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The Bactrocera dorsalis species complex: comparative cytogenetic analysis in support of Sterile Insect Technique applications.

Augustinos AA, Drosopoulou E, Gariou-Papalexiou A, Bourtzis K, Mavragani-Tsipidou P, Zacharopoulou A - BMC Genet. (2014)

Bottom Line: Therefore, the use of the available polytene chromosome maps for B. dorsalis s.s. as reference maps for all these five biological entities is proposed.Present data provide important insight in the genetic relationships among the different members of the B. dorsalis complex, and, along with other studies in the field, can facilitate SIT applications targeting this complex.Moreover, the availability of 'universal' reference polytene chromosome maps for members of the complex, along with the documented application of in situ hybridization, can facilitate ongoing and future genome projects in this complex.

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ABSTRACT

Background: The Bactrocera dorsalis species complex currently harbors approximately 90 different members. The species complex has undergone many revisions in the past decades, and there is still an ongoing debate about the species limits. The availability of a variety of tools and approaches, such as molecular-genomic and cytogenetic analyses, are expected to shed light on the rather complicated issues of species complexes and incipient speciation. The clarification of genetic relationships among the different members of this complex is a prerequisite for the rational application of sterile insect technique (SIT) approaches for population control.

Results: Colonies established in the Insect Pest Control Laboratory (IPCL) (Seibersdorf, Vienna), representing five of the main economic important members of the Bactrocera dorsalis complex were cytologically characterized. The taxa under study were B. dorsalis s.s., B. philippinensis, B. papayae, B. invadens and B. carambolae. Mitotic and polytene chromosome analyses did not reveal any chromosomal characteristics that could be used to distinguish between the investigated members of the B. dorsalis complex. Therefore, their polytene chromosomes can be regarded as homosequential with the reference maps of B. dorsalis s.s.. In situ hybridization of six genes further supported the proposed homosequentiallity of the chromosomes of these specific members of the complex.

Conclusions: The present analysis supports that the polytene chromosomes of the five taxa under study are homosequential. Therefore, the use of the available polytene chromosome maps for B. dorsalis s.s. as reference maps for all these five biological entities is proposed. Present data provide important insight in the genetic relationships among the different members of the B. dorsalis complex, and, along with other studies in the field, can facilitate SIT applications targeting this complex. Moreover, the availability of 'universal' reference polytene chromosome maps for members of the complex, along with the documented application of in situ hybridization, can facilitate ongoing and future genome projects in this complex.

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Polymorphic asynapses in different polytene chromosome regions. Variations in the appearance of the asynaptic region 73-74 of chromosome arm 5R: a) in B. carambolae and (b, c) in the B. dorsalis s.s. × B. carambolae hybrid. Minor asynapses in the B. dorsalis s.s. × B. carambolae hybrid within: d) regions 43 of chromosome arm 4L and e) regions 78-79 of chromosome arm 5R. Asterisks indicate the asynaptic regions. Scale bar represents 10 μm.
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Figure 2: Polymorphic asynapses in different polytene chromosome regions. Variations in the appearance of the asynaptic region 73-74 of chromosome arm 5R: a) in B. carambolae and (b, c) in the B. dorsalis s.s. × B. carambolae hybrid. Minor asynapses in the B. dorsalis s.s. × B. carambolae hybrid within: d) regions 43 of chromosome arm 4L and e) regions 78-79 of chromosome arm 5R. Asterisks indicate the asynaptic regions. Scale bar represents 10 μm.

Mentions: A comparison of the polytene elements of all analyzed strains with the reference map of B. dorsalis s.s. [50] revealed perfect correspondence of the banding patterns. No fixed chromosome rearrangements were detected. Consequently, all the strains can be regarded as homosequential and the available polytene chromosome maps of B. dorsalis s.s. can be used for all of them. Furthermore, the heterochromatic mass of the centromeric regions was identical in quality and quantity in all analyzed members of the complex, providing a useful landmark for the identification of each polytene chromosome. The characteristic polymorphic asynapsis on the right arm of chromosome 5 (sections 73-74), previously found in B. dorsalis s.s. [50], was also observed at varying frequencies (10-50 %) in all samples (Figure 2a-c). A few additional minor polymorphic asynapses were distributed over the polytene arms (Figure 2d-e).


