Potential for Genetic Improvement in Salinity Tolerance in Legumes: Pigeon Pea

Leguminous crops are cultivated throughout the world because of their importance as a \nprotein source in the diets of humans and livestock. Furthcr, many leguminous species \nare cultivated as pasture, fodder, or green manure plants. Legumes thereby form essential \ncomponents of cropping systems, primarily because of their inputs of nitrogen \nfixed from the atmosphere but also for other benefits thcy offer, such as improving the \nsoil physical and chemical environment and breaking disease cycles (I). Among various \ncrop plants tested, however, legumes have generally been found to be more sensitive \nto soil salinity (2). With the emphasis given to increasing cereal production in \nrecent decades, the cultivation of legume crops has generally been forced to more \nmarginal lands, including those prone to salinity problems. Further, legumes grown on \nresidual soil moisture in the season after thc rains, such as chickpea and lentil, are particularly \npronc to salt damage: salts are progressively concentrated in the soil solution \nand precipitated toward the soil surface as the soil dries out. Thus, legumcs generally \nface a greater threat of salinity than cereals because of their greater salt sensitivity and \nan increasing likelihood of being exposed to saline environments. Thcreforc, improvement \nin the salinity tolerance of legumes is of immediate and increasing concern.