Genotypic variation in legumes for nutrient stress tolerance-a review

Availability of nutrient elements can be a major constraint to plant growth in many environments of world, especially the tropics where soils are extremely low in nutrients. Genotypic differences in nutrient use efficiency arc linked with root nutrient acquisition capacity or with utilization by the plant or both. Legumes express a wide array of phenotypic traits that improve adaptation to low nutrient availability, including increased biomass allocation to roots, root architectural traits that enhance topsoil foraging, increased density of root system and root hairs. Plant root exudates also have a major effect on the acquisition of mineral nutrients required for plant growth. Nutrient movement across roots to xylem is also responsible for variations in nutrient use efficiencies. The utilization efficiency can be measured as agronomic efficiency or physiological efficiency.