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Breeding of sweet potato and evaluation of advanced breeding lines and imported varieties in off-station trials in South Africa
... M. incognita race 4 primarily occurs in cotton-producing regions of South Africa (Kleynhans et al. 1996). Despite intensified research efforts in biofortification and agronomic performance of sweet potato (Ipomoea batatas) genotypes, scant attention had been paid to the nematode-sweet potato relation in South Africa (Laurie et al. 2004). The latter is viewed as a breeding centre for sweet potato propagation materials for SADC countries. ...
... Certain exotic orange-fleshed sweet potato cultivars were imported from South and North America for breeding with the local lines , without any attention to nematode host-status. Additionally, the SPP had since 2001 been exporting high-quality sweet potato cultivars as propagation materials to SADC countries (Laurie et al. 2004), and no information existed on host-status to Meloidogyne species. This leniency could be ascribed to the then availability of synthetic chemical nematicides. ...
Experimental system: Due to serious economic challenges posed by root-knot (Meloidogyne species) nematodes in sweet potato (Ipomoea batatas) production, the Sweet Potato Programme (SPP) of the Agricultural Research Council (ARC) in South Africa has since included screening for nematode host-status in its breeding-selection activities. Procedures: 20 sweet potato lines were screened against M. javanica, M. incognita race 2 and M. incognita race 4 in parallel trials inoculated with 3000 eggs and second-stage juveniles (J2) per established cutting. Results: At 56 days after inoculation, the reproductive potential (RP) of all test Meloidogyne species on sweet potato line 1990-10-2 was zero, whereas RP values on other lines were 19.48–342.7, 31.9–995.1 and 10.3–380.44 ranges for M. javanica, M. incognita race 2 and M. incognita race 4, respectively. Conclusion: Among the test sweet potato lines, line 1990-10-2 was non-host to populations of tropical Meloidogyne species in South Africa and could, therefore, be subjected to nematode resistance tests.
... M. incognita race 4 primarily occurs in cotton-producing regions of South Africa (Kleynhans et al. 1996). Despite intensified research efforts in biofortification and agronomic performance of sweet potato (Ipomoea batatas) genotypes, scant attention had been paid to the nematode-sweet potato relation in South Africa (Laurie et al. 2004). The latter is viewed as a breeding centre for sweet potato propagation materials for SADC countries. ...
... Certain exotic orange-fleshed sweet potato cultivars were imported from South and North America for breeding with the local lines , without any attention to nematode host-status. Additionally, the SPP had since 2001 been exporting high-quality sweet potato cultivars as propagation materials to SADC countries (Laurie et al. 2004), and no information existed on host-status to Meloidogyne species. This leniency could be ascribed to the then availability of synthetic chemical nematicides. ...
Zucchini or squash (Cucumis pepo), also referred to as the green baby marrows, are highly susceptible to Meloidogyne species, without any genotype with resistance to the nematode genus. Cucurbitacin-containing phytonematicides are being used as alternatives to methyl bromide in various crops, with limited information on whether the product could induce auto-allelopathy in C. pepo cultivars. The objective of the study was to investigate the effects of Nemafric-BL phytonematicide on suppression of M. incognita and growth of zucchini under greenhouse conditions. Zucchini cv. ‘Cartesa’ seedlings were inoculated with 5000 eggs and second-stage juveniles (J2) of M. incognita and then managed at weekly basis using Nemafric-BL phytonematicide at 0, 2, 4, 8, 16 and 32%. Eight weeks after the treatments, relative to untreated control, the treatments reduced eggs (95-100%) and J2 (99-100) in roots, J2 (86-110%) in soil and final nematode population densities (97-100), but increased dry fruit mass (5-14%) and fruit number (66-137%), without affecting other plant variables. Nemafric-BL phytonematicide could be used in managing population densities of Meloidogyne species in zucchini production under greenhouse conditions without inducing phytotoxicity. © 2018, Gaurav Society of Agricultural Research Information Centre. All rights reserved.
... M. incognita race 4 primarily occurs in cotton-producing regions of South Africa (Kleynhans et al. 1996). Despite intensified research efforts in biofortification and agronomic performance of sweet potato (Ipomoea batatas) genotypes, scant attention had been paid to the nematode-sweet potato relation in South Africa (Laurie et al. 2004). The latter is viewed as a breeding centre for sweet potato propagation materials for SADC countries. ...
