Department of Biology/DBI - Plant Cytogenetics Laboratory, Federal University of Lavras (UFLA), P.O.Box 3037, Lavras, Minas Gerais State, Brazil.
Embrapa Gado de Leite, Juiz de Fora, Minas Gerais State, Brazil.
Chromosome Res. 2019 Dec;27(4):333-344. doi: 10.1007/s10577-019-09616-y. Epub 2019 Sep 4.
The genus Urochloa includes most of the important grasses and hybrids currently used as pastures in the tropical regions. Cytogenetic analyzes have identified some aneuploid hybrids that provide new perspectives for genetic breeding. The objective was to analyze the meiotic behavior in euploid (2n = 4x = 36) and aneuploid (2n = 4x = 36 + 2) hybrids of U. ruziziensis x U. decumbens and U. ruziziensis x U. brizantha. Later, the chromosomes and respective genomes involved in pairing configurations and abnormalities were identified through GISH, with an emphasis on tracking the behavior of the additional chromosomes in the aneuploid hybrid U. ruziziensis x U. decumbens (BBBB genomes). The aneuploid U. ruziziensis x U. decumbens shows a higher frequency of univalents, reduction of bivalents, and higher index of irregularities compared with the euploid hybrid. For the aneuploid U. ruziziensis x U. brizantha, there was a reduction in the frequency of univalents, an increase in bivalent and trivalent rates and a lower frequency of abnormalities when compared with the euploid hybrid. The rates of meiotic abnormalities and pairing configurations are parental genotype-dependent and influenced by trisomy. The chromosomes of the B and B genomes of the aneuploid hybrid (U. ruziziensis x U. decumbens) are involved in the formation of univalents, bivalents, and multivalents in inter-, intra- and inter-intragenomic pairings. In general, the segregation times of chromosomes of the genomes are different, since the chromosomes of the B genome segregate more slowly.
该属包括大多数重要的草种和杂种，目前被广泛应用于热带地区的牧场。细胞遗传学分析已经鉴定出一些非整倍体杂种，为遗传育种提供了新的视角。本研究的目的是分析 Urochloa ruziziensis x U. decumbens 和 U. ruziziensis x U. brizantha 这两个二倍体（2n=4x=36）和非整倍体（2n=4x=36+2）杂种的减数分裂行为。随后，通过 GISH 鉴定了涉及配对构型和异常的染色体和各自的基因组，重点跟踪非整倍体杂种 U. ruziziensis x U. decumbens（BBBB 基因组）中额外染色体的行为。与二倍体杂种相比，非整倍体 U. ruziziensis x U. decumbens 表现出更高的单价体频率、二价体减少和更高的不规则指数。对于非整倍体 U. ruziziensis x U. brizantha，与二倍体杂种相比，单价体频率降低，二价体和三价体频率增加，异常频率降低。减数分裂异常和配对构型的频率与亲本基因型有关，并受三体的影响。非整倍体杂种（U. ruziziensis x U. decumbens）的 B 和 B 基因组的染色体参与了单价体、二价体和多价体在种间、种内和种内基因组间配对的形成。总的来说，基因组染色体的分离时间不同，因为 B 基因组的染色体分离得更慢。
