THE INFLUENCE OF THE INOCULUM ON VARIABILITY IN COMPARATIVE NUTRITIONAL EXPERIMENTS WITH FUNGI

Abstract

This study was designed to determine whether the method of preparing an inoculum could influence the results obtained from comparative nutritional experiments.The quantity of inoculum used to start cultures of Claviceps purpurea clearly affected the rate of growth, and to a lesser extent total growth on mannitol, and growth rate varied directly with increasing inoculum size.The quantity of inoculum used to start cultures also affected the uniformity of growth among replicas. As the amount of inoculum decreased, the variation among replicas increased and this affected the power of the experiment to distinguish between similar mean growth responses. These observations suggested that standardization of the quantity of inoculum might be profitable. It is proposed that the smallest amount of inoculum represented by a coefficient of variation of about 10% be considered an acceptable inoculum. Such an inoculum is large enough that growth among replicas is not too irregular and small enough that nutrients are not unnecessarily added to the experimental medium through the inoculum.The effect of heterokaryosis on uniformity of growth is demonstrated with Isaria cretacea van Beyma.