Abnormal spindle orientation during microsporogenesis in an interspecific Brachiaria (Gramineae) hybrid

Abstract

This paper reports a case of abnormal spindle orientation during microsporogenesis in an interspecific hybrid of the tropical grass Brachiaria. In the affected plant, prophase I was normal. In metaphase I, bivalents were regularly co-oriented but distantly positioned and spread over the equatorial plate. In anaphase I, chromosomes failed to converge into focused poles due to parallel spindle fibers. As a consequence, in telophase I, an elongated nucleus or several micronuclei were observed in each pole. In the second division, the behavior was the same, leading to polyads with several micronuclei. A total of 40% of meiotic products were affected. The use of this hybrid in production systems needing good-quality seeds is discussed.

Spontaneous Occurrence of Meiotic Spindle Abnormalities in 'Long Headed Poppy' (Papaver dubium L.) from Indian Cold Regions

“…These plants which depict the presence of normal 14 bivalents at MI, show irregular spindle behaviour resulting into abnormal anaphases/telophases, irregular microsporogenesis, some pollen malformation and heterogeneous sized pollen grains. Similar abnormal spindle activity leading to high percentage of laggards, bridges, unoriented chromosomes during anaphases/telophases and consequently to tetrads with micronuclei or microcytes and polyads during meiosis is reported in the colchicine induced tetraploid of Physalis pubescens (Lydia and Raja Rao 1982), and of heavy metal induced tetraploid of Helianthus annuus (Srivastava and Srivastava 2004 interspecific Brachiaria hybrid (Mendes-Bonato et al 2006). The present report of spontaneous occurrence of abnormal spindle activity in the PMCs during male meiosis in the tetraploid cytotype of P. dubium is reported for the first time.…”

Analysis of meiotic behavior in selecting potential genitors among diploid and artificially induced tetraploid accessions of Brachiaria ruziziensis (Poaceae)

“…2o, p). This abnormality was also recorded in a Brachiaria hybrid (Mendes-Bonato et al 2006b;M. Felismino, unpublished data) and was attributed to a meiotic mutation in a gene involved in the spindle microtubules convergence, known as dv (divergent spindle), Wrst reported in maize by Clark (1940), and more recently by Staiger and Cande (1990) and Shamina et al(2000).…”

Meiotic behavior in apomictic Brachiaria ruziziensis × B. brizantha (Poaceae) progenies

“…Several putative meiotic mutations have been reported among Brachiaria accessions (Mendes-Bonato et al, 2002bRisso-Pascotto et al, 2003, 2005bMendes-Vieira et al, 2005;Boldrini et al 2006;Gallo et al, 2007;Adamowski et al, 2007;Calisto et al, 2008) and in hybrids (Mendes-Bonato et al, 2004, 2006bRisso-Pascotto et al, 2005a;Fuzinatto et al, 2007ab;Adamowski et al, 2008;Felismino et al, 2008Felismino et al, , 2010. These putative mutations are frequently be-Sci.…”

“…v.69, n.6, p.380-385, November/December 2012 ing expressed in different genotypes of Brachiaria suggesting that these genes are present in the gene pool of this genus. One of these genes is the 'divergent spindle' (dv), reported in another Brachiaria hybrid resulting from a different cross between B. ruziziensis × B. brizantha (Mendes-Bonato et al, 2006b;Felismino et al, 2008). This gene affects spindle organization such that chromosomes do not converge to focused poles.…”

“…The percentage of cells expressing the divergent spindle phenotype was variable among progenies. Variations in penetrance and expressivity of dv were reported in maize and Brachiaria (Golubovskaya and Mashnenkov, 1981;Staiger and Cande, 1990;Shamina et al, 2000;Mendes-Bonato et al, 2006b;Felismino et al, 2008). This gene leads to genome fractionation, causing pollen sterility.…”