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Fusarium crown rot (FCR) causes significant yield and quality loss of wheat in the Pacific Northwest (PNW) of the United States. The green bridge, defined in the 1980s as a phytopathological phenomenon at a landscape level, refers to any living plant material that can act as an intermediate host for pathogens and pests. Since its definition, the advent of herbicide-resistant wheat and increased in-crop grassy herbicide use merited investigation of the green bridge concept at a smaller scale: within the field. This study examined downy brome ( Bromus tectorum L.), the most prevalent grassy weed in dryland wheat production of the PNW, as a model system to study the role of grassy weeds in FCR occurrence and potential transmission. In crop years (CYs) 2023 and 2024, B. tectorum samples were collected from three counties in northeast Oregon (Umatilla, Morrow, and Sherman), and qRT-PCR was used to quantify the DNA concentration of Fusarium culmorum and F. pseudograminearum. The results indicated the colonization of both FCR pathogens on living B. tectorum for all site-years. The DNA concentration of F. culmorum was higher in Sherman and Umatilla counties compared with Morrow County in CY 2024 only, whereas the DNA concentration of F. pseudograminearum was similar among the study sites in both CYs. This preliminary study highlights B. tectorum as a host to FCR pathogens with potential transmission to wheat and provides a foundation for further research to improve FCR control through weed management and weigh disease risk potential when utilizing grassy herbicides. Formula: see text Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
Mahato et al. (Tue,) studied this question.