Mature root
The roots were washed three times with sterile deionized water, blotted dry, and 85 mg of root tissue was placed in a 2 mL microcentrifuge tube with a metal bead. The microcentrifuge tubes were placed in liquid nitrogen, then put in a TissueLyzer II machine (Qiagen, MD, USA) for two minutes at a frequency of 30 1s-1 or until a fine powder was formed in the tube. DNA was extracted using DNeasy Plant Mini Kit (Qiagen, MD, USA).