Seed germination and plant management
In 2018, the 300 seeds from GM and wild soybean samples were grouped into three replicates, and three replicates of 100 seeds each and all 54 F1 seeds were then placed individually in a 12-well cell culture plate (Corning Costar, New York, USA) with two layers of filter paper. Finally, 400 μL sterile distilled water was added to each well, and plates were kept in climate chambers (Binder model KBF 720, Tuttlingen, Germany) under 55% RH, 25 ± 2 °C and continuous dark conditions for 21 days. The number of germinated seeds per day was recorded (i.e., radicle protrusion > 5 mm) and was expressed as a percentage of the total number of tested seeds (germination percentage). The germinated seeds were removed immediately once they were counted to prevent any counting errors. Germination experiments of GM soybean, wild soybean, hybrid F2 and hybrid F3 seeds were carried out under the same experimental conditions in 2019 and 2020.
The germinated seeds were each transplanted and grown in a plastic pot (730 mm × 560 mm × 230 mm) filled with mixed soil containing farmland soil and soil composite (25% peat, 25% compost, 25% perlite, 25% vermiculite) at a ratio of 1:1. A bamboo pole (diameter of 1.5 cm and height of 230 cm) was inserted into the pot and carefully fixed to allow for plant climbing. During the plant growing season, weeds were manually removed from cultivation pots, and agricultural agents such as plant growth regulators, insecticides, and fertilizers were not applied.