Indigenous floriculture crops | Indigenous/traditional African vegetables | Potatoes | Genebanks | Biotechnology | Agro-processing | Commercial Vegetables___________________________________________________________________________________________________________________________________________________________________________
Team Leader: Dr. Sunette Laurie
Breeding - Andrè van den Berg, Whelma Mphela, Lesego Selokela, Sidwell Tjale, Musa Mtileni, Piet Ribisi, Lazarus Masuku, and Obed Moikangwe
Glasshouse genebank maintenance - Vusi Nkosi and Lesego Selokela
In vitro gene bank maintenance - Nokuthula Myeza
Disease-indexing multiplication scheme - Lesego Selokela and Vusi Nkosi
Virus diagnostics, molecular markers, genomics and transgenic research - Dr Inge Gazendam
PDP student - Sonia Naidoo
Sweet potato may be not as popular as other vegetables such as potatoes and tomatoes, but still plays an important role in South Africa in terms of food security and alleviating malnutrition. Sweet potato is grown by many resource-poor farmers in virtually all provinces of South Africa. The major production areas are in Limpopo, Mpumalanga, KwaZulu-Natal and Western Cape. For many resource-poor farmers and households it is a reliable source of food because it is a hardy crop, and for other South Africans it is the traditional “soet patat” or batata.
Sweet potato is an excellent source of carbohydrates and has a low glycaemic index (GI). Orange-fleshed types are rich in beta-carotene, a pro-vitamin A carotenoid that is converted to vitamin A by the human body. Orange-fleshed sweet potato is promoted for alleviation of vitamin A deficiency in many parts of the world, including Sub-Saharan Africa, and South and East Asia. In South Africa, this food source is of great importance as a recent survey indicated that 43.6% of children 1-5 year olds (a level which is considered as a serious public health problem) and 27% of women in reproductive age are vitamin A deficient.
Use of orange-fleshed sweet potato in alleviation of vitamin A deficiency: A crop-based approach to address Vitamin A deficiency in South Africa.
Research on sweet potato include the following areas: sweet potato breeding and cultivar trials,
sweet potato genebank, sweet potato disease-indexing scheme, dissemination of varieties and
processing or orange-fleshed sweet potato.
Sweet potato disease-indexing scheme
At Roodeplaat the ARC maintains the only disease-indexing collection (genebank) of sweet potato in South Africa. Viruses are the most limiting factor in production of sweet potato causing considerable loss of yield and also influence the quality. Already in the 1960’s, yield degeneration was experienced by commercial farmers to such extent that it was uneconomical to grow those sweet potato cultivars. Every year healthy material of popular cultivars is taken from the virus-tested stock plants in the glass house for multiplication and sold to vine growers and farmers in 5 liter nursery bags or seedling trays. These are planted in multiplication blocks and then cuttings from there are used to produce sweet potato. This limit the transmission of diseases to clean soils, reduces distribution of viruses causing yield loss and also ensures that the cultivars remains true to type. In this way the sweet potato industry in South Africa remains profitable. Annually approximately 20000 plantlets in seedling trays are produced.
Sweet potato breeding
The ARC-VOP has an excellent history in sweet potato breeding since 1952. To date, 25 cultivars have been released from the breeding program. Most of these cultivars are cream-fleshed and three of these are the main commercialized cultivars currently planted in South Africa, namely,
Blesbok, Bosbok and Ribbok. For the informal market, the leading cultivars are
Ndou (cream-fleshed) and
The breeding efforts aim at traits that are of importance to resource-poor farmers, namely, high dry matter content combined with high yield and high beta-carotene content, as well as additional tolerance to drought and disease. The breeding efforts also aim at traits of importance to the commercial industry, such as high quality, as well as high yielding sweet potato varieties for export, local markets and processing, e.g. frozen products, crisps, baby foods, etc. Current research efforts give attention to tolerance to Fusarium wilt, stem and leaf blight and nematodes.
