Orange is the new white: New sweetpotato data is something to be thankful for

Only a few weeks remain until millions of Americans will prepare to brave the congested aisles of the local super market to gather the necessary ingredients for this year’s Thanksgiving feast. Navigating the labyrinth of comestibles, they’ll maintain a tight grip on a torn-out piece of loose-leaf paper that features everything needed to ensure this year’s dinner measures up to those their parents hosted. On this scrap you’ll undoubtedly find “sweetpotatoes” etched between the college-ruled spaced lines, and while this is a must-have item to ensure your holiday dinner lives up to family expectations, for millions of others it’s a staple crop that offers hope for a healthy future.

Sweetpotato (Ipomoea batatas) is a globally important staple food crop, and has highly recognized potential to alleviate hunger, vitamin A deficiency, and poverty in Sub-Saharan Africa (SSA), where it is predominantly grown in small plot holdings by poor women farmers. Biofortification with pro-vitamin A-rich orange-fleshed sweetpotato (OFSP) in SSA has led to millions of Africans being spared the devastating effects of vitamin A deficiency, a main cause of illness, blindness and death in children under five years. To recognize these efforts, four scientists were awarded the 2016 World Food Prize and OFSP was chosen as one of Time magazine’s Top Inventions for 2016.

 

Sweetpotatoes are hexaploid and are genetically complex. The lack of information regarding the sweetpotato genome makes it difficult to “design” improvements. That’s why an international team generated genome sequences for sweetpotato wild relatives I. trifada and I. triloba, which were published in Nature Communications on November 2^nd, 2018. This new research provides genomic resources for sweetpotato improvement that can be shared with breeders and farmers.

“Sweetpotato improvement across the world faces major constraints due to the lack of knowledge of the genetic and molecular basis of key agronomic traits. To provide high-quality reference genome resources, we generated chromosome-scale genome assemblies of I. trifida and I. triloba, two diploid wild relatives of sweetpotato.” According to Zhangjun Fei, an associate professor at the Boyce Thompson Institute (BTI) and one of the leaders of this project.

By developing these genome sequences, researchers created a resource that offers hope for faster turnaround times for stronger, more nutritious sweetpotatoes.

“We demonstrated that the genome sequences of I. trifida and I. triloba can be used as robust references to facilitate sweetpotato breeding. The genomic resources developed in this study set the stage for increased rates of genetic gains for key traits such as yield, resistance to disease, and high beta-carotene,” said Shan Wu, a BTI postdoctoral researcher and one of the lead authors of the study.

Understanding the origin of sweetpotato has implications for the potential utility of wild relatives in breeding programs.  Whereas others have suggested that the polyploid sweetpotato was derived from a single wild relative population, multiple lines of evidence from this work suggest the at least two genetically distinct populations if not separate species had contributed to the ancestral sweetpotato gene pool. In addition, this work provides insights into the evolutionary history of the sweetpotato genome.

“Comparative analyses using the diploid genome sequences revealed an ancient whole genome triplication event specific to the Ipomoea genus, which has contributed to additional gene copies that may play a role in adaptive stress responses and function in storage root development.” Said Wu.

The researchers emerged from their “time travel” equipped with the necessary findings to shift their focus to contemporary Africa, where they used sequencing data to connect the past with the present.

“We also resequenced 16 cultivars and landraces widely used in African breeding programs,” explains Wu. “This allowed for refinement of the genetic relationships among these key accessions, and identification of genes and alleles associated with high beta-carotene content, highlighting how genomic tools can enable more efficient improvement of sweetpotato.”

As you’re maneuvering your way through the grocery store in an attempt to assemble the perfect Thanksgiving dinner, consider all the scientists who are working to understand the genetics of sweet potatoes in hopes of bringing a more nutritious variety to your table. The development of open-source data tools for breeders attempting to produce more nutrient-rich food for tens of millions of people is truly something to be thankful for.

 

 

This research was supported by grants from the Bill & Melinda Gates Foundation (OPP1052983), National Natural Science Foun- dation of China (31461143017), National Key Research and Development Program of China (Coarse cereal Fund), National Science Foundation (DEB-1601251), The North Carolina SweetPotato Commission, and the North Carolina State University Agricultural Research Service. Research at CIP was undertaken as part of the CGIAR Research Program on Roots, Tubers and Bananas (RTB) and supported by CGIAR Fund Donors (http://www.cgiar.org/about-us/our-funders/). This research was also supported by the use of the NeCTAR Research Cloud, by QCIF and by the University of Queensland’s Research Computing Centre (RCC). The NeCTAR Research Cloud is a collaborative Australian research platform supported by the National Collaborative Research Infra- Structure Strategy.