Exudation from 14C-labeled fungal propagules in the presence of specific microorganisms

Abstract

Exudation from 14C-labeled conidia of Cochliobolus victoriae and sclerotia of Macrophomina phaseolina was greater in the presence of cells of five bacterial species or propagules of four fungal species in phosphate buffer or in sterilized soil than in buffer without other microorganisms. In most instances, the increased exudation was statistically significant at P = 0.05. High population densities of bacterial cells or fungal propagules induced greater exudation than lower densities. 14C exudation from C. victoriae conidia in the presence of specific microorganisms was 1.5–9.9% of total label in buffer and 1.0–3.8% on soil; exudation from M. phaseolina sclerotia was 1.4–3.2% of total label in buffer and 1.3–3.2% on soil. All microorganisms tested, except Actinoplanes utahensis and M. phaseolina, suppressed germination of conidia of C. victoriae and sclerotia of M. phaseolina in vitro. Exudation of 14C-labeled compounds was inversely correlated with germination of C. victoriae conidia (r = −0.72) and M. phaseolina sclerotia (r = −0.74). The results indicate that specific microorganisms can enhance exudation from fungal propagules and that the enhanced exudation may be related to the imposition of mycostasis.