1. Breeding Drought Tolerance for Rainfed Lowland
Rice in the Mekong region
Presented by Boonrat Jongdee, BRRD, Thailand and
Jaquie Mitchell, The University of Queensland, Australia.
Other contributors:
NAFRI, Laos: Phoumi Inthapanya, Phetmanyseng Xangsayasane,
Thavone Inthavong, Sipaseuth
CARDI, Cambodia: Ouk Makara, Veasna Touch
The University of Queensland, Australia): Shu Fukai
BRRD, KKU and DOA: Grienggrai Pantuwan, Tidarat Monkham
and Grissana Linwattana

2. Area harvest Production Yield
(million ha) (million tons) (tons/ha)
Vietnam 7.3 35.6 4.9
Indonesia 12.2 57.0 4.7
Myanmar 8.2 32.6 4.0
Philippines 4.3 16.0 3.8
Laos 0.8 2.9 3.5
Malaysia 0.7 2.2 3.4
Thailand 10.4 27.9 2.7
Cambodia 2.5 6.0 2.4
Rice area, production and yield in 2007
Source: FAOSTAT(2007)

3. % Irrigated Rainfed lowland Upland Deepwater
Total F D DS S MD
Cambodia 16 75 7 22 43 0 3 1 8
Indonesia 54 35 20 4 0 3 8 11 0
Laos 14 65 21 22 22 0 0 21 0
Malaysia 66 21 15 0 0 5 1 12 1
Myanmar 30 59 24 6 0 15 14 4 7
Philippines 67 30 15 5 1 3 6 3 0
Thailand 20 74 6 38 18 9 3 2 4
Vietnam 53 39 15 8 0 12 4 5 3
Rainfed lowland rice production area
F: favorable, D: drought prone, DS: drought and submergence prone,
S: submergence prone, MD: medium deep
Source: Mackill et. al. 1996, IRRI(2005)
Large areas of rainfed lowland areas with drought-prone and drought- &
submergence-prone environments in the Mekong region
65% of total rice land in Cambodia, 44% in Laos, 56% in Thailand

4. Our previous work on rice drought
tolerance improvement in the region
• Supported by The Rockefeller Foundation and ACIAR
• A concept for improving drought tolerance
• Development of drought screening
• Identification of drought tolerant traits
• Selection of parental materials for drought tolerance
• Development of drought tolerance populations
•Evaluation the advanced lines for drought tolerance

5. A concept for improving drought tolerance
Nil Severe
Severity of drought
Drought
resistance
traits
Drought
escape
YIELDPotential yield
Unpredictable
Predictable
Timingofdrought
(Fukai and cooper, 2001)

6. Water condition under rainfed lowland rice field
Rain Rain
Flood Dry DryWet Flood
Rain
Anaerobic Aerobic Anaerobic Aerobic

7.  Developing effective selection strategies for drought tolerance
and high yield potential (wide adaptation)
 To identify effective traits that are related to drought tolerance
and general adaptation that can be used for selection in
breeding program
Selecting genotypes that are high yielding in drought prone
areas and that can be released as varieties
To characterize drought environment, ie frequency, magnitude
and timing of the drought events for use in identifying target
areas that can utilize the drought tolerance traits identified and
the genotypes selected in the project
Objectives of current project

8. Two series of experiments in each country
• Water condition, on-station experiments for 3
years (2009-2011)
– Fully flooded
– Aerobic (Intermittent drought)
– Prolonged drought (Terminal drought)
• Multi-location trials for 2 years (2010-2011)
– Selected lines from water condition experiments
– 6 locations in each country in each year
– Top and low paddy positions

9. Major achievements
• New drought screening methods developed
• Drought tolerant characters determined
• High yielding, drought tolerant lines identified
for each country
• Drought maps developed

10. New screening method
On-station: Agriculture Research enter, Vientiane, Central Laos
Year and season: 2010 and 2011 wet and dry seasons
Grown conditions: flood, aerobic and drought
Genotypes: common 25 genotypes
Multilocation trial: Vientiane, Savannakhet, Champasack
Year: 2010 and 2011 wet season
Paddy positions: Top and bottom positions

