Genes and genomics in breeding cultivars suitable to high and low temperature

1. GENES AND GENOMICS IN BREEDING
CULTIVARS SUITABLE TO HIGH AND LOW
TEMPERATURE
PRESENTED BY:
Mr. SHIVAJI RAVASAHEB SURYAVANSHI
M.Sc. (AGRONOMY),
RCSM COLLEGE OF AGRICULTURE, KOLHAPUR
MAHATMA PHULE KRISHI VIDYAPEETH, RAHURI.

2. • Temperature is basic to life processes.
• Each genotype has an optimum range of temperature for its normal
growth and development.
• When temperature moves beyond this optimal range, it generates
temperature stress.
Temperature stress may be grouped into the
following three categories:
• Heat stress
• Chilling stress
• Freezing stress

3. High temperature :-
Heat stress: The adverse effects on plants of
temperature higher than the optimal is considered as Heat
stress
Heat would affect:
1. Survival of cells and tissues
2. Growth and development
3. Physiological effects
i. Respiration
ii. Photosynthesis
iii. Photosynthate translocation
iv. Membrane composition and stability
v. Heat Shock Proteins (HSP)

4. Heat stress resistance: It is defined as the ability of some
genotypes to perform better than others when they are subjected to the
same level of heat stress.
Mechanisms of heat resistance
1. Heat avoidance: Ability of genotype to dissipate radiation energy and
avoid a rise in plant temperature to a stress level.
i. Transpiration
ii. Light reflectance.
2. Heat tolerance: Ability of some genotypes to withstand/perform better
than others when their internal temperatures are comparable and in the
realm of heat stress.
Heat tolerance may involve following components:
i. Membrane stability.
ii. Thermosensitivity of Photosystem II.
iii. Photosynthate translocation.
iv. Stem reserve mobilization.
v. Osmoregulation.

5. Sources of heat tolerance: In most crops, sources of heat
tolerance are available within the breeding germplasm,
the only condition being that the materials should have
been properly evaluated for the concerned traits.
• In general, use of exotic genetic resources is not essential
for attaining progress in heat tolerance.
Selection environment:
1. Normal field environment.
2. Abnormal field environment.
3. Programmed environment.
4. In vitro environment.

6. Low Temperature :-
Cold resistance: When temperatures remain above freezing i.e.
>00C, it is called chilling, while freezing describes temperatures
below freezing i.e. <00C.
Chilling stress: Chilling stress may be described either
1. At the plant/organ level or
2. At subcellular level
Chilling tolerance: Ability of some genotypes to survive/perform
better under chilling stress than other genotypes.
Chilling tolerance involves:
1. Membrane lipid unsaturation
2. Reduced sensitivity of photosynthesis
3. Increased chlorophyll accumulation
4. Improved germination
5. Improved fruit and/or seed set
6. Improved pollen fertility

7. • Sources of chilling tolerance
1. Well adapted breeding populations
2. Germplasm
3. Cold tolerant mutants
4. Somaclonal variants
5. Related wild species
Selection environment: Selection for chilling tolerance can be
effective only if appropriate selection pressure is
applied.
Selection may be carried out
1. In the field or
2. In a controlled environment

8. Freezing stress: When plants are subjected to subzero
temperatures, a complex array of stresses and strains
develop within them; they are all included in freezing
stress.
Freezing resistance: The ability of a genotype to survive
freezing stress and to recover is known as freezing
resistance.
Freezing resistance involves two distinct strategies
1. Freezing avoidance
2. Freezing tolerance

9. Freezing avoidance: Ability of plant tissues/organs to avoid
ice formation at subzero temperatures is called freezing
avoidance.
1. Supercooling is mechanism of freezing avoidance.
2. It is controlled by lack of ice nucleators and is favoured
by small cell size, little or no intercellular space, low
moisture content, barriers against external nucleators
and the presence of antinucleators.

10. • Freezing tolerance: Ability of plants to survive the stresses
generated by extracellular ice formation and to recover is known as
freezing tolerance.
• The various components of freezing tolerance are as follows
1. Osmotic adjustment
2. Amount of bound water
3. Plasma membrane stability
4. Cell wall properties
5. Cold responsive proteins

11. Problems in breeding for freezing tolerance:
1. Freezing tolerance can not be readily measured,
especially under the field environments.
2. Breeding work generally has to be carried out under
the field environment, which is inherently variable,
and is subject to biotic stresses during recovery and
growth.
3.Field survival shows poor heritability.

13. GENES AND GENOMICS IN BREEDING CULTIVARS
SUITABLE TO LOW WATER REGIMES AND WATER
LOGGING AND SUBMERGENCE
 Presented by
 Mr. Pawar Madhukar Gopal
 Reg. No. K-17-063

14. WATER LOGGING
 Water logging refers to the saturation of soil with water.
 Water logging is often accompanied by soil salinity as
waterlogged soils prevent leaching of the salts.

15. CHEMICAL RESPONSE
Soil chemical responses to water logging
 Increased Mn concentration that could be toxic to plant
growth
 Decreased soil oxygen; generally greater at warmer
temperatures
 Decreased Mo availability
 Denitrification of both organic and inorganic soil N
 Mineral (Fe) coating of epidermal surface of roots
 Volatile fatty acids and phenolic compounds accumulated in
soils high in organic matter affect root metabolism and
growth

16. PHYSIOLOGICAL RESPONSES TO
WATER LOGGING
1. Chlorosis of lower leaves.
2. Early senescence of lower leaves .
3. Decreased plant height .
4. Delayed ear emergence .
5. Reduced root and shoot growth .
6. Lower number of spike-bearing tillers .
7. Fewer grains per spikelet and reduced kernel weight.
8. Reduced diameter of metaxylem and protoxylem vessels
of the nodal root.
9. Enhanced formation of aerenchyma cells in the cortical
tissue of both seminal and nodal roots.
10. Leakage of cell electrolytes .

