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Effect of drought acclimation on
drought stress resistance in
potato (Solanum tuberosum L.) genotypes
Pankaj Banik and Karen Tanino

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Potato plants are sensitive to drought stress
 Sensitive to drought (van Loon 1981)
 Even a short period of water stress
• Tuber quality and production
 Critical stages (Onder et al. 2005)
• Stolon elongation
• Tuber initiation
• Delays tuber formation
• Decrease in tuber number, growth & yield
4 flower stage
( in cymose
inflorescence)

3. 0
5
10
15
20
25
30
35
Soilmc,%
1st DA 2nd DA 1st DS 2nd DS1st DS-R 2nd DS-R
Drought Acclimated & Drought Stressed (DAS)
Non-Acclimated & Drought Stressed (NAS)
Non-Acclimated & Non-Stressed (NA)
5 days 7-10 days 5-7 days

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Hypotheses
 Pre-exposure to water deficit will induce drought
acclimation in potato genotypes
 There are genotypic differences in drought stress
resistance
 Leaf and stem characteristics will distinguish genotypes
and ability to acclimate to drought stress

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Potato genotypes used
AAFC Potato breeding program, Lethbridge AB
• Fv12246-6 (Fv)
• ‘Vigor’ (V)
• ‘Russet Burbank’ (RB)

6. 0
50
100
150
200
250
300
350
400
Fv V RB NA DAS NAS
Genotype Treatments
Tuberwt./pot,g
0
5
10
15
20
25
30
Fv V RB NA DAS NAS
Genotype Treatment
Tubernumber/pot
0 5 10 15 20
Fv
V
RB
NA
DAS
NAS
Fv
V
RB
NA
DAS
NAS
Fv
V
RB
NA
DAS
NAS
Fv
V
RB
NA
DAS
NAS
Fv
V
RB
NA
DAS
NAS
<5g5-20g20-50g50-100g<100g
Tuber number
RB had higher tuber weight than Fv
Highest tuber number in ‘Vigor’ was a result of <5g category
There was no drought acclimation effect of tuber weight & number, BUT

7. Drought Acclimation DID induce a differential response in leaf wilting.
Drought Acclimation reduced leaf wilting under drought stress in RB.
Fv was sensitive to leaf wilting.
Leaf wilting is the
most visual index of
drought stress
What is the
mechanism of
acclimation to reduce
leaf wilting?
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
DAS NAS DAS NAS
Fv RB
Increasingwiltingscore

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Drought resistance mechanisms
Water
management
Increasing
water uptake
Reducing
water loss
Leaf
characteristics
Stem
characteristics

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Drought Acclimation induced the thickest
leaf epicuticular layer
0
50
100
150
200
250
300
350
400
Fv RB NA DAS NAS
Genotype Treatment
Thicknessofleafwaxylayer,µm

10. Acclimation and a series of stresses (DAS & NAS) induced smaller
pavement cells compared to controls (NA) in both genotypes
RB-NA RB-DAS RB-NAS
0
100
200
300
400
500
600
700
800
NA DAS NAS NA DAS NAS
Fv RB
Areaofepidermalcell,µm2

11. Drought stress induced
smaller stomata
Stomatal size did not
change in RB treatments
0
50
100
150
200
250
300
350
400
NA DAS NAS NA DAS NAS
Fv RB
Areaofstomata,µm2
0
5
10
15
20
25
30
NA DAS NAS NA DAS NAS
Fv RB
Areaofstomatalpore,µm2
Drought acclimation
induced more open
stomata

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Recovery Time: RB (5 hrs), V (12 hrs) and Fv (16 hrs)
Fv
Recovers
23 oC 22.6 oC 21.1 oC 20.6 oC
Maximum stress After 16 hrs of watering
NAS DAS NAS DAS

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 Literature on drought
stress focused:
• Leaves & roots
• What about
STEM ?
To distinguish the effect of
the main stem:
 Stress was imposed:
• On intact leaves on stem
• Excised leaves
Drought resistance mechanisms
Water
Management
Increasing
water uptake
Reducing
water loss
Leaf
characteristics
Stem
charactersitics

14. 86
87
88
89
90
91
92
93
94
95
Fv V RB
%Stemwatercontent
Genotype
78
80
82
84
86
88
90
Fv V RB
%Leafwatercontent
Genotype
When intact leaves on stems
were stressed
V/RB had higher %LWC than Fv at
maximum soil water deficit
Higher %Stem Water Content in V/RB
than Fv
= greater %LWC ?
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Fv V RB
Avrateofwaterloss,
mg/min
Genotype
When excised leaves (minus the stem) were stressed: V lost water by the highest rate

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Stem water might represent a water source to leaves
during drought stress
Leaves INTACT
on the stem
EXCISED from the stem
drought stress drought stress
V & RB had higher
%LWC than Fv
V lost water by the
highest rate
Stem > access to more
stored water for drought
stressed leaves
V, RB had > %stem
water content than Fv

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No difference in the length of xylem and pith between Fv and V
Source of additional %SWC did not relate to the length of xylem and pith
0
500
1000
1500
2000
2500
3000
3500
4000
Fv V RB NA DAS NAS
Genotype Treatment
Lengthofxylemandpith,µm
Xylem
Pith

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Summary
Genotype
Higherweightor
tubernumber
Drought resistant tools
Type
Reduced
Leaf
wilting
under
stress
Higher
%leaf
wc
under
stress
Higher
%Stem
wc
Smaller
Stomata
under
stress
Acclimation-
induced more
open stomata
Smaller
leaf
pavement
cells
under
stress
Equivalent
Pith and
Xylem
length
Faster
Recovery
from
maximum
stress
RB √ √ √ √ X √ √ √ √ Resistant
Fv X X X X √ √ √ X X Sensitive
V √ √ √ √ ? ? ? X
√
X
Moderate
resistant
Hypotheses
I There are genotypic differences in drought stress resistance
II Stem & leaf characteristics distinguish genotypes & ability to acclimate to drought stress
Most resistant type (RB) had the greatest number of
drought resistant tools (√)

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Summary
Reduced
Leaf wilting
More open stomata
under stress
Thicker leaf
epicuticular wax
under stress
Non-Acclimated and
Drought Stressed (NAS)
X X X
Drought Acclimated and
Drought Stressed (DAS) √ √ √
Without a DAS approach,
potentially key drought stress resistance mechanisms
will be MISSED
Hypothesis
III Pre-exposure to water deficit will induce drought acclimation in potato genotypes

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Acknowledgements
Supervisor
Prof. Karen Tanino
Advisory committee
Prof. Yuguang Bai
Prof. Tom Warkentin
Prof. Gordon Gray
Funding agency
SAGES Project
Greenhouse Team
Eldon Siemens
Jackie Bantle
SEM
Guosheng Liu
Rob Peace
Confocal / microscopy
Shanna Benmann
Louise Elisabeth Arve
Prof. Jorunn Olsen
Statistics
Prof. Sakti Jana
Prasanto Mondol
Ting Wei
Spatial analysis
Dr. Winston Zeng
Ting Wei
Lab members
Terri Lynn Paulson

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Thank you
Questions ?