Directed crosses of sweet potato
In summary, breeding entails the following: Germplasm
with traits required in the breeding program are imported from, e.g. the
USA or the International Potato Center (CIP). Both directed crosses and
polycrosses are used to incorporate selective characteristics in to the
sweet potato population. In some cases, parents are grafted on
to Ipomoea setosa to induce flowering.
The seeds are harvested (±15 000), scarified and raised
in small pots. After 2-3 months, the small roots are sectioned and
orange genotypes (±2000) transferred to a field seedling nursery. After
stringent selection (±80-100), lines progress to the preliminary yield
trial for two years. Only promising lines proceed to the intermediate
yield trial at two locations. Finally, advanced lines are evaluated in
cultivar trials at 2-3 sites in South Africa for two years.
Farmers/consumers take part in the selection of preferred types. These
results are used to identify lines to release as cultivars and for
Commercial companies may enter into a
Material Transfer Agreement with ARC to evaluate new breeding lines for
the commercial industry on their premises. Lines are available with
attractive purple skin and orange flesh.
The ARC also has
several programs aimed at dissemination of new cultivars to
small-holder farmers, promoting cultivation of new cultivars for food
security, nutrition and income generation. The institute also provide
training in production practices of sweet potato.
Cultivar development of sweet potato has, up to now, been largely
phenotype-based selection. There is therefore a need to integrate modern
breeding tools into applied breeding efforts for this crop. Anticipated
activities will include the identification of molecular markers linked to
agronomic, nutritional and resistance traits and using this information in the
ARC breeding program to ultimately generate improved cultivars, leading to
increased production under unfavourable biotic and abiotic conditions.
CULTIVARS AND PRODUCTS
New varieties and lines have been released for the various markets in South Africa
PRODUCTION MANUAL - Guide to Sweet potato production
Adebola P.O., Shegro A., Laurie S.M., Zulu L.N. & Pillay M. 2013. Genotype x environment interaction and yield stability estimate of some sweet potato [Ipomoea batatas (L.)Lam] breeding lines in South Africa. Journal of Plant Breeding and Crop Science Vol. 5(9): 182-186.
Faber, M., Laurie, S.M., van Jaarsveld, P.J. (2013). Total
β-carotene content of orange sweetpotato cultivated under optimal conditions and at a rural village. African Journal of Biotechnology Vol. 12(25): 3947-3951
GRÜNEBERG, W.J., D. MA, R.O.M. MWANGA, E.E. CAREY, K. HUAMANI, F. DIAZ, R. EYZAGUIRRE, E. GUAF, M. JUSUF, A. KARUNIAWAN, K. TJINTOKOHADI, Y.-S. SONG, M. HOSSAIN, E. RAHAMAN, ATTALURI, K. SOME, S. AFUAPE, K. ADOFO, E. LUKONGE, L. KARANJA, J. NDIRIGWE, G. SSEMAKULA, S. AGILI, J.-M. RANDRIANAIVOARIVONY, M. CHIONA, F. CHIPUNGU, S. LAURIE, J. RICARDO, M. ANDRADE, F. RAUSCH FERNANDES, A. S. MELLO, A. KHAN, D.R. LABONTE, AND G.C. YENCHO. 2015. Chapter 1
Advances in sweetpotato breeding from 1993 to 2012 (pg 1-77). In: Nyongesa, M., Quinn, S., Parker, M., & Low, J.
Potato and sweetpotato in Africa: transforming the value chains for food and nutrition security. CABI.
Hundayehu, M., Du Toit, E., Laurie, S., Steyn, M., Greyling, R., Myeza, N. 2014. Effect of long-term invitro sub-culturing on quality degeneration of sweet potato varieties: Morpho-anatomic assessment and simple sequence repeats (SSR) analysis.
Journal of Agricultural Science and Technology A&B 4(10A):811-821.
LAURIE S.M. & BOOYSE, M., 2015. Employing the GGE SREG model plus Elston index values for multiple trait selection in sweetpotato.
LAURIE, S.M., BOOYSE, M., LABUSCHAGNE, M.T., GREYLING, M.M., 2015. Multi-environment performance of new orange-fleshed sweetpotato varieties in South Africa. Crop Science 55(4): 1585-1595.
