This study evaluated 59 orange-fleshed sweetpotato genotypes for drought tolerance using an in vitro screening technique with polyethylene glycol (PEG). The genotypes were grown in media with 0%, 10%, and 15% PEG to simulate drought stress. Results showed significant differences between genotypes and PEG levels for traits like root length, shoot growth, and dry weight. Ten genotypes performed best under drought stress and were identified as tolerant. The in vitro screening was found to effectively evaluate drought tolerance in a large number of genotypes in a short time compared to field trials. Some genotypes identified as tolerant through in vitro screening were later confirmed in field conditions as well.

1. In vitro evaluation of
Orange-Fleshed
Sweetpotato (Ipomoea
batatas Lam) genotypes for
drought tolerance using
polyethylene glycol
Agili, Sammy, Nyende B, Ngamau K,Masinde
P
30th June to 4th July 2013
9th Triennial Conference of APA, Naivasha, Kenya

2. Presentation outline
Introduction
Materials and Methods
Results
Overall conclusions and recommendations

3. Importance of Sweetpotato
Rank 7th among food crops of the world
(CIP, 1997); Area under cultivation world
wide is 9M hectares
95% of the world’s sweetpotato output is
from developing countries
Predominantly grown in small plots by
poor farmers, hence known as poor man’s
crop

4. Importance of Sweetpotato
Major source of food/nutrition
Ability to produce under adverse weather
conditions
Short maturity period/possible to have two
crops in a year
OFSP types-contains sufficient levels of beta
carotene

5. Importance of Drought in Sweetpotato
production
Drought is often a major environmental
constraint for sweet potato production in areas
where it is grown under rain fed conditions
Under field conditions drought severity, timing
and duration vary from year to year and a
cultivar which is successful in one year might
fail in another year

6. Importance of drought in
sweetpotato production, cont.
The unpredictable and variable forms in
which drought manifest complicates the
selection of superior plant materials as well
as breeding programs

7. In vitro culture technique for drought screening
• In vitro culture techniques minimizes
environmental variations due to defined nutrient
media, controlled conditions and homogeneity
of stress application; can handle a large
number of materials
• Osmotica/ PEG6000- stimulate water deficit
conditions in cultured cells in a manner similar
to that observed in the cells of intact plants
subjected to true drought conditions

8. The technique has been used for various crops
Wheat genotypes (Hsissou and
Bouharmont,1994)
Tomatoes(Manoj and Uday,2007)
Rice(Shankhodhar et al 2000)
Green grams(Gulati and Jaiwal, 1993)
In vitro screening, cont.

9. To Screen a large number of orange-fleshed
sweetpotato genotypes at earlier stages of
development for drought tolerance under in vitro
conditions simulating stress drought conditions
Place-Tissue culture laboratory, Kenya plant
Health Inspectorate Service Quarantine station,
Muguga, Kenya
Objective of the study

10. Genetic material
Consisted of 59 OFSP genotypes with
contrasting beta carotene and mineral content
levels received from CIP, Lima
For initial propagation the materials were
transferred into in vitro and routinely propagated
from the nodal cutting(0.2-0.5cm), each circle
lasting 2-4 weeks.

11. Planting material/preparation of growth
media
Propagation of planting material for the 59 genotypes
were from nodal done in MS media
MS basal media containing 30g/l sucrose and 2.8g/l
phytogel maintained at PH 5.7 + PEG (6000) at 0,10 and
15g/l was used as the growth media
5cuttings with2-3nodes/kilner jar/genotype/
Factorial/CRBD/ two factor factorial design with 3
replications
Growth condition-10 hours per day; photon light flux
density of 70µmol m²/s, 28ºC for 65 days

12. Data gathered
Root length (cm)
Root dry weight (g)-dried
for 48h at 65ºC
Leaf Area (cm²)
Shoot length (cm)
Shoot fresh weight (g)
Shoot dry weight (g)-
dried for 48h at 65ºC
Data analysis-SAS
version 8

13. Results

14. ANOVA
Analysis of variance indicated genotypes,
salt levels and salt level x genotype
interaction, were highly significant (p<0.001)
with respect to all the traits
This shows the presence of variability,
different responses to genotypes to different
salt levels

15. Effect of water stress on root length (cm) and Root dry weight (g) of 59 sweetpotato genotypes during in vitro screening using different
concentrations of polyethylene glycol
Root
length(cm)
Salt concentration
(g/l)
Root dry
(g)
Salt concentration
(g/l)
Genotype 0 10 15 Mean Genotype 0 10 15 Mean
Marooko* 26.0a 22.0a 21.3a 23.1 Marooko* 1.3a 1.6a 2.2a 1.7
189135.9 33.0a 33.5a 35.3a 34.0 189135.9 6.0b 7.9a 5.0bc 6.3
194515.5 31.3a 33.3a 30.7a 31.8 194515..5 4.8a 0.6b 3.8a 3.1
441097 32.5a 34.2a 25.3a 30.7 441097 1.3bc 1.3b 3.5a 2.0
441768 32.7a 25.8a 22.2a 26.9 441768 5.9b 0.3a 5.4bc 3.9
441724 29.3a 25.0a 29.7a 28.0 441724 0.8b 2.7a 0.9c 1.5
440031 5.3a 4.3a 3.8a 4.5 440031 0.0a 0.0a 0.01a 0.0
440286 11.9a 2.9a 1.4a 5.4 440286 0.3a 0.0a 0.0a 0.1
420027 17.8a 3.6a 2.6a 8.0 420027 0.1a 0.0a 0.0a 0.0
K566632** 13.7a 8.0a 4.5a 8.7 K566632** 0.1a 0.0a 0.0a 0.0

