Moisture deficit at any stage of plant development can reduce soybean seed yield. However, the magnitude differs with plant growth stage, planting date, maturity group and duration of drought. This study, with the purpose of evaluation of response of commercial soybean varieties of different maturity groups (III, IV, and V) to water stress condition at the late reproductive stage, was conducted under water stress and non-stress conditions, using group balanced block design with 4 replications. Significant differences were found for most traits except for plant height, number of pods/plant, 100-seed weight and number of seeds/plant among maturity groups as well as among varieties within maturity groups. With respect to seed yield, significant differences were observed only among maturity groups under water stress conditions. Traits affected most by water stress were seed yield, 100-seed weight, number of pods/plant and duration of seed filling period. Since stress intensity for maturity groups of III and IV was high, (SI = 0.62), and for maturity group V low, (SI=0.28), therefore, the subsequent analyses on maturity groups III and IV were done together and separate from maturity group V. Under non-water stress condition, both harvest index and number of pods/plant for maturity groups III and IV as well as duration of seed filling period and harvest index for maturity group V were recognized as the effective traits associated with the soybean seed yield. Under water stress condition, for all maturity groups, harvest index and number of pods/plant were recognized as the most effective traits affecting seed yield.
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