DNA was extracted from 30 to 50 mg freeze-dried leaf material in extraction tubes arranged in the 96-well format (Matrix Technologies, Wehrheim, Germany). Leaves were ground to a fine powder by rapidly shaking the tubes with two 3.5-mm tungsten beads added to each sample. Total genomic DNA was extracted using the DNeasy plant mini kit (QIAGEN, Hilden, Germany) according to the supplier's instructions. DNA quality and quantity were evaluated under UV illumination after ethidium bromide staining on 1% agarose gels.