5.water use efficiency in field crops

WUE

1. Water use efficiency in field crops with
emphasis on Plant archituture modification
AKSHAY S. SAKHARE
SUDHIR KUMAR
DIVISION OF PLANT PHYSIOLOGY
ICAR -INDIAN AGRICULTURAL RESEARCH
INSTITUTE

2. Putative physiological traits applied in
breeding
•Emergence characteristics/vigor
•Nutrient acquisition/uptake efficiency
•Leaf development & photosynthesis
•Water use efficiency (WUE) component traits
•Deep root development
•Canopy temperature/stomata regulation
•Osmotic Adjustment/relative water content
•Hormonal control: ABA, GA , Ethylene
•Stay green/senescence
•Grain number maintenance
•Grain fill duration and rate
•Harvest index under drought
•Yield & its components under drought etc…

3. CO
2 + H
2O (CH
2O) + O
2
CO
2IS REDUCED
H
2O IS OXIDIZED
Role of water

4. Some definitions of WUE:
CO
2assimilated/Water lost
Harvest Index or total biomass/Applied water
Harvest Index or total biomass/Water transpired
Harvest Index or total biomass/Water uptake
Harvest Index or total biomass/Water available
WUE can be defined either in terms of an instantaneous
measurement of the efficiency of carbon gain for water
loss; or an integral of this efficiency over time (as a ratio
of water use to biomass or yield accumulation). Important
to define terms precisely.

5. There is a clear relationship between the amount of water transpired and
yield across a diverse range of crop species, water loss is an inescapable
trade-off for carbon gain.
Passioura (1977) had proposed that the yield is a function of transpiration,
transpiration efficiency (TE) defined as the biomass production per unit of
water transpired, and harvest index.
Yield = T×TE×HI

6. The difficulty to measure TE has prompted the search of
surrogates traits for TE.
●Carbon discrimination ratio (Δ
13
C)
●SPAD chlorophyll meter reading (SCMR )
●Specific leaf area (SLA)
●Specific leaf nitrogen (SLN)
.
Measurement of Transpiration efficiency

7. Transpiration efficiency (TE)
12
C
13
C
12
C
13
C
Low WUE High WUE
C3 C4

8. carbon isotope discrimination:
Two stable isotopes of carbon are found in molecular CO
2(
13
C and
12
C) with a ratio of
1:99 in atmospheric air. Plant tissues contain considerably less
13
C. They are said to
discriminate against it. This is a function of its larger molecular mass, which slows its rate
of diffusion.
A lower C
i/C
aresults in decreased discrimination (Δ
13
C) against
13
C as the driving force
for CO
2 diffusion is increased. Consequently, carbon isotope signatures demonstrating
low Δ
13
C are diagnostic of a CO
2 fixation environment with a relatively low C
i/C
a.
There is a strict relationship between the degree of Δ
13
C and WUE in crop species, such
that tissue with low Δ
13
C exhibits, enhanced instantaneous WUE. In other words low Δ
13
C
is indicative of a low Ci/Ca
(Condon et al. (2004) JXB 55: 2449).

9. SPAD chlorophyll meter reading
Variation of SPAD Chlorophyll Meter Readings (SCMR) has been
correlated with transpiration efficiency (TE) In Ground nut, Chickpea and
Pigeon pea.
SCMR is a direct linear relationship through extracted leaf chlorophyll and
also related to leaf nitrogen concentration.
Arunyanark et al. (2008) J. agron. Crop sci. 194: 113-125.

10. SCMR reading is related to SLA
and SLN
Nageswara Rao et al. (2001) J. agron. Crop sci. 189: 175-182.

11. Improved transpiration efficiency (TE)
Increased axial resistance in wheat
Anthesis-silkinginterval in maize
Osmotic adjustment in wheat
Conversion of C3 into C4 Plants
Change in Root Architecture
TRAITSFORBETTERWATERUSEEFFICIENCY

12. Increased axial resistance in wheat
More water for grain filling
Use of subsoil water is slowed
if there is a large hydraulic
resistance in the seminal roots.
Reduction from 65 μm to 55 μm
leads to 8% increase in yield
Richards and Passioura (1981) Crop Sci. 21: 249-255.

