RADIAL SPINDLE AND THE PHENOTYPE OF THE MAIZE MEIOTIC MUTANT, <i>DV</i>

Shamina, N. V.; Дорогова, Н. В.; Trunova, S. A.

doi:10.1006/cbir.2000.0533

Cited by 25 publications

(27 citation statements)

References 19 publications

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“…One abnormality, however, was recorded for the first time during the present study in two of the hybrids, HBGC313 and HBGC325. Similar abnormality had been widely reported in maize (Clark, 1940;Staiger and Cande, 1990;Shamina et al, 2000) and it was designated divergent spindle (dv), a putative mutation that affects the orientation of spindle fibers (Figure 2).…”

Section: Resultssupporting

confidence: 72%

Meiotic behavior of interspecific hybrids between artificially tetraploidized sexual Brachiaria ruziziensis and tetraploid apomictic B. brizantha (Poaceae)

Felismino

Pagliarini

Valle

2010

Sci. agric. (Piracicaba, Braz.)

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The meiotic behavior of four interspecific promising hybrids was evaluated by conventional cytological methods. The female genitors were two artificially tetraploidized sexual accessions of B. ruziziensis (R41 and R44, 2n = 4 χ = 36), which were crossed to an agronomically superior natural tetraploid apomictic genotype of B. brizantha (B140 -BRA003395). Three of them (HBGC313, HBGC 315, and HBGC324) were sexual and one (HBGC325) apomictic. Analyses of some cells in diakinesis revealed multivalent chromosome configurations, suggesting that genetic recombination and introgression of some genes could be present. The four hybrids had different types of meiotic abnormalities at various frequencies. Abnormalities related to irregular chromosome segregation due to polyploidy were common among these hybrids, and characterized by precocious chromosome migration to the poles, laggard chromosomes, both generating micronuclei in telophases and tetrads and, as a consequence, unbalanced gametes. One abnormality genotype-specific, related to spindle orientation (a putative divergent spindle mutation), was recorded for the first time in two of the hybrids, HBGC313 and HBGC325. The sexual hybrid HBGC324 had the lower rate of abnormalities, and it could be used as a female genitor in future crosses in the breeding program. The abnormalities present in these hybrids may impact fertility and affect seed production. Based on the results, HBGC324 is the single hybrid recommended to the breeding program. Hybrids must produce a good amount of viable seeds, besides good overall dry matter production and nutritive value, in order to be widely utilized and adopted in production systems. Due to pseudogamy, the desirable superior apomictic hybrids need viable pollen grains to fertilize the secondary nucleus of the embryo sac and thus ensure normal and vigorous endosperm development and plenty of seed set. Key words: Brachiaria, Brazil, cytogenetics, forage grasses, meiosisComportamento meiótico de híbridos interespecíficos entre tetraplóides artificiais de Brachiaria ruziziensis e tetraplóides apomíticos de B. brizantha (Poaceae) RESUMO: O comportamento meiótico de quatro híbridos interespecíficos promissores de Brachiaria foi avaliado por metodologia citogenética convencional. Os genitores femininos eram dois acessos sexuais tetraploidizados artificialmente de B. ruziziensis (R41 e R44, 2n = 4χ = 36), os quais foram cruzados com um genótipo tetraplóide natural apomítico agronomicamente superior de B. brizantha (B140 -BRA003395). Três deles (HBGC313, HBGC 315 e HBGC324) eram sexuais e um (HBGC325) apomítico. A análise de algumas células em diacinese revelou a presença de configurações cromossômicas multivalentes, sugerindo que recombinação genética e introgressão de alguns genes poderão estar presentes. Os quatro híbridos apresentaram freqüências e tipos variados de anormalidades meióticas. Anormalidades relacionadas à segregação irregular de cromossomos devido à poliploidia foram comuns entre os híbridos e caracterizadas pela pre...

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Section: Resultssupporting

confidence: 72%

Meiotic behavior of interspecific hybrids between artificially tetraploidized sexual Brachiaria ruziziensis and tetraploid apomictic B. brizantha (Poaceae)

Felismino

Pagliarini

Valle

2010

Sci. agric. (Piracicaba, Braz.)

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“…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). The manifestation of this gene in the diploidized R46 accession of B. ruziziensis limits its use as a female genitor in crosses with other Brachiaria species since it severely compromises the meiotic product by aVecting pollen viability.…”

Section: Resultsmentioning

confidence: 69%

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 normal microsporocytes the spindle converged to form focused poles, bivalents occupied a small portion in the center of the metaphase plate and telophase nuclei presented spherical shape in both divisions (Figure 1) but in the PMCs with abnormal spindle orientation a typical phenotype similar to that of divergent spindle (dv) of maize (Clark, 1940;Staiger and Cande, 1990;Shamina et al, 2000) was recorded. Although the bivalents regularly Genetics and Molecular Biology, 29, 1, 122-125 (2006) Short Communication co-oriented themselves at the metaphase plate, they were distantly positioned and spread over the equatorial plate (Figure 2a), sometimes from one side of the cell wall to another.…”

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confidence: 98%

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

2006

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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.

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RADIAL SPINDLE AND THE PHENOTYPE OF THE MAIZE MEIOTIC MUTANT, DV

Cited by 25 publications

References 19 publications

Meiotic behavior of interspecific hybrids between artificially tetraploidized sexual Brachiaria ruziziensis and tetraploid apomictic B. brizantha (Poaceae)

Meiotic behavior of interspecific hybrids between artificially tetraploidized sexual Brachiaria ruziziensis and tetraploid apomictic B. brizantha (Poaceae)

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

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

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