Orange-fleshed Sweetpotato Cultivars Research Articles

Identification of genes associated with abiotic stress tolerance in sweetpotato using weighted gene co-expression network analysis.

Sweetpotato, Ipomoea batatas (L.), a key food security crop, is negatively impacted by heat, drought, and salinity stress. The orange-fleshed sweetpotato cultivar "Beauregard" was exposed to heat, salt, and drought treatments for 24 and 48 h to identify genes responding to each stress condition in leaves. Analysis revealed both common (35 up regulated, 259 down regulated genes in the three stress conditions) and unique sets of up regulated (1337 genes by drought, 516 genes by heat, and 97 genes by salt stress) and down regulated (2445 genes by drought, 678 genes by heat, and 204 genes by salt stress) differentially expressed genes (DEGs) suggesting common, yet stress-specific transcriptional responses to these three abiotic stressors. Gene Ontology analysis of down regulated DEGs common to both heat and salt stress revealed enrichment of terms associated with "cell population proliferation" suggestive of an impact on the cell cycle by the two stress conditions. To identify shared and unique gene co-expression networks under multiple abiotic stress conditions, weighted gene co-expression network analysis was performed using gene expression profiles from heat, salt, and drought stress treated 'Beauregard' leaves yielding 18 co-expression modules. One module was enriched for "response to water deprivation," "response to abscisic acid," and "nitrate transport" indicating synergetic crosstalk between nitrogen, water, and phytohormones with genes encoding osmotin, cell expansion, and cell wall modification proteins present as key hub genes in this drought-associated module. This research lays the groundwork for exploring to a further degree, mechanisms for abiotic stress tolerance in sweetpotato.

Quality diets for better health: Integrated orange‐fleshed sweetpotato intervention improved dietary practice in southern Ethiopia

AbstractPoor diet quality for women and children under 2 years of age is the major public health problem in developing countries claiming lives of millions of children and mothers. Nutrition‐sensitive, climate smart orange‐fleshed sweetpotato (OFSP) [Ipomoea batatas (L.) Lam] intervention has been proved to be an effective approach to ensure enhanced diet quality and reduce the health burden faced by women and children. The objective of this study is to contribute to evidence generation effort by assessing the effectiveness of the introduction of vitamin A‐rich, OFSP cultivars alongside social and behavior change communication strategy and agronomic practice in improving diet quality. Cluster‐randomized control trial design was implemented on cross‐sectional data collected from project beneficiary and control households in 2017 (n = 1451) and 2019 (n = 2065). Quasi‐experimental double difference analysis is used to measure the impact of the intervention on key nutrition outcome indicators. Nutrition‐sensitive climate smart agriculture focused on OFSP cultivars with integrated nutrition behavioral change social communication and agronomic training presented significant potential to improved food security, dietary diversity, and frequency of vitamin A food‐rich intake among the rural population of southern Ethiopia. Thus, it is concluded that enhanced investment in nutrition dense agricultural commodities such as orange fleshed‐sweetpotatoes with appropriate training on both nutrition and agronomic can be effective and cheaper means to address the diet quality problem.

Orange Fleshed Sweet Potato Response to Filter Cake and Macadamia Husk Compost in Two Agroecologies of KwaZulu-Natal Province, South Africa

