Chickpea: Role and responses under abiotic and biotic stress - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 73

MAS is being deployed in chickpea at ICRISAT (India)
to introgress QTL alleles associated with a large root size
into elite germplasm (Saxena et al., 2002). Terminal
drought can cut chickpea yield by amounts ranging
from 20% to more than 50%. Hence, a deep root system
capable of extracting additional soil moisture should
positively impact yield in drought-prone areas (Crouch &
Serraj, 2002).

lines was more pronounced and increased significantly
in the leaves when exposed to water stress along with a
decrease in free radicals as measured by a decrease in
levels of malonaldehyde (MDA), a lipid peroxidation
product (Bhatnagar-Mathur et al. 2009). However, the
overexpression of proline appeared to have no benefi-
cial effect on biomass accumulation since only a few
transgenic lines showed a significant increase in biomass
production towards the end of the progressive drying
period. In any case, the overexpression of P5CSF129A
gene resulted in only a modest increase in the transpira-
tion efficiency (TE), thereby indicating that the
enhanced proline had little bearing on the components
of yield architecture that are significant in overcoming
the negative effects of drought stress in chickpea (Reddy
et al., 2012). These results agree with earlier reports in
other crops (Turner et al., 1980; Morgan, 1984; Serraj &
Sinclair, 2002).

4.6.4 transgenomics
The use of transgenic technology, or 'transgenomics',
potentially offers a more targeted gene-based approach
for understanding the mechanisms governing stress tol-
erance, providing a complementary means for genetic
enhancement of field crops, thereby alleviating some of
the major constraints to crop productivity in developing
countries (Sharma & Ortiz, 2000).
Various transgenic technologies for improving stress
tolerance have been developed involving the expres-
sion of functional genes including those encoding for
enzymes required for the biosynthesis of osmoprotec-
tants (Tarczynski et al., 1993; Kavi Kishore et al., 1995;
Hayashi et al., 1997) or modifying membrane lipids
(Kodama et al., 1994; Ishizaki-Nishizawa et al., 1996),
late embryogenesis proteins (Xu et al 1996) and detoxi-
fication enzymes (McKersie et al., 1996).
Osmoregulation is one of the best mechanisms for
abiotic stress tolerance, especially if osmoregulatory
genes could be triggered in response to drought, salinity
and high temperatures. A prokaryotic osmoregulatory
choline oxidase gene ( codA ) has been targeted at the
chloroplasts to enhance the potential of the photosyn-
thetic machinery of chickpea to withstand oxidative
damage (Reddy et al., 2012). Chloroplasts from plants of
transgenic lines were evaluated for their efficacy to
withstand photo-inhibitory damage. The the loss in
photosystem II (PSII) activity in chloroplasts of wild-type
plants exposed to high light intensity was significantly
greater than that in chloroplasts of transgenic chickpeas.
The results indicated that H 2 O 2 produced by choline oxi-
dase as a by-product during synthesis of glycine-betaine
is responsible for building a stronger antioxidant system
in chloroplasts of transgenic chickpea plants (Sharmila
et al., 2009). Similarly at ICRISAT, the P5CSF129A gene
encoding the mutagenized D1-pyrroline-5-carboxylate
synthetase (P5CS) for the overproduction of proline was
introduced into chickpea (Reddy et al., 2012). The
accumulation of proline in several of these transgenic

4.7 Biotic stress

Diseases, insects, pests and plant-parasitic nematodes
are the major biotic stressors that can drastically affect
chickpea yield (Basandrai et al., 2011).

4.7.1 Chickpea and diseases
The major diseases are ascochyta blight ( Ascochyta
rabiei ), fusarium wilt ( Fusarium oxysporum f. sp. Ciceri ),
phytophthora root rot ( Phytophthora medicaginis ) and
botrytis grey mould ( Botrytis cinerea ) (Ahmad et al., 2005;
Knights et al., 2008; Singh et al., 2008).

4.7.2 Chickpea and insect pests
The major pests include helicoverpa pod borer
( Helicoverpa armigera and Helicoverpa punctigera ) and leaf
miner ( Liriomyza cicerina ) (Ahmad et al., 2005; Materne
et al., 2011).

4.7.3 Chickpea and plant-parasitic
nematodes
Plant-parasitic nematodes reported in the major chickpea-
growing areas include reniform nematode ( Rotylenchulus
reniformis ), root-knot nematodes ( Meloidogyne spp.), root-
lesion nematodes ( Pratylenchus spp.) and cyst-forming
nematodes ( Heterodera spp.); they are estimated to cause
annual yield losses of 14% (Castillo et al., 2008; Materne
et al., 2011).