Abstract
Knowledge about the pollen viability is important to ensure success in controlled hybridizations and, consequently, support breeding programs. The aims of this study were to evaluate the pollen viability in progenies of artificially induced tetraploid accessions of Brachiaria ruziziensis , and to verify if the position of the flower buds on the raceme affects the pollen viability rate. Staining of aborted and non-aborted pollen (Alexander’s technique) was used to determine the viability of the pollen grains. Tetraploid accessions of B. ruziziensis plants had high pollen viability (x = 76.8% to x = 99.6%). Some of these plants had viability rates similar to diploid B. ruziziensis , showing that the induction of chromosome duplication by colchicine did not result in abnormalities in production and morphology of pollen grains. Pollen grains from middle and apical regions of the raceme presented higher viability rates (x = 97.9% and x = 97.7% respectively). The viability of pollen grains in artificially induced tetraploid accessions of B. ruziziensis plants was high, which may favor obtaining fertile descendants in possible crosses
Highlights
Grasses of the genus Brachiaria (Trin.) Griseb.[(syn
The result of analysis of variance detected significant differences for pollen grain viability among the plants derived from the tetraploid B. ruziziensis population and in comparison with the control plants (Table 1)
Group 2, formed of 11 plants, had mean pollen viability of 82.2%, and group 3 gathered most of the plants, including diploid B. ruziziensis, with a mean value of 96.7% (Table 1)
Summary
Grasses of the genus Brachiaria (Trin.) Griseb. [(syn. Biological Sciences as well as interspecific crosses involving B. brizantha, B. decumbens and B. ruziziensis (SOUZA SOBRINHO, 2005) Another interesting strategy has been artificial tetraploidization of B. ruziziensis to allow undertaking interspecific hybridizations with genotypes of B. brizantha and B. decumbens (ISHIGAKI et al, 2009) and exploit the genetic variability of the genus for selection of superior materials (PEREIRA et al, 2001; SOUZA SOBRINHO, 2005). Viability data allow correlations to be made with genetic factors such as chromosome imbalances caused by meiotic abnormalities or a high percentage of normal tetrads as a consequence of meiotic stability (RISSO-PASCOTTO et al, 2006) These data may assist in selection of genotypes and in determination of the best regions of the raceme of Brachiaria for pollen collection, which will be reflected in the efficacy of the crosses. The aims of this study were to evaluate the viability of pollen grains in artificially induced tetraploid accessions of B. ruziziensis progenies, as well as to verify possible effects of the position of the flower buds on the raceme in regard to the pollen viability rate
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