Field experiments were carried out during the summer/autumn (first trial) and winter/spring (second trial) seasons of 2019 and 2021 in the Dlangubo, Ngwelezane, and Mtubatuba areas of KwaZulu-Natal Province of South Africa to study the drought amelioration effects and impact of two locally available organic wastes (filter cake—a residue derived from sugar cane filtration (FC) and macadamia husk compost (MHC)) on the productivity and physiological responses of four orange-fleshed sweet potato cultivars (Beauregard cv., Impilo, W-119 and 199062.1). The effects of FC and MHC were compared with that of inorganic fertilizer (IF) [2:3:2 (30)], FC + IF, MHC + IF, and the control. The soil amendments were applied in the first trials only. Climatic data such as humidity, temperature, and rainfall were taken via remote sensing. The results of the first trial indicated that filter cake and IF significantly performed better than MHC. The strength of filter cake may be attributable to its rich array of mineral nutrients such as calcium, magnesium, potassium, sodium, zinc, copper, manganese, iron, and phosphorus. The limited performance of MHC may be attributable to its ability to hold water. Furthermore, a positive correction occurred between the yield of the test orange-fleshed sweet potato (OFSP) cultivars, rainfall, and vegetation indices (normalized difference vegetation index, enhanced vegetation index, and normalized difference water index) investigated in the study. In season two, IF treatment did not have any significant effect on the growth and productivity of any of the tested sweet potato cultivars, but, FC, FC + IF, and MHC treatments largely maintained their performances. In conclusion, the use of FC is highly recommended in the production of the test OFSP cultivars. Furthermore, the study indicates that both FC and MHC may not only supply the needed plant nutrients but has the capacity to reduce the impact of drought on the growth of the test cultivars. These findings are of great value to farmers, especially the resource-poor ones.

Comparative transcriptome analysis of purple-fleshed sweet potato and its yellow-fleshed mutant provides insight into the transcription factors involved in anthocyanin biosynthesis in tuberous root.

In various plant species, many transcription factors (TFs), such as MYB, bHLH, and WD40, have been identified as regulators of anthocyanin biosynthesis in underground organs. However, the regulatory elements of anthocyanin biosynthesis in the tuberous roots of sweet potato have not been elucidated yet. Here, we selected the purple-fleshed sweet potato cultivar “Zhezi1” (ZZP) and its spontaneous yellow-fleshed mutant “Xinli” (XLY) to investigate the regulatory mechanism of the anthocyanin biosynthesis in the tuberous roots of sweet potato. By analyzing the IbMYB1 genotype in ZZP and XLY, we found that the IbMYB1-2, a MYB TF involved in anthocyanin biosynthesis, was missing in the XLY genome, which might lead to an extreme decrease in anthocyanins in XLY. A comparative transcriptome analysis of ZZP and XLY was conducted to find the TFs involved in anthocyanin biosynthesis in ZZP and XLY. The anthocyanin structural genes were significantly enriched among the differentially expressed genes. Moreover, one MYB activator (IbMYB1), one bHLH (IbbHLH2), three WRKY activator candidates (IbWRKY21, IbWRKY24, and IbWRKY44), and two MYB repressors (IbMYB27 and IbMYBx-ZZ) were highly expressed in ZZP accompanied with anthocyanin structural genes. We also tested the expression of these TFs in six purple- and two orange-fleshed sweet potato cultivars. Interestingly, most of these TFs were significantly positively correlated with anthocyanin contents in these cultivars. The function of the anthocyanin biosynthesis repression of IbMYB27 and IbMYBx-ZZ was verified through transient co-transformation with IbMYB1 into tobacco leaves. Further functional verification of the above TFs was conducted by Y2H, BiFC, and dual-luciferase assays. These tests showed that the MYB-bHLH-WD40/MYB-bHLH-WD40-WRKY complex activated the promoter of anthocyanin structural gene IbDFR and promoters for IbWRKY44, IbMYB27, and IbMYBx-ZZ, indicating reinforcement and feedback regulation to maintain the level of anthocyanin accumulation in the tuberous roots of purple-fleshed sweet potato. These results may provide new insights into the regulatory mechanism of anthocyanin biosynthesis and accumulation in underground organs of sweet potatoes.

