The role of proline and root traits on selection for drought-stress tolerance in soybeans: a review

Abstract

Drought stress is a major limiting factor in soybean production. It reduces both the yield and its components. This is dependent on the level and occurrence of drought stress with respect to the growth stages of the plants. Breeding for drought stress tolerance can sustainably reduce the impact of drought stress. However, occurrence of drought stress is irregular over locations and seasons, making selection for drought tolerance challenging. Effort is being put into using proline accumulation as a measure to monitor stress tolerance of higher plants. It is evident that proline accumulates with increased drought stress. Genotypic differences exist in proline accumulation among soybean cultivars of different sensitivities to drought stress. There is a positive correlation between stress-induced proline accumulation and drought tolerance. The capacity of root traits to explore spatial domains with limited water and their ability to dynamically respond to soil-water deficit are also being investigated as indicators for drought stress tolerance. Root traits response to available soil water is a heritable trait and genotypic variation is evident in soybeans. This paper reviews the effects of drought stress and advances in the use of proline accumulation and root traits as selection tools for drought tolerance in soybean.