17. Lower leaf chlorosis
Water logging reduces the number
spike-bearing tillers.

18. MECHANISM OF WATER LOGGING
TOLERANCE
 Plants which can withstand water logging condition have
mechanisms such as
 Increased availability of soluble sugar
 Aerenchyma formation
 Greater activity of glycolytic pathway and fermentation
enzymes,
 Involvement of antioxidant defense mechanism to cope
with the oxidative stress induced by water logging.

19. Hypoxia and Anoxia –
Hypoxia, reduction of oxygen below
optimum level, is the most common form
of stress which occurs during partial
submergence of plant due to short-term
flooding where the root goes under water
and shoots remain in the atmosphere.
Anoxia, another kind of water stress
where plant goes under water completely,
hence complete absence of oxygen
occures.

20. Ethylene Production
 Accumulation of ethylene in waterlogged soil and plants occurs
at concentration of 10 cm3 dm−3
 This accumulation of ethylene occurs in mainly two ways
1. Ethylene diffusion rate from root to water is 10 times slower than
in air.
2. Ethylene synthesis is increased in the hypoxic root system and in
the aerobic shoot

21.  Role of Ethylene in Aerenchyma Formation-
The soft tissues with large intercellular spaces to
render low-resistance internal pathways for the
exchange of gases between aerobic shoot to the
anaerobic root are called Aerenchyma
Formation of aerenchyma is initiated by ethylene,
which is one of many adaptive features of plants at
submergence to avoid anaerobiosis by increasing the
availability of oxygen.

22. MARKER ASSISTED BREEDING FOR
WATER LOGGING TOLERANCE
 Identification of QTL.
 Manipulation of QTL for Developing Water logging Tolerant
Variety.

23. SUBMERGENCE
 A submergent plant or submergent vegetation is a plant
that is completely beneath the surface of water.
 Most submergent plants are firmly rooted in the soil.

24. TWO TYPES OF FLOODING CAUSING SUBMERGENCE
1. Flash flooding, which results in rapid ascending of water
levels with submergence for 1-2 weeks.
2. The second type is deepwater where water depth exceeds 100
cm.

25. EFFECT OF SUBMERGENCE ON CROP-
i. Shortage of oxygen restricting respiration.
ii. Drastic inhibition to the entry CO2 restricting
photosynthesis.
iii. The damaging effect of the subsequent reversal back
to fully aerobic condition (post-anoxic shock) when
flood water recedes.
iv. Siltation on leaves causes mechanical damage and
affects light and gas diffusion.

26. FACTORS THAT AFFECTS SURVIVAL OF CROP-
 Gas diffusion-
 Gas diffuse 104 times more slowly in solution than in air.
 Limited gas diffusion is the most crucial component which
affect growth, metabolism and survival of crop.
 Depletion of O2 induces hypoxia (low oxygen) or anoxia (zero
oxygen) around the shoot and root tissues or germinating seeds.
 O2 deficiency tends to accelerate breakdown of carbohydrates.

27.  Light –
 Brightest profile of submerging water enhances photosynthesis.
 Turbid profile reduces photosynthesis due to reduced light
transmission and deposited silt on leaves.
 Temperature-
 Higher temperature accelerates mortality due to decrease in O2
and CO2 and also accelerates anaerobic respiration leading to
starvation and death of plant.
 Low temperature improves survival.

28. SUBMERGENCE TOLERANCE
Major physiological traits involved submergence avoidance are-
1. Maintenance of high carbohydrate concentration.
2. Minimum elongation growth.
3. Optimum rates of alcoholic fermentation.
4. Up regulation of antioxidants system when water recedes.
5. Low synthesis or sensitivity to ethylene during submergence.

29. SCREEN FOR SUBMERGENCE TOLERANCE AND
AVOIDANCE
 Plants which are tolerant to complete submergence are
selected.
 Plants having elongation ability are screened for
submergence avoidance.
 Elongation ability of leaves and internodes are essential
to keep pace with increasing water levels and to escape
complete submergence.

30. COMMON TRAITS NEEDED IN
SUBMERGENCE TOLERANT LINES:
*Vegetative vigor
*High tillering ability
*Erect leaves
*Longer, wide and
thick leaves
*High fertility
*Maturity
*Photoperiod sensitivity
*Grain dormancy
*Grain quality
*Eating quality
*Tolerance to other soil stresses
*Tolerance to pest

31. COMMON TRAITS NEEDED IN SUBMERGENCE
AVOIDANCE LINES:
 Plant height: useful than elongation ability for areas that
commonly experience shallow flooding
 Lodging resistance: minimize yield loss and maintain
grain quality

32. MAS BREEDING
 Useful alleles of candidate genes could be tagged and
used for MAS breeding. These genes/alleles need to be
incorporated into varieties that are most popular in the
target environments to accelerate adoption and diffusion.
 Other important QTLs/candidate genes need to be
tagged to facilitate molecular breeding.

33. THANK YOU