Thermal Image Analysis May Help Screen Salt Stress Tolerant Soybean (Glycine max)

Non-destructive high throughput phenotpying based on phenomics is an emerging technology for screening and breeding. In this study, we provided the successful case of using phenomics to screen salt stress response in soybean. To investigate the physiological response of soybean (Glycine max) to salt stress, two-week-old seedlings of soybean in V2 stage were treated with 0, 12.5, 25, 50, and 100 mM NaCl for salt stress. Three physiological parameters, photosynthesis rate, stomatal conductance and chlorophyll fluorescence, decreased significantly, while another parameter like soybean leaf temperature increased by positive correlation with NaCl concentration (P<0.01). Soybean leaf temperature was significantly different at 50 mM NaCl, although no visual symptom was observed. We selected leaf temperature as a major physiological parameter for salt stress, because its measurement is much easier, faster, and cheaper than that of other physiological parameters. Therefore, soybean leaf temperature can be used for evaluating the response to salt stress in soybean as a non-destructive and phenomic parameter. In this study, we evaluated non-destructive diagnosis in salt stress, using chlorophyll fluorescence, PI, and leaf temperature as parameters, which would contribute to the future breeding program for salt stress tolerance in soybean cultivars.