Chickpea: Role and responses under abiotic and biotic stress - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 71

Soil salinity is another of the abiotic stresses that
adversely affect plant growth and development. Soluble
salts in surplus quantity in the soil lead to the osmotic
stress that results in specific ion toxicity and ionic imbal-
ance (Munns, 2003) and the consequences of these can
lead to the death of the plant (Rout & Shaw, 2001).
Therefore, to overcome the salinity threat, we have to
find and select relatively salt-tolerant genotypes within
a species, through conventional selection or breeding
techniques.
Chickpea has been reported as salt sensitive due to
pre-dawn leaf water potential expressed as a water
stress day index during the growing period and
according to soil salinity (Katerji et al. 2003). B. Singh et
al. (2005) reported that salt stress affects nodulation,
carbon fixation, plant water status, and H 2 O 2 scavenging
enzymes in chickpea cultivars. Recently, Rasool et al.
(2013) reported that the tolerance of the chickpea geno-
types SKUA-06 and SKUA-07 to salinity seems to be
related to the efficiency of the antioxidant enzymes
superoxide dismutase (SOD), catalase (CAT), ascorbate
peroxidase (APX) and glutathione reductase (GR) in
preventing accumulation of reactive oxygen species
(ROS), thereby maintaining redox homeostasis and the
integrity of cellular components.
A number of salt-tolerant chickpea genotypes were
identified that differed in the uptake and distribution of
Na + and Cl - ions (CSG 88101, CSG 8927, CSG 8977,
CSG 8962 and CSG 8943) (Dua & Sharma, 1995).
Another tolerant variety that can be grown in saline
soils with an electrical conductivity (EC) of 4 to 6 dS/m
is the desi variety Karnal Chana-1 (CSG 8963), which
was was released in India (Millan et al., 2006). On the
whole, the kabuli type was more tolerant than the desi
type after screening 252 genotypes and breeding lines
(Serraj et al., 2004). Maliro et al. (2007) screened about
200 genotypes and wild Cicer genotypes for salt toler-
ance in Australia. The most tolerant were CPI 060546,
ILC 01302 (from Turkey), ICC 06772 and ICC 6474
(from Iran), ICC 8294, ICC 438, CPI 53008 (from India)
and UC 5 (from USA); none of the wild relatives
screened were tolerant. This indicates that selection and
breeding of some cultivated genotypes on saline soils
has occurred, but screening for salt tolerance is limited
by its huge potential for interaction with other environ-
mental stresses, which makes it difficult to separate
genetic and environmental variations (Flowers, 2004;
Toker et al., 2007).

Deficiencies of some elements in agricultural soils
decrease yields of chickpea. For example, nitrogen (N)
and phosphorus (P) deficiencies in chickpea have been
reported to cause worldwide yield losses of 709,000 and
653,000 t/year, respectively. Similarly, yield losses
caused by micronutrient deficiencies have been esti-
mated at about 360,000 t/year (Ryan, 1997; Toker &
Mutlu, 2011). Iron-induced deficiency has been
reported in chickpea (Wallace, 1960; Toker et al., 2010;
Toker & Mutlu, 2011). Chickpea was found to be more
sensitive to Zn deficiency than oilseeds and cereals
(Tiwari & Dwivedi, 1990; Toker & Mutlu, 2011).
Anthropogenic activities are generally responsible for
heavy metal toxicity on agricultural land. About 235
million hectares of land has been polluted by toxic heavy
metals (Giordani et al., 2005). Arsenic is one of the pri-
mary toxic metals, mostly found in the oxidized state as
arsenite (As(III)) and arsenate (As(V)). Arsenic is a non-
essential element for both plants and animals. Soils
enriched with arsenic are considered to be the main
sources of contamination in the food chain and water
supplies, and are of great environmental concern because
arsenic is known to be a carcinogen and mutagen (Fayiga &
Ma, 2006). Arsenic is mainly taken up as arsenate by the
plant, arsenate exposure causes stress in plants including
inhibition of growth, physiological disorders and ulti-
mately death of the plant (Stoeva & Bineva, 2003; Stoeva
et al., 2005). Cytoplasmic arsenate is reduced to arsenite
and interferes with metabolic processes involving phos-
phate, giving it the potential to be toxic to the plant
(Meharg & Hartley-Whitaker, 2002; Stoeva & Bineva,
2003). Though the arsenic is not a redox metal, there is
still the chance that the exposure of plants to inorganic
arsenic results in the generation of ROS, which readily
cause conversion of arsenate to arsenite in plants
(Meharg & Hartley-Whitaker, 2002). This problem is
severe if arsenic can contaminate the food chain; the
solution is to localize the metalloid in non-edible parts of
the crops and seedlings (Sahu et al., 2007). So, thorough
screening is needed to select varieties that can live on
contaminated sites with good growth and yield and have
the potential to localize metalloids in their roots.
A few varieties of chickpea, like cv.CSG-8962, are
tolerant to heavy metal stress (Gupta et al., 2002a). It
has been found that chickpea is very capable of pro-
ducing phytochelatins (PCs) and homo-phytochelatins
(hPCs) in response to low concentrations of cadmium in
hydroponics culture and in soils contaminated by fly-ash