Drought Tolerance of Crops: Progress and Challenges€¦ · drought that further strengthened the...
Transcript of Drought Tolerance of Crops: Progress and Challenges€¦ · drought that further strengthened the...
Drought Tolerance of Crops: Progress and Challenges
Dr. Viswanathan Chinnusamy
Principal Scientist
Division of Plant Physiology
IARI, New Delhi 110012
Email: [email protected]
OUTLINE
• Introduction to drought stress
• Target Environment
• Mechanisms of drought tolerance
• Physiological and molecular genetic
basis of drought tolerance
• Yield stability under drought
• Challenges:
o MIADE
o Realistic, accurate and high
throughput Phenotyping
o Molecular genetics of crop plants
•Water - deficit, hypoxia, anoxia
•Temperature- Low, High
•Nutrients – deficiency, toxicity
•Light - low, high
•pH – acidity, alkalinity
ABIOTIC STRESSES
Scarcity or excess of essential
environmental factors
•Ionic toxicity - salinity,
alkalinity, heavy metals
•Air pollution
•UV-B radiation
Excess of non-essential
environmental factors
Quantity of factor G
row
th
Quantity of factor
Gro
wth
Drought
Soil moisture
PWP FC Water
logging
Cro
p Y
ield
Meteorological drought: Deficit in precipitation over a long term average
Agricultural drought: Soil moisture deficit that leads to reduction in growth,
development and yield of crops
Drought = moisture deficit stress
water stress
Target environment
Water Availability
Yie
ld
50 100 25
Water scarcity
Wate
r avail
ab
ilit
y
Crop growth stage
FC
PWP
Terminal Intermittent
Drought Stress Tolerance is No More a Myth
• It is very common to state that drought tolerance is a “very complex
trait” and it is not tractable for genetic improvement.
• It is often believed that “drought tolerance is a nebulous term that
becomes more nebulous the more closely we look at it, much as
a newspaper photograph does when viewed through a
magnifying glass” (Passioura 1996).
• This opinion emerged rather due to a global view of yield response of
plants under illdefined experimental conditions or agricultural
situations. Hence the results are confusing and non-reproducible.
• Omics of plant stress response revealed massive change in
epigenome, transcriptome, proteome and metabolome in response to
drought that further strengthened the opinion that drought tolerance is
a very complex trait.
• "Clearly, recently we have seen some very promising advances in terms of
drought tolerances in crop plants," says Nguyen. "Now it's a question of how
to optimize the system."
• Tester is also optimistic: Ultimately, "I think there will be a palette of genes from
which breeders and crop scientists will select for putting together the
drought tolerance for a particular region.” (Pennisi E. 2008)
Complex traits are amenable for easy modification
• GA regulated genes are more than 1100 in Arabidopsis seedlings.
• Yield improvement in green revolution is brought about by single gene mutation that
resulted in gibberellin (GA) deficiency in rice (semi-dwarf1/sd1) and GA insensitivity
in wheat (Reduced height/Rht).
The mechanisms causing minimum loss of yield in a water
deficit environment relative to the maximum yield in a water
constraint free management of the crop.
Drought Tolerance Drought Resistance
Drought Tolerance
Dehydration
Avoidance
Dehydration
tolerance
Drought Tolerance
Constitutive
mechanisms
Acquired
mechanisms
where: WU= water transpired by the crop
WUE = water use efficiency (=biomass/unit water transpired)
HI = harvest index (economic yield/total biomass)
Passioura (1977)
GY = WU x WUE x HI
Yield Stability
Phenotypic &
developmental
plasticity
Water Mining (WU) Minimizing
water loss
WUE &
EUW
Cellular tolerance
Drought Tolerance
Root traits-
Morphological &
anatomical changes
Aquaporins
OA
Transpiration -Stomata
LAI (Leaf area, no.
Leaf rolling & drying)
leaf reflectance
characters (wax load
and pubescence, leaf
angle, leaf rolling)
Metabolic homeostasis
Xanthopyll cycle
Photorespiration
Maintenance respiration
Osmoprotection
Cell membrane stability
Oxidative Stress Mgmt.
