Cereals, legumes and tubers (root) arethe major classes of crops that give rise to a healthy balanced diet. Legumesare a rich source of dietary proteins and have high nutritional value (Table1). Legumes accounts for 27% of the global crop production and is ranked thirdafter cereals and oilseeds productions (Ashraf et al.
, 2010; Kudapa et al., 2013)For centuries, legumes have been an integral food crop in developing countriesand are often called “poor man’s meat”. Moreover leguminous crops such assoyabean and groundnut account for 35 % of the global processed vegetable oil (Sharma et al.,2010; Mantri et al., 2013). The other miscellaneous uses oflegumes include fodder for animals and green manure (as they are involved innitrogen fixation). Legumes are being considered worldwide as a sustainablefood source in the near future with the United Nations declaring 2016 as the “InternationalYear of Pulses” (FAO, 2016).
Taxonomically, legumes fall under the Fabaceae/ Leguminosae family comprising over 18000 species. The dry seedsobtained harvesting the legumes are termed as pulses. Legumes are classifiedinto 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 aretermed as cool season food legumes. They include broad bean (Vicia faba),lentil (Lens culinaris), lupins (Lupinus spp.), dry pea (Pisumsativum), chickpea (Cicer arietinum) and grass pea (Lathyrussativus) (Toker & Yadav, 2010).
These are grown evenly in allcontinents excluding Antarctica. The second group is called the tropical seasonfood legumes. These legumes require hot and humid climatic conditions for theirgrowth. This group includes include pigeon pea (Cajanus cajan), cowpea (Vignaunguiculata), soybean (Glycine max L.), mung bean (Vigna radiata var.radiata) and urd bean (Vigna mungo)( FAOSTAT 2009; Andrews &Hodge, 2010).The global legumeproduction between 2011- 13 was 72.3 million metric tons of grains producedfrom 80.
3 million hectares of crop area. (Joshi et al.,2017). Dry beans is themajor legume grown, accounting for 32% of the global legume production. It isfollowed 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 thelargest producer of legumes (20.
3%) followed by Maharashtra(13.8%), Rajasthan (16.4), Uttar Pradesh (9.5%), Karnataka (9.3%), AndhraPradesh (7.9%),Chhattisgarh (3.8%), Bihar (2.
6%) and Tamil Nadu(2.9%). Indiaalone accounts for 19 % of the world production behind China (largestproducer).
Despite the exceptional nutritionalimportance and wide application of legumes for human race, the productivity oflegumes is significantly affected by abiotic stress conditions in the semi aridregions (SAT). The SAT region is the major producer of grain legumes andspreads 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 cropproduction. According to FAO, 2010 drought and salinity affects 60 and 10.
5 million km2 area respectivelyand are collectively responsible for approximately 70% loss in annual cropyield (Wild, 2003). It is also reported that 90% of the global arable land isunder the effect of one or more abiotic stresses and crop cultivation on suchlands leads to production of crops more vulnerable to biotic stress factors(Dita et al., 2006). They affects plant growth, thereby minimizingoverall seed quality and subsequently contribute to crop yield reduction (Cattivelli et al., 2008). In addition, changes in general climatepattern, sporadic rainfall along with loss of agricultural land predominantlydue 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, groundnut, mung bean, millet, pigeon pea, common bean etc.) (Jaleel et al., 2009)Plant response toabiotic stresses such as drought, salinity, extreme temperatures, and oxidativestress are often correlated, inducing cellular damage. The effects of salinityand drought are expressed by a series of morphological, physiological,metabolic and molecular changes in plants( Figure-1).
Hence as we strive todevelop superior salt and drought tolerant cultivars of these legumes withimproved seed quality and yield, it is of outmost importance to elucidate themolecular basis of abiotic stress tolerance based on these morphological andphysiological traits. In this review, we discuss the salinity and droughtstress response in legumes and identify the various physiological traits suchas plant water relations and transpiration efficiency, photosynthesis andstomatal conductance, ion concentrations, yield parameters etc in response tothe stress conditions. These physiological traits have been identified acrossmajor economically important legumes and can be utilized for quantifying plantgrowth and survival status when subjected to salinity and drought and can alsohelp in developing cultivars with multi stress tolerance.
