Characterization and evaluation of South African sweet potato (Ipomoea batatas (L.) LAM) land races

A total of 57 sweet potato accessions, consisting of 51 South African land races and six local cultivars, were subjected to characterization in a glass house and in follow-up field experiments. The accessions were morphologically characterized using the Bioversity International descriptors and, in addition, screened for drought and heat tolerance. Significant differences were observed for the following drought–heat screening parameters: number of days to severe wilting and number of severely wilted plants. A number of land races showed tolerance to both drought and heat, namely A3026, A3027, A2316 and A46. The multivariate cluster analysis and principal component analysis divided the 57 accessions into three groups consisting of 17, 21 and 19 accessions, respectively. The commercial varieties were all allocated to group 3, except the old cultivar Mafutha, which was in group 1. The most important characters for distinction of the accessions were leaf outline, leaf lobe type, leaf lobe number, and shape of the central leaf lobe. The study provided comprehensive information concerning locally available sweet potato germplasm and is of vital importance for advancement in the sweet potato improvement program in South Africa. The information will also be useful to SASHA (a regional network for sweet potato breeding), ensuring wider utilization of these germplasms within Sub-Saharan Africa.

► 51 South African sweet potato land races could be distinguished into three groups.
► Leaf outline, lobe type and number, and central leaf lobe shape were most distinctive.
► Thirteen land races with early vegetative heat–drought tolerance were identified.
► The results provide comprehensive information on traditional local sweet potatoes.