Uncovering the genomic diversity of the wild forage crop Setaria sphacelata.

Grasses are considered one of the most important angiosperm groups in economic terms. The complex is an intriguing species with considerable variation in genome size (GS). It is currently being explored from a genomic perspective especially because of its great adaptability under winter periods. Repetitive DNA sequences are known to contribute significantly to GS diversity, which in turn can play a role in impacting the ecology and evolution of a species. This study is aimed to characterize the GS and repetitive elements of different germplasm accessions of . . We analyzed 540 plants from 70 accessions collected worldwide. Flow cytometry was used for GS estimation, together with chromosome counting, fluorescent in situ hybridization (FISH), and bioinformatic analysis. Most (i.e., 80%) accessions were tetraploids (2 = 4 = 36) with GS ranging from 3.0 to 3.7 pg/2C. Additionally, a low number of diploids (2 = 2 = 18; ∼1.6 to 2 pg/2C), pentaploids (2 = 5 = 45: ∼4 pg/2C), hexaploids (2 = 6 = 54; ∼4.4 pg/2C), and octoploids (2 = 8 = 72; ∼6 pg/2C,) were detected. The greatest variation was found in accessions from South Africa. RepeatExplorer2 showed that 39% and 43% of the genomes of two diploid accessions comprised repetitive sequences, with Ty3/gypsy retrotransposons being the most abundant repeats. However, variation in the percentage of two Ty3/gypsy sublineages, Athila and Ogre, suggests different process of amplification and deletion of repeats during the evolution of the species complex. In contrast, FISH revealed some satellite repeats with a conserved localized distribution in pericentromeric regions between accessions. Although differences in the distribution of the FISH signals over the chromosomes were observed between the different ploidy levels, the data suggest that increases in the ploidy level were associated with the occurrence of hybridization and DNA loss. Grasses are one of the most significant angiosperm groups, present worldwide. In this context, studying genome size and cytogenetics is essential for understanding their adaptive capabilities. In this study, we characterized the genome size and repetitive elements of different germplasm accessions of , an intriguing species. Most plants were tetraploids (2 = 4 = 36), with a smaller number of diploids (2 = 2 = 18), pentaploids (2 = 5 = 45), hexaploids (2 = 6 = 54), and octoploids (2 = 8 = 72) also detected. The greatest variation was found in accessions from South Africa, and molecular cytogenetics revealed some satellite repeats with a conserved localized distribution in the pericentromeric regions. Overall, our findings highlight the complex genetic and evolutionary factors that contribute to the diversity of .

Project(s)

Priority 2: Trait Diversity and Function

Funder

Funder name	Awards
Fundação de Amparo à Pesquisa do Estado de Minas Gerais, Brazil	CRA-RED-00053-16 - RED-00060-23 - APQ‐03630
Conselho Nacional de Desenvolvimento Científico e Tecnológico, Brazil	314443/2021-5 - 406455/2022-8
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil	Finance Code 001