... Certain exotic orange-fleshed sweet potato cultivars were imported from South and North America for breeding with the local lines , without any attention to nematode host-status. Additionally, the SPP had since 2001 been exporting high-quality sweet potato cultivars as propagation materials to SADC countries (Laurie et al. 2004), and no information existed on host-status to Meloidogyne species. This leniency could be ascribed to the then availability of synthetic chemical nematicides. ...
Density-dependent growth patterns suggested that under phytonematicides population densities of plant-parasitic nematodes could either be stimulated, neutral or inhibited, thereby resulting in 'inconsistent results' concept. The objective of this study was to determine whether post-application sampling of the citrus nematode (Tylenchulus semipenetrans Cobb) population densities under untreated control, Nemarioc-AG phytonematicide and aldicarb on rough lemon (Citrus jambhiri Lush.) seedlings could provide quantitative evidence of 'inconsistent results'. Uniform three-month old C. jambhiri seedlings in plastic pots containing 2700 ml growing mixture were each inoculated with 10000 T. semipenetrans eggs and second-stage juveniles (J2). A week after inoculation, seedlings were split into three groups of seventy each and subjected to once-off treatment of untreated control, 2 g Nemarioc-AG phytonematicide and 2 g aldicarb. Five seedlings from each group were randomly placed on greenhouse benches to serve as a sampling block, with a total of 14 blocks. The entire block was sampled on a weekly basis and assessed for final nematode population density (Pf). After the final assessment, Pf under untreated control over increasing sampling intervals exhibited positive quadratic relations, with the model explaining 90% associations, with optimum Pf of 13804 eggs and J2 at six weeks postapplication. In contrast, Pf over increasing sampling intervals under phytonematicide and aldicarb exhibited negative quadratic relations, with the model explaining 95 and 92% associations, respectively. The two had minimum Pf at 974 eggs and J2 and 2205 eggs and J2, respectively, each at approximately six weeks. In conclusion, opposite temporal cyclic nematode population growth patterns post-application of nematicidal products and untreated control provided empirically-based evidence of 'inconsistent results' in nematode management under phytonematicides.
... M. incognita race 4 primarily occurs in cotton-producing regions of South Africa (Kleynhans et al. 1996). Despite intensified research efforts in biofortification and agronomic performance of sweet potato (Ipomoea batatas) genotypes, scant attention had been paid to the nematode-sweet potato relation in South Africa (Laurie et al. 2004). The latter is viewed as a breeding centre for sweet potato propagation materials for SADC countries. ...
... Certain exotic orange-fleshed sweet potato cultivars were imported from South and North America for breeding with the local lines , without any attention to nematode host-status. Additionally, the SPP had since 2001 been exporting high-quality sweet potato cultivars as propagation materials to SADC countries (Laurie et al. 2004), and no information existed on host-status to Meloidogyne species. This leniency could be ascribed to the then availability of synthetic chemical nematicides. ...
Globally, most of the crop-related developmental projects collapsed due to the existence of aggressive plant-parasitic nematodes. Intensive South African biofortification efforts using exotic and local sweet potato (Ipomoea batatas) cultivars have hardly considered the inclusion of nematode resistance in plant breeding, despite the withdrawal of most nematicides from agrochemical markets. The objective of this study was to screen 12 selected biofortification sweet potato cultivars for host-status to South Africa tropical root-knot (Meloidogyne species) nematodes. Three exotic orange-fleshed, three local orange-fleshed and six cream-fleshed cultivars were used in three separate experiments of M. javanica and races 2 and 4 of M. incognita. In each experiment, 6000 eggs and second-stage juveniles/plant were used for inoculation, with nematode assessment performed at 56 days after inoculation. All tested biofortification exotic (except for cv. ‘W-119’) and local cultivars were hosts to Meloidogyne species and races, whereas three non-biofortication local cultivars, namely, ‘Bosbok’, ‘Blesbok’ and ‘Mvuvhelo’ were non-hosts. In conclusion, the findings suggested the likelihood of the existence of non-host-status in certain exotic and local sweet potato cultivars for use in plant breeding programmes against South African Meloidogyne species and races.
... [12][13][14] The ARC has been involved in developing improved varieties of the OFSP. [15,16] Sweet potato has a much higher carbohydrate content (26.3 g/100 g) than other foods, such as maize porridge (15.6 g/100 g), sorghum porridge (17.0 g/100 g) and potatoes (18.5 g/100 g); [17] however, the protein content is lower than in potatoes and other grain crops. [17] The nutritional composition of the OFSP and the WFSP is shown in Table 1. ...
