Meiotic behavior as a selection tool in the breeding of Brachiaria humidicola (Poaceae) Kellen Regina Boldrini • Eleniza de Victor Adamowski • Hugo Message • Vergı ´lio Calisto • Maria Suely Pagliarini • Cacilda Borges do Valle Received: 28 July 2010 / Accepted: 19 February 2011 / Published online: 15 March 2011 Ó Springer Science+Business Media B.V. 2011 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 broad- ening 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 chromo- somes. Chromosome pairing in hexavalent association at diakinesis and metaphase I suggested that the basic chromosome number for this species is x = 6. Cyto- logical 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 agro- nomic characteristics. Keywords Brachiaria humidicola Á Breeding Á Forage grass Á Hybridization Á Meiosis Introduction Brachiaria (Syn. Urochloa P. Beauv.) is the single most important genus of forage grass for pastures in the tropics. The forage potential of the genus was recognized in the 1960s, initially in Australia and a decade latter in South America. A handful of Brachiaria cultivars, derived directly from naturally occurring germplasm, have greatly impacted animal production systems throughout the tropics in the past 25–30 years. It became the major component of sown pastures and the basis for beef and dairy production in the lowlands and tropical savannas (Miles et al. 1996, 2004). A number of cultivars have been released in the last three decades. In Brazil, there are 10 registered cultivars listed on the National Service for Cultivar Protection and, except for one, the others are apomictic ecotypes that, for all practical purposes, are ‘clones’ through seeds, therefore creating monocrops. The K. R. Boldrini Á E. de Victor Adamowski Á H. Message Á V. Calisto Á M. S. Pagliarini (&) Department of Cell Biology and Genetics, State University of Maringa ´, Maringa ´, PR 87020-900, Brazil e-mail: mspagliarini@uem.br C. B. d. Valle Embrapa Beef Cattle Research Center, Campo Grande, MS, Brazil 123 Euphytica (2011) 182:317–324 DOI 10.1007/s10681-011-0402-5