Sweetpotato breeding, genebank and on-farm trials
Key Project Information
Sweet potato, as excellent source of both pro-vitamin A and starch, can contribute to address two South African national priorities namely vitamin A deficiency and food security. The project aims at development, maintenance and promotion of sweetpotato varieties improved yield, good storage root quality and high β-carotene content with increased tolerance to drought, pest and diseases. Conventional breeding activities include polycross containing 20-40 parents, some directed crosses, polycross seedling nursery (4000-5000), initial evaluation trial (80-100 lines), preliminary yield trials (60-70 lines), intermediate yield trials (20 lines; 3 locations) and advanced yield trials (27 lines; 3 locations). The breeding efforts resulted during 2003 till 2013 in the release of nine orange-fleshed and eight cream-fleshed varieties developed by the ARC. Currently, the most widely promoted of these are the orange-fleshed cultivar Bophelo, which is disseminated on wide scale for addressing vitamin A deficiency, and cream-fleshed cultivar Ndou, both grown widely for the informal market. Research on genetic analysis of yield traits and root beta-carotene, and induced mutation in sweet potato aimed at improved quality and drought adaptation (MSc studies) were recently completed. A preliminary trial on resistance to Fusarium Wilt, identified an imported cultivar from Louisiana State University as resistant to the local isolate and the cultivar is being used in crosses with local cultivars. The sweet potato germplasm collection comprises 505 accessions including 30 ARC cultivars, 317 breeding lines, 32 RSA and 21 NPGRC landraces, 101 imported cultivars and five varieties from the University of KwaZulu-Natal. The accessions are maintained in glass houses with back-up collection in vitro. All material are virus-indexed. Upon selection of lines from the polycross seedling nursery, those are added to the collection initially in quarantine till virus-indexing was completed. A sweet potato disease testing scheme is run together with tissue culture technology for rapid multiplication of mother stock to provide disease-indexed planting materials. Across 2010/11 to 2014/15, the scheme issued between 14840 and 22314 seedling tray plantlets and between 150 and 1010 nursery bags to vine growers, producers, commercial entities and emerging farmers, while 500 to 9030 4-node cuttings were provided to international clients. Promotion of ARC cultivars is amongst others achieved through on-farm demonstration trials. This is generally based on requests by Provincial Departments of Agriculture to introduce farmers to new cultivars. Between 5 and 8 trials are conducted per year and contains 6 cultivars namely Ndou, Monate and Mvuvhelo (sweet, dry, high yield), Blesbok (commercial control), Bophelo and Impilo (medium dry; orange-flesh).
PROJECT GROUP LEADER: Dr Sunette Laurie
MEMBERS: Mr Musa Mtileni, Dr Patrick Adebola, Mr Andre van den Berg, Ms Whelma Mphela, Ms Itumeleng Kgang, Ms Nokuthula Myeza, Mr Thakhani Ramathavhana, Julia Mulabisana, Rene Sutherland, Michelle Cloete, Wubetu Legesse, Olivia Baloyi, Sonia Naidoo, Dr Ian du Plooy