Análise citogenômica revela padrões de sequências repetitivas nos cromossomos de espécies do complexo ‘humidicola’ de urochloa p. Beauv

Abstract

The genus Urochloa P. Beauv. (Brachiaria (Trin.) Griseb.), known for its agronomic importance, includes species such as Urochloa humidicola and Urochloa dictyoneura, which form the 'humidicola' complex. These species are noted for their similar morphological characteristics, leading to taxonomic debates regarding their classification. The objective of this study was to located satDNA repetitive sequences on the chromosomes of U. humidicola and U. dictyoneura accessions using fluorescence in situ hybridization (FISH) in order to enhance the understanding of the genome structure and composition. The analyses revealed significant variations in the distribution, intensity, and pattern of FISH signals among the evaluated accessions. The hybridization patterns of satDNA sequences demonstrated substantial genomic complexity, reflecting chromosomal rearrangements and variations in the copy number of repetitive sequences. The comparison between U. humidicola and U. dictyoneura revealed the conservation of certain satDNA sequences, consistent with the "library model," where related species share a repertoire of satDNAs inherited from a common ancestor. However, interspecific variations were also observed, reflecting the rapid evolution of these repetitive elements. The results of this study significantly expand the understanding of the genomic structure and organization of U. humidicola and U. dictyoneura. The identification of distinct satDNA hybridization patterns among cytotypes and species suggests that these markers can be useful in chromosome discrimination and in understanding the evolutionary relationships within the genus Urochloa.