Agriculture Reference
In-Depth Information
modern tools, a number of strategies are now available to develop abiotic
stress tolerant varieties.
13.5.5 BREEDING STRATEGIES
13.5.5.1
DROUGHT TOLERANCE
Insufficient availability of water, that is, drought, is presumably the most
common stress experienced by terrestrial plants. On the cellular level
drought stress will affect vital metabolic functions and maintenance of
turgor pressure. Cell expansion and cell wall formation are therefore espe-
cially sensitive to water limitation. In order to minimize water loss, plants
respond to lower water availability with the closure of stomata. However,
this protective measure is not without drawbacks for the plant as this will
also decrease the CO
2
supply within the plant leaves and finally affect pho-
tosynthesis (Tippmann et al., 2009).
13.5.5.2
CONVENTIONAL APPROACHES
Using the available sources of resistance one can incorporate such species
in the breeding program to transfer the genes of interest. For instance in
case of roses
Rosa canina
hardy species adaptable to drought and alka-
line conditions (Hartmann and Kester, 1972) can be used as one of the
parents to cross with cultivated varieties belonging to
Rosa hybrid
a. Simi-
larly
Rosa indica
(
var, odorata
) can be incorporated in the inter specific
hybridization program as it is well adapted to both excessively dry or wet
soil conditions and can withstand high soil pH. In Carnations,
Dianthus
aydogduii
is salt tolerant species, which can be used as one of the parents
to introduce the trait in to cultivated Dianthus.
13.5.5.3
BIOTECH APPROACHES
The major signal during drought induced stress comprises of the formation
of Reactive Oxygen Species (ROS) likesinglet oxygen (
1
O
2-
), superox-
ide anions (O
2-
), hydrogen peroxide (H
2
O
2
) and hydroxyl radicals (OH)
which are highly reactive and damage cells by ROS mediated oxidative
