Meiotic behavior as a selection tool in the breeding of Brachiaria humidicola (Poaceae)

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.

FISH-based mitotic and meiotic diakinesis karyotypes of Morus notabilis reveal a chromosomal fusion-fission cycle between mitotic and meiotic phases

“…Boldrini et al . 27 used the diakinesis chromosome to estimate the basic chromosome number of Brachiaria humidicola . In this study, we obtained a systemic diakinesis karyotype of M. notabilis by analyzing chromosome morphology, relative chromosome length, and FISH signals (Figs 2 and 3 ).…”

Leaf transcriptome of two highly divergent genotypes of Urochloa humidicola (Poaceae), a tropical polyploid forage grass adapted to acidic soils and temporary flooding areas

“…Koronivia grass is an outcrossed and wind-pollinated perennial tropical grass that primarily reproduces through facultative apomixis, although a single sexual genotype has been identified [12, 13]. This species shows variable levels of ploidy (6x to 9x) and a basic chromosome number of x = 6 [14, 15].…”

Cytogenetic characterization of Tropaeolum pentaphyllum Lam

“…According to Pagliarini (2000), irregular chromosome segregation is the most common meiotic abnormality in both cultivated and native species, being characterized by the presence of chromosomes in precocious chromosome ascension and laggard choromosome. These abnormalities have been reported in Zeas mays (Ricci et al 2007), Saccharum officinarum (Pagliarini et al 1990), Avena sativa (Baptista-Giacomelli et al 2000), in species of the genus Paspalum Dahmer et al 2008), in genus Capsicum L. (Souza et al 2012), and in Brachiaria (Boldrini et al 2009, Boldrini et al 2011, Mendes-Bonato et al 2006.…”