Genotype × environment interaction for the agronomic performance of high β-carotene sweetpotato

Sweetpotato (Ipomoea batatas L.) is an important tuber vegetable for human health worldwide owing to its nutritional value and productivity. Consumption of orange-fleshed sweetpotato is beneficial to combat vitamin A deficiency in the world, including Brazil, as these tubers are rich in β-carotene, a precursor of vitamin A. The genotype × environment interaction is one of the greatest challenges in plant breeding, specifically in the selection and approval of cultivars. In this context, adaptability and stability analyses are warranted to evaluate the performance of various genotypes in terms of general or specific adaptations to certain environments and to identify genotypes responsive to environmental variations. Thus, the objective of this study was to evaluate the genotype × environment interaction as well as to estimate the adaptability and stability of sweetpotato genotypes for identifying and selecting promising candidates for breeding. The experiments were performed in four environments: Vera Cruz in São Paulo, Selvíria in Mato Grosso do Sul, and one organic and another intercropped production system in Sete Barras in São Paulo. A randomized block design with two replicates was adopted. A total of 265 genotypes were tested, and the orange-fleshed sweetpotato cultivar ‘Beauregard’ was used as the control. The additive main effects and multiplicative interaction model was used to study environmental stratification, adaptability, and stability. The genotype × environment interaction was evident in all environments. The genotypes CERAT21-13 (marketable root yield, 22.30 t ha-1 in the four environments), CERAT29-26 (27.74 t ha-1), and CERAT52-22 (20.24 t ha-1) were the most adapted in general to the four environments. CERAT25-23, CERAT29-23, and CERAT29-26 were the most adapted to the environment in Vera Cruz; CERAT29-26, CERAT34-14, and CERAT56-32 to the environment in Selvíria; and CERAT31-10, CERAT35-19, and CERAT52-22 to the two environments in Sete Barras.

Structural and functional analysis of a resistance gene and resistance gene analogs in local cultivars of Ipomoea batatas Lam. from Barbados

Many viruses affect sweet potato, but there are few reports of resistance genes against viruses in sweet potato. Therefore, we characterized resistance genes using genomic data of two RNA sequencing (RNA-seq) libraries derived from orange-fleshed sweet potato cultivars in Barbados. The resistance gene, SAMDC1, and twelve resistance gene analogs were present in both libraries. Protein models of SAMDC1 matched 100% to the resistance protein Q7FYG9 in Protein Data Bank (PDB), with a global distance test score (GDT) of 78 (P = 7.8e−14). Two clusters, RGA I and RGA II, broadly representing both cultivars were also revealed by phylogenetic analysis.

Bioactive compounds of two orange-fleshed sweet potato cultivars (Ipomoea batatas (L.) Lam.) in fresh, stored and processed roots

Sweet potatoes are a rich source of bioactive compounds, which are considered to promote human health. This study aimed to analyse the main bioactives of two orange-fleshed sweet potato cultivars, Beauregard and Colorado INTA, freshly harvested, after storage, and after processing of sweet potato paste, a solid dessert widely consumed in Argentina. In the flesh, phenolic compounds, carotenoids, anthocyanin contents, and radical scavenging activity were significantly higher in Colorado INTA cultivar. The carotenoid contents were 555 and 712 µg β-carotene/g dw in the flesh of Beauregard and Colorado INTA, respectively. In the peel of both cultivars, phenolic contents and antioxidant activities were notably higher than in the flesh. Extended storage has markedly increased phenolics and antioxidant properties in the flesh of Colorado INTA, further accentuating the differences between both cultivars. Paste processing negatively affected all parameters, particularly in Beauregard. The major phenolic compounds in both cultivars, chlorogenic and 3,5-dicaffeoylquinic acids, were the most affected by processing. The main reductions of bioactives stemmed from sugar addition. The inclusion of the peel, traditionally discarded during processing, could confer an additional value to the paste. The high bioactive contents of Beauregard and Colorado INTA cultivars, especially the latter, can contribute to provide health benefits and to reduce vitamin A deficiency. The valuable attributes of these cultivars could represent a useful tool for sweet potato producers to add value to this product and to foment its consumption.

Marketing Healthy Food in an African City: Consumer Motivations for Adopting Orange-Fleshed Sweet Potato in Maputo, Mozambique.

