Screening Soybeans for Drought Resistance. I. Growth Chamber Procedure1

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Abstract
The effects of soil moisture stress on root (RWP) and shoot (SWP) water potential, leaf lamina surface area (LSA) and dry weight (LDW), and photosynthesis (PIA) were studied in 21 to 22‐day‐old potted soybean (Glycine max (L.) Merr.) seedlings. Twenty cultivars were studied in an effort to detect differential response patterns to soil moisture stress. Analysis of the pooled data revealed a significant decline for all variables measured with increasing soil moisture stress. However, significant cultivar ✕ soil moisture treatment interaction exists for all variables measured, indicating variation in cultivar response patterns to decreasing soil moisture. Cultivars were classified as drought resistant, intermediate or susceptible for each variable based on individual performance relative to average seedling response to soil moisture stress. An overall estimate of drought performance was made for each cultivar. The results suggest that soybean seedlings differ in drought response. However, cultivars were not consistently classified by the several variables measured. This suggests that assessment of cultivar drought response should be based on observations of a combination of characteristics. Comparison of the results of this procedure to those of an independent field study suggest the desirability of further testing of the material in the field.