Comparison of culture methods for production ofColletotrichum truncatumspores for use as a mycoherbicide

Abstract

Four culture systems were compared: (1) dialysis membranes (MF), (2) liquid shake flasks (LF), (3) solid particles with humidity control (SFC), and (4) solid particles without humidity control (SFE). A Plackett-Burman fractional factorial experimental design was employed with 10 total variables. Eight media components, plus two levels of inoculum, were tested in all systems. Other variables were light vs. dark for MF, agitation level for LF, vermiculite vs. rice hulls for SFC, and particle size for SFE. High yeast extract (1 g/l) produced more (P < 0.01) spores than low (0.3 g/l) for all culture systems. Carbohydrate (sucrose) at 20 g/l produced more spores than at 40 g/l for SFC. MgSO4·7H2O at 2 g/l was better than none for LF and SFC. For MF, LF, SFC, and SFE, respectively, the overall average numbers of spores per ml of medium were 0.53, 0.72, 0.28, and 0.073×107, while the highest numbers of spores were 1.25, 2.75, 1.52, and 0.46×107. Thus, the method of production cannot be decided at this stage but must await further studies of recovery and storage.