Background Sweetpotato (Ipomoea batatas [L.] Lam.) is an important food crop. However, the genetic information of the nuclear genome of this species is difficult to determine accurately because of its large genome and complex genetic background. This drawback has limited studies on the origin, evolution, genetic diversity and other relevant studies on sweetpotato. Results The chloroplast genomes of 107 sweetpotato cultivars were sequenced, assembled and annotated. The resulting chloroplast genomes were comparatively analysed with the published chloroplast genomes of wild species of sweetpotato. High similarity and certain specificity were found among the chloroplast genomes of Ipomoea spp. Phylogenetic analysis could clearly distinguish wild species from cultivars. Ipomoea trifida and Ipomoea tabascana showed the closest relationship with the cultivars, and different haplotypes of ycf1 could be used to distinguish the cultivars from their wild relatives. The genetic structure was analyzed using variations in the chloroplast genome. Compared with traditional nuclear markers, the chloroplast markers designed based on the InDels on the chloroplast genome showed significant advantages. Conclusions Comparative analysis of chloroplast genomes of 107 cultivars and several wild species of sweetpotato was performed to help analyze the evolution, genetic structure and the development of chloroplast DNA markers of sweetpotato.

Sweetpotato (Ipomoea batatas (L.) Lam.), whose roots are rich in starch, is widely grown around the world and plays a prominent role in ensuring food security. At present, there are no reports on the genetic diversity of sweetpotato germplasm revealed by InDel markers. In this study, we developed a set of 30 InDel markers to evaluate the genetic diversity and relationships of 240 accessions, comprising 77 landraces, 80 introduced accessions, 82 improved varieties released in China, and a diploid wild relative Ipomoea trifida. A total of 94 reliable loci were obtained, with a mean of 3.13 loci per primer, and the PIC value ranged from 0.143 to 0.821. The whole population could be divided into three sub-populations according to a structure analysis based on the Bayesian model, which was consistent with the results of principal component analysis (PCA). A neighbor-joining tree was constructed based on Nei’s genetic distance ranging from 0 to 0.556 and discriminated the panel of the population into three main groups (Ⅰ, Ⅱ, Ⅲ). Group Ⅲ was further split into seven subgroups (ⅢA–ⅢG). The clustering pattern of the 240 accessions was unrelated to their geographic origins. Most of the accessions, whether landraces, improved varieties released in China or introduced germplasm, were mixed, which revealed the high level of genetic similarity among accessions from different regions. There was little difference in the level of genetic diversity between landraces and improved varieties, which was probably due to the exchange and utilization of accessions from different regions. More efforts should be made to collect and utilize sweetpotato germplasm resources and further broaden the genetic basis of sweetpotato cultivars.

Following publication of the original article [1], the author's reported an error in the authorship list.The name of Bettina Heider was incorrectly given as 'Bettina Heida'. The original article has been corrected.