Since the late 1990s, the International Potato Center has promoted orange-fleshed sweet potato (OFSP) cultivars in Mozambique as a healthy food, emphasizing its capacity to reduce the prevalence of vitamin A deficiency among mothers and young children. This article seeks to reveal why consumers in Maputo, the capital city of Mozambique, adopt or reject OFSP looking at the role of food systems and consumer characteristics in access and acceptance of healthy food and at the positioning of OFSP on the market in terms of lifestyle and need satisfaction.The results of 255 street interviews confirm that OFSP is widely known. Information reaches people mainly via informal channels (relatives and retailers). Nonadoption is the result of the positioning of OFSP as food for young children and sick people. The OFSP appeals most to the hedonistic and conservative lifestyle segments. Adoption is associated with the perception of OFSP as a source of vitamins that builds up muscles and improves physical appearance and self-fulfillment. While women are typically responsible for domestic tasks, male adopters emphasize the role of OFSP in family health and well-being more than female adopters. This first attempt to understand the marketing of healthy food in Mozambique exposes many similarities between the urban consumers in Maputo and those in developed countries. The results indicate that future marketing should exploit informal channels such as vendors and emphasize its nutritious value for all consumers instead of focusing on mothers and young children.

Nutrient-Dense Orange-Fleshed Sweetpotato: Advances in Drought-Tolerance Breeding and Understanding of Management Practices for Sustainable Next-Generation Cropping Systems in Sub-Saharan Africa

Almost half of children < 5 years old living in sub-Saharan Africa (SSA) suffer from vitamin A deficiency and 60% suffer from iron deficiency. Thus, there has been a strong commitment to breeding for, promoting awareness of, and delivering adapted pro-vitamin A rich orange-fleshed sweetpotato (OFSP) in SSA during the past two decades and for enhanced iron content since 2014. This review article focuses on major breeding efforts in SSA to enhance the drought tolerance of OFSP and reviews integrated crop management practices for improved and sustained sweetpotato production in SSA farming systems. Under climate change, the frequency and severity of droughts is expected to increase. Technical issues are presented in the context of addressing challenges along the entire value chain to ensure adoption. First, the use of an accelerated breeding scheme reduced the breeding cycle from 8–10 to 4–5 years. Since 2010, 19 drought-tolerant OFSP cultivars have been released in Mozambique, 7 in Malawi, and 2 in South Africa. Moreover, research in four breeding populations using the heterosis exploiting breeding scheme (HEBS) demonstrated that within one breeding cycle of 5 years, clones with significantly higher root yield, abiotic tolerance, host plant resistance to pests and diseases, and early maturity can be produced. In the future, HEBS will be combined with greater use of modern genomic tools, new phenotyping tools, and CRISPR/Cas9-mediated gene editing. Second, beyond genetic enhancements, evidence is presented that using improved crop management systems, existing sweet potato yields can be increased 2–4 times. Current knowledge is reviewed concerning sweetpotato’s role in diverse farming systems, but integrated crop management is clearly under researched. Third, the outlook for drought tolerance breeding indicates that two distinct classes of nutrient-rich cultivars are emerging: (1) Early maturing cultivars (< 4 month growing period) that escape drought but also serve humid environments with small landholding size per capita; and (2) Medium maturing (4–6 month growing period) cultivars that avoid drought, are drought tolerant and exhibit continuous root formation. Increasing commercialization of the crop and climate change will drive demand, and the willingness of farmers to invest in improved sweetpotato crop management.

