After co-culture was over, the explants were directly transferred to the selection medium MSB2 (MSB1+Cef500mg/L+Km100mg/L) for three weeks.

• 共培养完成后，将外植体直接转入筛选培养基MSB_2(MSB_1+500mg/L Cef+100mg/L Km)中进行分化培养，每3周继代一次。