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Types and frequency of cells with meiotic abnormalities (%), and frequency of viable pollens (%) for American napier grass  pearl millet hexaploid hybrids.
Source publication
The production of hybrids between napier grass (Pennisetum purpureum, 2n = 4x = 28, genomes A′A′BB) and pearl millet (P. glaucum, 2n = 2x = 14, genome AA) results in sterile triploid plants. Such sterility of the triploid hybrid creates a hurdle for napier grass breeding programs, since it prevents propagation through seeds. Fertility can be restor...
Contexts in source publication
Context 1
... rates were high for all hybrids. For the Brazilian hybrids (Table 1) varying from 65.14% (hybrid 05) to 74.72% (hybrid 32) and for the American hybrids (Table 2) from 59.46% (hybrid 02) to 70.84% (hybrid 20). Relative to the cell number evaluated per meiotic phase, the highest abnormality rate was observed in meiosis I. ...Context 2
... configurations and chromosome number in 50 diakineses per hybrid were evaluated in order to quantify pairing alterations (Tables 1 and 2). The means of abnormal diakineses ranged from 74.60% to 84.44% for Brazilian and from 69.86% to 80% for American hybrids. ...Context 3
... general mean among American hybrids was 41.51 μm (Table 3). Hybrid 02 also had the lowest rate of abnormality (Table 2) and irregular meiotic products (4.57%), again indicating the relationship between chromosome elimination and pollen diameter. ...Context 4
... highly frequent abnormality was the presence of anaphase bridges, especially in anaphase I, for all analyzed hybrids (Tables 1 and 2). In some cells, the bridges were followed by laggard chromosomes. ...Context 5
... frequencies of viable pollens obtained by means of in vitro germination ( Figure 1L) for three Brazilian hybrids varied from 25.24% (hybrid 89) to 30.71% (hybrid 35), whereas for the three American hybrids there was a high variation, from 8.82% (hybrid 20) to 86.17% ("Paraíso") (Tables 1 and 2). It is interesting to note that the viability results obtained by germination were superior or close to those obtained by staining. ...Similar publications
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Partitioning duplicated chromosomes equally between daughter cells is a microtubule-mediated process essential to eukaryotic life. A multi-protein machine, the kinetochore, drives chromosome segregation by coupling the chromosomes to dynamic microtubule tips, even as the tips grow and shrink through the gain and loss of subunits. The kinetochore mu...
Citations
... As well as asynchronism occur because these chromosomes do not reach the telophase phase for regular chromosomal segregation (Soares-Scott et al. 2003;Corrêa et al. 2005;Damasceno et al. 2010;Kiihl et al. 2011;Souza and Pereira, 2011). In addition, paracentric translocations and inversions can cause the emergence of chromosomal bridges (Levin 2002;Paiva et al. 2012). In studies based on cereals, it was reported that sticky chromosomes may have caused the origin of chromosomal bridges in the phases of anaphases (Paiva et al. 2012). ...
... In addition, paracentric translocations and inversions can cause the emergence of chromosomal bridges (Levin 2002;Paiva et al. 2012). In studies based on cereals, it was reported that sticky chromosomes may have caused the origin of chromosomal bridges in the phases of anaphases (Paiva et al. 2012). ...
Interspecific hybrids can be studied using methodologies in which the male gamete with high reproduction potential, viability, and fertility is prioritized. Passiflora species, with lush, showy, and exotic colors, have great potential for the ornamental plant market. In addition, artificial Passiflora hybrids were developed without many difficulties because of weak reproductive barriers. Thus, meiotic and post-meiotic behaviors were analyzed with 2% acetic carmine staining. Confirmation of interspecific hybridization was performed using SSR markers and GISH technique was used to detect genomic differentiation. The pollen viability of the parental and hybrids genotypes was tested using Alexander`s solution, fluorescein diacetate and in vitro germination tests were performed using culture medium. The meiotic behavior was regular and displayed haploid number n = 9 with nine bivalent (II) chromosomal, and pairing in 90% of the cells in diakinesis. There was a significant difference (p < 0.05) in terminal and interstitial chiasma frequencies. Meiotic irregularities observed were as follows: early and/or delayed chromosomes, disorientation of spindle fibers, transverse spindles, tripolar spindles, and asynchrony; and consequently irregular post-meiotic products were observed: monads, dyads, triads, and polyads. GISH was used in the interspecific hybrids and pairing between homeologous chromosomes, and bivalent and tetravalent formation were observed. From this study, we could conclude that hybrid genotypes are fertile and pollen grains are viable and can be used in breeding programs.
