Cytogenetic evidence for genome elimination during microsporogenesis in interspecific hybrid between Brachiaria ruziziensis and B. brizantha (Poaceae)

Mendes-Bonato, Andréa Beatriz; Risso-Pascotto, Claudicéia; Pagliarini, Maria Suely; Valle, Cacilda Borges do

doi:10.1590/s1415-47572006000400021

Cited by 19 publications

(23 citation statements)

References 10 publications

(10 reference statements)

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“…Such meiotic behavior is typical of recently formed natural hybrids resulting from parental genomes with dissimilar meiotic rhythms. This phenomenon has previously been found in 1 accession of P. subciliatum Chase (Adamowski et al, 1998), has been reported several times in species of Brachiaria, and is presently accepted (Shirasuna, 2012) within the circumscription of Urochloa (Risso-Pascotto et al, 2004;Mendes-Bonato et al, 2006;Boldrini et al, 2009Boldrini et al, , 2010Ricci et al, 2010). Although several polyploids were formed as a result of genome duplication events occurring several millions of years ago, Wendel and Doyle (2005) consider it an active and ongoing process, termed paleopolyploidization; the meiotic behavior of the P. jesuiticum accessions reported here reinforces this view.…”

Section: Meiotic Behavior and Evidence Of Recent Natural Hybridizationsupporting

confidence: 69%

Complete asynapsis resulting in 2n pollen formation in Paspalum jesuiticum Parodi (Poaceae)

Filho¹,

Santos²,

Souza³

et al. 2014

Genet. Mol. Res.

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ABSTRACT. Cytological investigation revealed complete asynapsis during microsporogenesis in 2 wild accessions of Paspalum jesuiticum collected in distinct Brazilian regions. Both accessions were hexaploid (2n = 6x = 60) and 60 univalents could be counted at diakinesis. In this phase, the majority of meiocytes exhibited univalents with both chromatids. After alignment at the metaphase plate, the chromatids segregated to the poles. Only 1 meiotic division (equational) occurred, and after cytokinesis, a dyad with 2n microspores was formed. The genetic constitution of the 2n gametes was equivalent to that of first division restitution (FDR). Since recombination did not occur, 100% transmission of parental heterozygosity could be expected from the FDR 2n gametes. The meiotic behavior of both accessions suggested that they resulted from a recent natural hybridization event. The potential use of the 2n gametes in Paspalum breeding programs has been discussed.

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Section: Meiotic Behavior and Evidence Of Recent Natural Hybridizationsupporting

confidence: 69%

Complete asynapsis resulting in 2n pollen formation in Paspalum jesuiticum Parodi (Poaceae)

Filho¹,

Santos²,

Souza³

et al. 2014

Genet. Mol. Res.

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“…DiVerent plants of the same parental species have produced diVerent results in relation to meiotic behavior in hybrids (M. Felismino unpublished data). Chromosome elimination of one parental genome by asynchrony during meiosis was reported in Brachiaria hybrids when some of these accessions were used in crosses (Risso-Pascotto et al 2004;Mendes-Bonato et al 2006c). The results obtained until now from analysis of meiotic behavior in the sexual B. ruziziensis, and the apomictic male genitors, B. brizantha/B.…”

Section: Resultsmentioning

confidence: 96%

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

et al. 2008

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Sexuality is correlated with diploidy and apomixis with polyploidy in the Brachiaria genus. Brachiaria ruziziensis is a key species in Brachiaria breeding due to its obligate sexuality and intrinsic agronomic qualities. InterspeciWc crosses in the genus became feasible only when a few diploid accessions of B. ruziziensis were artiWcially tetraploidized and remained sexual. Hybridization has been done since, using natural tetraploid apomictic accessions of B. brizantha or B. decumbens as pollen donors. Twenty two accessions of B. ruziziensis from the Embrapa Beef Cattle germplasm collection (Campo Grande, MS, Brazil) were cytologically analyzed: 16 are natural diploids (2n = 2x = 18) and six are artiWcially induced tetraploids (2n = 4x = 36). The meiotic behavior in the 16 diploid accessions varied. The mean of meiotic abnormalities per accession ranged from zero to 24.46%. Meiotic behavior in the induced tetraploid accessions also varied with the mean of meiotic abnormalities ranging from 5.20% to 54.71%. The most common abnormalities observed in both the diploid and the tetraploid accessions, were those related to irregular chromosome segregation. In one tetraploid accession, with a high frequency of those, other irregularities involving chromosome orientation at metaphase plate and chromosome convergence to the poles, a meiotic mutation known as divergent spindle, were recorded. Meiotic behavior should be considered in selecting potential genitors for breeding.

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“…In the accessions D53 and D71, and in the other cases of hybridization followed by a genome elimination in Brachiaria (Mendes et al, 2006;Risso-Pascotto et al, 2006b;Boldrini et al, 2009aBoldrini et al, ,b, 2010 it was evident that both parental genomes did not display the same meiotic rhythm. Genomes organizing their own metaphase plate and the presence of two nucleoli observed in natural accessions (Mendes et al, 2006;Risso-Pascotto et al, 2006b;Boldrini et al, 2009aBoldrini et al, ,b, 2010, and in interspecific artificial Brachiaria hybrids (Mendes-Bonato et al, 2006b;Adamowski et al, 2008) as well as in nonaploid accessions of B. humidicola (Boldrini et al, 2009a) also show that these parental genetic systems are not able to share the same cytoplasm immediately after hybridization and some accommodations are required for these genotypes to be successful.…”

Section: Resultsmentioning

confidence: 99%

Genome elimination during microsporogenesis in two pentaploid accessions of Brachiaria decumbens (Poaceae)

Ricci¹,

Pagliarini²,

Valle³

2010

Genet. Mol. Res.

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ABSTRACT. Polyploidy is a prominent and significant force in plant evolution, taking place since ancient times and continuing until today. Recent cytogenetic studies in the genus Brachiaria using germplasm collected from wild African savannas in the 1980s revealed that most species and accessions within species are polyploid. Diploid, tetraploid, and pentaploid accessions have been found. We found asynchronous meiosis during microsporogenesis, followed by genome elimination, in two pentaploid (2n = 5x = 45) accessions (D53 and D71) of a hardy, invasive pasture grass, introduced from Africa to Brazil, Brachiaria decumbens. In these accessions, chromosomes paired as 18 bivalents and nine univalents during diakinesis, suggesting that these accessions resulted from a recent event of natural hybridization. The lack of chromosome associations in the genomes suggests that these accessions resulted from hybridization between two genotypes that are not closely related, with low genome affinity and with different meiotic rhythms. This supposition is reinforced by the meiotic behavior of the nine univalents, which were always laggard in relation to the other chromosomes and eliminated as micronuclei Genome elimination in Brachiaria decumbens in microspores. The behavior of these accessions, which have an odd level of ploidy and confirmed genome elimination, supports the general assumption that a polyploid accession can undergo a new event of polyploidization by natural hybridization (neopolyploidyzation). This evidence for natural hybridization in Brachiaria shows that this is a wild genus in an ongoing evolutionary process.

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Cytogenetic evidence for genome elimination during microsporogenesis in interspecific hybrid between Brachiaria ruziziensis and B. brizantha (Poaceae)

Cited by 19 publications

References 10 publications

Complete asynapsis resulting in 2n pollen formation in Paspalum jesuiticum Parodi (Poaceae)

Complete asynapsis resulting in 2n pollen formation in Paspalum jesuiticum Parodi (Poaceae)

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

Genome elimination during microsporogenesis in two pentaploid accessions of Brachiaria decumbens (Poaceae)

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