Yield and tuber quality of orange-fleshed sweet potato cultivars under drought stress in greenhouse

Water shortage is an environmental stress that affects the growth, quantity and quality of sweet potato production. The study objective was to analyse the effect of drought stress on the quantity and quality of orange-fleshed sweet potato. Field research has been carried out in April to July 2019 in the greenhouse. This research used a randomized block design with two factors, the first factor was sweet potato cultivars (Beta-1 variety, Perbaungan cultivar, Cengkeh Turi cultivar and Tanah Seribu cultivar) and the second factor was drought stress with different watering level namely severe drought (watered until 1 month and until 2 months with 10 days interval, respectively) and control (watered until 4 months with 10 days interval). The results showed that the orange-fleshed sweet potato cultivars produced significantly different average tuber weights, the number of tubers, beta carotene content, starch content and tuber moisture content were not significantly different. Drought stress influences the yield and quality of tubers which causes a very significant decrease in the parameters of number of tuber, tuber weight, beta carotene content, starch content and tuber water content. The higher the level of drought will cause a decrease in the quantity and quality of sweet potato production.

Sweetpotato Cultivar Trials on Hawai‘i Island

Twelve sweetpotato (Ipomoea batatas var. batatas) accessions/cultivars/landraces (entries) were evaluated for yield, resistance to pests, and quality in five field trials planted at Pepe`ekeo, Hawai‘i Island, and replicated over time with blocks planted on May and Oct. 2014, Feb. and July 2015, and Jan. 2016. Plots were harvested at 4.5 to 6 months after planting. In the first two field trials, local entries planted were ‘Okinawan’, ‘Mokuau’, and ‘Kona B’, as well as PI 531094, ‘Beauregard’, PI 573309, PI 573330, ‘Darby’, ‘Pelican Processor’, and ‘Picadito’. Yields of ‘Mokuau’ and ‘Kona B’ were low and were replaced in the latter three field trials with ‘Murasaki-29’ and ‘LA 08-21p’ from Louisiana State University (LSU) AgCenter, Baton Rouge. At harvest, storage roots were graded according to State of Hawai‘i standards and marketable yields included grades AA, A, and B. Then, injuries of storage roots due to infestations of sweetpotato weevil (Cylas formicarius elegantulus) in each category were estimated. Finally, sugar concentrations, anthocyanins, and β-carotene contents were measured in storage roots. Marketable fresh weight yields of entries differed significantly, with ‘LA 08-21p’ having the greatest marketable yield. However, ‘LA 08-21p’ also had the greatest incidence of damage due to sweetpotato weevil, perhaps because of its growth habit as a tight cluster of storage roots located close to the soil surface. Entries also had significantly different sugar concentrations (fructose, glucose, sucrose, maltose, and total sugars). Concentrations of sucrose ranged from 25 to 68 mg·g−1 fresh weight and were greater than those of monosaccharides analyzed. ‘Beauregard’ had the highest sucrose concentration and total sugars. Purple-fleshed cultivars Okinawan and LA 08-21p contained total monomeric anthocyanins that ranged from 34 to 37 mg/100 g dry weight. Orange-fleshed cultivars Beauregard and Darby contained β-carotene that ranged from 5485 to 8302 µg/100 g fresh weight. These results provide yields of storage roots, susceptibility to sweetpotato weevils, and amounts of antioxidants in purple- and orange-fleshed sweetpotato cultivars to growers interested in producing new sweetpotato cultivars.

Kinetics of starch digestion in native and modified sweetpotato starches from an orange fleshed cultivar

Starch from orange-fleshed sweet potato cultivar was modified using dual autoclave retrogradation, annealing and lintnering modification treatment and their digestibility properties studied. The rate and extent of digestion were suitably predicted with a first-order kinetic model derived in the course of the study. The starches clearly displayed monophasic digestograms while modified starches were observed to have lower glycemic load and glycemic index when compared to the unmodified starch. This study clearly demonstrates the effect of various starch modification treatments on the digestibility of sweet potato starches and also predicted it digestion kinetics parameters.