Background. Vitamin A deficiency (VAD) is a major public health problem that affects South African children and is a major contributor to the mortality of children under five years of age. VAD can result in visual impairment, diarrhoea and increased risk of severe measles and death. Orange-fleshed sweet potato (OFSP), a staple crop biofortified with provitamin A, has the potential to improve vitamin A intake in infants, especially when used as a complementary food. Objective. To assess the acceptance of an OFSP complementary food by infant caregivers. Methods. This study was conducted at the Newtown Community Health Centre, Inanda, in the eThekwini District of KwaZulu-Natal (KZN). Sixty-three infant caregivers assessed the acceptance of complementary foods made from OFSP and white-fleshed sweet potato (WFSP) (control), using a five-point hedonic rating test. In addition, ten caregivers participated in two focus group discussions, using pre-determined questions. Results. There were no statistically significant differences in the sensory attribute ratings of complementary foods made from WFSP and OFSP. The OFSP complementary food was well-accepted, especially its colour and soft texture. None of the focus group discussion participants had seen or tasted the OFSP before. Caregivers were willing to buy the OFSP, if it were available and cheaper than the WFSP. Conclusion. The complementary food made from the OFSP was highly acceptable to infant caregivers attending the Newtown Community Health Centre in KZN. It has the potential to be used in complementary feeding and to improve the vitamin A status of infants. © 2018, Health and Medical Publishing Group. All rights reserved.
... All varieties had cream to yellow-orange flesh color, namely, Ndou (1995-13-2), Monate (1989-17-1), Mokone (1987-16-1), Letlhabula (1995-10-1), Phala (1984-2-201), Amasi (1985-6-3), Mamphenyane (1984-10-340) and Serolane (1998-12-3). The varieties were commercially released based on the first set of offstation trials conducted from 2000/1 to 2002/3 (Laurie et al. 2004;Laurie and Magoro 2008). Two existing varieties were included as standards: Mafutha (informal market) and Blesbok (commercial market). ...
Sweetpotato is a good source of energy,
easy-to-grow and hardy and thus useful in contributing
to food security. The current study aimed at identification
of the best sweetpotato varieties for multiple
desirable traits such as good yield, adaptability
(including vine vigor) and tastiness (high dry mass
content; taste). Ten South African sweetpotato varieties
were evaluated during the period 2002/3–2007/8
at six locations each over two seasons. The sites
regression model (SREG) of the genotype plus
genotype by environment interaction (GGE) biplot
analysis was performed with GenStat to determine
stability and adaptability of the varieties. Subsequently,
multiple trait selection was performed by
using the ranking from Elston index selection. To
enable inclusion of varietal stability in multiple trait
selection, a stability value was calculated. High
yielding varieties included Blesbok, Monate, Ndou
and Letlhabula, of which Monate and Letlhabula had
stable performance. The advantage, particularly for
resource-poor farmers, of a specifically adapted,
responsive variety such as Ndou, is the ability to
respond to changes in the environment. Based on
multiple trait selection varieties Ndou and Monate
were recommended for production. The results present
an innovative use of Elston index selection, including
a stability value, in combination with GGE SREG for
recommending varieties with multiple desirable traits.
The recommended varieties are of significance for
future use to improve food security.
... Vegetable garden projects in South Africa originally used some of the US varieties (particularly Resisto, W-119 and Excel). After several years of crossing, evaluation and selection, three orange-fleshed varieties (Khano, Serolane and Impilo) were released from the ARC programme between 2006 and 2008 (38,39). The breeding programme is developing sweet potato cultivars with high b-carotene content, good yield, good taste, drought tolerance and tolerance to major diseases, and is linked with the HarvestPlus Sweet Potato Biofortification Program (40,41). ...
Home gardening, focusing on provitamin A-rich vegetables, is a long-term strategy that can contribute to combating vitamin A and other nutritional deficiencies which are of public health significance in developing countries. The provitamin A carotenoid content of foods and their potential contribution towards meeting the vitamin A requirements of the target population are predominant considerations in the selection of crops to be planted. This chapter describes a home garden approach that integrates gardening activities with nutrition education, using community-based growth monitoring as entry point. Studies using this approach in South Africa showed a favourable effect on maternal knowledge of vitamin A nutrition, dietary intake of provitamin A-rich vegetables, caregiver-reported child morbidity and children's vitamin A status. Provitamin A-rich vegetables and fruits contributed significantly towards achieving the recommended dietary intake of vitamin A and various other micronutrients. Seasonal availability of provitamin A-rich vegetables and fruits needs to be taken into consideration to ensure year-round availability of provitamin A-rich foods. The approach is flexible and entry points other than community-based growth monitoring can be used to promote production and consumption of provitamin A-rich vegetables and fruits. Demonstration gardens to serve as training centres, community-based nurseries for orange-fleshed sweet potato cuttings and a seed distribution system are important components of the home garden projects. Various constraints experienced with vegetable gardens and possible solutions are highlighted. Participation in gardening projects is self-selective. Non-participating households within the project areas are, however, exposed to the promotion activities, resulting in a spill-over effect to non-participating households.
