Meiotic behaviour in the first interspecific hybrids between Brachiaria brizantha and Brachiaria decumbens

Abstract

Brachiaria brizantha and Brachiaria decumbens constitute the two most widely used tropical forage species for cultivated pastures and support both beef and dairy cattle production in the tropics. Two apomictic cultivars -B. brizantha cv. ÔMaranduÕ and B. decumbens cv. ÔBasiliskÕ -cover more than 100 million hectares of cultivated pastures throughout Latin America and Southeast Asia. This paper discusses the cytogenetic data of the first successful attempt in obtaining interspecific hybrids between these two species. Artificial hybridization between two diploid (2n = 2x = 18) sexual accessions (B. brizantha, B105 · B. decumbens, D004) was performed in the greenhouse. Only three hybrids were recovered. One of them was treated with colchicine in tissue culture and two amphidiploid plants were obtained. Meiosis in the diploid genitors was quite normal, while in the diploid hybrid parental genome separation was observed together with some irregular chromosome segregation. Genome separation was also observed in several cells in the two 4n amphidiploid hybrids. In these, a high number of meiocytes with chromosomes chaotically spread in the cytoplasm was recorded during meiosis. The abnormalities observed compromised the meiotic products characterized by polyads. Chromosomes associated generally as bivalents but some association as quadrivalents in diakinesis in one of the amphidiploid hybrids indicates taxonomic proximity between these two species. Moreover, it indicates that introgression of desirable genes may be feasible between these two most important agronomic species of the genus.

Inducing autotetraploids in cassava using oryzalin and colchicine and their in vitro morphophysiological effects

“…Colchicine is the most widely used and successful antimitotic (Ishigaki et al, 2009;Quesenberry et al, 2010;Souza-Kaneshima et al, 2010). However, according to Nassar (2006), colchicine has been used since the 1960s without effective success in the generation of polyploid cassava varieties, probably due to the genetic instability of the plants generated, because they have often presented tissues with different ploidy (mixoploidy).…”

Meiotic behavior during microsporogenesis of Alchornea triplinervia (Sprengel) Müller Argoviensis

“…The chromosomes in precocious migration in metaphases I may have originated from univalents in diakinesis or have been a result of precocious terminalization of chiasma and the late terminalization of these chiasmas makes the laggard chromosomes in anaphase I (SOUZA-KANESHIMA et al, 2010).…”

Meiotic behavior of Brachiaria decumbens hybrids

“…In Brachiaria, the various meiotic abnormalities observed in cytogenetic analyses compromise normal chromosome behavior and lead to the formation of infertile gametes (Risso-Pascotto et al, 2005;Mendes-Bonato et al, 2002Fuzinatto et al, 2007;Felismino et al, 2008, Ricci et al, 2010Souza-Kaneshima et al, 2010;Pagliarini et al, 2012a,b).…”