Plant pathogenic fungi harbor as endophytes in Rhododendron spp. native to the Eastern U.S.

Authors: Widmer, Timothy; McMahon, Michael - Mike; Luster, Douglas - Doug

Submitted to: Fungal Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2020
Publication Date: 5/20/2020
Citation: Widmer, T.L., Mcmahon, M.B., Luster, D.G. 2020. Plant pathogenic fungi harbor as endophytes in Rhododendron spp. native to the Eastern U.S.. Fungal Ecology. Fungal Ecology 47:100949. https://doi.org/10.1016/j.funeco.2020.100949.
DOI: https://doi.org/10.1016/j.funeco.2020.100949

Interpretive Summary: Invasive plant pathogens cause a substantial loss of yearly revenue and in environmental changes. The movement of plants is considered to be the main avenue for introduction of invasive plant pathogens. Regulatory agencies try and reduce the risk of introductions by legislation and inspections. However, limited personnel and high volumes of imported plants make this job difficult. In addition, inspectors are normally focused on known plant pathogen-host associations and do not consider that known plant pathogens can infect plants that are not considered hosts without showing any symptoms. This study surveyed Rhododendron plants in native stands in the Eastern U.S. and cultured microbes from the native plants. Approximately 22% of the identified fungal microbes cultured from rhododendron plants are known plant pathogens of other plants. Two of the fungi were tested to see whether they caused disease on their hosts, oak and lupine. Both fungi were demonstrated to be pathogenic, demonstrating that plant pathogens living within non-host plants could escape detection and be transported to new locations where their host is present, posing a risk to the host and the environment. This study is important because it highlights that present detection methods and techniques may not be adequate to detect the potential importation and spread of new invasive species.

Technical Abstract: Invasive plant pathogens cause a substantial loss of yearly revenue and in environmental changes. The movement of plants is considered to be the main avenue for introduction of invasive plant pathogens. Government agencies try and reduce the risk of introductions by legislation and inspections. However, limited personnel and limited detection methods make this job difficult. In addition, inspectors are normally focused on known plant pathogen-host associations and do not consider that known plant pathogens can infect plants as endophytes that are not considered hosts without showing any symptoms. This study surveyed Rhododendron maximum and R. catawbiense plants in native stands in the Eastern U.S. and isolated associated endophytes. Approximately 22% of the identified endophytes are known plant pathogens on hosts that are not rhododendrons. Two isolates, identified as Biscogniauxia atropunctata and Colletotrichum lupini were tested for their pathogenicity on their respective hosts, oak and lupine. Both isolates were demonstrated to be pathogenic proving that plant pathogens living as endophytes can be moved around threatening new locations if their host is present. This study is important because it highlights that present detection methods and techniques are not adequate to detect the potential importation and spread of new invasive species.