English

This study evaluated the sensory properties and consumer acceptance of boiled, fried, and mashed orange-fleshed sweet potato (OFSP), by rural lactating women (n=80) and their children <2 years old (n=77). Sensory evaluation and acceptability were performed using a 7-point hedonic scale. Intake parameters (food intake and eating rate), and vitamin A content in the OFSP were measured. The relationships between the sensory descriptors and the type of OFSP preparations was analysed using principal component analysis (PCA) plot. Frying and boiling the OFSP decreased the vitamin A content by 50%, but an acceptable level of retinol was maintained. For all sensory attributes, mothers preferred fried OFSP over boiled, while their children gave high acceptability scores to both boiled and mashed OFSP. The success of the OFSP cultivar, which is newly introduced in Kaffrine, and its high acceptability are promising for the prevention of maternal and child vitamin A deficiency in the rural areas of Senegal.   Key words: Orange-fleshed sweet potato, sensory evaluation, consumer acceptance, Senegal.

Changes in physical properties of sweet potato due to effects of thermal pre-treatments for puree production

In response to increasing consumer demand for high-quality, easy-to-prepare foods, it is necessary to develop innovative ways to use roots and tubers, such as sweet potatoes, in processed foods. Thus, two thermal processes were evaluated, freezing-cooking (F+C) and blanching-freezing-cooking (B+F+C) on the physical properties of the orange-fleshed sweet potato (OFSP) cultivar, which has a high content of β-carotene, in terms of drip loss (Δm), volume variation (ΔV), color, and texture. Cylindrical samples of OFSP were used. Blanched and unblanched samples were stored by freezing, at -18 °C for 2 months, and subsequently cooked at 95 °C. The blanching process was carried out at 95 °C for 2 min. The results showed that, when blanching was used as a pre-treatment for freezing-cooking, a product with fewer physical changes, with a lighter and more intense color (chroma), and with a lower loss of elasticity (Ed) and firmness (F) was obtained.

Nutritive Profile and Provitamin A Value of Sweet Potatoes Flours (Ipomoea batatas Lam) Consumed in Côte d’Ivoire

Sweet potato is an important food security crop in Sub-Saharan Africa. In Côte d’Ivoire, the roots are widely consumed as supplementary staple food or secondary food. The present study is conducted to highlight the nutritive composition, antinutrients and β-carotene contents of local sweet potatoes consumed in Côte d’Ivoire. The nutritive properties and antinutritive factors of these sweet potatoes were investigated using standard methods. Results confirmed the energetic value (363±1.63-374.08±0.56 kcal/100 g DM) of whole sweet potato flour, mainly due to its high carbohydrate content (86.75±0.40%-90.87±0.12%). Whole flour recorded low contents of moisture (4.50±0.10-6.30±0.15%), lipids (0.63±0.08-1.94±0.95%) and proteins (0.94±0.36-1.91±0.15%). The antinutritive factors ranged from 55.84±0.13 to 70.52±0.07 mg/100 g DM and 52.30±5.81-92.44±11.10 mg/100 g DM for oxalates and phytates, respectively. The mineral contents were: magnesium (49.37±1.09-540.87±0.82 mg/100 g DM), calcium (50.28±1.14-110.53±0.79 mg/100 g DM), phosphorus (25.12±1.04-42.75±0.82 mg/100 g DM), potassium (906.25±0.33-1625±0.61 mg/100 g DM), and iron (5.62±0.84-26.89±0.76 mg/100 g DM). The sweet potato flours highlighted polyphenols and antioxidant activity varying from 92.80±98.20±1.72 to 224.46±0.86 mg GAE /100 g DM, and 31.03±0.52-58.63±0.60%, respectively. While β-carotene levels of flours varied from 0.19±0.08 to 22.71±0.67 µg/g DM for white to orange cultivars. At the whole, the orange fleshed sweet potato cultivars recorded an appreciable amount of minerals (magnesium, iron and calcium), polyphenols and greater antioxidant activity. This indicates that these sweet potato cultivars may present a potential asset for their using as natural antioxidants to prevent chronic diseases and undernourishment caused mineral deficiency. The results also showed that the orange-fleshed varieties may contribute for vitamin A deficiencies alleviation in children of rural areas of Côte d’Ivoire.

