Plant pathogenic fungi are harbored as endophytes in Rhododendron spp. native to the Eastern U.S.A.

Abstract

Invasive plant pathogens cause a substantial loss of yearly revenue and often lead to environmental change. The movement of plants is considered to be the main avenue for introduction of invasive plant pathogens. Government agencies attempt to reduce the risk of introductions by legislation and inspections. However, inspectors may not consider that plant pathogens can infect plants as endophytes that are not considered hosts without showing symptoms. This study surveyed endophytes in rhododendron (Rhododendron maximum and Rhododendron catawbiense) plants in four native stands in the Eastern U.S.A. We isolated associated endophytes from the plant leaves and identified them using a molecular sequencing method. Fifteen (21%) of the identified samples matched with a known plant pathogen not reported to be pathogenic on rhododendron. We demonstrated pathogenicity of selected rhododendron endophytes on red oak, flowering dogwood and lupine. 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 invasive species. • Over 600 fungal endophyte isolates were collected from 2 Rhododendron spp. • 210 samples were analyzed by sequencing; 70 matched to sequences in GenBank. • 21% matched with a fungal pathogen not reported on rhododendron. • We demonstrated that plant pathogens could harbor as endophytes in non-hosts.