Stress proteins
Activity &
Efficiency of
rubisco at low Ci
Phenology
Flowering
Development
Dehydration Avoidance Dehydration tolerance
Recovery, growth, yield + ABA
-CK, Ethylene
+ ABA
+CK, Auxin, GA,
Traits & Genes:
Water Mining
Root-ABA1, a major constitutive
QTL, affects maize root architecture
and leaf ABA concentration
Giuliani et al. 2005. J Exp Bot. 56: 3061–3070
Root-yield-1.06, a major constitutive QTL
for root and agronomic traits in maize
across water regimes
Landi et al. 2010. J Exp Bot. 61: 3553–3562
QTLs for Root System Architecture
PW
RK
Y6::
CK
Xo
x
Root-specific manipulation of single gene expression can increase root traits
CL, Culm length
PL, panicle length
NP, number of panicles per hill
NSP, number of spikelets per panicle
TNS, total number of spikelets
FR, filling rate
NFG, number of filled grains
TGW, total grain weight
1,000GW, 1,000 grain weight.
NT RCc:OSNAC10
Plant Physiology, May 2010, Vol. 153, pp. 185–197,
cDNA microarray of drought stress response in rice SNAC1 with 5.6 fold
enhanced expression was isolated from the upland rice cultivar IRAT109.
WT 35S::SNAC1
Hu et al. PNAS USA 103: 12987–12992
Application of omics technologies has contributed to the development
of stress-tolerant crops in the field
The hrd-D mutant showed more
secondary roots in Arabidopsis
Genes for root traits
+ ABA + Auxin - CK - Ethylene
QTLs for osmotic adjustment in rice
Traits & Genes: Osmotic Adjustment
High OA Low OA
Garg et al. 2002. 99:15898-15903
Traits & Genes: WUE
Crop No. of QTLs References
Wheat 10 QTLs affecting per plant WUE (Total dry
matter/ amount of water used by per plant)
Zhang et al., 2002
Rice 7 QTLs located in 5 chomosomal regions. Xu et al., 2009
ERECTA, a putative leucine -rich repeat receptor-like kinase (LRR-RLK), known for its
effects on inflorescence development, is a major contributor to a 13C QTL on chr2.
ABA pathway engineering:
Minimization of water loss &
Enhancement of cellular tolerance
ab
a2
W
T
/aba3
90% ~30% RH,
10 min WT aao3
Isomerase/A
BA4
ABA2
BG1
NCED3-ox WT
vp14
WT
Traits & Genes: Transpiration control & Cellular tolerance
• ABA: Water mining – Regulate primary root growth; Minimization of transpiration –
Stomatal Control; Osmotic adjustment – regulates gene expression; Cellular tolerance
Negative regulators and effectors are shown in red for clarity. Colors in boxes
represent relative expression level of a gene before and after ABA treatment
(+ABA).
Plant Cell 16:596-615 (2004)
ABA Signal Transduction
The DH12075 (a) and YPT2-RD29A-
antiAtFTP (b) plants were subjected to a
4-day drought treatment starting on day 8
after flowering. The pictures were taken
on day 8 of re-watering after the drought
stress
Drought tolerance of rd29A:anti-AtFTB canola during flowering
In (a) the solid bars represent
seed yields for the two-
irrigation condition, and the
dotted bars represent seed
yields for the one irrigation
condition. Irrigation was
conducted during the
flowering period.
Seed yields of WT and transgenic canola in 2003 (a) and 2004 (b) confined field trials
Wang et al. 2005. Plant J. 43: 413–424
Oh et at. 2005. Arabidopsis CBF3/DREB1A and ABF3 in transgenic rice
increased tolerance to abiotic stress without stunting growth. Plant
Physiology 138:341-351
ABA confers dessication tolerance – from moss to higher plants
Red Arrow indicates re-watering
2009 Science’s TOP 10
Identification of the ABA receptors and its mechanism of action
Science Breakthrough 2009
“These results are a boon for plant biology—and possibly beyond. The PP2C and the
ABA receptors both belong to highly conserved families of proteins whose roles in other
organisms may become clearer now that their function in plants has been nailed down”
ABF3
P
Hubbard K E et al. (2010) Genes Dev. 24:1695-1708
Traits & Genes: Transpiration control & Cellular tolerance
Overexpression of ABA Receptor enhances drought tolerance
Wheat seedlings grown in vermiculite
and severely desiccated under drought.
