HCN production was detected by the modified method of
Bakker & Schippers (1987). Yeast inoculum was prepared by
cultivation in 5 ml YPD broth, and tube cultures were incubated on a reciprocal shaker at 180 strokes/min at 28 Æ 2 C
for 24 h. Inoculum intensity was adjusted to an OD600 of
0.10, and 3 ml was transferred onto YPD agar, amended with
4.4 g lÀ1 glycine by streaking. A disk of Whatman filter paper
No. 1 was dipped into 0.5 % picric acid, and 2 % Na2CO3 was
placed on the lid of the Petri plates. The plates were sealed
with parafilm. After 1e7 d incubation at 28 Æ 2 C, any colour
change of the filter paper was noted and the HCN production
potential of the antagonists was assessed.