Post-Harvest Quality of Two Orange-Fleshed Sweet potato [Ipomoea batatas (L) Lam] Cultivars as Influenced by Organic Soil Amendment Treatments

Two orange-fleshed sweet potato cultivars: Apomuden and “Nane” were grown on cow dung-, chicken manure-, compost-amended soils and untreated soil. Apomuden is a variety while “Nane” is being evaluated to be released in Ghana. The storage roots (SRs) were harvested at 3 months, cured by heaping the SRs and covering with the sweet potato foliage for 7-days in the field. The cured SRs were kept in an evaporative cool chamber to study the effect of soil amendment treatments on weight loss, rot, some nutrient composition and sensory attributes. Boiled SRs were assessed by 70 untrained panelists after 7-weeks of storage based on: general appearance, sweetness, finger-feel firmness and overall acceptability using a 5-point hedonic scale (1=dislike extremely to 5=like extremely). Percent rot for “Nane” showed a linear trend while that of Apomuden was non-linear. Both cultivars showed similar trends in terms of cumulative weight loss with “Nane” recording lower weight loss compared with Apomuden. A significant (p<0.001; r=0.71) strong positive correlation was observed between weight loss and rots. “Nane” had higher dry matter (37.15% vs. 30.19%; p<0.001, respectively) and starch content (59.16% vs. 51.86%; p<0.001, respectively) than Apomuden. Stored SRs grown on chicken manure-amended soil recorded the highest protein (6.41%; p<0.001) and β-carotene (16.64 mg/100 g; p<0.001) content than the other treatments. There was a 35% decline in β-carotene for Apomuden, while “Nane” increased by 24% at the end of the 7-weeks storage. “Nane”, the cultivar with high dry matter content had good storage properties than Apomuden. Stored SRs cultivated on soils amended with chicken manure had higher β-carotene and protein content. All sensory attributes ranged from 3.35 to 3.68 indicating a good consumer preference for both cultivars irrespective of the soil amendment treatment applied.

Yield, nutritional quality and stability of orangefleshed sweetpotato cultivars successively later harvesting periods in Mozambique

Abstract Long-term storage of sweetpotato roots is a great challenge for smallholder farmers in Mozambique. Piecemeal harvesting allows several months supply of roots for household consumption provided weevil infestation is avoided. The objectives of the present studies were to determine yield and changes in key macro- and micronutrients associated with early or late harvesting of orange-fleshed sweetpotato cultivars in Mozambique. Four trials representing harvesting periods of 3, 4, 5 or 6 months after planting were established at Gurue in 2015. The randomized complete block design with three replications was laid in each trial. Yield measurements were done in the field and samples were selected and scanned for dry matter, beta-carotene, iron, zinc and carbohydrate using Near Infrared Spectrometry. Collected data were statistically analysed (SAS 1997 software). Yield, dry matter, starch, iron and beta-carotene increased linearly in some cultivars as time to harvest was prolonged. Iron was not affected by harvesting period. Stability of micronutrients such as iron, zinc and beta-carotene is essential when piecemeal harvesting. The study allowed accurate grouping of the cultivars tested into maturity groups for the first time.

Wound healing and dry matter content of orange-fleshed sweetpotato cultivars as influenced by curing methods

