Physiological and molecular responses to drought and salinity in soybean

Drought and salinity are severe environmental stresses and limit soybean growth. In this study, a comparative analysis of physiological and molecular responses of two soybean (Glycine max L.) genotypes to these stresses was carried out. Plants of drought-tolerant genotype RD (cv. FD92) and sensitive genotype SD (cv. Z1303) were exposed to 15 % (m/v) PEG 6000, which simulated drought stress, or 150 mM NaCl. The RD plants maintained larger leaf area and higher net photosynthetic rate, chlorophyll content, stomatal conductance, and relative water content compared with the SD plants. Leaf proline content increased under both stresses more in RD than in SD. The drought tolerance of RD plants was also correlated with greater antioxidant activity and lower content of hydrogen peroxide and malondialdehyde under stress conditions. Amounts of abscisic acid, jasmonic acid, and salicylic acid under stress increased to a greater extent in RD than in SD plants. At the molecular level, the effects of 20-d stress treatments were manifested by relatively higher expression of drought- or salt-related genes: GmP5CS, GmDREB1a, GmGOLS, GmBADH, and GmNCED1 in RD plants than in SD plants. These results form the basis for understanding the mechanisms of the drought- and salt-stress tolerance in soybean.