Salt stress and leguminous crops: Present status and prospects - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 29

that populations of R. tropici strain CIAT899 and natural
Rhizobium were decreased with raised salinity levels.
The plant root and shoot dry weight, chlorophyll
content, plant height, root length, total nitrogen, symbi-
otic efficiency and efficiency rate were affected by salt
stress in tested plants with both inoculations. Total
nitrogen content decreased significantly at the highest
level of salinity (Uyanöz & Karaca, 2011).
Flavonoids from root exudates of P. vulgaris cv. Bush
Blue Lake (BBL) obtained under control conditions, salt
stress (50 mM) and/or the presence of the plant growth-
promoting rhizobacterium (PGPR) Chryseobacterium
balustinum Aur9 were analysed by high-performance
liquid chromatography (HPLC) coupled to electrospray
ionization-tandem mass spectrometry (ESI-MS/MS).
Six flavonoids - naringenin, isoliquiritigenin, quercetin,
umbelliferone, 7′,4-dihydroxyflavone and hesperetin -
were identified in the root exudates. The latter three
flavonoids have not previously been reported in bean
root exudates. The presence of C. balustinum , but not salt
stress, modified the pattern of flavonoids exuded by the
bean roots (Dardanelli et al., 2012).
Faghire et al. (2013) studied the effect of salt stress,
under glasshouse conditions, on plant biomass, nodula-
tion, and activities of acid phosphatases (APase, EC
3.1.3.2) and trehalose 6-phosphate phosphatase (TPP,
EC 3.1.3.12) in the symbiosis between common bean
and rhizobia nodules. Salinity stress generally reduced
acid phosphatase and trehalose phosphate phosphatase
activities in nodules, which were less affected in plants
inoculated with RhM11. It was noted that nodule phos-
phatase activity may be involved in salinity tolerance in
common beans, and that levels of salt tolerance depend
principally on the specific combination of the rhizobial
strain and the host cultivar (Faghire et al., 2013).
The genus Vigna includes some well-known culti-
vated species, including former members of the genus
Phaseolus such as the adzuki bean ( V. angularis ), the
black gram ( V. mungo ), the moth bean ( V. aconitifolia )
and the mung bean ( V. radiata ) (Table 2.1). The other
food species include cowpea and Bambara beans. In
mung bean salinity induced negative effects on nodula-
tion, Lb content and nitrogenase; these were
metabolically regulated and operated through the inter-
vention of some key regulatory substances (Garg et al.,
1988).
Nandwal et al. (2000) subjected two phenotypically
different mung bean genotypes, K-851 (trifoliate) and a

mutant (pentafoliate), to increasing levels of salt stress.
Salinity led to decreases in the osmotic potential and
relative water content (RWC) of nodules. The osmotic
potential was reduced more in the mutant than in geno-
type K-851, while the reverse was true for RWC. A
sharp rise in the proline content of leaves, roots and
nodules was noticed. Lb levels also fell in both the culti-
vars after the application of saline irrigation (Nandwal
et al., 2000). Panda (2001) reported increases in the
activity of antioxidative enzymes like CAT, guaiacol per-
oxidase and SOD in root and shoot tissues of V. radiata
under salinity stress.
Kabir et al. (2004) studied the effect of potassium on
salinity tolerance of mung bean and reported that
salinity decreased RWC and water retention capacity,
while water saturation deficit and water uptake capacity
increased. Reduced dry matter distribution in different
plant parts as well as decreased total dry matter in mung
bean plants was also observed. Similarly, yield and
yield-contributing characters were also affected by
salinity, except number of seeds per pod.
A reproducible and efficient transformation system
utilizing the nodal regions of the embryonal axis of black
gram has been established via Agrobacterium tumefaciens.
Genetic transformation of V. mungo using the glyoxalase
I gene driven by a novel constitutive Cestrum yellow leaf
curling viral promoter has been performed for alleviating
salt stress. Exposure to salt stress (100 mM NaCl) of T1
transgenic plants as well as untransformed control plants
revealed that the transgenic plants survived under salt
stress and set seed whereas the untransformed control
plants failed to survive. The higher level of glyoxalase I
activity in transgenic lines was directly correlated with
their ability to withstand salt stress (Bhomkar et al.,
2008).
A comparative study was conducted by Nazar et al.
(2011) to assess the physiological processes in salt-toler-
ant (Pusa Vishal) and salt-sensitive (T44) cultivars of
mung bean under the influence of salicylic acid and salt
stress. Cultivar T44 accumulated higher leaf Na + and Cl −
content and exhibited greater oxidative stress than Pusa
Vishal. Activity of the antioxidant enzymes ascorbate
peroxidase (APX) and glutathione reductase (GR) was
greater in Pusa Vishal than T44. In contrast, the activity
of SOD was greater in T44. The greater accumulation of
leaf nitrogen and sulphur through higher activity of
their assimilating enzymes, nitrate reductase (NR) and
ATP-sulfurylase (ATPS), increased reduced glutathione