This document summarizes research on water-saving traits in pulses. It discusses two main traits - limited transpiration under high vapor pressure deficit (VPD) and maintenance of transpiration at lower soil water contents (FTSW). Studies found genetic variability in VPD and FTSW responses in crops like chickpea, lentil, and pearl millet. Crop modeling showed improved varieties with VPD-sensitive traits could increase soybean yields in Africa. Breeding efforts are now targeting these physiologically important drought tolerance traits to develop new varieties for water-limited conditions.

1. Michel E. Ghanem, Hélène Marrou, Shiv Kumar,
Vincent Vadez, Thomas R. Sinclair
Dissecting water-saving traits
in pulses
Crop Physiology Laboratory
ICARDA – Rabat Platform
m.ghanem@cgiar.org

2. Sensitive Tolerant
No major water extraction differences in sensitive and
tolerant chickpea
Yield and water use
Zaman-Allah et al. 2011 JXB

3. 0
1
2
3
4
5
6
7
8
9
10
21 28 35 42 49 56 63 70 77 84 91 98
Waterused(kgpl-1)
Days after sowing
Sensitive
Tolerant
Low early vigor
Low leaf Gs
Tolerant: less WU at vegetative stage, more water left
for reproduction and grain filling
Yield and water use
Zaman-Allah et al. 2011 JXB
Vegetative Reprod/ Grain fill
CHICKPEA

4. A plant that has:
 enough water for grain filling
 no more water after grain filling
Hypotheses:
 Looking for new sources of water
 Save/manage water
Focus on traits affecting plant water budget
What is a drought tolerant plant ?

5. Vapor Pressure Deficit (VPD; kPa)
Transpirationrate(gcm-2h-
1)
0 2 4
0
1
VPD
Basic research on “Building block” of Water Use
(WU)
FTSW
0.00.20.40.60.81.0Normalizedtranspiration
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Stage I
Stage II
Stage III
FTSW

6. Limited transpiration rate under elevated midday
vapor pressure deficit (i.e., low relative humidity)
Water conservation traits
Sinclair et al., 2005, FPB
6 9 12 15 18
0.0
0.5
1.0
1.5
2.0
2.5
3.0
< 0.6 mm h-1
< 0.4 mm h-1
VPD
0.0
0.2
0.4
0.6
0.8
1.0
Tr
Time
VaporPressureDeficit(kPa)
TranspirationRate(mmh-1)
Exploratory studies (modeling): simulation of relative grain yield (sorghum)
Yield gain in 75 % of the cases

7. What would be the impact of limited transpiration under high
VPD trait for soybean production in Africa?
Base line scenario Scenario with improved
variety
• Change value of 1 parameter :
• VPD thereshold : 4 1.8 KPa
7
Soltani et Sinclair, 2012
Using crop modeling

8. 8H. Marrou, Montpellier Supagro
What would be the impact of limited transpiration under high
VPD trait for soybean production in Africa?
Modeling 50 different years allows risk assessment
Sinclair, Marrou et al., 2014, GFS
(g/m2)
Using crop modeling

9. 0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0.045
0.50 1.00 1.50 2.00 2.50 3.00 3.50
VPD (kPa)
H77/2 833-2
PRLT-2/89-33
Transpiration(gcm-2h-1)
Kholova et al 2010 – J. Exp. Bot
Transpiration response to VPD in pearl millet:
Terminal drought
Sensitive (VPD-insensitive)
Terminal drought
Tolerant (VPD-sensitive)
Water conservation traits
2 mechanisms of water saving:
• Low TR at low VPD
• Further restriction of TR at high VPD

10. VPD response in pulses
• Common bean
• Chickpea
• Peanut
• Lentil
• Soybean

11. FTSW
0.00.20.40.60.81.0
Normalizedtranspiration
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Stage I
Stage II
Stage III
Plants don’t suffer stress until >60% soil water is depleted
How plants manage water when there is water is critical
Basic response of plant exposed to
water deficit
Conserving water by early stomata closure
in soil drying cycle in lentil

12. NTR
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
FLIP 2009-55L
JL1
FTSW
0,00,20,40,60,81,0
NTR
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
Ghanem, et al. unpublished
Conserving water by early stomata closure
in soil drying cycle in lentil
Sensitive
Tolerant
Water conservation traits
• Tolerant line have higher FTSW
threshold for transpiration decline
under water deficit

13. FTSW response in pulses
• Common bean
• Chickpea
• Peanut
• Lentil
• Soybean (no variation yet found !)
• Cowpea

14. • Two traits have been extensively explored
for expression and genetic variability
• VPD
• FTSW
• Breeding is now underway based on these
results for physiologically-targeted drought
traits
Summary

15. • Professor Thomas R. Sinclair
North Carolina State University - USA
• Dr. Vincent Vadez
• Dr. Hélène Marrou
UMR SYSTEM-Montpellier SupAgro - France
International Crops Research Institute for the
Semi-Arid Tropics - India