A significant increase in the number of macrospermatids is found in individuals with B's. This is more pronounced in follicles containing odd numbers of supernumerary chromosomes. A possible explanation based on an assumed influence of B univalents on the maintenance of intercellular connections is discussed. Key words: B chromosomes, spermiogenesis, insect cytogenetics.

Undertransmission of a supernumerary chromosome segment through heterozygous females possessing B chromosomes in the grasshopper Eyprepocnemis plorans

Genome ◽  
1994 ◽  
Vol 37 (4) ◽  
pp. 705-709 ◽  
Author(s):  
M. D. López-León ◽  
M. C. Pardo ◽  
J. Cabrero ◽  
J. P. M. Camacho
Keyword(s):  
Extra Chromosome ◽  
Natural Populations ◽  
Supernumerary Chromosome ◽  
B Chromosomes ◽  
Chromosome Segment ◽  
Transmission Ratio ◽  
Eyprepocnemis Plorans ◽  
Mendelian Transmission

The transmission ratio (ks) for a supernumerary chromosome segment was studied in a total of 54 heterozygous females collected from two Spanish natural populations of the grasshopper Eyprepocnemis plorans. Our analysis clearly demonstrated that ks is negatively dependent on the number of B chromosomes in the female. The possible mechanisms by which B chromosomes may cause undertransmission of the supernumerary segment, and the implications of this phenomenon for the maintenance of this extra chromosome segment, are discussed.Key words: supernumerary segments, B chromosomes, Mendelian transmission, grasshoppers.

Mycorrhizae, mycorrhizospheres, and reforestation: current knowledge and research needs

1987 ◽  
Vol 17 (8) ◽  
pp. 929-940 ◽  
Author(s):  
D. A. Perry ◽  
R. Molina ◽  
M. P. Amaranthus
Keyword(s):  
Environmental Factors ◽  
Mycorrhizal Fungi ◽  
Current Knowledge ◽  
Seedling Survival ◽  
Natural Populations ◽  
Tree Seedlings ◽  
Ecosystem Structure ◽  
Clear Cutting ◽  
Mycorrhiza Formation ◽  
Sphere Of Influence

Although not a panacea, management of mycorrhizae and associated organisms is an important reforestation aid. Its three major components are protection of the indigenous soil community and evaluation of inoculation needs, integration of inoculation programs into existing reforestation technology, and research. Clear-cutting frequently results in reduced mycorrhizae formation, particularly when reforestation is delayed and no other host plants are present to maintain fungal populations. Implications of such reductions for reforestation vary with environmental factors and tree species. Adequate mycorrhiza formation is especially critical for ectomycorrhizal trees growing on poor soils or in environments where seedlings must establish quickly to survive. It may also be important where early successional, noncrop plants do not support the same mycobiont as the crop. In such circumstances, a self-reinforcing trend may develop, with poor mycorrhiza formation reducing seedling survival and poor tree stocking leading to further loss of mycorrhizal inocula. Inoculating nursery seedlings with mycobionts holds promise for improving outplanting performance only if site-adapted fungi are used. A practical alternative is to improve nursery practices to enhance natural populations of mycorrhizal fungi. Seedlings leaving the nursery with diverse mycorrhizae may perform better than those leaving with only one or a few nursery-adapted types. Research is needed in three broad areas: on adaptations of mycorrhizal fungi to particular environmental factors; on interactions between tree seedlings and processes occurring within the sphere of influence of roots (the rhizosphere) or of mycorrhizal roots (the mycorrhizosphere); and on the role of mycorrhizae and associated organisms in ecosystem structure and processes, particularly nutrient cycling, plant-plant interaction, and soil structure.

scholarly journals Revision of the banding sequence pool and new data on chromosomal polymorphism in natural populations of Chironomus agilis Shobanov et Djomin, 1988 (Diptera, Chironomidae)

2021 ◽  
Vol 15 (4) ◽  
pp. 527-541
Author(s):  
Veronika V. Golygina ◽  
Oksana V. Ermolaeva
Keyword(s):  
Qualitative Analysis ◽  
Natural Populations ◽  
Chromosomal Polymorphism ◽  
B Chromosomes ◽  
Medium Level ◽  
Banding Sequence ◽  
First Time ◽  
Two Populations

