The method
involved soaking seeds in 5% sodium hypochlorite for 10
min, washing with tap water, and placing in a petri dish having
two layers of filter paper pad for germination in incubator under
the constant temperature of 28 C. When the radicle was 5 mm
long, the seeds were sown individually into plastic pots filled
with steam-sterilized propagation substrates. Propagation substrate
was composed of peat, vermiculite, and soil from
vegetable fields (2:1:1, volume basis) and was steam sterilized
at 134 C for 30 min. Seedlings were placed in a growth chamber
held at 25/20 C day/night with a 16-h photoperiod. Illumination
was provided by high-pressure sodium lamps at 50 Wm–2.