Legumes and breeding under abiotic stress: An overview - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 5

temperatures near 0 °C (Bhattacharya & Vijaylaxmi,
2010; Hasanuzzaman et al., 2013).
Oktem et al. (2008) investigated the effects of cold and
drought stress on growth parameters and antioxidant
responses in shoots and roots of lentil seedlings subjected
to drought and cold (4 °C) stress for 5 days. They
reported that the length and fresh weight of shoots
decreased significantly under both stress conditions,
contrary to the increase in these growth parameters for
roots under the same conditions. The increase in proline
levels was more pronounced under cold stress in shoots
and roots. The oxidative damage resulted in increase of
malondialdehyde (MDA), and hydrogen peroxide
(H 2 O 2 ) was markedly higher in shoots under cold stress.
Both stress conditions caused a significant increase in
malondialdehyde levels in root tissues. SOD activity was
differentially altered in shoot and root tissues under
drought and cold stress. The CAT activity was higher in
roots under drought stress, whereas APX activity
increased in root tissues under cold stress (Oktem et al.,
2008; Bhattacharya & Vijaylaxmi, 2010).

Al toxicity on SNF; it might be considered as a main
limitation on the contribution of legumes to the global
N cycle (Valentine et al., 2011).

1.2.6 Legumes under nutrient deficiency
In agricultural soils, deficiency of some elements nega-
tively affects nitrogen fixation in legumes and
consequently reduces their yield. Toker and Mutlu (2011)
reported that in chickpea, N and P deficiencies resulted in
yield losses of 790,000 and 653,000 t/year, respectively,
worldwide. In most legume-growing soils, N and P are at
either low or medium levels, whereas potassium (K) is
usually sufficiently available to support growth, although
it can be deficient in some soils (Srinivasarao et al., 2003).
Ca and Mg are generally deficient in acid soils (pH < 5.5).
Sulphur (S) deficiency has been reported on light-
textured soils in India, and the application of S at 20 kg/
ha is recommended for these soil types (Srinivasarao
et al., 2003). S deficiency is also seen in calcareous soils
with a pH of 8.0 or higher (Toker et al., 2011). Iron (Fe)
deficiency has been recorded in many legume crops
such as chickpea, lentil, lupin, pea, bean and soybean
(Erskine et al., 1993; Toker et al., 2010).
Al toxicity induced reduction of SNF due to (i) the
inhibition of rhizobial growth in the soil; (ii) the retar-
dation of nodulation; and (iii) the possible alteration in
organic acid metabolism (Valentine et al., 2011). Boron
(B) toxicity or deficiency induced suppression of normal
growth in pea or faba bean (Dwivedi et al., 1992; Poulain &
Almohammad, 1995).
Toker and Mutlu (2011) reported that in legume
species the relative sensitivity to zinc (Zn) deficiency is
high for common bean relative to soybean (Alloway,
2009). Lentil, chickpea and pea were found to be more
sensitive to Zn deficiency than oilseeds and cereals
(Tiwari & Dwivedi, 1990). Differential Zn efficiency was
reported among navy bean genotypes (Jolley & Brown,
1991; Moraghan & Grafton, 1999). Zn deficiency caused
delay in pod maturity in bean (Blaylock, 1995).

1.2.5 Legumes under soil acidity
Approximately 40% of the world's arable land is consid-
ered to be acidic (Valentine et al., 2011). In natural
ecosystems, soil acidity determines the availability of
mineral nutrients such as phosphorus (P) and also deter-
mines the level and severity of phytotoxic elements such
as aluminium (Al), manganese (Mn) and iron (Fe)
(Muthukumar et al., 2014). Al ions present in acidic soils
cause (i) induction of ROS and lipid peroxidation, which
limit crop yield in these soils (Yamamoto et al., 2002;
Muthukumar et al., 2014); and (ii) extrinsic toxicity
through calcium (Ca) and magnesium (Mg) deficiency
(Kinraide et al., 2005; Muthukumar et al., 2014).
Three possible groups of mechanisms appear to
operate in plants that can tolerate acidic conditions
(Muthukumar et al., 2014). These include the following:
1 Exclusion of toxic ions such as Al and Mn from the
root apex.
2 Tolerance to toxic levels of Al and Mn through detox-
ification in the plant symplasm.
3 Enhanced efficiency in the uptake of limiting nutri-
ents from acid soils (Kochian et al., 2004; Bhalerao &
Prabhu, 2013).
Soil acidity is a major factor affecting the growth and
yield of legumes in many of the world's agricultural sys-
tems, due to the effect of phosphorus (P) deficiency and

1.3 Breeding of cool season food
legumes

In 1970s, the breeding of legumes started with the
establishment of the International Centre for
Agricultural Research in Dry Areas (ICARDA) in Syria
and the International Crops Research Institute for