High input - Phosphorus in Soils and Plants

Breeding for enhanced P efficiency
in rice
Matthias Wissuwa & Terry Rose
JIRCAS
Question 1: what is our target environment ?
Low input
High input
Sri Lanka
Ghana
•
•
•
•
low-P sandy soil
typically no P fertilizer inputs
drought likely
Yield level 1.5 - 2 t/ha
Objective: increase yield by 1 t/ha
•
•
•
•
fertile lowland soil
high P fertilizer inputs
irrigated
Yield level 4 - 6 t/ha
Objective: maintain yield at reduced P application
P efficiency research & breeding: 2 scenarios
Improve P uptake and efficiency in
low-input environments
•
Upwards shift of P response
curve at lowest end
•
Extend plateau into lower P
application
•
Improved response to small P
inputs
•
‘withdraw from bank’ of
accumulated soil-P
2.
7
7
6
6
5
5
Grain yield (t/ha)
1.
Grain yield (t/ha)
Prevent yield reductions as P inputs
decrease in high-input systems
4
3
2
1
4
3
2
1
0
0
0
20
40
60
P fertilizer application (kg/ha)
80
0
20
40
60
P fertilizer application (kg/ha)
80
P efficiency research & breeding: 2 scenarios
Is it being
high-input scenario
done?
•
Improved access to soil-bound P at high soil P content (‘wet sponge’)
2.
Where on the curve are we now ?
2. 7
6
Grain yield (t/ha)
5
extra P uptake
4
3
critical P concentration
2
1
0
0
20
40
60
P fertilizer application (kg/ha)
80
It can take several years until we
have a yield reduction effect
P uptake
Because we simply reduce luxury
P uptake in the first years
0.5
1.0
1.5
2.0
2.5
Tissue P concentration (mg/g)
3.0
→ prevent drop in P uptake
P efficiency research & breeding: 2 scenarios
Improve P uptake and efficiency in low-input environments
•
Improved P uptake of P fixed in soil
•
Enhanced P utilization efficiency
1.
7
6
5
Grain yield (t/ha)
1.
4
3
2
1
0
0
20
40
60
P uptake
P fertilizer application (kg/ha)
80
Summary
Low input:
• increase yield without additional input
• by enhancing P uptake and utilization
• assume multiple stresses limit yield (drought, N deficiency, toxicities…)
 Breeding efforts on their way
High input:
• yield reduction not acceptable, maintain yield at lower P input
• enhancing P uptake from P stored in soil
• and by accessing a higher proportion of fertilizer P
• long-term balance between P input and P removal
 Breeders is high-input focus on ‘more important’ issues
How to breed for higher P uptake - genotypic variation
Danyi - Togo
DRR – Hyderabad - India
Genotypic variation for P efficiency exists within the rice germplasm
Traditional varieties are typically showing higher efficiency and uptake
Can we identify specific root traits enhancing P uptake ?
What is the ideal root type for P uptake?
Bigger is better?
Shallow?
Small but efficient?
