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ARS Home » Northeast Area » Geneva, New York » Plant Genetic Resources Unit (PGRU) » Research » Publications at this Location » Publication #427232
Research Project: Conservation, Characterization, Evaluation, and Utilization of Hemp Genetic Resources and Associated Descriptive Information

Location: Plant Genetic Resources Unit (PGRU)

Title: Screening diverse Cannabis sativa germplasm for resistance to Golovinomyces ambrosiae

Author
item VIGNALE, LUCIA - Cornell University
item SCHWARTZ, JOCELYN - Cornell University
item Stansell, Zachary
item Gordon, Tyler
item SMART, LAWRENCE - Cornell University
item SMART, CHRISTINE - Cornell University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/2025
Publication Date: 11/29/2025
Citation: Vignale, L., Schwartz, J.A., Stansell, Z.J., Gordon, T.C., Smart, L.B., Smart, C.D. 2025. Screening diverse cannabis sativa accessions for susceptibility to golovinomyces ambrosiae. Plant Disease. 0:1-26. https://doi.org/10.1094/PDIS-07-25-1591-RE.
DOI: https://doi.org/10.1094/PDIS-07-25-1591-RE

Interpretive Summary: Powdery mildew is a common disease of hemp and can cause significant quality losses. Using resistant cultivars is one of the only effective powdery mildew management strategies available to hemp producers. In this study, diverse hemp accessions from the USDA hemp repository were evaluated in the field over two years to identify new sources of resistance to powdery mildew. Ten accessions were identified with resistance to powdery mildew in both years. Resistant accessions will be valuable to hemp breeders and farmers and can facilitate the development of improved cultivars and identification of molecular markers linked with resistance loci.

Technical Abstract: Powdery mildew is one of the most common diseases affecting indoor hemp (Cannabis sativa L. <0.3% tetrahydrocannabinol) cultivation. It is mostly caused by the biotrophic fungus Golovinomyces ambrosiae, whose polycyclic nature and short latent phase allow it to rapidly cause disease and spread to other plants. Control strategies that rely on the use of fungicides are limited by the low number of chemistries that are registered for use on hemp, thus the breeding of resistant cultivars is critical. Two resistance genes and one susceptibility gene involved in powdery mildew resistance have been described for C. sativa. In the present work, we evaluated the susceptibility to G. ambrosiae of 81 C. sativa entries in one year and 105 in a second year, most of which were accessions in the United States Department of Agriculture – Agricultural Research Service germplasm repository or commercial cultivars. Accessions represented different geographic origins, levels of improvement, and market classes. The trials were inoculated with an isolate of G. ambrosiae that was previously described, and disease severity was rated multiple times on a weekly basis. A wide range of disease severity was observed among and within accessions. There were several accessions and some commercial cultivars that displayed no or very low levels of disease, suggesting that they have genetic resistance to powdery mildew. This screening provides a foundation for further characterization of the mechanisms of powdery mildew resistance in hemp.