11. Province
Field
position Yield
(g/m2
)
Water level
(cm)
pH
(H2O)
OM N-total
(%) (ppm)
Vientiane Low 320** -3.1 3.86 0.9 1.42
Top 150ns -8.8 3.5 0.8 1.02
Savannakhet Low 176ns -5.6 4.2 0.5 0.26
Top 305** -9.5 4.6 1.1 0.98
Champasack Low 280ns -5.4 5.87 0.9 2.45
Top 215** -12.2 5.28 0.5 1.35
Yield, water level from soil surface, soil pH, organic matter, and
soil nitrogen (N) available in top and low field positions

12. Mean grain yield (g/m2)
in flood
150 200 250 300 350 400 450
Meangraininmultilocation(g/m2)
150
200
250
300
350
400
450
Mean grain yield (g/m2
)
in terminal drought
150 200 250 300 350 400 45
r=0.49 ** (a)
Mean grain yield (g/m2
)
in intermittent drought
150 200 250 300 350 400 450
r=0.50 ** (b) (c)
Relationships between mean grain yield
on-station screening and MLTs in Laos
Intermittent drought screening can select varieties
that produce high yield in farmers field.

13. DRI
-2.0 -1.5 -1.0 -.5 0.0 .5 1.0 1.5 2.0 2.5
r=0.42 *
Mean potential GY (g/m
2
)
150 200 250 300 350 400 450
MeanGYinmultilocation(g/m
2
)
150
200
250
300
350
400
450
r=0.79 ** (a) (b)
Relationships between mean GY in MLT and mean PGY (a)
and GY in MLT and DRI
Genotypes with high potential yield and drought tolerance produced high yield in MLT

14. GY estimated from DRI and potential GY (g/m2
)
150 200 250 300 350 400
GYinonfarm(g/m2)
150
200
250
300
350
400
450
(f)r=0.86**
Relationship between grain yield in MLT and
yield estimated from DRI and potential yield

15. DRI-intermittent drought
-1.5 -1.0 -.5 0.0 .5 1.0 1.5
DRI-terminal
-1.5
-1.0
-.5
0.0
.5
1.0
1.5
r=0.46 **
Some drought tolerant genotypes identified in intermittent drought
conditions can be also tolerant against prolonged terminal stress

16. 2. Drought tolerance traits
• Short delay in flowering under drought
– Tolerant varieties may minimize the delay
• Photoperiod sensitivity
– Common in Thailand and Cambodia
– Useful trait for maturing before severe terminal
drought develops
– Its usefulness to tolerate drought is not well known

17. Estimating flowering duration and delay due to
drought at Ubon, Thailand
Day after sowing (days)
60 70 80 90 100 110
Flowering(%)
0
20
40
60
80
100
Population 1
population 4
TTC
TF50
X0

18. TTC: Time to commencement flowering from sowing time
X0: From TTC to 50% flowering
TF50: Time from sowing to 50% flowering
TTC X0 TF50
Flood Drought Flood Drought Flood Drought
pop.1 86 88 6.7 5.9 93 99
pop.2 90 91 6.8 6.3 96 99
pop.4 80 80 9.5 8.5 89 88
pop.5 78 79 7.1 6.5 85 86
Mean 83 84 7.5 6.8 91 93
p-value
Genotypes <0.001 0.071 <0.001
Water 0.844 0.043 0.445
W x G 0.125 0.623 0.019

19. Correlation coefficient among delay in
flowering, yield reduction and flowering
duration in drought conditions
Flowering at 84-88 DAS Delay Yield reduction
Yield reduction (%) 0.58** --
Flowering duration 0.69** 0.65**
Flowering at 94-98 DAS
Yield reduction 0.18ns --
Flowering duration 0.32ns 0.18ns
Similar correlation matrix were also found
at Chum Phae, Thailand

20. CPA-Drought
Numberper4hills
10
20
30
40
r=0.1641ns
r=0.3806**
CPA-Flood
TF50
75 80 85 90 95 100 105
Numberper4hills
10
20
30
40
panicle
tiller
r=0.4033**
r=0.4816**
UBN-Drought
Numberper4hills
0
10
20
30
40
r= -0.3788**
r=0.4500**
UBN-Flood
TF50
70 80 90 100 110 120
Numberper4hills
0
10
20
30
40
panicle
tiller
r=0.2794*
r=0.2740*
Relationships between TF50 and tiller and panicle numbers

