Meiotic behavior as a selection tool in the breeding of <Emphasis Type="Italic">Brachiaria humidicola</Emphasis> (Poaceae) |
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| Authors: | Kellen?Regina?Boldrini Eleniza?de?Victor Adamowski Hugo?Message Vergílio?Calisto Email author" target="_blank">Maria?Suely?PagliariniEmail author Cacilda?Borges?do?Valle |
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| Institution: | 1.Department of Cell Biology and Genetics,State University of Maringá,Maringá,Brazil;2.Embrapa Beef Cattle Research Center,Campo Grande,Brazil |
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| Abstract: | Brachiaria humidicola is a tropical grass that grows in seasonally swampy grasslands in Africa. In Brazil, two apomictic cultivars (2n = 54) of this species are widely used as pastures in poorly drained soils. The recent discovery of a sexual polyploid accession
(2n = 36) in the germplasm collection at the Embrapa Beef Cattle Research Center allowed intraspecific hybridization with the
objective of broadening the genetic variability and selection of superior genotypes in this species. Hybridization, however,
depends on accessions with the same ploidy level. Cytological analyses of 55 accessions revealed that 19 apomictic accessions
also presented 2n = 36 chromosomes. Chromosome pairing in hexavalent association at diakinesis and metaphase I suggested that the basic chromosome
number for this species is x = 6. Cytological analysis revealed abnormalities in variable frequencies in the meiosis of these hexaploid (2n = 6x = 36) accessions. The most common were those related to irregular chromosome segregation which led to unbalanced gamete formation,
but chromosome stickiness was also recorded. These results clearly demonstrate the value of cytogenetics in the choice of
genitors and for superior hybrids to be obtained in the breeding of this species. For that both the ploidy level and the frequency
of abnormalities need to be considered, besides other favorable agronomic characteristics. |
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