This document summarizes the results of on-farm trials of sweet potato cultivars developed by the ARC for the informal market in South Africa. The trials found significant differences between cultivars and locations, with the cultivar 199062.1 having the highest total and marketable yields overall. On average, yields were 26.8 tons/ha for total yield and 15.8 tons/ha for marketable yield. Over 2 million vines were distributed in 2014-15 to farmers across various provinces. The trials demonstrated the potential of sweet potato to contribute to food security, income generation and enterprise development in smallholder systems in South Africa.

1. Performance of ARC informal market
sweet potato cultivars in on-farm
trials
APA, Addis Ababa, 11/10/2016
Sunette Laurie, M Mtileni, W Mphela, S Tjale
ARC-Vegetable and Ornamental Plants (ARC-VOP),
Pretoria, South Africa

2. Introduction
• Sweet potato is an important indigenized root
crop in SA
• Features prominently in smallholder cropping
systems
 because of its versatility, ease to grow,
hardiness
 Orange cultivars presents a rich source of
provitamin A
• Vitamin A deficiency (VAD) in South Africa
– 43.6% of 1-9 years old (2012) – national
public health problem
– 27% of women at childbearing age (2005)

3. • Food security in SA (SANHANES, 2012):
 45.6% of population food secure (score of 0),
 28.3% were at risk of hunger (score 1–4) &
 26.0% experienced hunger (food insecure)
• Promoted by the ARC for food security, nutrition, income
generation and enterprise development
• Informal market estimated at 25000 – 30 000 t
• Large potential for processing into various products
Introduction (cont.)

4. 199062.1Ndou Monate Mvuvhelo
Bophelo
Impilo
Introduction (cont.)
• Breeding has focused on high yield, good root
quality, adaptability, high dry mass and sweet
taste (also β-carotene content)
• Cultivars released: Ndou & Monate (2003),
Impilo (2007), Bophelo (2011), Mvuvhelo (2013),
199062.1 (CIP: 2010)
• Trials across 5 research stations indicated:
o 29.5 – 36.2 t/ha (33.5) for total yield
o 17.3 – 24.6 t/ha (20.0) for marketable yield

5. Objectives
• Study objective: to test the performance of ARC
informal market cultivars in on-farm trials
• Present progress with vine distribution of new
cultivars

6. Materials and methods
• On-farm trials were conducted in 15 localities: 9 in
KwaZulu-Natal, 4 in Gauteng, 1 each in Eastern
Cape and Mpumalanga provinces across 2011/12
– to 2014/15.
• RCBD: 3 replicates; 6-7 cultivars (+Blesbok)
• 30/40 plants per plot
• Preplant 500 kg/ha 2:3:4
• Supplementary irrigation
• 5 months
Blesbok

7. *
*
*
*
Loc
Code
Location
name
Location details Region
PON Pongola Pongola Khiphunyawa
2013-14
Subtropical
*
*
* *
*
*
****
**
NEB Nebo Nebo Mamphokgo 2014-15 Cool
subtropical
DUM Paulpieters-
burg
Dumbe Paulpietersburg
2014-15
Cool
subtropical
BUL Nongoma 1 Bululwane - Nongoma
2012-13
Cool
subtropical
MLA Ulundi 1 Mhlabatsini - Ulundi 2012-13 Cool
subtropical
MAYE Nongoma 2 Maye - Nongoma 2014-15 Cool
subtropical
CEZ Ulundi 2 Ceza 1 Ulundi 2014-15 Cool
subtropical
KUT Soshanguve Kutlwano - Soshanguve
2011-12
Temperate
SIM Ekangala 2 Simajado - Bronkhorstspruit
2011-12
Temperate
WIN Winterveldt Winterveldt 2011-12 Temperate
SYA Ekangala 1 Siyathuthuka -
Bronkhorstspruit 2011-12
Temperate
MON Vryheid 1 Vryheid Mondlo 2013-14 Temperate
MVU Vryheid 2 Vryheid Mvynyane 2013-14 Temperate
MAP Ladysmith Maphophomeni Ladysmith
2014-15
Temperate
MJI Kokstad Mjila - Kokstad 2012-13 Temperate
Materials and methods (cont.): Localities
*
*
*

8. • Data collection: marketable root yield, unmarketable root
yield classes, dry mass, taste acceptability of small
informal panels
• Combined analysis of variance (SAS): cultivar, locality,
region
• Genotype x Environment analysis: AMMI model
(Genstat): cultivar * location
• Discriminant analysis (XLSTAT) to determine most
prominent characteristics
Materials and methods (cont.)