Abstract Curing in sweetpotato is a crucial pre- or postharvest practice that could guarantee improved shelf life,but rarely practised by sweetpotato farmers in Sub-Saharan Africa, principally due to lack of knowledge. Wound healing ability of cultivars has been associated with good root storability. In this study, two orange fleshed sweetpotato cultivars (Apomuden and Nane) were either cured in-ground by dehaulming prior to harvest or field-piled over a seven-day period to study their responses to wound healing and changes in dry matter content. Apomuden is a low dry matter content(19%) variety in Ghana while Nane is a high dry matter content (27%) farmer cultivar under evaluation for formal release. A potato peeler was used to deliberately create the wounds on 21 storage roots. The curing treatment was applied and the subsequent post-treatment quality status of the storage roots was monitored daily over a seven-day period. Wound healing ability was scored as follows: 0 = no lignification, 0.5 = patchy lignification and1= complete lignification. Wound healing ability score was not significantly different for Apomuden and Nane (0.83,0.78, respectively; p = 0.120). However, storage roots curedby field-piled curing method resulted in significantly better wound healing ability than dehaulming (0.86, 0.75,respectively, p = 0.001). Over the seven-day curing period,Nane had a significantly higher and stable dry mattercontent compared with Apomuden (p = 0.008), whose dry matter content was lower and fluctuating. The field-piled curing resulted in higher (p = 0.020) dry matter content,24%, compared with in-ground curing (22%). The field piled curing method, which can easily be adopted by sweetpotato farmers, increased the dry matter content of the storage roots; therefore, it could potentially reduce the post-harvest losses in sweetpotato. The high dry matter content of Nane is a desirable root quality attribute for orange-fleshed cultivars and could augment existing cultivars in Ghana.

English

A 2×2×3 factorial design was used to investigate the effect of two orange-fleshed sweetpotato cultivars, three curing treatments and two homestead storage methods on the general appearance, finger-feel firmness, sweetness and overall acceptability of boiled roots. The cultivars were Apomuden and Nane, and the two homestead storage methods were the sand box and the heap storage. In-ground curing (dehaulming) and field-piled curing, for seven days and then uncured treatment were the curing options investigated. A hedonic scale ranging from 1 = extremely dislike to 5 = like extremely was used. For cultivars, the sensory scores ranged from 3.20 to 3.84 (farming season I) and 3.32 to 3.93 (farming season II), indicating good consumer preference. Curing type significantly (p 0.05) in all sensory attributes in both farming seasons except for sweetness and the heap storage had significantly higher (3.84 vs. 3.47, p<0.0001; respectively) score relative to sand box in the first year. Apart from general appearance (3.64 vs. 3.32, p = 0.002) and finger-feel firmness (3.51 vs. 3.25; p = 0.006) in which females had a significantly higher score than males in the first farming season, all the other sensory attributes were similarly ranked by males and females for both years. In-ground and field-piled curing methods, there is increased consumer acceptability and it should be encouraged. Key words: Curing, Field-piled, Gender, Sensory, in-ground, orange-fleshed sweetpotato.

Release of orange-fleshed sweetpotato (Ipomoea batatas [l.] Lam.) cultivars in Mozambique through an accelerated breeding scheme

SUMMARYSweetpotato breeding requires at least 5 years to obtain an advanced breeding clone for further testing with the goal of cultivar release. An accelerated breeding scheme (ABS) can be feasible if the genotype × year interaction is low. The objectives of the present study were to describe an ABS for sweetpotato and to investigate the efficiency of this breeding scheme for selecting high-yielding and well-adapted orange-fleshed sweetpotato (OFSP) cultivars with high β-carotene (BC) content. More than 198 500 seeds from two crossing blocks were germinated and rapidly multiplied for evaluation in observation trials at four breeding locations in Mozambique. Breeding clones with storage root yields above 10 t/ha were advanced to preliminary and advanced yield trials across four sites and for 3 years. As a result, 64 high-yielding OFSP breeding clones were selected and evaluated in four mega-environments following a randomized complete block design with three replicates at Angónia, Chókwè, Gurúè and Umbelúzi. Data from multi-environment trials were subjected to single site and combined analysis of variance as well as to stability analysis. The genotype × environment interaction was highly significant for storage root and vine yields, dry matter (DM) and BC content. Storage root yield and DM content for 15 OFSP breeding clones ranged from 14·9 to 27·1 t/ha and from 24·8 to 32·8%, respectively. BC content, iron and zinc ranged from 5·9 to 38·4, 1·6 to 2·1 and 1·1 to 1·5 mg/100 g dry weight, respectively. The OFSP breeding clones also met the culinary tastes required by local consumers in Mozambique. The proposed ABS seems to be an attractive scheme for genetic enhancement of sweetpotato.