Sequencing the yam genome to improve food security

An international research collaboration has provided a genome sequence for the white Guinea yam — a staple crop with huge economic and cultural significance on the African continent.

Yams are a staple part of the Nigerian diet, but at current rates of consumption, demand is beginning to outstrip supply. Furthermore, unlike other staple crops such as wheat, maize and rice, the crop is relatively undomesticated. Understanding the genomics of this crucial plant will thus help farmers increase yields and sustainability.

Researchers from the UK, Germany, Japan and Nigeria have now performed genome analysis of white Guinea yam, enabling them to assemble a 594 Mb genome. Published in the journal BMC Biology, their research has been particularly beneficial in identifying the regions of the genome that determine the yam’s sex.

Dioecy — the occurrence of separate male and female plants — is relatively rare and occurs only in about 5–6% of flowering plants, including yams and asparagus. Therefore, understanding the process in yams could help in improving other economically important crops.

Furthermore, knowledge of this rare feature is vital for improving the speed of marker-assisted breeding projects. With assisted breeding programs, the yam crop could be better domesticated, boosting food security and economic wellbeing.

“Having a reference sequence for the white Guinea yam gives us the unique opportunity to gain a better understanding of dioecy — a very rare trait in flowering plants — in a species that’s very evolutionarily differentiated from most of what’s been sequenced so far,” said study co-author Benjamen White, from the Earlham Institute in the UK. “Understanding this trait and having a genomic resource for white Guinea yam will be invaluable in breeding a better yam — one that will improve food security in West and Central Africa, and the livelihood of smallholder farmers there.”

“This is an important breakthrough,” added Dr Robert Asiedu, director, research for development, for The International Institute of Tropical Agriculture-West Africa, Nigeria. “It means that yam has joined those crops with a full DNA sequence, a development which started with rice some years ago. The implications are profound.

“The full DNA sequence will greatly facilitate our understanding of the genetic control of key traits such as flowering, diseases and others including quality traits, and this in turn will make the breeding of new varieties both faster and more precise.”

“This will help to overcome some of the many challenges facing yam farmers in Africa and other parts of the world,” concluded Professor Ryohei Terauchi, lead author on the study, from Kyoto University and the Iwate Biotechnology Research Centre. “These include pests and diseases, post-harvest losses and the need to develop more sustainable systems of farming for the crop.”

Image caption: Yams for sale at Oje market, Ibadan, Nigeria.