Research Article

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Apomixis origin; Centers of diversity; Electrophoresis; Evolution; Interspecific hybridization; Polyploidy; Unreduced gametes

About 98 species of Manihot are known. All of them are native to the New World and are concentrated in four regions in Brazil and Central America. All the Manihot species so far examined have 2n = 36 chromosomes. Interspecific hybrids between cassava and its wild relatives show relatively normal meiosis, and further generations can be obtained. Electrophoresis shows ... more

N.M.A. Nassar
Amphibians; Evolution; Gene redundancy; Polyploidy; Speciation

The evolution of the metazoa has been characterized by gene redundancy, generated by polyploidy, tandem duplication and retrotransposition. Polyploidy can be detected by looking for duplicated chromosomes or segments of orthologous chromosomes in post-polyploid animals. It has been proposed that the evolutionary role of polyploidy is to provide extra-copies of genes, whose subsequent ... more

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Apomixis; Interspecific crosses; Polyploidy

A new species was synthesized artificially by chromosome doubling in a hybrid. The ensuing polyploid type exhibits an apomictic nature and maintains its morphological characteristics in the progeny. It showed a frequency of multiembryonic sacs of 29% in the ovules examined, whereas sacs were absent in the diploid type.

*In honor of deceased Professor Vieira who dedicated a part ... more

N.M.A. Nassar
Chromosomal size evolution; Genome size evolution; Incongruent patterns; Oryza sativa; Polyploidy

To investigate genome size evolution, it is usually informative to compare closely related species that vary dramatically in genome size. A whole genome duplication (polyploidy) that occurred in rice (Oryza sativa) about 70 million years ago has been well documented based on current genome sequencing. The presence of three distinct duplicate blocks from the polyploidy, of ... more

X. Guo; G. Xu; Y. Zhang; X. Wen; W. Hu; L. Fan
Cytogenetics; cytotaxonomy; morphology; Polyploidy

Somatic chromosome numbers were determined for 20 new germplasm accessions of Paspalum, belonging to 17 species collected in Brazil. Chromosome number is reported for the first time for P. reduncum (2n = 18), P. cinerascens (2n = 20), P. cordatum (2n = 20), P. filgueirasii (2n = 24), P. ammodes (2n = 36), P. bicilium (2n = 40), ... more

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Brachiaria decumbens; Evolution; Genome elimination; Microsporogenesis; Natural hybridization; Polyploidy

Polyploidy is a prominent and significant force in plant evolution, taking place since ancient times and continuing until today. Recent cytogenetic studies in the genus Brachiaria using germplasm collected from wild African savannas in the 1980s revealed that most species and accessions within species are polyploid. Diploid, tetraploid, and pentaploid accessions have been found. ... more

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Myrtle is an evergreen shrub or small tree widespread throughout the Mediterranean region. In Turkey, both cultivated and wild forms, differing in plant and fruit size and fruit composition, can be found. These differences may have resulted from the domestication of the cultivated form over a long period of time. We investigated whether wild and cultivated forms of myrtle differ in ... more

S. Serçe; E. Ekbiç; J. Suda; K. Gündüz; Y. Kiyga
Cryptonephridial system; Endoreduplication; Malpighian tubules; Myrmeleon uniformis; Neuroptera; Polyploidy

The land arthropod secretory system is formed by structures called Malpighian tubules. These tubules are extremely important in insects because they maintain osmoregulation. They are located in the body cavity and are either free or inserted in the rectum wall, forming an arrangement known as the cryptonephridial system. The Malpighian tubules may have morphologically different regions, ... more

C.A. Pacheco; T.L. Silva
Asteraceae; Chromomycin A3 banding; Karyotype evolution; Polyploidy

Hypochaeris is an excellent system for studying different modes of chromosome evolution in plants. We carried out a cytogenetic analysis on populations of 2 Hypochaeris species, comprising 10 populations of H. catharinensis and 5 of H. lutea, to assess possible changes on chromosome organization in this interesting genus. Conventional Feulgen staining ... more

F.G. Fiorin; P.M. Ruas; M.A. Ortiz; E. Urtubey; N.I. Matzenbacher; C.F. Ruas
Adventitious embryony; Aneuploidy; Apospory; Hybridization; Polyploidy; Sterility

Cassava is the most important staple crop in the Tropics and Subtropics. Apomixis may revolutionize its production due to various attributes. These potential advantages include production by true seed, maintaining cultivar superiority over generations without segregation, and avoiding contamination by bacteria and viruses. Historically, apomixis was initially observed by International ... more

D.Y.H. Freitas; N.M.A. Nassar