Sweet potato is one of the most economically important crops for addressing global food security and climate change issues, especially under conditions of extensive agriculture, such as those found in developing countries. However, osmotic stress negatively impacts the agronomic and economic productivity of sweet potato cultivation by inducing several morphological, physiological, and biochemical changes. Plants employ many signaling pathways to respond to water stress by modifying their growth patterns, activating antioxidants, accumulating suitable solutes and chaperones, and making stress proteins. These physiological, metabolic, and genetic modifications can be employed as the best indicators for choosing drought-tolerant genotypes. The main objective of sweet potato breeding in many regions of the world, especially those affected by drought, is to obtain varieties that combine drought tolerance with high yields. In this regard, the study of the physiological and biochemical features of certain varieties is important for the implementation of drought resistance measures. Adapted genotypes can be selected and improved for particular growing conditions by using suitable tools and drought tolerance-related selection criteria. By regulating genetics in this way, the creation of drought-resistant varieties may become cost-effective for smallholder farmers. This review focuses on the drought tolerance mechanisms of sweet potato, the effects of drought stress on its productivity, its crop management strategies for drought mitigation, traditional and molecular sweet potato breeding methods for drought tolerance, and the use of biotechnological methods to increase the tolerance of sweet potato to drought.
Sweetpotato is grown in diverse environments of South Africa by both commercial and subsistence farmers. The aim of the present study was to assess the stability, agronomic performance and palatability of new ARC cultivars bred for the informal market, and to make cultivar recommendations. Eight new cultivars with cream to yelloworange flesh were evaluated in multi-environment trials using a randomised complete block design in six provinces. Data were recorded on root yield, percentage dry mass, palatability and vine vigour. An additive main effects and multiplicative interactions model was employed for data analysis. New cultivars with high potential were Ndou, Letlhabula and Monate, with root yields similar to or slightly lower than the commercial control cultivar Blesbok. Ndou and Monate had vigorous vine growth, high dry mass and good end-user acceptability and offered the best combination of important traits for the informal market. Letlhabula seemed more suitable for the commercial market owing to lower dry mass. The new improved cultivars will be advantageous, firstly, to farmers as a result of high yield and, secondly, to consumers owing to better palatibility.
Three sweet potato cultivars (A40, A45 and 199062.1) were planted in three small-scale farms located under different agro-ecological zones of KwaZulu-Natal. The objective was to assess growth, physiological responses and yield of the sweet potato cultivars under low-input agricultural system and different environmental conditions. Sweet potato planted at Richards Bay (28°19'S; 32°06E), a coastal sandy soil location, recorded low stomatal conductance(SC; 102.2 m moles m−2 s−1) and chlorophyll content index (CCI; 29.4). This consequently resulted in reduced vine length, leaf number and branching of sweet potato plants. Environmental conditions in that location (Richards Bay) such as high evapotranspiration, high temperatures and low water retention capacity of sandy soils created drought stress condition. This caused reduction in photosynthetic activities and translocation to the harvestable plant parts. The other two locations (Deepdale at 28°01'S; 28°99'E and Umbumbulu at 29°98'S; 30°70'E) located further from the coast and characterized by clayey soils recorded higher SC and CCI. Branching and number of leaves were significantly influenced by locations and growing season while vine length varied with locations, indicating specific varietal adaptation. Biomass and storage root yield followed a similar trend as plant growth and physiology. Richards Bay recorded very low biomass and storage root yield (5.4 and 5.0 t ha−1) in both seasons while Deepdale recorded higher yields (42.0 t ha−1) during the first growing season. Yields reduced by 67% (13.6 t ha−1) in the second season. Storage root yields from Umbumbulu were stable in both growing seasons (29.4 and 28 t ha−1 during seasons one and two, respectively). Adding fertilizer only improved storage roots yield in Richards Bay, otherwise cultural practises were responsible for storage root yield increases in Deepdale and Umbumbulu. Orange-fleshed sweet potato cultivar A45 showed good environmental plasticity while cultivar 199062.1 responded well to fertilizer application. This indicated its suitability for use in food security programmes under low-input agriculture.
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