the finely ground endosperm in 150 ml distilled water for 2 min. The endosperm was then removed by passing the mixture through several layers of muslin. The standard medium (IPS) use is described by de Barjac (1979). All media were adjusted to pH 7.3 with 1 mol/1 KOH and 50 ml of the medium added to a 250 ml flask and autoclaved.