The Bactrocera dorsalis species complex: comparative cytogenetic analysis in support of Sterile Insect Technique applications.

Augustinos AA, Drosopoulou E, Gariou-Papalexiou A, Bourtzis K, Mavragani-Tsipidou P, Zacharopoulou A - BMC Genet. (2014)

Polymorphic asynapses in different polytene chromosome regions. Variations in the appearance of the asynaptic region 73-74 of chromosome arm 5R: a) in B. carambolae and (b, c) in the B. dorsalis s.s. × B. carambolae hybrid. Minor asynapses in the B. dorsalis s.s. × B. carambolae hybrid within: d) regions 43 of chromosome arm 4L and e) regions 78-79 of chromosome arm 5R. Asterisks indicate the asynaptic regions. Scale bar represents 10 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4255788&req=5

Figure 2: Polymorphic asynapses in different polytene chromosome regions. Variations in the appearance of the asynaptic region 73-74 of chromosome arm 5R: a) in B. carambolae and (b, c) in the B. dorsalis s.s. × B. carambolae hybrid. Minor asynapses in the B. dorsalis s.s. × B. carambolae hybrid within: d) regions 43 of chromosome arm 4L and e) regions 78-79 of chromosome arm 5R. Asterisks indicate the asynaptic regions. Scale bar represents 10 μm.
Mentions: A comparison of the polytene elements of all analyzed strains with the reference map of B. dorsalis s.s. [50] revealed perfect correspondence of the banding patterns. No fixed chromosome rearrangements were detected. Consequently, all the strains can be regarded as homosequential and the available polytene chromosome maps of B. dorsalis s.s. can be used for all of them. Furthermore, the heterochromatic mass of the centromeric regions was identical in quality and quantity in all analyzed members of the complex, providing a useful landmark for the identification of each polytene chromosome. The characteristic polymorphic asynapsis on the right arm of chromosome 5 (sections 73-74), previously found in B. dorsalis s.s. [50], was also observed at varying frequencies (10-50 %) in all samples (Figure 2a-c). A few additional minor polymorphic asynapses were distributed over the polytene arms (Figure 2d-e).

Bottom Line: Therefore, the use of the available polytene chromosome maps for B. dorsalis s.s. as reference maps for all these five biological entities is proposed.Present data provide important insight in the genetic relationships among the different members of the B. dorsalis complex, and, along with other studies in the field, can facilitate SIT applications targeting this complex.Moreover, the availability of 'universal' reference polytene chromosome maps for members of the complex, along with the documented application of in situ hybridization, can facilitate ongoing and future genome projects in this complex.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Background: The Bactrocera dorsalis species complex currently harbors approximately 90 different members. The species complex has undergone many revisions in the past decades, and there is still an ongoing debate about the species limits. The availability of a variety of tools and approaches, such as molecular-genomic and cytogenetic analyses, are expected to shed light on the rather complicated issues of species complexes and incipient speciation. The clarification of genetic relationships among the different members of this complex is a prerequisite for the rational application of sterile insect technique (SIT) approaches for population control.

Results: Colonies established in the Insect Pest Control Laboratory (IPCL) (Seibersdorf, Vienna), representing five of the main economic important members of the Bactrocera dorsalis complex were cytologically characterized. The taxa under study were B. dorsalis s.s., B. philippinensis, B. papayae, B. invadens and B. carambolae. Mitotic and polytene chromosome analyses did not reveal any chromosomal characteristics that could be used to distinguish between the investigated members of the B. dorsalis complex. Therefore, their polytene chromosomes can be regarded as homosequential with the reference maps of B. dorsalis s.s.. In situ hybridization of six genes further supported the proposed homosequentiallity of the chromosomes of these specific members of the complex.

Conclusions: The present analysis supports that the polytene chromosomes of the five taxa under study are homosequential. Therefore, the use of the available polytene chromosome maps for B. dorsalis s.s. as reference maps for all these five biological entities is proposed. Present data provide important insight in the genetic relationships among the different members of the B. dorsalis complex, and, along with other studies in the field, can facilitate SIT applications targeting this complex. Moreover, the availability of 'universal' reference polytene chromosome maps for members of the complex, along with the documented application of in situ hybridization, can facilitate ongoing and future genome projects in this complex.

Show MeSH
Related in: MedlinePlus