This document provides an outline and overview of breeding approaches for drought tolerance in cereals. It discusses the types of drought, mechanisms of drought tolerance including drought escape, avoidance and tolerance. It describes breeding methods for drought tolerance, including conventional methods like hybridization and non-conventional methods using biotechnology and genetic engineering. Examples of research from different countries evaluating drought tolerance in crops like wheat, rice and barley are presented. The document concludes that drought tolerance is complex and future work should identify signaling elements and cross-talk between pathways to develop crops tolerant to both drought and heat stress.

1. WELCOM
E

3. Breeding
Approaches for
Drought
tolerance in
Cereals

4. Outline
1. Introduction
2. Types of drought
3. Drought affected area in the world
4. Mechanism of drought tolerance
5. Mechanisms of resistance to drought and the methods to increase the
resistance
6. Breeding approach
7. Breeding method for drought tolerance
8. Research papers
9. Achievements
10. Conclusion
11. Limitation
12. Summary

5. Introduction
• Drought is a period or condition of unusually dry weather
within a geographic area where there is a lack of precipitation.
• Drought is governed by various factors
extremes in temperature
photon irradiance
paucity of water.
• The characteristics features of drought stress is low water
potential due to high solute concentration.
• Low water supply causes soil mineral toxicities and can make a
plant more susceptible to damage from high irradiance.

6. Global water scarcity threatens sustainable crop farming, as agricultural
activities account for about 75% of global water consumption, and, in particular,
irrigation represents over 90% of water used in many developing countries.
Stresses such as drought and salinity affect the productivity of most field crops
to variable degrees, depending on the onset time, duration, and intensity of the
stress.
Rice (Oryza sativa), one of the most important food crops in the world, is very
sensitive to drought stress because of its limited adaptation to water-deficit
conditions.
Maize (Zea mays), another staple crop, is also very sensitive to water-deficit
stress (Boyer and Westgate, 2004), as its pollination and embryo development
during and post flowering are greatly affected by soil water supply

7. Types of Drought
• Meteorological Drought:- It is related to deficiencies
• in rainfall compared to the average mean seasonal
rainfall in an area.
• Agricultural Drought:- Deficit rainfall over cropped
areas during their growth cycle can destroy crop or lead
to poor crop yields.
• Hydrological Drought:- It is a deficiency in surface and
sub-surface water supply. It is measured as stream flows
and also as lake, reservoir and groundwater levels.

8. Drought affected area in the world

12. MECHANISM OF DROUGHT TOLERANCE
• DROUGHT ESCAPE: It is defined as the ability of a plant to
complete its life cycle before supply of water in soil is depleted and
form dormant seeds before the onset of dry season. These plants are
known as drought escapers since they escape drought by rapid
development.
• DROUGHT AVOIDANCE: It is the ability of plants to maintain
relatively high tissue- water potential despite a shortage of soil-
moisture. Drought avoidance is performed by maintenance of
turgor through roots grow deeper in the soil, stomatal control of
transpiration and by reduction of water loss through reduced
epidermal i.e. reduced surface by smaller and thicker leaves.
• DROUGHT TOLERANCE: It is the ability to withstand water-
deficit with low tissue water potential. Drought tolerance is the
maintenance of turgor through osmotic adjustment (a process which
induces solute accumulation in cell), increase in elasticity in the cell
and decrease in cell size.

14. Figure: Drought Avoidance : Reduced surface by smaller
and thicker leaves

16. Drought resistance mechanisms and methods to
increase the resistance
1. Morphology: Increase in water absorption and transportation,
declination of transpiration
a. Developed root system and higher ratio of root to shoot.
b. Thick leaf, smaller leaf area and thick cuticle
c. Developed veins and bundle ， smaller and more stomata
2. Physiology and biochemistry:
a. Stomatal regulation: ABA accumulation→stomatal closure
b. Increase in capacity of resistance to dehydration of
cytoplasm: Rapid accumulation of Pro, glycinebetaine, Lea
protein, dehydrin, osmotins and ion etc.

17. EFFECT OF DROUGHT STRESS
• Effect on Growth: Reduction in Turgor Pressure, due to cell
sizes will be smaller.
• Effect on Photosynthesis: Photosynthesis decreases due to
disruption of PS II (Photo System II), stomatal closure,
decrease in electron transport.
• Decrease in nuclear acids and proteins: Protease activity↑,
free aa↑, RNAase activity↑ ， RNA hydrolysis, DNA content
falls down.
• Effect on Nitrogen Metabolism: Nitrate reductase activity↓,
nitrite reductase activity insensitive
• Effect on Carbohydrate metabolism: Loss of starch and
increase in simple sugars, carbohydrate translocation
decreases.

