Grasses with desirable traits for agriculture and livestock production are continually being sought. The genus Urochloa comprises many species of good forage potential, although studies have mostly focused on commercial cultivars. Karyotype data can be used to characterize species and generate information for taxonomy and evolutionary studies and contribute to breeding programs. The mode of reproduction is also an essential piece of information to determine breeding strategies. This study aimed to characterize the karyotypes of Urochloa arrecta (Hack. ex T. Dur. & Schniz) O. Morrone & F. Zuloaga and a pentaploid cytotype of U. brizantha (Hochst. ex A. Rich.) R. Webster, including the mapping of ribosomal DNA (rDNA) sites and nuclear DNA content and indicating the mode of reproduction. Slides were prepared using the flame drying technique and were subjected to fluorescent in situ hybridization with 35S and 5S rDNA probes. DNA content was estimated by flow cytometry. The classification of the reproduction mode was based on the amplification of the primers N14 and p779/p780. Urochloa arrecta presented 2C = 2.66 pg of DNA, karyotype formula 2n = 4x = 34 m + 2sm, four chromosomes with 35S rDNA sites, and four other chromosomes with 5S rDNA sites. The absence of amplification products with the primers N14 and p779/p780 provided evidence of sexual reproduction. Urochloa brizantha presented 2C = 4.52 pg of DNA and karyotype formula 2n = 5x = 45 m. Five chromosomes presented 35S rDNA, and eight other chromosomes displayed 5S rDNA sites. Polymerase chain reaction results indicated that this cytotype has an apomictic mode of reproduction. The organization of karyotypes suggests an allopolyploid origin for both genotypes. Possible applications of the information found are discussed.

中文翻译：

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两种 Urochloa P. Beauv 的核型分析和繁殖方式。

一直在寻找具有适合农业和畜牧生产的理想特性的草。Urochloa属包括许多具有良好牧草潜力的物种，尽管研究主要集中在商业栽培品种上。核型数据可用于表征物种并为分类学和进化研究生成信息，并有助于育种计划。繁殖方式也是确定育种策略的重要信息。本研究旨在表征Urochloa arrecta (Hack. ex T. Dur. & Schniz) O. Morrone & F. Zuloaga 的核型和U. brizantha 的五倍体细胞型(Hochst. ex A. Rich.) R. Webster，包括核糖体 DNA (rDNA) 位点和核 DNA 含量的映射，并指示繁殖方式。使用火焰干燥技术制备载玻片，并用 35S 和 5S rDNA 探针进行荧光原位杂交。DNA含量通过流式细胞术估计。繁殖方式的分类基于引物N14和p779/p780的扩增。Urochloa arrecta呈现 2C = 2.66 pg DNA，核型公式 2 n  = 4 x  = 34 m + 2sm，四条染色体具有 35S rDNA 位点，其他四条染色体具有 5S rDNA 位点。引物 N14 和 p779/p780 扩增产物的缺失提供了有性繁殖的证据。紫菖蒲提出 2C = 4.52 pg DNA 和核型公式 2 n  = 5 x  = 45 m。5条染色体显示35S rDNA，其他8条染色体显示5S rDNA位点。聚合酶链反应结果表明该细胞型具有无融合生殖模式。核型的组织表明两种基因型都来自异源多倍体。讨论了所发现信息的可能应用。