What drives P uptake in rice – experimental evidence
200 diverse genotypes
30 diverse genotypes
14
12
P uptake (mg plant-1)
10
8
Root size genes & markers
6
Root efficiency genes & markers
4
2
R² = 0.7511
0
0
1
2
3
4
Root weight (g plant-1)
5
6
Wissuwa et al. 2002
Wissuwa unpublished 2012/13
Root size is the dominant factor for P uptake in rice
But genotypes with high root efficiency (RE: mg P uptake / root surface area) exist
Pup1 – a major P uptake QTL on chromosome 12
Kasalath
Nipponbare
NIL-Pup1
Major ‘P uptake gene’ at Pup1: OsPSTOL1
promoter::GUS
node
* CRP
*
PV
ꜜ ECR
PC
& OP
ꜜ
200 µm
lateral
roots
*
seminal
root
EP
RC
1 cm
root tip
100 µm
• OsPSTOL1 is a protein kinase mainly expressed at the
earliest stages of crown root development
• Expression is typically upregulated under P deficiency
Gamuyao et al. 2012, Nature
10 mm
• The gene is completely absent in most modern
rice varieties
developed for favorite irrigated lowland conditions
PSTOL1 and crown root number
Kasalath
Kasalath - RNAi
Gamuyao et al. 2012, Nature
IR64 wt
•
High expression of PSTOL1 is
linked to crown root number
•
The functional link remains
unclear (kinase)
IR64 35S::OsPSTOL1
 Move Pup1 / PSTOL1 to application in breeding
Pup1 – from research to application in breeding
Crossed Pup1 into IR64
60
50
IR64-Pup1-2
grain yield (g)
40
New donor (Pup2)
30
20
10
IR64-Pup1
IR64
0
0
IR64
20
40
60
fertilizer P supply (kg/ha)
IR64-Pup1-1
• Very first data on IR64-Pup1 suggests it may work at
medium-P range in irrigated lowlands
• This may be different as water supply decreases and soil
types change
Pup1 breeding network
IR64-Pup1-2
IR64
IR64-Pup1-1
Contacts: Dr. Chin at IRRI for IR64-Pup1 donors
M Wissuwa at JIRCAS for markers
IR64-Pup1-1
Marker assisted introgression into locally important
rice varieties, done by local partners
Phosphorus flows in low-input crop production
X
Erosion
X
Removal of
P in grain
80% of plant P is
in in the grain
pollution
Mining of soil
P reserves
Phosphorus flows in high-input crop production
Erosion
Accumulation
and fixation
Removal in
grain
pollution
Grain-P concentrations:
2.5 mg g-1 (2-4 mg g-1 )
Removal of P with seeds drives pollution, need for P fertilization to balance
take-off, or loss of soil fertility
Seed P facts
• Every year about 2.1 Mt of fertilizer phosphorus (P) are applied to
rice at a cost exceeding US$ 11 Bn
• The global rice crop removes about 1.5 Mt P annually = a ‘loss’ of P
equivalent to about US$ 7.5 Bn !!
• Reducing seed-P concentrations by 20% could save US$ 1.5 Bn
annually in P fertilizer costs
• Or help maintain soil fertility in low-input farming
• And reduce pollution
So why has nobody worked on that?
Concerns that reduced seed-P reserves will affect seedling vigor
Does seed-P affect seedling vigor ?
• Produce batches of seed with different
seed-P concentrations (within genotypes)
• Seedling biomass at 3-5 WAS
 No effect of seed P on vigor and yield on
‘normal’ soil (2-year data, 6 varieties)
• Transplant to ‘normal’ paddy field after
raising seedlings in different medium
 No effect on grain yield
• But possibly small negative effects on P
deficient soils
• Genotype-specific (general seedling vigor?)
Fears about loss of productivity due to
low seed-P reserves are overstated
Pyramiding genes controlling
complementary P efficiency traits
MAS ongoing
GWAS and G x E
Candidate genes
Donors, crosses,
physiology
Candidate
genes
Pup1
Seed-p
Reduce seed P
concentrations
PUE
P utilization
efficiency
P utilization efficiency
P Acquisition Efficiency
root exudates: P solubilization & plantmicrobe interactions
Root traits
Root hairs - root branching – root angle
P uptake
efficiency
Thanks and Acknowledgements
The JIRCAS group:
Juan Pariasca-Tanaka
Asako Mori
Katsu Kondo
Takuya Fukuta
Salirian Claff
Chen Pu
Wang Fanmiao
Josefine Nestler
Taro Matsuda
IRRI collaborators:
Tobias Kretzschmar
JH Chin
Yoichi Kato
Glenn Gregorio
Africa Rice
Saito, Elke, Nani
Southern Cross
Terry Rose, Kwanho
DRR Hyderabad
RDDI - Sri Lanka
Lalith

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