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Characterisation of orange-fleshed sweetpotato varieties in South Africa: agronomic traits, consumer acceptability and n

Characterisation of orange-fleshed sweetpotato varieties in South Africa: agronomic traits, consumer acceptability and nutrient content. S.M. Laurie Agricultural Research Council - Roodeplaat Vegetable and Ornamental Plant Institute Sweetpotato Breeders Meeting, 27 June 2011, Maputo.

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Characterisation of orange-fleshed sweetpotato varieties in South Africa: agronomic traits, consumer acceptability and n

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  1. Characterisation of orange-fleshed sweetpotato varieties in South Africa: agronomic traits, consumer acceptability and nutrient content S.M. Laurie Agricultural Research Council - Roodeplaat Vegetable and Ornamental Plant Institute Sweetpotato Breeders Meeting, 27 June 2011, Maputo

  2. Formal market: 50 000 – 60 000 Mt/annum + informal market ± same; mostly CFSP Recent large increase OFSP for frozen vegetable industry: Beauregard 425 ha, Purple Sunset (ARC) 225 ha VAD: 64% of 1-9 year olds, 27% women at child-bearing age Food security: 30% households at risk Background

  3. Require improved OFSP to expand production Breeding aimed at good yield, good β-carotene content, dry mass %. USA imports, ARC lines/variety 2006-8 Aim: to characterize OFSP … agronomic performance consumer acceptability, sensory traits 3) mineral and β-carotene content in order to recommend varieties for addressing VAD and for use in new markets. Rationale

  4. 1. Varieties 9 OFSP varieties/lines: Khano, Serolaneand Impilo; lines 1999-1-7 and 2001-5-2; Excel, W-119 and Resisto from USA, Beauregard (USA variety) commercial use; 3 CFSP: Blesbok (Com), Ndou & Monate (dry, sweet) 2. Multi-location trial sites Two seasons per site at four sites during 2005/6 to 2008/9. EC1 & EC2: Communal garden (Eastern Cape); (temperate) E1 & E2: Elsenburg Agric. College (Western Cape); (dry, hot) OS1 &OS2: Owen SitholeCollege (KwaZulu-Natal);(sub-tropical) R1 & R2: Research center Roodeplaat(Gauteng); (temperate) 3 reps x 30 plants Supplementary irrigation & fertilization Growing period 4.5 – 5.5 months Methodology

  5. 3. Sensory evaluation Cooked samples evaluated by trained panel for appearance (yellow-green color, orange color, dark edges, discoloration), flavor (sweetness, sweetpotato flavor, pumpkin flavor) and texture (firmness, graininess, wateriness) Instrumental color and texture Content of free sugars (glucose, fructose, sucrose, maltose) and starch. 4. Consumer acceptability Tested by a panel comprising 168 primary school children and 48 adults in Dassenhoek, KwaZulu-Natal, using a Balanced Incomplete Block Design.

  6. 5. Nutrient content - Randomly collected 8 medium roots - From 4 geographical areas (ARC-Roodeplaat, Empangeni, Giyani and Hazyview). - Send intact to analytical labs - Content of 6 minerals (by OES) & trans-β-carotene (by HPLC) 6. Data processing & analysis -ANOVA - GXE: SREG model of GGE Biplot (G main effect plus G x E interaction) - Correlation analysis between sensory & consumer data, PLS to indicate most distinctive attributes, group varieties - Elston Selection Index

  7. Impilo Impilo Results Appearance of sweetpotato cultivars Impilo

  8. GGE Biplot: Total yield

  9. Unmarketable yield classes • XXL (early maturing): Beauregard • XXS: Serolane, Impilo, 1999-1-7 and Khano. • Root cracks: Excel, Impilo and Khano. • Insect damage: Beauregard, Ndou and Impilo • Mechanical damage (long roots) W-119 • Long curved (slender): 1999-1-7 • Sprouting to some extent in Impilo • Mean root weight: • Beauregard and W-119 (high), an indication of early maturity. • Serolane, Excel, Impilo and 2001-5-2 (intermediate). • 1999-1-7, Khano and Resisto (small).

