A Nylon Fabric Technique for Studying the Ecology ofPythium aphanidermatumand Other Fungi in Soil

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Abstract
A nylon fabric was used to support and recover propagules of P. aphanidermatum after burial in clay loam and sandy loam soils. Oospores were trapped in the fabric mesh, buried in soil, incubated, retrieved and examined microscopically. Destruction of the oospores was estimated from percentages that apparently were disintegrating and their viability was determined by dislodging them from the fabric and plating them on a medium selective for Pythium. Fungistasis of soil to oospores could be assessed by burying nylon-mounted oospores in asparagine-amended soil and nonamended soil and comparing germination. Lysis of mycelia of P. aphanidermatum and production of sporangia from mycelia buried in soil were determined by assessing the number of mycelial strands and digitate sporangia present in unit areas of fabric. The nylon fabric also allowed convenient examination of fungal structures by scanning electron microscopy. Other structures examined by the nylon fabric method were zoospores of P. aphanidermatum; oospores of P. ultimum, P. myriotylum and Aphanomyces euteiches; mycelia of Rhizoctonia solani; sclerotia of Sclerotinia minor; microconidia of Fusarium oxysporum; and microsclerotia and conidia of Verticillium dahliae.