16. Effect of water stress on shoot fresh and dry weight (g) of 59 sweetpotato genotypes during in vitro screening using different concentrations of
polyethylene glycol
shoot
fresh
weight (g)
Salt concentration
(g/l)
shoot dry
weight (g)
Salt concentration
(g/l)
Genotype 0 10 15 Mean Genotype 0 10 15 Mean
Marooko* 1.6a 1.6a 2.2b 1.8 Marooko* 0.7a 0.7a 1.0a 0.8
189135.9 6.45c 5.6b 2.8a 5.0 189135.9 2.8bc 2.4b 1.2a 2.1
194515.5 4.8a 4.3a 2.7b 4.0 194515.5 1.8bc 2.1b 2.6a 2.2
441097 4.1a 4.5a 5.7b 4.8 441097 2.0bc 1.9b 1.2a 1.7
441768 5.5c 4.8b 2.2a 4.2 441768 2.5bc 2.2b 4.4a 3.0
441724 6.1a 5.7a 3.1b 5.0 441724 1.4a 4.3c 0.1b 1.9
440031 0.3a 0.2a 0.0a 0.2 440031 0.1a 0.1a 0.0a 0.1
440286 0.3a 0.3a 0.1a 0.2 440286 0.2a 0.0a 0.2a 0.1
420027 0.3c 0.2b 0.3a 0.3 420027 0.4a 0.0a 0.0a 0.1
K566632** 0.2a 0.3a 0.0a 0.2 K566632** 0.1a 0.0a 0.0a 0.1

17. Effect of water stress on leaf area (cm²) and shoot length (cm) of 59 sweetpotato genotypes during in vitro screening using different
concentrations of polyethylene glycol
Leaf area
(cm²)
Salt concentration
(g/l)
shoot
length (cm)
Salt concentration
(g/l)
Genotype 0 10 15 Mean Genotype 0 10 15 Mean
Marooko* 5.5a 6.5a 5.7a 5.9 Marooko* 7.2a 5.2a 8.5a 7.0
189135.9 7.0a 7.3a 5.2b 6.5 189135.9 15.3a 12.8a 13.2a 13.8
194515.5 4.2a 6.3b 6.4b 5.6 194515.5 10.3a 14.7b 12.2ab 12.4
441097 5.1a 9.5b 5.8c 6.8 441097 10.3bc 11.5b 18.2a 13.3
441768 5.7a 10.0b 6.5a 7.4 194539.36 9.3bc 10.0b 16.7a 12.0
441724 7.0a 11.3b 3.8c 7.5 441724 16.2a 16.0a 12.7ab 15.0
440031 0.6a 0.6a 1.5a 0.9 187017.1 10.3b 13.8a 14.9a 13
440286 1.1a 1.5a 0.6a 1.1 440286 5.8b 1.0a 1.2a 2.7
420027 2.8a 0.9a 0.8a 1.5 420064 10.3bc 11.5b 18.2a 13.3
K566632** 11.2a 2.0b 1.7b 5.0 K566632** 4.5a 3.5a 1.9a 3.3

18. Treatment effects
0
0.5
1
1.5
2
2.5
0 10 15
Salt level PEG g/litre
weight(g)
Shoot fresh weight (g)
Root weight (g)
Shoot dry weight (g)
0
5
10
15
20
25
0 10 15
Salt level PEG g/litre
Length(cm)
Shoot length (cm)
Root length (cm)
Effect of different salt levels on shoot fresh weight, root fresh weight and shoot dry
weight (a) and shoot and root length (b) for the screened 59 sweetpotato genotypes
during in vitro screening using different concentrations of polyethylene glycol.

19. Genotype 440429 (Drought tolerant) Genotype 440286 (susceptible)

20. Conclusions
10 genotypes were identified as drought
tolerant:194515.5, 194539.36, 441724, 441538,
189135.9, 401055, 441768,192033.5, 440027 and
440429. All showed higher leaf expansion, higher
stem length elongation, high root and shoot growth
and high dry matter production at high salt
concentration level
Correct/clear expression of genotypes can be
evaluated by this method using different PEG
concentrations

21. Conclusions
In vitro screening method using PEG (6000) was
found to be a simple enough to be used for evaluation
of drought tolerance in a large number of genotypes
in very short time.
Out of the 10 genotypes identified as drought tolerant
under in vitro screening 5 were confirmed to be
tolerant under field conditions suggesting that in vitro
screening can be a simple method of evaluating
OFSP genotypes drought tolerance

22. Acknowledgment
HARVEST PLUS
CIP/SASHA
JKUAT
KARI-KIBOKO/MARIGAT
KEPHIS MUGUGA