13. Anthesis-silking interval (ASI) in maize
Drought delays ear silking
but the timing of pollen shed
from the tassle is unaffected.
This reduces grain set and yield
Due to poor partitioning

14. Monneveux et al.(2006) Crop sci. 46: 180-191.
ASI in relation with grain yield

15. Canopy architecture Modification
PlantyTypeshowbetterphotosynthesisrate,
BiomassandwateruseefficiencyoverPlantx
undersameconditions
InriceJaponicaisYtypewhileIndicaisXtype.
X Y
Long et al., 2005

16. Kiniry et al., 1989
Advantage of C4 over C3

17. ConversionofC3plants
intoC4willboostwater
useefficiency!

18. Transgenic plant show better performance than wild one
Material Photosynthesis rate (µ
mol m
-2
S
-1
)
C
i (internal CO2 concentration (µmol
mol
-1
)
Transgenic line A24.20±1.86 286.00±13.70
Transgenic line B25.36±1.76 283.70±12.50
Control 19.56±2.40 267.02±9.33
Bandyopadhyay et al.,2007
Bandyopadhyayetal.(2007)studiedthephotosynthesis,internal
CO
2,1000grainweightandharvestindexinwildtypeand
transgenicricelineshavingmaizePEPCgene.

19. REDUCTION IN
PHOTORESPIRATION

20. E. coliglycolate catabolic pathway(red)superimposed on plant
photorespiration(black).
Kebeish et al. 2007. Nature BiotechnologyKebeish et al. 2007. Nature Biotechnology

21. Rewards of taming Photorespiration
Transgenic plants expressing the glycolate pathway in their
chloroplast have a larger leaf area
The rosette diameter of the transgenic plant increased with
increase in total fresh weight and dry matter which reflect with
increase in total plant productivity
The transformed plant have enhanced rates of carbon fixation
,Growth, biomass production, better WUE and NUE at low CO
2
concentration
Khan et al.,2007,Trends in Biotechnology

22. HVA1gene and its
role in water use
efficiency

23. ABAresponsivebarleygeneHVA1,amemberof
group3lateembryogenesis abundant
(LEA)proteingensintroducedinspringwheat
throughbiolisticbombardmentmethod.
Highlevelsofexpressionwasregulatedby
maizeubi1promoterinleavesandroot
Sivamani et al 2000
Plasmid map of pAB1

24. Growth Performance of trangenic wheat
Line T. Dry
Mass(g)
Seed Weight
(g)
Shoot dry
weight( g)
WUE
(g/Kg)
Transgenic line 12.581 0.750 2.183 0.679
Transgenic line
2
2.566 0.867 2.160 0.675
Wild line 2.160 0.707 1.907 0.568
In moderate water deficit conditions
Sivamani et al 2000

25. Growth Performance of trangenic wheat
Line T. Dry
Mass(g)
Seed Weight
(g)
Shoot dry
weight( g)
WUE
(g/Kg)
Transgenic line 115.617 4.394 13.463 0.822
Transgenic line 213.145 2.493 11.670 0.692
Wild line 14.054 3.964 11.954 0.740
In well watered conditions
Sivamani et al 2000
Transgenic lines show significantly greater total dry mass, root dry
weight and Shoot dry weight .
Transgenic lines show higher water use efficiency

26. • Recently the Farquhar group reported the
identification of ERECTA, the first gene that regulates
transpiration efficiency. ERECTA and other members
of the gene family are involved in the control of guard
cell density and mesophyll structure.
Masle, Gilmour and Farquhar 2005, Nature436, 866-
870
Shpak et al., 2005, Science309, 290-293 .

27. ●ERECTA, a putative leucine-rich repeat receptor-like kinase (LRR-RLK) known for its
effects on inflorescence development is a major contributor to a locus for ∆ on Arabidopsis
chromosome 2.
●Mechanisms include, but are not limited to, effects on stomatal density, epidermal cell
expansion, mesophyll cell proliferation and cell–cell contact.

28. Leaf anatomical features contributing to the effects of
ERECTA on transpiration efficiency.
Gilmour and Farquhar 2005

29. ERECTAimproved transpiration efficiency under both well watered and
drought conditions.
Gilmour and Farquhar 2005

30. ERECTA controls carbon discrimination ratio and hence
Transpiration Efficiency inArabidopsis
ERECTA gene-controls stomatal conductance and
photosynthetic rate by regulating leaf gas exchange
Leaf anatomical features also contribute to the effects of
ERECTA on transpiration efficiency.
Rewards of ERECTA Expression
Gilmour and Farquhar 2005

31. Change in Root
Architecture

32. Roottraitscanmoderatetheeffectsofdroughteitherbyincreasingthe
rateofwateruptakethroughincreasedroot-lengthdensityorby
allowingagreateramountofwaterextractionthroughincreasedroot
lengthdistributionatdepth
Architecturaltraitssuchasgrowthangleofseminalaxesmayplaya
significantroleinadaptationofwheattowater-deficitenvironments.
Rootarchitectureislikelytobeassociatedwithgenotypicadaptationto
thesecontrastingenvironments.
Lateralrootdevelopmentinfavourofadeeperrootsystemtoincrease
accesstowaterfromthedeepersoillayersduringthecriticalgrain
fillingphaseappearstobedesirableinthenorthernenvironments.