Quantitative and qualitative analysis of chromosomal polymorphism in 19 natural populations of Ch. agilis had been performed. Most studied populations showed a medium level of chromosomal polymorphism: on average 45±3.0% of specimens are heterozygotes with 0.52±0.01 heterozygotic inversion per larvae. Besides inversions, B-chromosomes were found in two populations. The total number of banding sequences found in banding sequence pool of Ch. agilis is 16. Three banding sequences – p’agiB3, p’agiD3, p’agiF3 – are described for the first time.

scholarly journals Biology and use of the Pacific fat sleeper Dormitator latifrons (Richardson, 1844): state of the art review

2021 ◽  
Vol 49 (3) ◽  
pp. 391-403
Author(s):  
Fernando Vega-Villasante ◽  
Luis E. Ruiz-González ◽  
Olimpia Chong-Carrillo ◽  
Mao E.R. Basto-Rosales ◽  
David J. Palma-Cancino ◽  
...  
Keyword(s):  
Latin America ◽  
Geographic Distribution ◽  
Fish Species ◽  
State Of The Art ◽  
Current Knowledge ◽  
Natural Populations ◽  
Systematic Research ◽  
Review Of The Literature ◽  
The Pacific ◽  
Cultivation Techniques

The present work is a review of the literature on the native Mexican fish Dormitator latifrons. The aim is to contribute to the integration and systematization of current knowledge to make it easier to identify existing knowledge gaps and breakthroghs Moreover, promote the successful cultivation and protection of this species whose consumption is increasing in Latin America. A review of the articles related to D. latifrons published in international and regional databases was carried out. The articles reviewed focus on taxonomy and systematics, phylogenetic, geographic distribution, ecology, physiology, reproduction, development, pathology, health, and the technologies used to cultivate this fish species. The conclusion is that, even though the cultivation of D. latifrons is of commercial interest in some countries, there are still significant gaps in our knowledge of biology and, consequently, the domestication potential of the species. Filling these gaps will require systematic research efforts on protecting natural populations and improving mass cultivation techniques.

scholarly journals Annual dynamics of Zymoseptoria tritici populations in wheat cultivar mixtures: a compromise between the efficiency and durability of a recently broken-down resistance gene?

2021 ◽  
Author(s):  
Carolina Orellana-Torrejon ◽  
Tiphaine Vidal ◽  
Anne-Lise Boixel ◽  
Sandrine Gélisse ◽  
Sébastien Saint-Jean ◽  
...  
Keyword(s):  
Resistance Gene ◽  
Fungal Pathogen ◽  
Current Knowledge ◽  
Natural Populations ◽  
Pure Stand ◽  
Zymoseptoria Tritici ◽  
Trade Offs ◽  
Pathogen Populations ◽  
Dual Objectives ◽  
Cultivar Mixtures

AbstractCultivar mixtures slow polycyclic epidemics but may also modify the evolution of pathogen populations by diversifying the selection pressures exerted by their plant hosts at field scale. We compared the dynamics of natural populations of the fungal pathogen Zymoseptoria tritici in pure stands and in three binary mixtures of wheat cultivars (one susceptible cultivar and one cultivar carrying the recently broken-down Stb16q gene) over two annual field epidemics. We combined analyses of population ‘size’ based on disease severity, and of population ‘composition’ based on assessments of changes in the frequency of virulence against Stb16q in seedling assays with more than 3000 strains. In the field, disease levels were lower in mixtures, with each cultivar providing the other with reciprocal protection. The three cultivar proportions in the mixtures (0.25, 0.5 and 0.75) modulated the decrease in (i) the size of the pathogen population relative to the two pure stands, (ii) the size of the virulent subpopulation, and (iii) the frequency of virulence relative to the pure stand of the cultivar carrying Stb16q. Our findings suggest that optimal proportions may differ slightly between the three indicators considered. We identified potential trade-offs that should be taken into account when deploying a resistance gene in cultivar mixtures: between the dual objectives ‘efficacy’ and ‘durability’, and between the ‘size’ and ‘frequency’ of the virulent subpopulation. Based on current knowledge, it remains unclear whether virulent subpopulation size or frequency has the largest influence on interepidemic virulence transmission.

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