Iowa State University (ISU) researchers have overcome the quirks of the soybean cyst nematode's DNA to sequence its genome. Soybean cyst nematodes are parasitic roundworms that infect soybean roots and devastate yields in infected fields. Nematode populations not only build up in fields but stay for years.

The challenges with the genetics of the soybean cyst nematode kept scientists from assembling the full genome for years. The researchers sequenced the genome first by sequencing smaller portions and then piecing those portions together into the full genome. About a third of the nematode's 29,769 genes are repetitive, which complicated the sequencing and assembly process, said Rick Masonbrink, an associate scientist in the ISU Office of Biotechnology and lead author of the study. 

Andrew Severin, co-author of the study and manager of the ISU Genome Informatics Facility, likened the genome to a jigsaw puzzle of a blue sky in which all the pieces are identical in shape and color. But long-read sequencing technology made it possible to assemble a high-quality genome.

For more details, read the ISU news release.

Figure: Soybean cyst nematodes infect soybean roots, where the pests mature into adults while feeding. The mature adult females become so large that they protrude from the infected roots and can be seen with the naked eye as white spheres on the root surface, as pictured here. They later on turn into brown cysts containing hundreds of eggs. (Posted Mar 1, 2019 9:30 am, Iowa State University).