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- Title
Complex polyploid and hybrid species in an apomictic and sexual tropical forage grass group: genomic composition and evolution in Urochloa (Brachiaria) species.
- Authors
Tomaszewska, Paulina; Vorontsova, Maria S; Renvoize, Stephen A; Ficinski, Sarah Z; Tohme, Joseph; Schwarzacher, Trude; Castiblanco, Valheria; Vega, José J de; Mitchell, Rowan A C; Heslop-Harrison, J S (Pat)
- Abstract
Background and Aims Diploid and polyploid Urochloa (including Brachiaria , Panicum and Megathyrsus species) C4 tropical forage grasses originating from Africa are important for food security and the environment, often being planted in marginal lands worldwide. We aimed to characterize the nature of their genomes, the repetitive DNA and the genome composition of polyploids, leading to a model of the evolutionary pathways within the group including many apomictic species. Methods Some 362 forage grass accessions from international germplasm collections were studied, and ploidy was determined using an optimized flow cytometry method. Whole-genome survey sequencing and molecular cytogenetic analysis were used to identify chromosomes and genomes in Urochloa accessions belonging to the ' brizantha ' and ' humidicola ' agamic complexes and U. maxima. Key Results Genome structures are complex and variable, with multiple ploidies and genome compositions within the species, and no clear geographical patterns. Sequence analysis of nine diploid and polyploid accessions enabled identification of abundant genome-specific repetitive DNA motifs. In situ hybridization with a combination of repetitive DNA and genomic DNA probes identified evolutionary divergence and allowed us to discriminate the different genomes present in polyploids. Conclusions We suggest a new coherent nomenclature for the genomes present. We develop a model of evolution at the whole-genome level in diploid and polyploid accessions showing processes of grass evolution. We support the retention of narrow species concepts for Urochloa brizantha , U. decumbens and U. ruziziensis , and do not consider diploids and polyploids of single species as cytotypes. The results and model will be valuable in making rational choices of parents for new hybrids, assist in use of the germplasm for breeding and selection of Urochloa with improved sustainability and agronomic potential, and assist in measuring and conserving biodiversity in grasslands.
- Subjects
AFRICA; POLYPLOIDY; SIGNALGRASS; BRACHIARIA; SPECIES; DNA probes; PANICUM
- Publication
Annals of Botany, 2023, Vol 131, Issue 1, p87
- ISSN
0305-7364
- Publication type
Article
- DOI
10.1093/aob/mcab147