breeding for salt tolerance – response of plants to salinity – symptoms – mechanisms of salt tolerance – breeding methods for salt tolerance – problems – achievements; Cold tolerance – chilling resistance – effects of chilling stress on plants – mechanism of chilling tolerance – sources of chilling tolerance – selection criteria –freezing resistance – effects of freezing – mechanism of freezing resistance – genetic resources for freezing tolerance – selection criteria – problems in breeding for freezing tolerance.

1. PRESENTED BY:
Rajesh Biswal
Admn No: 42C/14
3rd Year B.Sc(Ag)
PRESENTED BEFORE:
Dr Kaushik Kumar Panigrahi
Assistant Professor,
Department of Plant Breeding
and Genetics
College of Agriculture, OUAT,
Chiplima

2. BREEDING FOR SALT TOLERANCE
 Plant species vary in how well they tolerate
salt-affected soils. Some plants will tolerate
high levels of salinity while others can tolerate
little or no salinity.
 The relative growth of plants in the presence
of salinity is termed their salt tolerance.

3.  It is a global problem as saline and alkali soils are
fond in almost all the countries of the world, more in
Semi Arid Tropic (SAT) of world.
Problem of salinity can be overcome by
two ways:
 Soil reclaimation : costly, time consuming and short
lived.
 Resistant varieties : less costly, more effective, long
lasting require longer period to develop.

5. • Retardation of growth
• Necrosis
• Leaf abscession
• Loss of turgor
• Cessation of growth
• Ultimate death of plant

8. 2 types of mechanisms
 Salt Tolerance : Plants respond to salinity
stress by accumulating salt, generally in their
cells or glands and roots etc.
 Salt avoidance : plants avoid salt stress by
maintaining their cell salt concentration
unchanged either by water absorption.
Mechanisms of salt tolerance :

11. Common methods are:
 Sand culture by using nuturient solution in sand
& irrigation with saline water
 Solution culture by using solution culture tanks
(Hydroponic culture)
 Microplot techniques by using small microplots

12. When
temperatures
remain above-
freezing i.e. >00C
to <100-150C it is
called chilling
When
temperature.
remain below
freezing i.e.<00C
it is called
Freezing

13.  Many species of plants especially those
native to tropical and subtropical regions are
susceptible to chilling injury.
 The plants native to temperate regions or
those glowing at high altitudes, are usually
genetically adapted to colder temperatures
and are therefore, resistant to chilling
injuries.

14. As a result of chilling
injury, the plants
invariably show:
(i) Reduced growth,
(ii) Chlorosis and
lesions on leaves,
(iii) Appearance of
foliage as if soaked in
water for long and
(iv) In extreme cases,
wilting of the plant
and its death.

16.  Ability of some genotypes to survive /
perform better under chilling stress than
other genotypes is called chilling
tolerance.

17. (i) Reduced growth,
(ii) Chlorosis and lesions on leaves,
(iii) Appearance of foliage as if soaked
in water for long and
(iv) In extreme cases, wilting of the
plant and its death.

18.  Late adopted breeding population
Eg: Maize
 Germplasm
 Induced mutants for cold tolerance.
 Cold tolerance somaclonal variation.
 Related wild species. Eg : Tomato

19. Frost-sensitive plants are killed or
seriously injured when exposed to temperatures
low enough to cause ice formation in them. This
type of injury is called as frost or freezing
injury and is frequently encountered in
temperate zone plants. Thus Freezing resistance
largely involves surviving freezing stress in
such a manner as to enable subsequent regrowth
when the temperature rises. As water in plants
cools below 00C, it may either Freeze i.e.
 Form ice OR
 Super cool without forming ice

21. Effects of freezing
stress
1. Ice formation : Two
types Intercellular ice
formation Intracellular
ice formation
2. Membrane disruptions
3. Suspercooling :Stress
due to external factors

23.  Freezing avoidance:
ability of plant tissues
/ or genes (but the
whole plants) to avoid
ice formation at sub
zero temperature
 Freezing Tolerance :
Ability of plants to
survive the stresses
generated by extra
cellular ice formation

24. The various components of freezing tolerance
are as follows:
 Osmotic adjustment.
 Amount of bound water.
 Plasma membrane stability.
 Cell wall components properties.
 Cold-responsive proteins.
Selection criteria:
Based on
1. Field survival
2. Freezing test in laboratory
3. Cryofreezing
4. Osmoregulation