Chlamydospores and Survival in Soil Fungi

Abstract

MANY of the fungi found in soil are centred around particles of organic debris^1,2, and from these food bases the fungi may spread into the soil matrix to a greater or lesser extent³. It is not known how far the fungi in the soil are dependent upon the undissolved organic matter or to what degree the nutrients in the soil solution support their growth. The work described in this communication forms part of an investigation into this question. The dilute solutions in which the fungi were grown were based on the formula given by Erikson⁴. To this inorganic artificial soil solution dextrose was added to give solutions varying from 0.005 gm./l. to 0.02 gm./l., so that the solutions might simulate a considerable range of true soil solutions. A 0.2-ml. drop of the dilute nutrient solution was placed on the surface of a clean microscope slide resting on a bent glass support in a Petri dish, the base of which contained 5 ml. sterile distilled water. A loopful, containing 20–25 conidia, of a washed spore suspension of the fungus under test was added to the culture drop, and the dishes incubated on the laboratory bench at 17.0–24.4° C. Microscopic observation of the subsequent development was made over a period of fourteen days, after staining with acid fuchsin/lactophenol. Botrytis cinerea Pers., Mycogone perniciosa Magn., Trichoderma viride Pers. ex. Fr., Trichothecium roseum Link., Fusarium oxysporum Schl. var. cubense (E. F. Sm.) Wollenweber and Reinking, and Stemphylium sarcinaeforme (Cav.) Wilts, were the fungi used.