... As well as, asynchronism occur because these chromosomes do not reach the telophase phase for regular chromosomal segregation (Soares-Scott et al. 2003;Corrêa et al. 2005;Damasceno et al. 2010;Kiihl et al. 2011;Souza and Pereira, 2011). In addition, paracentric translocations and inversions can cause the emergence of chromosomal bridges (Levin 2002;Paiva et al. 2012). In studies based on cereals, it was reported that sticky chromosomes may have caused the origin of chromosomal bridges in the phases of anaphases (Paiva et al. 2012). ...
... In addition, paracentric translocations and inversions can cause the emergence of chromosomal bridges (Levin 2002;Paiva et al. 2012). In studies based on cereals, it was reported that sticky chromosomes may have caused the origin of chromosomal bridges in the phases of anaphases (Paiva et al. 2012). ...
Interspecific hybrids can be studied using methodologies in which the male gamete with high reproduction potential, viability, and fertility is prioritized. Passiflora species, with lush, showy, and exotic colors, have great potential for the ornamental plant market. In addition, artificial Passiflora hybrids were developed without many difficulties because of weak reproductive barriers. Thus, meiotic and post-meiotic behaviors were analyzed with 2% acetic carmine staining. Confirmation of interspecific hybridization was performed using SSR markers and GISH technique was used to detect genomic differentiation. The pollen viability of the parental and hybrids genotypes was tested using Alexander solution, fluorescein diacetate and in vitro germination tests were performed using culture medium. The meiotic behavior was regular and displayed haploid number n = 9 with nine bivalent (II) chromosomal, pairing in 90% of the cells in diakinesis. There was a significant difference ( p < 0.05) in terminal and interstitial chiasma frequencies. Meiotic irregularities observed were as follows: early and/or delayed chromosomes, disorientation of spindle fibers, transverse spindles, tripolar spindles, and asynchrony; and consequently irregular post-meiotic products were observed: monads, dyads, triads, and polyads. GISH was used in the interspecific hybrids and pairing between homeologous chromosomes, and bivalent and tetravalent formation were observed. From this study, we could conclude that hybrid genotypes are fertile and pollen grains are viable and can be used in breeding programs. We also hypothesize that interspecific hybrid genotypes of Passiflora can be obtained with regular meiosis, which could be viable and fertile.
... The triploid hybrid (2n = 3× = 21, AA'B) combines the favorable characteristics of both parents (Pereira et al., 2003) but it is sterile and the fertility can be restored by in vitro chromosome doubling, producing a hexaploid hybrid (2n = 6× = 42, AAA'A'BB). Hexaploid hybrids show mixoploidy with a chromosome number ranging from 14 to 42 (Abreu et al., 2006;Andrade-Vieira et al., 2013;Reis et al., 2016) and are partially fertile (Paiva et al., 2012) which allows the crossing. ...
... Synthetic hybrids commonly display phenotypic and genetic instability as a result of nuclear conflicts, such as chromosome and DNA fragment elimination (Ozkan et al., 2003;Ma and Gustafson, 2006). The elimination of chromosomes and fragments has also been related to the occurrence of abnormalities in meiosis (Baptista-Giacomelli, Pagliarini and Almeida, 2000;Paiva et al., 2012). Besides chromosome loss in mei-otic divisions, chromosome elimination in interspecific crosses can also occur during mitosis, resulting in the loss of one completely parental genome, as was observed in some Hordeum hybrids (Sanei et al., 2011) or generation of tissues with different chromosome numbers, as reported in wheat-barley hybrids (Koba, Handa and Shimada, 1991). ...
... Bridges in anaphase/telophase occurred at low frequencies and demonstrate the occurrence of chromosome rearrangements as a consequence of terminal breaks/deletions and allows inferring about elimination of fragments. The frequency of these mitotic alterations is smaller than that found in meiosis by (Paiva et al., 2012), which reported alterations at around 67% in synthetic hexaploids hybrids. These results suggest that the genomic instabilities happen during the growth of these plants and are not related to meiotic abnormalities. ...
... Techio et al. (2006) evaluated two cultivars of Napier grass and reported that the rate of viable pollen grains reached almost 99% using the Alexander staining technique (Alexander, 1980). On the other hand, Paiva et al. (2012) estimated the pollen viability in interspecific hybrids of Napier grass and pearl millet by pollen germination methodology developed by Shivanna and Rangaswamy (1992). Using this technique, they reported up to 30.71% viable pollen grains. ...
