Brachiaria

Meiotic behavior in nonaploid accessions of Brachiaria humidicola (Poaceae) and implications for breeding

K. R. Boldrini, Adamowski, E. V., Silva, N., Pagliarini, M. S., and Valle, C. B., “Meiotic behavior in nonaploid accessions of Brachiaria humidicola (Poaceae) and implications for breeding”, vol. 10, pp. 169-176, 2011.

Brachiaria humidicola is a grass adapted to seasonally swampy grasslands in Africa; two cultivars, ‘common’ and Llanero, are widely used in Brazilian pastures. New cultivars are in great demand in order to diversify current production systems to achieve improved quality and yield. Cytological analyses of 55 accessions of this species available from the Embrapa Beef Cattle germplasm collection revealed that 27 are apomictic and have 2n = 54 chromosomes.

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.

Mitotic behavior in root tips of Brachiaria genotypes with meiotic chromosome elimination during microsporogenesis

M. F. Felismino, Silva, N., Pagliarini, M. S., and Valle, C. B., “Mitotic behavior in root tips of Brachiaria genotypes with meiotic chromosome elimination during microsporogenesis”, vol. 7, pp. 336-341, 2008.

Three accessions of Brachiaria brizantha, three of B. humidicola, and two interspecific hybrids between B. ruziziensis and B. brizantha were analyzed with regard to their mitotic behavior in root tips. All these genotypes revealed chromosome elimination or lack of chromosome affinity in previous analyses of microsporogenesis. Analyses of root tips showed a normal mitotic division in all accessions and hybrids, reinforcing the notion that the genetic control of meiosis is totally independent of that of mitosis.

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.

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