Format: ORAL

Michael R. McKain1, Fae D. Bramblepelt1, Bishnu Adhikari1, Nathaniel Hofford1, MKalya Motley1, Bryan N. MacNeill1, Sontosh K. Deb1, Andrew Busby1, Alaina Dawkins1, Allison Hayes1, William A. Laycock1, Caitlin McCann1, Susie McLaughlin1, Kayln Pate1

1 Department of Biological Sciences, The University of Alabama, Tuscaloosa, Alabama, USA

Johnsongrass (Sorghum halepense (L.) Pers.) is an invasive, polyploid grass found throughout disturbed and agriculture areas of temperature, subtropical, and tropical regions. This species is thought to be an allotetraploid formed through the hybridization of sorghum (Sorghum bicolor (L.) Moench) and Sorghum propinquum (Kunth) Hitchc. Since its introduction into the United States in the early 1800s and secondary introduction into Arizona, Johnsongrass has spread throughout much of the Southeast, lower Great Plains, portions of the Midwest, Southwest, and California. The movement of this invasive has been facilitated by the transport of agricultural products and the development of major railway and highway systems where Johnsongrass thrives in the disturbed areas surrounding fields, railroads, and highways. In this study, we assembled four genomes, resequenced 38 accessions at either 20X or 40X coverage, and low-coverage whole genome shotgun sequenced approximately 50 additional populations of Johnsongrass from diverse regions of the United States. Using these data, we assess patterns of overall genetic diversity between subgenomes within individuals, among accessions, and across populations to determine how subgenomic variation might drive adaptation to varying habitats. We also explore homoeolog retention and loss patterns, leveraging phylogenetic relationships to identify potential loci contributing to Johnsongrasss success as an invasive species in the United States. Furthermore, we examine the abundance and dispersion of homoeologous exchange across the Johnsongrass genome and identify the extent to which different loci have either moved to homoeologous chromosomes or have been lost. Ultimately, this research sheds light on the impact of diploidization on the diversity of U.S. Johnsongrass germplasm, offering insights into how polyploidy influences patterns of invasion.