9. Analysis of Variance Table
Total Yield Marketable Yield
Source DF
Mean
Square Pr>F
Mean
Square Pr>F
Local 14 1297.05 <.0001 742.45 <.0001
Region 2 286.70 0.0018 649.66 <.0001
Rep(Local) 30 73.96 0.0201 42.40 0.0041
Cultivar 5 80.37 0.106 242.76 <.0001
Local*Cultivar 70 79.80 0.001 40.26 0.0007
Region*Cultivar 10 87.67 0.0349 76.26 0.0003
Error 150 43.38 21.45
Corrected Total 269
Results

10. Variable Minimum Maximum Mean
Taste score 1.3 4.6 2.5
Drymass% 16.2 35.8 25.5
Insect% 0.0 67.3 15.1
XXS% 0.0 25.6 6.5
Damaged% 0.0 19.9 5.7
Grooves% 0.0 30.0 5.1
XXL% 0.0 36.7 4.7
Veins% 0.0 55.0 4.3
Constrictions
% 0.0 20.0 3.6
Cracked% 0.0 26.3 2.9
Rat% 0.0 36.2 2.8
Rotten% 0.0 13.7 1.8
Curved% 0.0 22.0 1.7
Avg Weight
PerRoot (g) 130.7 514.3 242.5
Marketable% 21.2 86.4 59.1
Means across 15 sites
Total
yield t/ha
Mark
yield t/ha
199062.1 28.5a 199062.1 19.0a
Ndou 27.8a Ndou 17.8a
Monate 27.2ab Monate 15.8b
Bophelo 26.6ab Mvuvhelo 15.2bc
Mvuvhelo 25.9ab Bophelo 13.8cd
Impilo 24.8b Impilo 13.1d
Mean 26.8 15.8
CV% 24.6 29.33
Range
over loc’s
10.1-
37.9
5.0-
25.6
Blesbok (Control) at 8
sites produced lowest
Mark & Total yield

11. 10
15
20
25
30
35
40
199062.1 Bophelo Impilo Monate Mvuvhelo Ndou
TotalYield
Cultivars
RegionxCultivar Interaction Means
Coolsubtropical Subtropical Temperate
LSDp=0.05 = 6.97
0
5
10
15
20
25
30
199062.1 Bophelo Impilo Monate Mvuvhelo Ndou
MarketableYield
Cultivars
RegionxCultivar Interaction Means
Coolsubtropical Subtropical Temperate
LSDp=0.05 = 4.91

12. Genotype x environment interaction

13. Genotype x environment interaction (cont.)

14. 199062.1
Bophelo
Impilo
Monate
Mvuvhelo
Ndou
-4
-3
-2
-1
0
1
2
3
-4 -3 -2 -1 0 1 2 3
F2(36.86%)
F1 (50.98 %)
Centroids (axes F1 and F2: 87.84 %)
Centroids
F1 F2
Taste -0.136 -0.395
Constrictions -0.253 -0.137
Grooves -0.050 0.269
Veins -0.514 -0.202
Drymass% -0.185 0.710
XXS% 0.106 -0.123
XXL% 0.066 0.040
Cracked% 0.201 -0.241
Insect% 0.128 -0.056
Rat% 0.096 -0.229
Rotten% 0.119 -0.138
Damaged% -0.285 0.023
Curved% -0.300 -0.068
MarketableYield -0.248 0.212
WeightPerRoot -0.521 0.145
Marketable% -0.190 0.225
TotalYield -0.074 0.102
Taste
Constrictions
Grooves
Veins
Drymass%
XXS%
XXL%
Cracked%
Insect%
Rat%
Rotten%
Damaged%
Curved%
MarketableYield
WeightPerRoot
Marketable%
TotalYield
-1
-0.75
-0.5
-0.25
0
0.25
0.5
0.75
1
-1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1
F2(36.86%)
F1 (50.98 %)
Variables (axes F1 and F2: 87.84 %)
Discriminant analysis
Ranking exercise to recommend cultivars per site

15. 1 ha production Ms Mmakgomu
Sokhulumi
Bronkhorstspruit
Mr Moyo
Winterveldt
Yield (Total sold excluding quantities consumed by
household)
13.9 tons 19.6 tons
Limpopo
Gauteng
• Mean 13.5 t/ha
• Mean 16.7 t/ha
Farmer yield

16. Vine dissemination and production 2015
• Vine dissemination during 2014/15 raised to
2.1 mil cuttings from 10 nurseries, ~ 75 ha
• 66% were orange-fleshed sweet potato

17. Conclusions
• Significant interaction of Locality*Cultivar and
Region*Cultivar
• Mean marketable yield of 15.8 t/ha
• Insect infestation was the most prevalent
unmarketable root yield class
• Veins, dry mass and avg root mass were the
main variables distinguishing cultivars
• Increased availability of vines/fresh produce
• Large potential for income generation on
informal market

18. Acknowledgements
• ARC-VOP team
• ARC Biometry unit
• Department of Agriculture collaboration with
on-farm trials
• Funding by ARC for trials; Dept Rural
Development for vine and production
enterprise project

19. Thank YouThank you