Abstract
Sweetpotato (Ipomoea batatas) plays a critical role in food security and is the most important root crop worldwide following potatoes and cassava. In the United States (US), it is valued at over $700 million USD. There are two sweetpotato germplasm collections (Plant Genetic Resources Conservation Unit and US Vegetable Laboratory) maintained by the USDA, ARS for sweetpotato crop improvement. To date, no genome-wide assessment of genetic diversity within these collections has been reported in the published literature. In our study, population structure and genetic diversity of 417 USDA sweetpotato accessions originating from 8 broad geographical regions (Africa, Australia, Caribbean, Central America, Far East, North America, Pacific Islands, and South America) were determined using single nucleotide polymorphisms (SNPs) identified with a genotyping-by-sequencing (GBS) protocol, GBSpoly, optimized for highly heterozygous and polyploid species. Population structure using Bayesian clustering analyses (STRUCTURE) with 32,784 segregating SNPs grouped the accessions into four genetic groups and indicated a high degree of mixed ancestry. A neighbor-joining cladogram and principal components analysis based on a pairwise genetic distance matrix of the accessions supported the population structure analysis. Pairwise FST values between broad geographical regions based on the origin of accessions ranged from 0.017 (Far East – Pacific Islands) to 0.110 (Australia – South America) and supported the clustering of accessions based on genetic distance. The markers developed for use with this collection of accessions provide an important genomic resource for the sweetpotato community, and contribute to our understanding of the genetic diversity present within the US sweetpotato collection and the species.
Highlights
Sweetpotato, Ipomoea batatas (L.) Lam. (Convolvulaceae), is the sixth most important food crop worldwide, following rice, wheat, potatoes, maize, and cassava (International Potato Center, 2018)
Sweetpotato is widely produced throughout the tropical regions of the world and plays a critical role in food security
The United States (US) sweetpotato germplasm collections maintained by the Plant Genetic Resources Conservation Unit (PGRCU) and US Vegetable Laboratory (USVL) have a general lack of genetic information, which poses challenges for germplasm curators, breeders and geneticists, entomologists, horticulturalists, and plant pathologists
Summary
Sweetpotato, Ipomoea batatas (L.) Lam. (Convolvulaceae), is the sixth most important food crop worldwide, following rice, wheat, potatoes, maize, and cassava (International Potato Center, 2018). (Convolvulaceae), is the sixth most important food crop worldwide, following rice, wheat, potatoes, maize, and cassava (International Potato Center, 2018). This important root crop plays a critical role in food security, especially in developing countries. While global sweetpotato production has been relatively stable for the past 45 years (Padmaja, 2009), production and consumption in the US has increased considerably since 2000 (United States Department of Agriculture, Economic Research Service [USDA-ERS], 2016). The US produced 3.1 billion tons of sweetpotatoes in 2015 and is ranked in the top 10 countries in annual worldwide production of the crop (United States Department of Agriculture, Economic Research Service [USDA-ERS], 2016). Sweetpotatoes provide a source of carbohydrates, but are a major source of vitamins A (carotenoids from the orange-fleshed types), C, B1, B2 (riboflavin), B3 (niacin), B6, E, biotin, and pantothenic acid, as well as dietary fiber, potassium, copper, manganese, and iron; they are low in fat and cholesterol (Hill et al, 1992; Wang et al, 2016)
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