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Cereals, legumes and tubers (root) are
the major classes of crops that give rise to a healthy balanced diet. Legumes
are a rich source of dietary proteins and have high nutritional value (Table
1). Legumes accounts for 27% of the global crop production and is ranked third
after cereals and oilseeds productions (Ashraf et al., 2010; Kudapa et al., 2013)
For centuries, legumes have been an integral food crop in developing countries
and are often called “poor man’s meat”. Moreover leguminous crops such as
soyabean and groundnut account for 35 % of the global processed vegetable oil (Sharma et al.,
2010; Mantri et al., 2013). The other miscellaneous uses of
legumes include fodder for animals and green manure (as they are involved in
nitrogen fixation). Legumes are being considered worldwide as a sustainable
food source in the near future with the United Nations declaring 2016 as the “International
Year of Pulses” (FAO, 2016).

Taxonomically, legumes fall under the Fabaceae/ Leguminosae family comprising over 18000 species. The dry seeds
obtained harvesting the legumes are termed as pulses. Legumes are classified
into two groups based on their ability to thrive in different climate seasons.
The first group includes the legumes that grow in the cool season and are
termed as cool season food legumes. They include broad bean (Vicia faba),
lentil (Lens culinaris), lupins (Lupinus spp.), dry pea (Pisum
sativum), chickpea (Cicer arietinum) and grass pea (Lathyrus
sativus) (Toker & Yadav, 2010). These are grown evenly in all
continents excluding Antarctica. The second group is called the tropical season
food legumes. These legumes require hot and humid climatic conditions for their
growth. This group includes include pigeon pea (Cajanus cajan), cowpea (Vigna
unguiculata), soybean (Glycine max L.), mung bean (Vigna radiata var.
radiata) and urd bean (Vigna mungo)( FAOSTAT 2009; Andrews &
Hodge, 2010).

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The global legume
production between 2011- 13 was 72.3 million metric tons of grains produced
from 80.3 million hectares of crop area. (Joshi et al.,2017). Dry beans is the
major legume grown, accounting for 32% of the global legume production. It is
followed by chickpea (17%), dry peas (14.6%), cowpea (8.9%), lentils (6.5%),
pigeon pea (6.2%), and broad beans (5.8%). In India, Madhya Pradesh is the
largest producer of legumes (20.3%) followed by Maharashtra
(13.8%), Rajasthan (16.4), Uttar Pradesh (9.5%), Karnataka (9.3%), Andhra
Pradesh (7.9%),Chhattisgarh (3.8%), Bihar (2.6%) and Tamil Nadu(2.9%). India
alone accounts for 19 % of the world production behind China (largest
producer).

Despite the exceptional nutritional
importance and wide application of legumes for human race, the productivity of
legumes is significantly affected by abiotic stress conditions in the semi arid
regions (SAT). The SAT region is the major producer of grain legumes and
spreads across 55 developing countries with a population count of 1.4 billion
(Bray et al., 2000)

Abiotic stresses such as salinity,
drought and extreme temperatures lead to significant loss in global crop
production. According to FAO, 2010 drought and salinity affects 60 and 10.5 million km2 area respectively
and are collectively responsible for approximately 70% loss in annual crop
yield (Wild, 2003). It is also reported that 90% of the global arable land is
under the effect of one or more abiotic stresses and crop cultivation on such
lands leads to production of crops more vulnerable to biotic stress factors
(Dita et al., 2006). They affects plant growth, thereby minimizing
overall seed quality and subsequently contribute to crop yield reduction (Cattivelli et al., 2008). In addition, changes in general climate
pattern, sporadic rainfall along with loss of agricultural land predominantly
due to salinity and drought stress conditions threatens global food security.
Significant crop yield reduction has been reported in major cereal crops
(barley, rice, wheat, maize and wheat) as well as in legumes (chick pea, ground
nut, mung bean, millet, pigeon pea, common bean etc.) (Jaleel et al., 2009)

Plant response to
abiotic stresses such as drought, salinity, extreme temperatures, and oxidative
stress are often correlated, inducing cellular damage. The effects of salinity
and drought are expressed by a series of morphological, physiological,
metabolic and molecular changes in plants( Figure-1). Hence as we strive to
develop superior salt and drought tolerant cultivars of these legumes with
improved seed quality and yield, it is of outmost importance to elucidate the
molecular basis of abiotic stress tolerance based on these morphological and
physiological traits. In this review, we discuss the salinity and drought
stress response in legumes and identify the various physiological traits such
as plant water relations and transpiration efficiency, photosynthesis and
stomatal conductance, ion concentrations, yield parameters etc in response to
the stress conditions. These physiological traits have been identified across
major economically important legumes and can be utilized for quantifying plant
growth and survival status when subjected to salinity and drought and can also
help in developing cultivars with multi stress tolerance.

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