Nematophagous Pleurotus species consume some nematode species but are themselves consumed by others

Authors: MARLIN, MARIA - University Of Idaho; WOLF, AVERY - University Of Idaho; Carta, Lynn; NEWCOMBE, GEORGE - University Of Idaho; ALOMRAN, MARYAM - University Of Idaho

Submitted to: Forests
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2019
Publication Date: 5/10/2019
Citation: Marlin, M., Wolf, A., Carta, L.K., Newcombe, G., Alomran, M. 2019. Nematophagous Pleurotus species consume some nematode species but are themselves consumed by others. Forests. 10(5):404. https://doi.org/10.3390/f10050404.
DOI: https://doi.org/10.3390/f10050404

Interpretive Summary: Nematodes are often microscopic roundworms that include beneficial species in soil and parasites of plants and animals. The parasites cause billions of dollars of damage to crops and livestock in the U. S. each year. Farmers have a serious problem controlling them, as the traditionally used chemicals used against plant parasites are highly toxic or restricted in use, and resistance to drugs to protect humans and animals is developing in animal parasitic nematodes. Biocontrol agents of nematodes may provide alternative controls with more complex mechanisms that are harder for nematodes to resist. One problem with the development of biological control agents such as bacteria and fungi against parasitic nematodes is their variable effectiveness depending on nematode species. This unpredictability may be partly due to different modes of action that can begin to be revealed by identifying susceptible and resistant nematodes. Therefore an ARS scientist provided a range of easily cultivated soil nematodes from four families that are related to parasites to ecologists at the University of Idaho to see which ones were killed and which ones survived eating a mushroom that previously paralyzed and then killed some parasitic nematodes. Of thirteen species nine were susceptible and four were resistant from three different nematode families. The results are significant because they demonstrate that resistance already exists in many nematodes and provide certain key nematodes for further study of the underlying genes that control it. The results will be used by ecologists and agricultural researchers to predict outcomes and produce tools to better manage crops and forests.

Technical Abstract: Pleurotus species are said to be nematophagous because they paralyze and consume some bacterial-feeding nematodes. It has never been clear whether that means all nematodes. Here we tested thirteen bacterial-feeding nematode species: seven of family Rhabditidae, three of Cephalobidae (one with three populations), two of Panagrolaimidae, and one of Diplogastridae. Nematodes interacted on water agar with toxin-producing isolates of Pleurotus pulmonarius (Fr.) Quél. and Pleurotus ostreatus (Jacq.) P. Kumm. Of the thirteen species, nine were susceptible to P. pulmonarius (all individuals were paralyzed) but four (four populations of two cephalobid species, one rhabditid, and one panagrolaimid) survived exposure to P. pulmonarius. The resistant four species not only survived but multiplied their numbers by consuming P. pulmonarius. A similar trend was observed with nematodes interacting with P. ostreatus; however, six species were resistant to P. ostreatus. Interestingly, four of these six species were susceptible to P. pulmonarius, and interactions overall were differential. Pleurotus species are nematophagous toward some nematodes but are also consumed by others in three of the four families assayed. Species-specific interactions point to the need for studies of the host ranges of both “nematophagous” fungi and “fungivorous” nematodes, especially if they are to be used for biological control.