Production of hydrogen cyanide (HCN)
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 ± 2 °C for 24 h. Inoculum intensity was adjusted to an OD600 of 0.10, and 3 μl was transferred onto YPD agar, amended with 4.4 g l−1 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 1–7 d incubation at 28 ± 2 °C, any colour change of the filter paper was noted and the HCN production potential of the antagonists was assessed.