33. •Yuetal.(2008)conductedagain-of-functiongeneticscreenin
Arabidopsisthaliana.Onemutantwithimproveddroughttolerance
wasisolatedanddesignatedasenhanceddroughttolerance1(edt1).
•Themutanthasamoreextensiverootsystemthanthewildtype,
withdeeperrootsandmorelateralroots,andshowsareducedleaf
stomataldensity.
•Moleculargeneticanalysisandrecapitulationexperiments showed
thattheenhanced droughttoleranceiscausedbytheactivated
expression ofaT-DNAtaggedgenethatencodes aputative
homeodomain -STARTtranscriptionfactor(TF).
•Overexpressing thecDNAoftheTFintransgenictobaccoalso
conferred drought tolerance associated withimproved root
architectureandreducedleafstomataldensityandprovideakey
regulatorthatmaybeusedtoimprovewateruseefficiencyinplants.
Arabidopsis HD-START protein with improved root
system for better WUE

34. (H)Droughtstressofthemutantandwild-typeplantgrowninthesame
pot.Onemutantandonewild-typeplantweregrowninthesamepot
for4weeksundershort-dayconditionsbeforedroughtstresswas
imposed.Thephotosweretaken2weeksafterwateringwaswithheld.
(I)Comparison ofwaterlossrateofdetachedleavesfromthemutant
andwildtype.Four-week-oldplantswerederootedandallowedtodry
intheair.Freshweightwasmeasuredattheindicatedtimes.Waterloss
wasexpressedasthepercentageoftheinitialfreshweight.
Yu et al., 2008

35. Theprimaryrootof3-d-oldmutantseedlings(edt1)was
longerthanthatofthewildtypeofthesameageon
MurashigeandSkoog(MS)medium.
Yu et al., 2008

36. Twenty-day-old mutant seedlings (edt1) have more
lateral roots than wild-type seedlings of the same age.
Yu et al., 2008

37. Five-week-oldmutant(edt1)andwild-typeplants

38. Transgenicplantsshowsreducestomataldensity
Inthewildonesthesizeofstomataislower.
Stomatal density and stomatal size
Yu et al., 2008

39. Yu et al., 2008
Inwildoneswaterloss
astranspirationismore
whilephotosynthesisrate
ishigherintransgenic
plants

40. Improvement in WUE
TransgenicplantscarryingHDSTARTproteinshows1.5times
higherphotosynthatesproduced/waterusedratioi.e.WUEoverwild
ones.
Yu et al., 2008

41. Some traits successfully being used for improved yield under
water Scarce environment
Tuberosa and Salvi, 2006
TRENDS in Plant Science

42. Conclusions &Future prospects…..
Traditionalapproacheshasledtodevelopmentofimprovedwateruseefficient
genotypesandagronomicpractices.
Selectionforanunderlyingphysiologicaltraitthatlimityieldcouldbeeffectiveand
contributesubstantiallytoyieldimprovementprogrammes.Especiallywheredirect
selectionforyieldindryenvironmentisinefficientduetolargeseasonalvariation
inweatherandduetolargegenotype×environmentinteraction.
AlthoughseveralQTLshavebeenidentifiedandarebeingsuccessfullyutilizedin
breedingprogramsfordevelopingefficientgenotypesunderwaterscarce
environment,identificationofdirectgenewillhelpinacceleratingtheoverall
process.
DiscoveryofERECTAasdirectgeneticmarkerforTEopensnewwaysfor
evaluatingtheusefulnessofthisgeneforbreedingcropspecies.
Over-expressionofHDG-11genebringtherootarchitecturalchangewhichwill
leadstothedevelopmentofwateruseefficientgenotypes.
Since,WUEisacomplextrait,controlledbymanygenes,pyramidingofmultiple
traitswillleadtodevelopmentofwateruseefficienthighyieldinggenotypes.

43. Thank you

46. Yu et al., 2008

47. Yu et al., 2008

48. (A)and(B)Undershort-dayconditions,
4-week-oldwildtype(A)andmutant(B)plantsweresimilar,
exceptthatthemutanthadmorerosetteleaveswithshorter
leafpetiole.
(C)and(D)Underlong-dayconditions,
The4-week-oldmutantshowed morevigorousvegetative
growth(D)andhadmorerosetteleavesthanthewildtype(C).
Yu et al., 2008

49. Increase in stomatal conductance can bring the
better ventilation in the leaf.
Regulation of ABA, help in adjusting the sensitivity of
stomata
Decrease in canopy temperature helps in reduction in
water loss
Better transport for the CO
2in the leaf
Fischer et al., 1998
CHANGE IN STOMATAL CONDUCTANCE