Napier grass [Cenchrus purpureus (Schumach.) Morrone], also known as elephant grass, is an important tropical forage that has the potential to become an alternative feedstock for energy production. Knowledge about the mode of reproduction and outcrossing rate is essential to select the best strategy to apply in breeding programs to develop new cultivars for application in energy and forage production systems. The objective of this work was to evaluate the outcrossing rate in two Napier grass breeding populations. Six microsatellite markers were used to genotype 28 half‐sibling families totaling 588 individuals, and pollen viability was checked by fluorescein diacetate test (FDA) methodology. A total of 14,603 pollen grains were assessed; 7751 (53%) were considered viable, and 6852 (47%) were considered sterile. Forty‐two alleles were found among all evaluated individuals, and analysis of molecular variance results showed that 14% of variance occurred among half‐siblings and 86% occurred within half‐siblings. Comparison of molecular data among parental and half‐sibling populations found 95.3% of seeds derived from outcrossing, indicating that Napier grass is predominantly allogamous. Currently, directional crosses and hybrid formation in Napier grass depend on the inflorescence protection and pollen collection of selected individuals. Since our results suggest that the self‐fecundation rate is very low (5%), other strategies like unprotected directional crosses can be applied to implementation of large‐scale hybrid production.
... Napier grass is a cross-pollinating allotetraploid species with a chromosome number of 2n = 4x = 28 (genome A'A'BB) [11,31,32]. Although there is no clear information on the genetic origin of allotetraploidy in Napier grass, the A'A' genome has been reported to be homologous to the AA genome of pearl millet (Pennisetum glaucum (L.)) and the A' chromosomes are larger than the B chromosomes, which contribute genes controlling the perennial growth habit [31]. ...
Napier grass (Pennisetum purpureum Schumach.) is a fast-growing perennial grass native to Sub-Saharan Africa that is widely grown across the tropical and subtropical regions of the world. It is a multipurpose forage crop, primarily used to feed cattle in cut and carry feeding systems. Characterization and diversity studies on a small collection of Napier grasses have identified a moderate level of genetic variation and highlighted the availability of some good agronomic traits, particularly high biomass production, as a forage crop. However, very little information exists on precise phenotyping, genotyping and the application of molecular technologies to Napier grass improvement using modern genomic tools which have been applied in advancing the selection and breeding of important food crops. In this review paper, existing information on genetic resources, molecular diversity, yield and nutritional quality of Napier grass will be discussed. Recent findings on characterizing disease resistance and abiotic stress (drought) tolerance will also be highlighted. Finally, opportunities and future prospects for better conservation and use arising from the application of modern genomic tools in Napier grass phenotyping and genotyping will be discussed.
... Evidence reported by Techio et al. (2006) suggests that the A and A chromosomes are likely to be homeologous rather than homologous. In addition, meiotic irregularities have also been reported in triploid (Techio et al., 2006) and hexaploid (Paiva et al., 2012) pearl millet-napiergrass hybrids. Interestingly, most of LG 1 is biased in favor of the Tift 454 parent, suggesting that the A chromosome transmits more frequently, whereas LG 3 is biased in favor of Tift 99D 2 B 1 , suggesting reduced frequency of transmitting this A chromosome. ...
Pearl millet [Pennisetum glaucum (L.) R. Br; also Cenchrus americanus
(L.) Morrone] is an important crop throughout the world but
better genomic resources for this species are needed to facilitate
crop improvement. Genome mapping studies are a prerequisite
for tagging agronomically important traits. Genotyping-by-sequencing
(GBS) markers can be used to build high-density
linkage maps, even in species lacking a reference genome. A
recombinant inbred line (RIL) mapping population was developed
from a cross between the lines ‘Tift 99D2B1’ and ‘Tift 454’. DNA
from 186 RILs, the parents, and the F1 was used for 96-plex
ApeKI GBS library development, which was further used for sequencing.
The sequencing results showed that the average number
of good reads per individual was 2.2 million, the pass filter
rate was 88%, and the CV was 43%. High-quality GBS markers
were developed with stringent filtering on sequence data from
179 RILs. The reference genetic map developed using 150 RILs
contained 16,650 single-nucleotide polymorphisms (SNPs) and
333,567 sequence tags spread across all seven chromosomes.
