Antifungal Activity of Two Xenorhabdus Species and Photorhabdus luminescens, Bacteria Associated with the Nematodes Steinernema Species and Heterorhabditis megidis

Abstract

Antimycotic substances produced by phase one of Xenorhabdus nematophilus (two isolates from Steinernema carpocapsae ), Xenorhabdus bovienii (two isolates from Steinernema feltiae and one isolate from Steinernema intermedia ), and Photorhabdus luminescens (from Heterorhabditis megidis ) and by phase two of Xenorhabdus nematophilus (one isolate) were tested for their spectrum of activity against 32 species of fungi from a range of habitats. The plant pathogenic fungi, Botrytis cinerea , Ceratocystis ulmi , Ceratocystis dryocoetidis , Mucor piriformis , Pythium coloratum , Pythium ultimum , and Trichoderma pseudokingii , were completely inhibited by all phase one variants, whereas the mycorrhizal fungus Suillus pseudobrevipes was not inhibited. Wood decay and food spoilage fungi were partially inhibited by the phase one variant of most of the isolates. The degree of antifungal activity of the cell-free filtrates of the isolates of phase one was not significantly different from each other whereas that of phase two was significantly weaker.