Submitted to: Mycologia
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/25/2004
Publication Date: 4/1/2005
Citation: Meyer, S.L., Carta, L.K., Rehner, S.A. 2005. Morphological variability and molecular phylogeny of the nematophagous fungus monacrosporium drechsleri. Mycologia 97(2): 405-415. Interpretive Summary: Plant-parasitic nematodes are microscopic worms that cause ten billion dollars in U.S. crop losses annually. One problem facing growers is the lack of inexpensive, naturally occurring organisms that can biologically control nematodes. We have discovered a new nematode-attacking fungus in cultures of nematodes in the greenhouse. In this study, the ability of the fungus to kill different kinds of nematodes was determined. The results indicated that the fungus immobilized each nematode species tested. In addition, DNA sequence studies of this and related fungi were performed to determine the relationships between the new fungus and other fungi. The results are significant because they identify nematodes that can be attacked by the fungus, and because they provide information that helps to better understand the relationships in this group of fungi. A new isolate of a nematode-trapping fungus is now available for research. This research will be used by scientists developing environmentally safe methods for managing diseases caused by nematodes.
Technical Abstract: An isolate of the nematode-trapping fungus Monacrosporium drechsleri was collected from cultures of the root-knot nematode Meloidogyne arenaria that had been maintained on tomato roots in greenhouse pots in Beltsville, Maryland, USA. The plant-parasitic nematodes Heterodera glycines, Meloidogyne incognita, and Pratylenchus zeae, and the free-living nematodes Caenorhabditis elegans and Panagrellus redivivus, were placed on fungal colonies grown in Petri dishes. Within one day, none of the nematodes placed near adhesive knobs were motile. The ITS rDNA and EF1-alpha were sequenced here for M. drechsleri and Monacrosporium parvicolle, and for different populations of Dactylella lysipaga and Monacrosporium ellipsosporum from those in Genbank. Parsimony trees were constructed showing the closest molecular relative of M. drechsleri to be the newly sequenced isolate of M. ellipsosporum; the latter had a highly divergent sequence from a previously studied morphological isolate of M. ellipsosporum. The ITS trees are equivocal regarding the position of M. parvicolle relative to M. drechsleri or to two species of the recently revised genus Gamsylella. Because unique, ever-present and discrete morphological characters are absent in these related taxa, an independent molecular character should be considered essential for their accurate and rapid identification.