The overall average density of SNP markers was 23.23 SNP/cM
in the final map and 1.66 unique linkage bins per cM covering a
total genetic distance of 716.7 cM. The linkage map was further
validated for its utility by using it in mapping quantitative trait loci
(QTLs) for flowering time and resistance to Pyricularia leaf spot
[Pyricularia grisea (Cke.) Sacc.]. This map is the densest yet reported
for this crop and will be a valuable resource for the pearl
millet community.
... In the case of hybrids of Pennisetum studied herein, the stable chromosome number of the triploid seems to justify the elimination of chromosomes even with active centromeres in the polyploid hybrid. These results confirm that the biparental elimination of chromosomes in these hybrids results from abnormalities in chromosome pairing ( Paiva et al., 2012) and combination of the high degree of ploidy and high homology between the genomes( Andrade-Vieira et al., 2013;Reis et al., 2014). ...
Post-translational modifications on N-terminal tails of histones form nucleosomes, which are often associated with distinct biological functions. Some theories suggest that one of these changes, the phosphorylation of histone H3 at serine 10 (H3S10ph) plays an important role in chromosome condensation and sister chromatid cohesion. Although the histones are highly conserved, studies have been shown that the role and distribution of H3S10ph may differ between species. This study evaluated the effects of interspecific hybridization and polyploidization on the histone H3 phosphorylation at serine 10 (H3S10ph), using two model species Pennisetum purpureum Schum (elephant grass; 2n=4x=28) and Pennisetum glaucum (L.) R. Br. (Millet; 2n=2x=14). These species differ in ploidy levels and their hybrids are sterile. The fertility is restored by inducing chromosome doubling with colchicine. The effectiveness of inducing polyploidy and genomic behavior of duplicated hybrids were verified by meiotic analysis, chromosome counting in mitotic metaphase, cell cycle analysis and estimates of DNA content by flow cytometry. The H3S10 phosphorylation pattern was evaluated by immune-detection technique during the cell cycle in Pennisetum purpureum, Pennisetum glaucum and their triploid and hexaploid hybrids. First, roots were fixed in 4% paraformaldehyde. We primarily applied antibody (rabbit polyclonal IgG), which was detected with a secondary antibody (goat anti-rabbit IgG-FITC). The pattern of H3S10ph during mitosis showed coordination in space and time. The pattern was similar in parents and hybrids chromosomes. Phosphorylation was coincident with cohesion restricted to pericentromeric region. In triploid and partial hexaploid hybrids, bridges in anaphase and telophase were found, which showed signals of phosphorylation of H3S10, suggesting loss of chromosome fragments, mainly due the process of hybridization and polyploidization. In the hybrid hexaploid, metaphases with non-oriented chromosomes and anaphases with delayed and lost chromosomes with and without immune signal were found. This suggests that, after polyploidization, even chromosomes with functional centromeres, identified by phosphorylation of H3S10ph, are eliminated in hybrid Pennisetum, indicating that inactivation of the centromere is not a factor that contributes to chromosome elimination in Pennisetum partial hexaploid hybrids.
... incorrect chromosome pairing (formation of multivalents), problems to ensure correct chromosome allocation (formation of laggards and bridges) or formation of chromosome segments or micronuclei (e.g. Solís Neffa & Fernández 2000, Madlung et al. 2005, Rivero-Guerra 2008, Diao et al. 2010, Paiva et al. 2012. Therefore, pollen stainability has often been examined in studies of hybridization (e.g. ...
Background and aims – The genus Onosma (Boraginaceae) is a taxonomically and phylogenetically very complex plant group, with several taxa of hybrid or polyploid origin. An extensive pollen viability survey within the genus could help to solve some evolutionary or
taxonomic incertainties within the genus, but it has never been performed. The aim of the present study is to determine the degree of pollen viability of selected species of various ploidy levels and to investigate if microevolutionary processes, such as polyploidization and hybridization,
are associated with variation in pollen viability. Methods – Pollen staining with lactophenol blue was chosen as an indirect method for determining pollen viability. Ploidy level information was obtained from an extensive literature search. In mixed populations, the ploidy level
of individuals was determined based on flow cytometry screening. Key results – Considerable variation in pollen stainability is present among taxa of Onosma. Pollen stainability is high in most diploids (72–98% in mean), allotetraploids (90%) and allohexaploids (97%),
but lower in autotetraploids (71%) and allotriploids (2–49%). At the population level, considerable variation in pollen stainability was found in the allotriploid O. arenaria (14–83%), while the taxonomically related allotetraploid O. pseudoarenaria is less variable
(71–99%). Conclusion – This study shows the value of the staining method in the study of the genus Onosma. Low pollen stainability appears to be associated with autopolyploidization as well as recent hybridization processes suggesting the presence of microsporogenesis
or microgametogenesis abnormalities. In contrast, pollen stainability is high in stabilized allopolyploids indicating proper meiosis with maintenance of homologous pairing of parental chromosomes and correct pollen development.