21. Time to flowering (DAS) Grain yield (g/m2)
2009 2010 2011 Mean 2009 2010 2011 Mean
Flooded 91 93 113 99 220 408 333 320
Intermittent 95 95 114 101 114 301 253 223
Prolonged
drought 110 97 116 107 84 291 209 195
Mean 98 95 114 102 140 333 265 246
Delay in flowering (day) Reduction in grain yield (%)
Intermittent 4 2 1 2 48 26 24 30
Prolonged
drought 19 4 3 9 62 29 37 39
Days to flowering, grain yield, delay in flowering and
reduction in grain yield in 2009 (very late planting), 2010
(late planting) and 2011 (early planting) in Cambodia

22. 0.0 0.2 0.4 0.6 0.8 1.0
Delayinfloweringin2009
-10
0
10
20
30
40
0.0 0.2 0.4 0.6 0.8 1.0
Delayinfloweringin2010
-2
0
2
4
6
8
Drought condition; R2=0.58**
Aerobic condition; R2=0.11**
Drought condition; R2=ns
Aerobic condition; R2=ns
Photoperiod sensitivity index
0.0 0.2 0.4 0.6 0.8 1.0
Delayinfloweringin2011
-6
-4
-2
0
2
4
6
8
Drought condition; R2=0.60**
Aerobic condition; R2=ns
Relationships between
photoperiod sensitivity and delay
in flowering under intermittent
and prolonged drought
in 2009, 2010 and 2011 in
Cambodia
Shorter delay in flowering in
photoperiod sensitive genotypes

23. Strongly photoperiod sensitive lines produced higher yield with
better drought tolerance and shorter delay when flowered at the
same time (late planting)
Insensitive
(PSI<-0.3)
Mildly
sensitive
(0.3<PSI<0.5)
Moderately
sensitive
(0.5<PSI<0.7)
Strongly
sensitive
(0.7<PSI)
Number of genotypes 5 2 10 5
Days to Flowering (flood) 85 89 86 87
Flowering Delay -intermittent 2.9 4.0 2.2 2.1
- prolonged drought (days) 6.1 6.0 3.3 3.1
Yield Flooded 372 435 454 417
Intermittent drought 263 (70 %) 260 (59 %) 310 (68 %) 324 (77 %)
Prolonged drought 290 (78 %) 352 (80 %) 324 (71 %) 313 (75 %)
Mean drought response index -0.07 0.04 -0.07 0.33
Correlation with PSI – Yield -flood (0.47*), intermittent (0.54**),
-- Delay –intermittent (-0.47*), prolonged (-0.90**)

24. Drought tolerance traits
• Delay in flowering
– Requires observation in drought as well as flooded
conditions
– This can be used as selection trait in prolonged
drought with adjustment to flowering time under
flooded conditions
• Photoperiod sensitivity
– Potential trait; requires further evaluation

25. 3. High yielding, drought tolerant lines
are identified
• Phka Rumduol x Neang Tai Dun - F6 -3 appears
most promising in Cambodia-- strongly tolerant
to drought, strongly photoperiod sensitive and
moderately high potential yield.
• IRUBN050035-B-7-B, IRUBN040041-B-B-5,
Y329-UBN-13 and IRUBN050032-B-1-B are
high yielding from 10 multi-location trials in
Thailand across 2 years.

26. High yielding lines in Lao multi-location trials, and
their characteristics found in water experiments
High yielding lines had high potential yield or drought tolerance
(high drought response index DRI) or both.
Drought tolerant lines had shorter delay in flowering

27. 4. Environmental characterization - Drought
mapping
• Lowland water balance model with deep percolation
rate estimated from clay content (Inthavong et al. 2011).
• Start, end & length of growing period estimated, LGP is
closely associated with drought occurrence.
• Extended from province to whole country
Cambodia and Thailand.

28. Annual (median rainfall) and length of
growing period across Thailand, Laos and
Cambodia
Annual median rainfall (mm) Length of growing period

29. Laos drought prone
environments
identified by start,
end and length of
growing season

30. Conclusions
• New drought screening methods developed
– Intermittent stress
– Top paddy positions as drought screening
• High yielding lines identified for each country
– 6 Laos; 1 Cambodia; 4 Thailand
• Drought tolerant characters determined
– Yield potential, photoperiod sensitivity, delay in
flowering and DRI
• Drought maps developed for length of growing
period
– Laos, Cambodia, NE Thailand.

31. Products
 Simple drought screening technique that breeder can be used
 promising lines for high potential grain yield and
drought tolerance for each country
 Maps for drought prone areas in Laos, Cambodia and
NE Thailand
 Paper: 5 papers, 1 has been submitted
 Capacity building: there are 2 PhD students at KKU

32. Thank you