18. Breeding approach
FOUR APPROACHES
Breeding for high yield under optimum condition
No intentional selection for drought tolerance Breeding for other
characters indirectly effect drought Screening for drought is done
Lines perform well in optimal condition show decline in yield under
drought
Breeding for High yield under Stress condition
Choice of Parents
Selection under the stress environment Drought varies from year and
location
Breeding for High yield under both stress and non-stress
environment
Simultaneous selection
Use of conventional method
Multi disciplinary approach
Integrate drought tolerant mechanisms Use of genomic tools

19. 4
3
Breeding methods for drought
tolerance
1. Conventional
methods
2. Nonconventional
methods

20. • INTRODUCTION
• Primary
• Secondary
• SELECTION
• Desirable
• Adaptation
• HYBRIDIZATION
LINE A
High
yielding
LINE B
Drought
resistant
F
1
Conventional breeding focus on drought
avoidance than drought tolerance
Blum 2005
CONVENTIONAL METHODS

21. BIOTECHNOLOGY
GENETIC ENGINEERING
 Agrobacterium mediated gene
transfer
 Particle Bombardment (Gene Gun)
 Electroporation of protoplast
MAS
QTL
NON-CONVENTIONAL METHODS

23. Character GCV % PCV % h2 (B.S.) %
Genetic
Advance
GA % of
Mean
E % 12.83 13.52 90.1 20.783 25.09
FSL 12.21 12.85 90.3 2.806 23.89
FRL 12.57 13.65 98.7 4.987 25.73
FSW 16.32 16.60 96.6 0.02 33.05
FRW 21.36 21.91 95.0 0.015 42.87
DSW 22.48 23.14 94.4 0.002 44.99
DRW 24.99 25.32 97.4 0.002 50.79
R/S 22.87 24.03 90.6 0.203 44.83
Table 7:- Estimates on GCV, PCV, heritability in broad sense(h2 B.S.), Genetic advance
as percentage of mean (GA %) of seedling traits in 63 pearl millet genotypes
E %=Emergence %, EI= Emergence index, ERI= Emergence rate, FSL=Fresh Shoot Length,
FRL= Fresh Root Length, FSW=Fresh Shoot Weight, FSL= Fresh Root Weight,
DSW= Dry Shoot Weight, DRW= Dry Root Weight.
Coimbatore
(T.N.)
Arulselvi and Selvi (2009)

24. Europe Huseynova et al. (2010)

25. Figure 1. PCR amplification profiles of Triticum L. wheat genotypes using Р6
Figure 1. PCR amplification profiles of Triticum L. wheat genotypes using Р7

26. China Hu et al. (2006)
b
a
C
Fig. 1. Stress-inducible expression of SNAC1. (a) RNA gel blot analysis of
expression of the SNAC1 under drought (DT). (b) Diagram of the PSNAC1:GFP
construct. (c) Expression pattern of GFP driven by the SNAC1 promoter in
transgenic rice plants under normal conditions and drought condition for 5 hrs.
calli
ligule
root
root
nodes stems leaves
stamen &
pistil
lemma
calli
ligule
root nodes stems leaves
stamen &
pistil
lemma

27. b
Fig. 2. Improved drought resistance of SNAC1-overexpressing transgenic rice at
reproductive stage. (a) Overexpression contruct (Upper) and RNA gel blot
analysis
of SNAC1 in transgenic plants and the WT (Lower). (b) Appearance of one
positive (S19) and one negative (S18) transgenic families in the field with severe
drought stress.

28. Fig. 3. Improved drought resistance of SNAC1-overexpressing
transgenic rice at vegetative stage. (a) Recovery of the SNAC1-
overexpressing seedlings after drought stress (a; 12 days of water-
withholding at four leaves stage followed by 1 week of watering) .
Survival rate is indicated below.

29. Fig. 4. RWC and Increased stomatal closure of transgenic rice.
(a)Change of RWC in leaves during drought development.
(b)Percentages of closed stomatal pores observed in the leaves of transgenic and
WT plants under normal (three time points within a day) and drought stress (3 days
or 7 days after water deprivation) conditions.

30. Crops Varieties
Bread Wheat NP4, NP720, Pb9-D, C217, C281,
K46, RS 31-1, Ao88, Ao113, Ao115.
Durum Wheat Motia, Gulab, Jay, Vijay, Arnej
Rice Akashi
Barley Karan 280
Bajara BJ 104
Achievements

32. DROGHT TOLERANCE is a very complex plant trait, should be
evaluated in association with other major stresses.
Crops tolerant to drought as well as heat will be in immediate
demand for a world that is facing global climate change
scenario.
The challenge in the near future will be to identify the
signaling elements missing in our current models of pathways.
Understand the cross-talk between pathways.
The identification of commercial grade transgenes that
enhance crop performance under both drought and optimal
conditions.
Ultimately with use of the powerful molecular and genetic
tools available, such as stress-metabolite profiling, functional
genomics and proteomics, more and more of key regulators
will be identified.
Conclusion

33. Thank
You