A High Density Genetic Map of Sweetpotato [Ipomoea batatas (L.) Lam] Based on High Throughput Sequence-Based Diversity Array Technology Markers (DArTseq)

Sweetpotato is a food security crop especially for the poorest of the world, a polyploid crop (2n=6x=90) with a highly heterozygous genome with an estimated size of 4.4Gb. Consequently, genome analysis is difficult and genomic tools for sweetpotato improvement are scarce. Toward closing this gap, we followed the two-way pseudo-testcross approach to develop a genetic linkage map in the hexaploid mapping population of 292 progenies from a cross between a North-American-orange-flesh cultivar, “Beauregard” (female) and an African-white-flesh cultivar, “Tanzania” (male) using dominant markers, “SilicoDArTs”, from DArTseq platform in Australia. The female parental framework map was constructed using 3,733 single-dose and double single-dose markers, to which a further 1,013 double-dose markers are being added. The male parental framework map was constructed with 3,166 single-dose and double single-dose markers to which 938 double-dose markers are being added. The framework maps span 5,593.1 cM and 4,881.7cM with average distance between markers being 1.73 cM and 1.81 cM, respectively, for the female and male parental maps. A total of 94 linkage groups and 87 linkage groups were assembled for the female and male parental maps, respectively. The linkage groups will be assigned to homo(eo)logous groups once addition of double-dose markers to the linkage groups is completed. Increased quality of the sweetpotato genetic maps compared to previously published maps with regard to coverage and density promises high resolution QTL mapping and identification of markers tightly linked to disease resistance, nutrition, quality and yield-related traits, leading to accelerated and targeted breeding and gene discovery in sweetpotato.