  10. GGE Biplot: Marketable yield

  11. Ideal varieties have high PC1 scores (high yield) and small absolute PC2 scores (high stability), e.g. Impilo and Beauregard). • Stable, wide adaption, high yielding: Beauregard, Impilo • Unstable, specific adaption, high yielding : 2001-5-2, 1999-1-7 • responsive has the specific advantage that it may be able to respond to changes in environment • Stable, wide adaption, average to below average yields: Khano • Unstable, specific adaption, low yielding: Excel, Serolane • Stable, wide adaption, low yielding: Resisto, W-119

  12. Consumer acceptability of color and taste Means for varieties in a column followed by the same letter are not significantly different at P ≤ 0.05 1 Cream-fleshed varieties 2 Scale for scores: 1=very bad; 2=bad; 3=indifferent; 4=nice; 5=very nice

  13. Correlation analysis • Orange-fleshed varieties were lower in sweet potato-like flavor and higher in pumpkin-like flavor. • Orange-fleshed varieties were generally higher in graininess and pumpkin-like flavor. • And had higher sucrose content • Consumer panel taste scores associated most with sweet flavor, dry matter and maltose content; consumer panel color scores negative association with discoloration. • Adult consumer taste score negatively correlated to wateriness • Determination of dry matter and starch content, and sucrose equivalents in cooked roots can possibly be used in intermediate selection phases in breeding as indication of acceptable taste.

  14. Partial Least Squares Regression analysis

  15. Nutrient content: means of 4 sites(raw root) • Overall mean trans-β-carotene content of 9 OFSP varieties was 9706 µg/100 g raw root (varying between 5091 and 16456 µg/100 g). • Varieties with β-carotene content above the target level for use in the crop-based programs (5500 µg/100 g) were Resisto, Khano, 2001-5-2, W-119, Beauregard and 1999-1-7. • Impilo, Excel, Serolane (5109 to 5220 µg/100 g trans-β-carotene) are useful to populations with mixed dietary sources of vitamin A. • Overall mean mineral content in 9 varieties was as follows: 54 mg/100 g calcium, 29 mg/100 g magnesium, 40 mg/100 g phosphorous, 282 mg/100 g potassium, 0.96 mg/100 g iron, and 0.62 mg/100 g zinc.

  16. OFSP mostly superior in mineral content • In context of human nutrition in South Africa, all the orange-fleshed varieties, when boiling a raw portion of 100 g, have a potential contribution of ≥100% of the recommended intake for vitamin A, e.g. for 4 to 8 year old children, and 21% to magnesium, 12% to zinc and 9% to iron requirements.

  17. Index selection: Elston

  18. Improvements in yield coupled with good taste and dry matter content. Considerable root yield advantage over the USA imports Resisto, Excel and W-119 initially used in crop-based programs. Impilo and 2001-5-2 were found to be promising (all-round performance). Tolerance - virus drought tolerance: both intermediate stem blight: Impilo T; 2001-5-2 Interm. weevil and other insects: vine persistence: Impilo medium thick vine multiplication rate: 2001-5-2 higher Roodeplaat 2 ha Discussion Bophelo Venda 1 ha eManguzi 2 ha

  19. The ARC for research funding ARC - Biometry Unit: statistical analysis Dr Mieke Faber (MRC) and Dr Annalien Dalton for collaboration in the consumer analysis Ms Nina Muller and Ms Erika Moelich, University of Stellenbosch for conducting sensory profiling Dr Paul van Jaarsveld, MRC, for beta-carotene analysis. ARC-Institute for Soil Climate & Water for mineral analysis Department of Agriculture & communities for their role in execution of the agronomy trials ARC technicians assisting with trials at off-station locations: Mr Musa Mtileni, Ms Sharon Mulandana, Mr Sidwell Tjale. Prof Maryke Labuschagne, Department of Plant Sciences, University of Free State. Acknowledgements

  20. Development of a high throughput drought screening method • Year 1: • Rainout shelters – 4cv x 3 regimes x 3 reps (24 plants/plot) • Small shelters: 35 cv x 2 regimes x 2 reps (5 plants/plot) • Year 2: • Rainout shelters – 8cv x 2 regimes x 3 reps (24 plants/plot) • Field trials: 35 cv x 2 localities x 2 regimes x 3 reps (12 plants/plot) Leaf samples 212 Root samples 106 Leaf samples 464 Root samples 282

  21. LUTZVILLE RIETRIVIER C12:C13 partitioning Absicic acid Anti-oxidants – peroxidase, glutatione reductase

  22. GGE biplot: advantages of use • Offers breeders a complete, visual evaluation • Kang’s yield stability statistic, YSi, (Kang, 1993; Yan, 2001; Yan and Kang, 2003). • According to Yan et al. (2001) biplot readily visualizes: 1) the similarities and differences among environments in their discrimination of varieties; 2) the similarities and differences among varieties in their response to environments; and 3) the magnitude and type of interaction between varieties and environments. • The GGE biplot has been used in yam, another vegetative-propagated crop, by Otto and Asiedu (2009) • It allows more functions than AMMI (Ding et al., 2007). • E.g. yield relative to environment maximum (YREM), relationships among environments, discriminativeness & representativeness of test environments, ideal test environments, similarity of genotypes, mean performance and stability of the genotypes, and which-won-where analysis. Each of which has its own type of biplot.

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