Seed collection and surface sterilization

The wild, naturally growing halophyte S. glauca were obtained from their natural habitats in yingchengzi coastal saline beach (121.36^° E, 38.99^° N) in Dalian, Liaoning, China. Mature seeds from naturally grown plants that colonized in the same natural environment were harvested (at least 100 mother plants collected on October 25th,2018) and air-dried for 10 days at room temperature.

The dimorphic seedswere separated according to their phenotypic characteristics, and then two types of seeds were placed into 50 ml sterile conical tubes. Each seed sample type was replicated three times. To avoid environmental bacterial contamination, seed surface sterilization was done according to the following procedure: First, the seeds were rinsed with 30 ml sterilized distilled water at least 5 times or until no cloudiness was observed in the wash. Second, the washed seeds were immersed in 1.0% sodium hypochlorite for 2 min. Third, the bleached seeds were rinsed with 30 ml sterile distilled water for 1 min and then immersed in 30 ml 70% ethanol for 1 min. Fourth, the ethanol was removed and seeds were rinsed five times with sterilized distilled water. Finally, the surface-sterilized seeds were air-dried for 12 h in the sterilized 90 mm Petri-dish with double filter paper. To check the effect of surface sterilization, some seeds per treatment were randomly picked and placed on the TSA agar medium (TSA, Qingdao Hope Bio-Technology Co., Ltd., Qingdao, P.R. China). The plates were incubated for 3 days at 25 °C. The sterilized seed samples were put in 50 ml sterile conical tube, frozen in liquid nitrogen and then immediately stored at − 80 °C for later DNA extraction.