Laurie, S.M. & VAN HEERDEN, S.M. 2012. Consumer acceptability of four products made from beta-carotene-rich sweet potato.
African Journal of Food Science 6(4):96-103.
Laurie, S.M., Faber, M., van Jaarsveld, PJ, Laurie, R.N., du Plooy, C.P. & Modisane, P.C. (2012). β-carotene yield and productivity of orange-fleshed sweet potato (Ipomoea batatas L. Lam.) as influenced by irrigation and fertilizer application treatments.
Scientia Horticulturae 142: 180-184.
Laurie, S.M., van Jaarsveld, P.J., Faber, M., Philpott, M.F. & Labuschagne, M.T. (2012).
Trans-β-carotene, selected mineral content and potential nutritional contribution of 12 sweetpotato varieties.
Journal of Food Composition and Analysis 27:151-9.
Laurie, S.M., Faber, M., Calitz, F.J., Moelich, E.I., Muller, N. & Labuschagne, M.T. (2012). The use of sensory attributes, sugar content, instrumental data and consumer acceptability in selection of sweet potato varieties.
Journal of the Science of Food and Agriculture
Laurie S.M., Calitz F.J., Adebola P.O., Lezar, A. (2013). Characterization and evaluation of South African sweet potato (Ipomoea batatas (L.) LAM) land races.
SouthAfrican Journal of Botany 85: 10-16.
Laurie, S.M., Maja, M.N., Ngobeni, H.M., Du Plooy, C.P. 2014. Effect of Different Types of Mulching and Plant Spacing on Weed Control, Canopy Cover and Yield of Sweet Potato (Ipomoea batatas (L.) Lam). American Journal of Experimental Agriculture 5(5): 450-458.
Laurie, S.M., Tjale, S.S., van den Berg, A.A., Mtileni, M.M. & Labuschagne, M.T., 2015. Agronomic performance of new cream to yellow-orange sweetpotato varieties in diverse environments across South Africa.
South African Journal of Plant & Soil 32(3):147-155
Laurie S.M., Faber M., Adebola P., Belete A., 2015. Biofortification of sweet potato for food and nutrition security in South Africa. Food Research International 76: 962-970.
Laurie, R.N., Laurie, S.M., du Plooy, C.P., Finnie, J.F. & Van Staden, J., 2015. Yield of drought-stressed sweet potato in relation to canopy cover, stem length and stomatal conductance. Journal of Agricultural Science 7(1): 201-215 .
Magwaza LS, Naidoo SIM, Laurie SM, Laing MD, Shimelis H. 2016. Development of NIRS models for rapid quantification of protein content in sweetpotato [Ipomoea batatas (L.) LAM]. LWT – Food Science and Technology 72: 63-70 (May) ISI 2.71.
Malebana, M.E. (2014).
Induced mutation in sweet potato aimed at improved quality and drought adaptation. (Masters thesis). Bloemfontein: University of the Free State.
Naidoo, S.I.M. (2014). Genetic studies of sweetpotato for two important agronomic traits: yield and flesh colour (Masters thesis). Pretoria: University of Pretoria.
Naidoo S.I.M, Laurie, S.M., Odeny, D.A., Vorster, B.J., Mphela, W.M., Greyling, M.M. and Crampton, B.G. Genetic analysis of yield and flesh colour in sweetpotato, 2016. African Crop Science Journal 24(1): 63-71.
Omotobora, B.O., Adebola, P.O, Modise, D.M., Laurie, S.M., Gerrano, A.S., 2014. Greenhouse and field evaluation of selected sweetpotato (Ipomoea batatas (L.) LAM) accessions for drought tolerance in South Africa. American Journal of Plant Sciences 5(21):3328-3339. Doi:10.4236/ajps.2014.521347
Pofu K.M., Mashela P.W. & Laurie S.M. 2016. Host status to Meloidogyne javanica in sweet potato cultivars: A potential threat in developmental projects. Acta Agriculturae Scandinavica, Section B - Plant Soil Science 67(1):1-5 http://dx.doi.org/10.1080/09064710.2016.1220613
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