Application of the Plackett-Burman experimental design to evaluate nutritional requirements for the production of Colletotrichum coccodes spores

Colletotrichum coccodes is being examined as a biological weed control agent for velvetleaf (Abutilon theophrasti). A modified Richard's solution containing V-8 juice has been used to produce C. coccodes spores for growth-chamber and field experiments. Although C. coccodes sporulates well in this medium, V-8 is not available as a bulk commodity and is too expensive for commercial production. Eight substrates were evaluated as replacements for V-8 juice in modified Richard's solution. Soy protein and casamino acids were equal to V-8 juice for sporulation of C. coccodes. The Plackett-Burman experimental design was used to test the relative importance of various components of a complex medium based on soy protein on mycelium biomass production and sporulation of C. coccodes. A new medium composed of sucrose (20 g/l), soy protein (5 g/l), KNO₃ (5 g/l), KH₂PO₄ (5 g/l), MgSO₄ (2 g/l), CaCl₂ (0.5 g/l), and CuSO₄ (0.05 g/l) was selected as the base medium for further study in the development of a low-cost and effective medium for C. coccodes spore production. Received: 29 July 1996 / Received revision: 21 October 1996 / Accepted: 10 November 1996