... This explanation can be assumed in the present study since no elimination was observed in the triploid hybrid of the cross between NG and PM but only in the artificially duplicated hexaploid. Combination of higher ploidy level and high homeology between genomes A and A' may explain the irregularities in chromosome pairing (multiand univalents) and segregation (Paiva et al., 2012) that lead to elimination and its randomness. ...
... The process of chromosome elimination by colchicine activity usually occurs as a consequence of errors during the cell cycle, giving rise to chromosome abnormalities such as chromosome stickiness, laggard chromosomes in metaphases, later segregation in anaphase and/or telophase, and micronuclei. Irregularities in chromosome pairing and micronuclei formation in plants duplicated by colchicine have been described in an octoploid interspecific Avena hybrid (Aung et al., 2010), in a decaploid Triticum-Aegilops amphiploid (Tiwari et al., 2010), and in the hexaploid hybrid from the cross between P. purpureum and P. glaucum (Paiva et al., 2012). In all cases, chromosome elimination was also observed, but the effect of colchicine was not considered a potential cause. ...
This work aimed to study the dynamics of chromosome elimination from both parents in four interspecific hybrids (P1, H89, H40, and H42) originated from crosses between Napier grass (Pennisetum purpureum Schumach.) (2n = 4x = 28) and pearl millet [Pennisetum glaucum (L.) R. Br.] (2n = 2x = 14) after chromosome doubling. Large variation in somatic chromosome number was verified among and within hybrids. In P1 and H89, chromosome elimination was much less intense than in H40 and H42. Genomic in situ hybridization analysis revealed biparental and random elimination. The differences in chromosome number between P1–H89 and H42–H40 groups can be mainly attributed to the elimination of chromosomes from Napier grass. Higher ploidy level and homeology between genomes A and A’ are considered forces underlying the process of elimination. Effect of parental genotype is also taken into account to explain the differences in chromosome elimination. Potential of the partial hexaploid hybrids for Napier grass breeding is also discussed here.
... Meiosis is a sequence of highly coordinated mechanical, physiological and biochemical events and is controlled by a great number of genes, which culminate in gene recombination and the reduction of the number of chromosomes in gametes (Gottschalk and Kaul 1974;Golubovskaya 1979;Sosnikhina et al. 2005;Mercier and Grelon 2008). Meiosis during megaand microsporogenesis has been investigated in several plant species (Mendes-Vieira et al. 2005;Risso-Pascotto et al. 2009;Souza-Kaneshima et al. 2010;Vesselina and Mateus-Andrés 2010;Olkoski and Schifino-Wittmann 2011;Papini et al. 2011;Godoy et al. 2012;Paiva et al. 2012). ...
... Mistakes in the spindle organization process, chromosome segregation and irregular cytokinesis may produce microspores with changes in the quantity of genetic matter, called de-balanced microspores. Mistakes may also give rise to a type of polyad with a varied number of de-balanced microspores and unviable pollen grains (Kiihl et al. 2010;Souza-Kaneshima et al. 2010;Vesselina and Mateus-Andrés 2010;Paiva et al. 2012). ...
Cytogenetic studies are a useful tool for the study of systematics and evolution in plants. The current paper reports on polyad production during microsporogenesis of Hippocratea volubilis. The analyzed material was collected in the Ecological Station of Caiuá in Diamante do Norte, PR, Brazil. The meiotic analysis was performed using a squashing technique and the stain was 1% acetic carmine. The chromosome segregation process during meiotic division was normal. However, pollen mother cells (PMCs) were bonded in fours or twos, through cytoplasmic channels during the whole microsporogenesis. After telophase II, four-PMC complexes produced tetra-tetrads with 16 microspores, whereas two-PMC complexes produced bi-tetrads with eight microspores. Microspores formed in the process remained bonded and formed polyads with 16 or eight pollen grains.
