4. Drought Escape
• The simplest way of survival under drought conditions is to escape drought.
• Generally, drought occurs either in the mid or late-crop season.
• Drought escape is most common in case of plants grown in desert regions.
• They complete their life cycles in 4 to 6 weeks.
• Drought escape also plays an important role in some crop plants.
• For Example, yields of early varieties of wheat, sorghum, maize, and rice are
less affected by severe drought than late maturing ones.
• All these crops have determinate growth habit.
5. Drought Avoidance
• Drought avoidance refers to ability of the plant to maintain a
favourable internal water balance under moisture stress.
• In other words, plants which avoid drought retain high water
contents in their tissues.
• Drought avoidance can permit a longer growth period in the
crop through reduced water use or increased water uptake.
• However, drought avoidance leads to reduction in photosynthesis
and thereby reduction in the growth of aerial parts.
• It leads to increase in root development and therefore, is more
important than drought tolerance
6. • In cereals, drought avoidance operates during vegetative
phase, while tolerance operates during reproductive phase
• Drought avoidance mechanisms are of two types
• First those which reduce water loss through transpiration
• Such features include stomatal characteristics and shape,
size and orientation of leaves
• The second, those which maintain water uptake during
drought period
7. Drought tolerance
• The ability of crop plants to withstand low tissue water content
is referred to as drought tolerance.
• Drought tolerance is more desirable because the crop can
produce more yield at lower water potential.
• In cereals, drought tolerance generally operates during
reproductive phase.
• Tolerant cultivars exhibit better germination , seedling growth
and photosynthesis.
• Drought tolerance differs from drought avoidance in several
aspects.
12. MORPHOLOGICAL TRAITS
Earliness:- Early maturing varieties are ready for harvest before the
onset of drought.
Stomatal characters: -sunken type, small size, less number per unit area and
rapid closing nature.
-Adaxial stomata are more sensitive to water stress than abaxial
stomata.
Leaf characters:- Thick cuticle, waxyness of leaf surface
-Small and thick leaves with thick layers of palisade tissue,
-Glossiness and hairiness.
Root characters:- Root length, root density, root dry weight and root to
shoot ratio are important trait.
Growth habit:- Indeterminate genotypes are suitable to drought because
determinate gives only one flush of flower and if there is drought period
during flowering, it may lead to very heavy loss.
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Singh P. (2004)
15. Plant Breeding Methods for
Drought Resistance
Breeding methods for drought resistance are the same as for yield
and other economic characters.
Breeding for drought resistance refers to breeding for yield under
soil moisture stress condition.
In other words, it refers to yield improvement in environment
represented b water deficit. Four breeding methods, viz.
1)Introduction
2)Selection
3)Hybridization
4)Mutations are commonly used for development
of drought resistant crop cultivars.
16. Breeding methods for drought resistance
1. Adaptation to a specific environment : Varieties are developed
specifically for adaptation to moisture deficit environments, and
selection and evaluation are carried out under moisture stress.
2. Adaptation to a variable environment : It combines yield and
drought resistance. The yield stability of selected lines is
evaluated under several environments ranging from stress to non
stress conditions. Those showing high mean performance with
high stability may be released for cultivation.
3. Combining selection for drought resistance traits and high
yield potential : Selection for yield potential and drought
resistance traits such as cuticular wax are integrated in selection.
17.
18.
19. Source of Drought Resistance in Plant
Breeding
Cultivated varieties,
Germplasm collections, and
Wild relatives and wild species
