Update:
Three transgenic lines (S17-Gm17, S17-Gm3, and S17-Gm9) along with their wild type (Thorne) were tested under water stress and normal growing conditions. In preliminary drought studies in the greenhouse, these transgenic lines showed significantly higher seed-set and seed-weight than the wild-type control. The experiment was laid out in a randomized complete block design with four replicates. Blocking was done against the source of ventilation fitted on the greenhouse walls.
Both sets of treatments (control and stress) were grown in similar water availability and other management practices till plants begin pod development (R3). After R3, irrigation was cut in half for stress the treatment set while the control set was watered to saturation every 3rd day checking the moisture content of the tubes. Whenever the control is watered the stress treatment received half the amount of water given to the control set. Plants were harvested at maturity and data were collected on total biomass yield, number of pods per plant, number of seeds per plant, and seed yield per plant.
The stress treatment effect caused highly significant reductions in all traits across all genotypes (Table 1). Average reductions of 35% in biomass yield, 30% in number of pods per plant, and 31% in number of seeds per plant were observed while seed yield showed the highest reduction of 43%. Preliminary data indicated overexpression of the Arabidopsis glutaredoxin gene (AtGRXS17) in soybean resulted in higher seed number and seed weight under drought conditions. In this study, one of the transgenic lines, S17-Gm17, showed significantly higher (p < 0.05) seed number per plant than the wild-type Thorne in both growing conditions. However, the four genotypes did not show significant differences in biomass, number of pods, and seed yield in either the stress (drought), or control growing conditions.
Table 1. Mean performance of four soybean genotypes under drought stress and normal growing conditions in the greenhouse.
Genotype Treatment Biomass No. of pods/plant No. of seeds/plant Seed yield
g/plant g/plant
S17-Gm17 Control 25.3 30.0 64.2 10.2
S17-Gm3 Control 23.7 26.0 59.8 9.7
S17-Gm9 Control 25.8 32.3 52.3 9.9
Thorne (wt) Control 23.2 26.5 61.0 9.6
S17-Gm17 Stress 17.6 20.0 43.5 5.1
S17-Gm3 Stress 16.1 21.0 42.8 6.0
S17-Gm9 Stress 15.1 20.8 38.5 5.7
Thorne (wt) Stress 14.7 18.0 38.8 5.6
Three transgenic lines (S17-Gm17, S17-Gm3, and S17-Gm9) along with their wild type (Thorne) were tested under water stress and normal growing conditions. In preliminary drought studies in the greenhouse, these transgenic lines showed significantly higher seed-set and seed-weight than the wild-type control. The experiment was laid out in a randomized complete block design with four replicates. Blocking was done against the source of ventilation fitted on the greenhouse walls.
Both sets of treatments (control and stress) were grown in similar water availability and other management practices till plants begin pod development (R3). After R3, irrigation was cut in half for the stress treatment set while the control set was watered to saturation every 3rd day checking the moisture content of the tubes. Whenever the control is watered the stress treatment received half the amount of water given to the control set. Plants were harvested at maturity and data were collected on total biomass yield, number of pods per plant, number of seeds per plant, and seed yield per plant.
The stress treatment effect caused highly significant reductions in all traits across all genotypes (Table 1). Average reductions of 35% in biomass yield, 30% in number of pods per plant, and 31% in number of seeds per plant were observed while seed yield showed the highest reduction of 43%. Preliminary data indicated overexpression of the Arabidopsis glutaredoxin gene (AtGRXS17) in soybean resulted in higher seed number and seed weight under drought conditions. In this study, one of the transgenic lines, S17-Gm17, showed significantly higher (p < 0.05) seed number per plant than the wild-type Thorne in both growing conditions. However, the four genotypes did not show significant differences in biomass, number of pods, and seed yield in either the stress (drought), or control growing conditions.
Table 1. Mean performance of four soybean genotypes under drought stress and normal growing conditions in the greenhouse.
Genotype Treatment Biomass No. of pods/plant No. of seeds/plant Seed yield
g/plant g/plant
S17-Gm17 Control 25.3 30.0 64.2 10.2
S17-Gm3 Control 23.7 26.0 59.8 9.7
S17-Gm9 Control 25.8 32.3 52.3 9.9
Thorne (wt) Control 23.2 26.5 61.0 9.6
S17-Gm17 Stress 17.6 20.0 43.5 5.1
S17-Gm3 Stress 16.1 21.0 42.8 6.0
S17-Gm9 Stress 15.1 20.8 38.5 5.7
Thorne (wt) Stress 14.7 18.0 38.8 5.6