Salt stress and leguminous crops: Present status and prospects - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 34

Amdoun 1 than in INRAT 93-1 in the absence of salt.
This effect was associated with a significantly higher O 2
uptake by nodulated roots (510 vs 255 µmol O 2 per
plant/h) and nodule conductance (20 vs 5 µm/s) in
Amdoun 1 compared with INRAT 93-1. Salinity did not
significantly change the nodule conductance and nodule
permeability for INRAT 93-1 (L'taief et al., 2007).
A screening of 263 accessions of chickpea, including
211 accessions from ICRISAT's mini-core collection
(10% of the core collection and 1% of the entire collec-
tion), showed a six-fold range of variation for seed yield
under salinity (1.9 L of 80 mM NaCl per 7.5 kg Vertisol),
with several genotypes yielding 20% more than a for-
merly released salt-tolerant cultivar. The range of
difference in yields under salinity was similar in both
kabuli and desi chickpeas, showing that breeding for
salinity tolerance can be undertaken in both groups.
However, no significant correlation was found between
the shoot dry weight ratio and the yield ratio, signifying
that differences in salinity tolerance among genotypes
could not be concluded from measurements in the veg-
etative stage. The major trait connected to salinity
tolerance was the capacity to produce a large number of
filled pods, whereas seed size was similar in tolerant and
sensitive genotypes. Salinity tolerance was not associ-
ated with the shoot Na + or K + concentrations (Vadez
et al., 2007). Similarly, Samineni et al. (2011) reported
that chickpea is sensitive to salinity in both the vegeta-
tive and reproductive phases, with pod formation being
particularly sensitive.
The effects of different levels of Na salinity (0, 3, 6 and
9 dS/m on growth, yield and yield component of kabuli
(Hashem and Jam) and desi (Kaka and Pirooz) chickpea
cultivars were evaluated (Sohrabi et al., 2008). Seeds of
four chickpea cultivars were nurtured under 0, 3, 6 and
9 dS/m levels of salinity until maturity. Salinity dimin-
ished the plant growth, flower, pod and seed number
and seed weight. As salinity increased the negative
effect of Na + was more pronounced and reached the
highest value at 9 dS/m in all cultivars. Four chickpea
cultivars have different responses to salinity and the
kabuli cultivars appeared to have a greater capacity for
salt tolerance compared to desi cultivars. The Hashem
cultivar has the highest salinity tolerance among all the
cultivars (Sohrabi et al., 2008).
Six hundred accessions of chickpea landraces and
wild relatives from 28 different countries, available in
the Australian Temperate and Field Crops Collection

(ATFCC), were screened for tolerance to salt under
greenhouse conditions. The degree of salt tolerance was
based on necrosis scores and shoot biomass reduction
relative to unstressed controls. There was a wide varia-
tion in salinity tolerance evaluated by both measures.
Accessions from the Middle East and south Asia (regions
with salinity problems, a long history of chickpea culti-
vation and high diversity) showed greater potential for
getting salt-tolerant accessions (Moses et al., 2008).
Neil et al. (2013) conducted a study to determine the
degree of salt tolerance among chickpea genotypes, and
the relationship between salt tolerance and ion
accumulation in leaves and reproductive tissues. The
enhanced salt tolerance was positively associated with
higher pod and seed numbers, and higher shoot bio-
mass, but not with time to 50% flowering nor with the
number of filled pods in the non-saline treatment. Pod
abortion was higher in the salt-sensitive genotypes, but
pollen viability, in vitro pollen germination and in vivo
pollen tube growth were not affected by salinity in
either the salt-tolerant or salt-sensitive genotypes. The
concentrations of sodium and potassium ions, but not
chloride, in the seed were significantly higher in the
sensitive than in the tolerant genotypes. Sodium and
potassium, but particularly chloride, ions accumulated
in leaves and in pod walls, whereas accumulation in the
seed was much lower. Considerable genotypic variation
for salt tolerance exists in chickpea germplasm. The
study suggested that selection of genotypes with high
pod and/or seed numbers that accumulate low concen-
trations of salt in the seed would be beneficial (Neil
et al., 2013).

2.4.5 Cowpea
The cowpea, Vigna unguiculata (L.) Walp., is one of sev-
eral species of the widely cultivated genus Vigna . Four
subspecies are recognized, of which three are cultivated:
(i) Vigna unguiculata subsp. dekindtiana is the wild
relative of the cultivated subspecies; (ii) Vigna unguicu-
lata subsp. cylindrica is a cultivated species, common
name catjang; (iii) Vigna unguiculata subsp. sesquipedalis
is a cultivated species, common name yardlong bean;
and (iv) Vigna unguiculata subsp. unguiculata is a culti-
vated species, common name black-eyed pea. Cowpeas
are one of the most important food legume crops in the
semi-arid tropics covering parts of Asia, Africa, southern
Europe and Central and South America. It is a drought-
tolerant and warm-weather crop and well adapted to