Microsporogenesis

Abnormal male meiosis explains pollen sterility in the polyploid medicinal plant Pinellia ternata (Araceae)

Y. Liu, Hui, R. - K., Deng, R. - N., Wang, J. - J., Wang, M., and Li, Z. - Y., Abnormal male meiosis explains pollen sterility in the polyploid medicinal plant Pinellia ternata (Araceae), vol. 11, pp. 112-120, 2012.

Pinellia ternata is an important traditional Chinese medicinal plant. Its different populations in China have various ploidy levels, based on x = 13, as well as extensive aneuploid series. The microsporogenesis process was observed in specimens from three populations from three regions of Hubei Province; they were characterized by normal and abnormal meiotic divisions in pollen mother cells (PMCs) at all stages simultaneously.

Cytomixis and meiotic abnormalities during microsporogenesis are responsible for male sterility and chromosome variations in Houttuynia cordata

J. - Z. Guan, Wang, J. - J., Cheng, Z. - H., Liu, Y., and Li, Z. - Y., Cytomixis and meiotic abnormalities during microsporogenesis are responsible for male sterility and chromosome variations in Houttuynia cordata, vol. 11, pp. 121-130, 2012.

Houttuynia cordata (Saururaceae) is a leaf vegetable and a medicinal herb througout much of Asia. Cytomixis and meiotic abnormalities during microsporogenesis were found in two populations of H. cordata with different ploidy levels (2n = 38, 96). Cytomixis occurred in pollen mother cells during meiosis at high frequencies and with variable degrees of chromatin/chromosome transfer. Meiotic abnormalities, such as chromosome laggards, asymmetric segregation and polyads, also prevailed in pollen mother cells at metaphase of the first division and later stages.

Microsporogenesis in Brachiaria brizantha (Poaceae) as a selection tool for breeding

M. S. Pagliarini, Valle, C. B., Santos, E. M., Mendes, D. V., Bernardo, Z. H., Mendes-Bonato, A. B., Silva, N., and Calisto, V., Microsporogenesis in Brachiaria brizantha (Poaceae) as a selection tool for breeding, vol. 11, pp. 1309-1318, 2012.

The genus Brachiaria comprises more than 100 species and is the single most important genus of forage grass in the tropics. Brachiaria brizantha, widely used in Brazilian pastures for beef and dairy production, is native to tropical Africa. As a subsidy to the breeding program underway in Brazil, cytological studies were employed to determine the chromosome number and to evaluate microsporogenesis in 46 accessions of this species available at Embrapa Beef Cattle (Brazil).

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

G. C. L. Ricci, Pagliarini, M. S., and Valle, C. B., Genome elimination during microsporogenesis in two pentaploid accessions of Brachiaria decumbens (Poaceae), vol. 9, pp. 2364-2371, 2010.

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.

Evaluation of microsporogenesis in an interspecific Brachiaria hybrid (Poaceae) collected in distinct years

V. A. Fuzinatto, Pagliarini, M. S., and Valle, C. B., Evaluation of microsporogenesis in an interspecific Brachiaria hybrid (Poaceae) collected in distinct years, vol. 7, pp. 424-432, 2008.

Microsporogenesis in an interspecific Brachiaria hybrid, grown in the field under natural environmental conditions in Brazilian savannas, was analyzed in three distinct years of collection. Several types of meiotic abnormalities were recorded during those three years, but varied in type and frequency depending on the year. The average temperature and rainfall 15 days before collection was unusually high in those years. The percentage of abnormal meiocytes recorded was 62% in 2001, 73% in 2004, and 77% in 2005.

Microsporogenesis in Brachiaria dictyoneura (Fig. & De Not.) Stapf (Poaceae: Paniceae)

C. Risso-Pascotto, Pagliarini, M. S., and Valle, C. B., Microsporogenesis in Brachiaria dictyoneura (Fig. & De Not.) Stapf (Poaceae: Paniceae), vol. 5, pp. 837-845, 2006.

Microsporogenesis was analyzed in five accessions of Brachiaria dictyoneura presenting x = 6 as the basic chromosome number. All accessions were tetraploid (2n = 4x = 24) with chromosome pairing in bi-, tri-, and quadrivalents. The recorded meiotic abnormalities were those typical of polyploids, including precocious chromosome migration to the poles, laggard chromosomes, and micronucleus formation. The frequency of these abnormalities, however, was lower than those reported for other polyploid accessions previously analyzed for other Brachiaria species.

Evidence of allopolyploidy in Brachiaria brizantha (Poaceae: Paniceae) through chromosome arrangement at metaphase plate during microsporogenesis

C. Risso-Pascotto, Mendes, D. V., Silva, N., Pagliarini, M. S., and Valle, C. B., Evidence of allopolyploidy in Brachiaria brizantha (Poaceae: Paniceae) through chromosome arrangement at metaphase plate during microsporogenesis, vol. 5, pp. 797-803, 2006.

In the hexaploid (2n = 6x = 54) accession B176 of Brachiaria brizantha, one cytological characteristic differentiated it from the other accessions previously analyzed with the same ploidy level. Nearly 40% of meiocytes displayed the chromosome set arranged at two metaphase plates at the poles of the cell, close to the membrane. In these cells, both metaphase plates were arranged in an angle to form a typical tripolar spindle. Therefore, cells did not show normal chromosome segregation at anaphase I.

Abnormal cytokinesis in microsporogenesis of Brachiaria humidicola (Poaceae: Paniceae)

E. V. Adamowski, Boldrini, K. R., Pagliarini, M. S., and Valle, C. Bdo, Abnormal cytokinesis in microsporogenesis of Brachiaria humidicola (Poaceae: Paniceae), vol. 6, pp. 616-621, 2007.

Microsporogenesis was evaluated in the Brachiaria humidicola collection of the Embrapa Beef Cattle Center, represented by 60 accessions. One accession (H121) presented an abnormal pattern of cytokinesis that had never been reported in this genus. Among 900 meiocytes analyzed in the first division, 10.7% underwent precocious and multiple cytokinesis in metaphase I, fractionating the genome and the cytoplasm into two or more parts. The expected cytokinesis after telophase I did not occur.

Microsporogenesis in sexual Brachiaria hybrids (Poaceae)

V. A. Fuzinatto, Pagliarini, M. S., and Valle, C. B., Microsporogenesis in sexual Brachiaria hybrids (Poaceae), vol. 6, pp. 1107-1117, 2007.

Three sexual interspecific hybrids of Brachiaria (HBGC076, HBGC009, and HBGC014) resulting from crosses between B. ruziziensis (female genitor) and B. decumbens and B. brizantha (male genitors) produced by Embrapa Beef Cattle in the 1980s were cytologically analyzed by conventional methods for meiotic studies. The cytogenetic analysis showed the occurrence of common meiotic abnormalities among them. The most frequent abnormalities were those related to irregular chromosome segregation due to polyploidy.

Microsporogenesis in inbred line of popcorn (Zea mays L.)

G. C. L. Ricci, Silva, N., Pagliarini, M. S., and Scapim, C. A., Microsporogenesis in inbred line of popcorn (Zea mays L.), vol. 6. pp. 1013-1018, 2007.

Endogamy places genes for several characteristics in homozygosis, which include those related to meiosis causing abnormalities that may impair gamete viability. An original population (S0) of popcorn (CMS-43) produced by Embrapa Maize and Sorghum was self-pollinated for seven years, generating inbred lines (S1 to S7). Conventional studies of microsporogenesis revealed that meiotic abnormalities did not increase with endogamy.

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