Adaptation of plants to mineral stress in problem soils.

Crop production depends on interactions among genetic potentials of plants and various stress factors in the environment. Mineral stresses in the form of toxicity or deficiency are not always economically correctable with current technology. But plant species, and genotypes within species, differ widely in tolerance to different mineral stresses, and some of these differences are known to be genetically controlled. Hence, a viable alternative or supplemental approach is to adapt plants more precisely to soils. Soil fertility programmes of the past have emphasized 'changing the soil to fit the plant'. As a result, many crop cultivars have been developed under nearly ideal conditions of pH and soil fertility and hence cannot tolerate the stresses encountered in marginal soils. There is, therefore, a great need for stress-tolerant plant genotypes for use in a 'minimum input' system of agriculture for problem soils. The merits of tailoring the plant to fit the soil have only recently been recognized, even by the scientific community. However, within the last decade multidisciplinary teams of scientists have been formed in several countries, and considerable progress is being made in selecting and breeding plants for greater nutrient efficiency and for tolerance to such factors as aluminium toxicity and salinity. In view of problems in world food and energy production and distribution, this approach should receive the highest priority.