Department of Biology/DBI - Plant Cytogenetics Laboratory, Federal University of Lavras (UFLA), P.O. Box 3037, Lavras, Minas Gerais, Brazil.
Embrapa Gado de Corte - Campo Grande, Campo Grande, Mato Grosso do Sul, Brazil.
Mol Biol Rep. 2020 Feb;47(2):887-896. doi: 10.1007/s11033-019-05179-7. Epub 2019 Nov 16.
The genus Urochloa P. Beauv. [syn. Brachiaria (Trin.) Griseb.] comprises species of great economic relevance as forages. The genomic constitution for the allotetraploid species Urochloa brizantha (cv. Marandu) and Urochloa decumbens (cv. Basilisk) and the diploid Urochloa ruziziensis was previously proposed as BBBB, BBBB and BB, respectively. Evidence indicates U. ruziziensis as the ancestral donor of genome B in U. decumbens allotetraploidy, but the origin of the genomes B and B is still unknown. There are diploid genotypes of U. brizantha and U. decumbens that may be potential ancestors of the tetraploids. The aim of this study was to determine the genomic constitution and relationships between genotypes of U. brizantha (2x and 4x), U. decumbens (2x and 4x) and U. ruziziensis (2x) via genomic in situ hybridization (GISH). Additionally, chromosome number and genome size were verified for the diploid genotypes. The diploids U. brizantha and U. decumbens presented 2n = 2x = 18 chromosomes and DNA content of 1.79 and 1.44 pg, respectively. The GISH analysis revealed high homology between the diploids U. brizantha and U. decumbens, which suggests relatively short divergence time. The GISH using genomic probes from the diploid accessions on the tetraploid accessions' chromosomes presented similar patterns, highlighting the genome B present in both of the tetraploids. Based on GISH results, the genomic constitution was proposed for the diploid genotypes of U. brizantha (BB) and U. decumbens (B'B') and both were pointed as donors of genome B (or B'), present in the allotetraploid genotypes.
Urochloa 属 [同义词：Brachiaria (Trin.) Griseb.] 包括具有重要经济意义的饲用物种。先前提出的四倍体物种 Urochloa brizantha（Marandu 品种）和 Urochloa decumbens（Basilisk 品种）以及二倍体 Urochloa ruziziensis 的基因组构成为 BBBB、BBBB 和 BB。有证据表明 U. ruziziensis 是 U. decumbens allotetraploidy 中 B 基因组的祖先供体，但 B 和 B'基因组的起源仍不清楚。U. brizantha 和 U. decumbens 存在二倍体基因型，它们可能是四倍体的潜在祖先。本研究旨在通过基因组原位杂交（GISH）确定 U. brizantha（2x 和 4x）、U. decumbens（2x 和 4x）和 U. ruziziensis（2x）基因型的基因组构成和关系。此外，还验证了二倍体基因型的染色体数和基因组大小。二倍体 U. brizantha 和 U. decumbens 的 2n=2x=18 条染色体，DNA 含量分别为 1.79 和 1.44pg。GISH 分析显示，二倍体 U. brizantha 和 U. decumbens 之间具有高度同源性，这表明它们的分化时间相对较短。用二倍体材料的基因组探针在四倍体材料的染色体上进行 GISH 分析，显示出相似的模式，突出了两个四倍体中都存在的 B 基因组。基于 GISH 结果，提出了 U. brizantha（BB）和 U. decumbens（B'B'）二倍体基因型的基因组构成，并指出它们都是存在于 allotetraploid 基因型中的 B 基因组（或 B'）的供体。
