P-192 - Bipolaris zeicola causes leaf spot on cultivated Northern Wild Rice (Zizania palustris L.) in Minnesota, USA

Tuesday, August 5, 2025

9:30 AM - 10:15 AM HST

Location: Exhibit Hall 3

Presenting Author(s)

CC

Claudia V. Castell-Miller

Department of Plant Pathology, University of Minnesota, St. Paul, MN 55108, USA
Saint Paul, Minnesota, United States

Author(s)

DS

Deborah Samac

United States Department of Agriculture-Agricultural Research Service, Plant Science Research Unit, St. Paul, MN 55108, USA
Saint Paul, Minnesota, United States
JK

Jennifer Kimball

Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN 55108, USA
Saint Paul, Minnesota, United States

Abstract Text: Minnesota is one of the largest producers of Northern Wild Rice (NWR), surpassing 4,600 metric tons per year and thus, contributing to a stable supply of this gourmet grain to domestic and international consumers. However, a complex of fungal diseases occurs annually in commercial fields that can cause significant grain losses if left uncontrolled. Annual surveys are done to monitor the occurrence of new species and fluctuation of the known pathogen populations (e.g., Bipolaris spp.). In 2022, leaves with dark-round to oval spots were collected in two fields near Waskish (48° 09' 41" N, -94° 30' 45" W) and Gully (47° 46' 06" N, -95° 37' 29" W), Minnesota. Morphological and molecular identification of the causal agent indicated that it was Bipolaris zeicola, a pathogen that also causes diseases in white rice (Oryza sativa L.) and corn (Zea mays L.). Pathogenicity tests on NWR leaves, demonstrated that the fungus caused brown round to oblong spots of about 1 to 2 mm after 3 days post inoculation that enlarged to 5 to 9 mm, and with some larger lesions on the edges in a few leaves. Some spots had a tan center with a dark border. Tissue discoloration around the lesions was often observed. The pathogen was re-isolated and identified as B. zeicola, completing Koch’s postulates. Because several Bipolaris spp. cause similar lesions on NWR plants early in the season, precise identification of each species is imperative for implementing an efficient control within the NWR integrated disease management system.