A Chromosome-level Genome Assembly of the Beavertail Cactus, Opuntia basilaris

Abstract Few genomic resources currently exist for the American endemic family Cactaceae, a group of around 1850 species, which are world renowned for their amazing growth forms and succulent habits. These icons of arid landscapes across the Americas are threatened in many parts of their range, including in parts of California, and developing more comprehensive genomic data will aid efforts to better understand and preserve these plants. We sequenced and assembled the genome of the beavertail cactus, Opuntia basilaris, which is represented by three varieties in California, one of which is threatened, and another endangered. The genome assembly has a BUSCO complete score of 98.1%, and a total scaffold length of 980 Mb, with a scaffold N50 length of 83 Mb. The genome size of diploid O. basilaris is markedly smaller than other diploid members of Cactaceae that have been assembled to date. This is the first nuclear genome sequenced in subfamily Opuntioideae and the most complete nuclear genome for Cactaceae to date and will lay the foundation for future genomic work across the biologically and taxonomically complicated prickly pear cacti.