The seedling on the right received 0.1
µmol of ABA in the irrigation water
before the onset of stress. Control
seedlings received normal irrigation
water before on the left.
Vaccination ?
• Identification of new agonist chemicals
• Engineered receptors that can be
activated by the “off-the-shelf”
agrochemicals
Yield stability under field drought stress conditions
Molecular basis of spikelet fertility under drought stress needs to be studied
Spikelet Fertility
Reproductive stage stress tolerance
Regulated Expression of an Isopentenyltransferase Gene (PSARK::IPT) in
Peanut Significantly Improves Yield Under Field Drought Conditions
Qin et al. 2011. Plant Cell Physiol 52: 1904-1914
NT PSARK::IPT
Expression of IPT in
senescence associated
promoter in leaves increases
drought tolerance
Plant nuclear factor Y (NF-Y) B subunits improved corn yields under drought
Nelson et al. 2007. PNAS USA 104: 16450-16455
Castiglioni et al. 2008. Plant Physiology 147: 446–455
Bacterial RNA Chaperones Confer Improved Grain Yield in Maize under Water-
Limited Conditions
Vandana x Way Rarem qtl12.1
This QTL accounted for an increase in grain yield, harvest index, and biomass yield under
stress, and it was detected over seasons under field conditions. The QTL accounted for
51% of the genetic variance in yield under drought
Bernier J, Kumar A, Ramaiah V, Spaner D, Atlin G (2007). A large-effect QTL for grain
yield under reproductive-stage drought stress in upland rice. Crop Sci. 47:505-516
A QTL on chromosome 1 that accounts for 32% of the variation in yield under drought
stress in rainfed lowland rice.
Kumar R, Venuprasad R, Atlin GN (2007). Genetic analysis of rainfed lowland rice
drought tolerance under naturally-occurring stress in eastern India: heritability and
QTL effects. Field Crops Res.103:42-52.
QTL for Yield under drought
QTL qtl12.1 increases water uptake in upland rice:
Bernier et al. 2009. Field Crops Research 110: 139-146
qtl12.1 has a large and consistent effect on grain yield under upland drought stress
conditions, in a wide range of environments (21 field trials)
Bernier et al. 2009. Euphytica 166:207–217
Trends in Plant Science,
June 2011, Vol. 16, No. 6
Yang et al. 2010. Mol Plant 3: 469–490
Yang et al. 2010. Mol Plant 3: 469–490
Controlled environment phenotyping: Phenomics
Large scale phenotyping under natural field – A OPEN CHALLENGE
CHALLENGE - 1
Minimum Information about a Drought Experiment (MIADE)
1. Agronomic conditions of crop culture: Soil type, pH and Ec; nutrition;
spacing between plants
2. Soil water status: soil matric potential, amount and interval of irrigation
3. The crop growth stage at which the stress was imposed
4. Duration of stress
5. Plant water status: RWC or water potential and osmotic potential
6. Phenology, Yield and yield components
7. Weather data on rainfall, temperature and VPD
CHALLENGE - 2
1. Genotypes:
• Germplasm Cores Mini-cores
• Mutants – T-DNA/Transposon tagged lines
2. Genomics:
• OMICS and Bioinformatics
3. Efficient and Easy Transformation Protocols
– Rate limiting step in gene function validation
Crop Functional Genomics
CHALLENGE - 3
Rate limiting traits/processes/genes
Mutants
Phenotyping
Gene
cloning
Germplasm
Phenotyping
Contrasting
genotypes
QTL Mapping
Association
mapping (LD)
• WGA
GENES
MAS Breeding Transgenics
Genotype with improved stress tolerance
Rate limiting traits/processes/genes
Yield
Component
Pathways
Component Traits
Genes
Yield
CHALLENGE - 4
Potential combinations of environmental
stresses that can affect crops in the field
Yet to learn of the alphabets of the stress matrix
CHALLENGE - 5
Systems biology
CHALLENGE - 6
Collaboration & Translation of research findings in to products
YIELD
OmicsCellular
networksGrowth models
Drought tolerance can be improved – Drop by drop
– Gene by Gene
– Trait by Trait
X ?
Be SPECIFIC – Target Environment, Pyramid Traits
One who solves the problem of WATER is worth two NOBEL Prizes
one for SCIENCE and one for PEACE - John F. Kennedy
Thanks