Whole Genome Assembly and Annotation of Northern Wild Rice (Zizania palustris L.), a North American Grain

Abstract

Northern Wild Rice (NWR; Zizania palustris L.) is an aquatic grass native to North America that is notable for its nutritious grain. This is an important species with ecological, cultural, and agricultural significance, specifically in the Great Lakes region of the United States. Using long- and short-range sequencing, Hi-C scaffolding, and RNA-seq data from eight tissues, we generated a whole genome de novo assembly and annotation of NWR. The assembly is 1.29 Gb, highly repetitive (~76.0%), and contains 46,421 protein-coding genes. Comparative analyses revealed conservation of large syntenic blocks with Oryza sativa L., which were used to identify putative seed shattering genes. Estimates of divergence times revealed the Zizania genus diverged from Oryza ~26-30 million years ago (MYA), while NWR and Zizania latifolia diverged from one another ~6-8 MYA. Comparative genomics revealed evidence of a whole genome duplication in NWR ~5.3 MYA after the NWR-Z. latifolia speciation event. This high-quality genome assembly and annotation provides is a valuable resource for comparative genomics in the Oryzeae tribe and provides an important resource for future conservation and breeding efforts of NWR.