Low dose of gamma irradiation enhanced drought tolerance in soybean

Abstract

Drought stress is the main limiting factor in soybean production. However, no work has been done on how the application of a low dose of gamma rays could help to overcome water deficits during critical stages of soybean development. Gamma rays at a dose of 20 Gray (Gy) were applied to dry seeds of soybean before planting. Two levels of soil moisture (80% field capacity for well-watered control and 35% for drought-stressed treatment) were applied at pod initiation. Gamma irradiation increased biomass accumulation and seed yield in both treatments. It also increased the chlorophyll content, photosynthetic activity (14CO2fixation) and leaf water potential and enhanced the enzyme activities of RuBPCase and PEPCase of control plants compared with drought-stressed plants. Gamma irradiation (20 Gy) increased the soluble sugars, protein and proline content and the activities of peroxidase and superoxide dismutase in drought-stressed soybean leaves. It also increased the chloroplast size, which was reduced by drought treatment, and rebuilt, to some extent, the chloroplast ultrastructure. However, it decreased the malondialdehyde concentration and the electrical conductivity of the leaves under drought stress. Overall, the results indicated that pre-treatment with gamma rays (20 Gy) to dry seeds of soybean before planting could be used to enhance drought tolerance and minimize the yield loss caused by water deficit.