Early generation clonal selection of sweetpotato ( Ipomoea batatas (L.) Lam) using an accelerated breeding scheme

The breeding stages of a clonally propagated crop entails several steps and can take more than five years from hybridisation till cultivar release. The Accelerated Breeding Scheme (ABS) in sweetpotato relies on the use of multiple locations at the early breeding stages to reduce the years required for field evaluation. The aim of the study was to select the best progenies based on the ABS in sweetpotato towards the development of genotypes that combine high protein content with other important agronomic traits. Botanical seeds were generated from crosses between two diverse sets of parents, crossed using a North Carolina II design. F1-progenies (n = 363) were planted in a lattice design at three distinct locations during the 2017/18 planting season. Parameters recorded included pest and disease infestation, storage root traits and yield components, root protein content and nutrient related traits. Nutrient content was determined by near-infrared spectrometry. Analysis of variance and multiple t-distribution test and best test grouping were performed. There were significant differences ( p < 0.001) among the genotypes for total number of roots, total root yield, marketable number of roots and marketable yield. The severity of Alternaria blight was significantly higher at Jozini. Forty progenies were selected (12.8% selection pressure) based on agronomic performance. Using the nutrient content results, four promising orange-fleshed clones (NC12-9, NC53-11, NC55-8, NC55-2) and one cream-fleshed clone (NC51-1) were identified with high storage root protein, iron and zinc contents. NC51-1 and NC55-2 produce promising storage root yields. The ABS approach is resource-demanding in the first phase but advances progenies rapidly to the subsequent breeding phases for cultivar release.