Identification and characterization of Pythium deliense causing sugar beet (Beta vulgaris) root rot in Grand Forks, North Dakota.

Authors: BHUIYAN, ZIAUR - North Dakota State University; Lakshman, Dilip; LUIS, DEL RÍO MENDOZA - North Dakota State University; Ismaiel, Ed - Ed; KHAN, MOHAMED - North Dakota State University

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2023
Publication Date: 4/5/2024
Citation: Khan, M., Bhuiyan, Z., Lakshman, D.K., Luis, D., Azizi, A. 2024. First report of Pythium deliense Meurs causing sugar beet (Beta vulgaris L.) root rot in North Dakota, USA. Plant Health Progress. https://doi.org/10.1094/PHP-06-23-0058-RS.
DOI: https://doi.org/10.1094/PHP-06-23-0058-RS

Interpretive Summary: 08North Dakota (ND) is a major sugar beet-growing state in the USA. During a field disease survey, in Grand Forks, ND, sugar beet plants with wilted pale green leaves and tap roots with dark brown to black color and with irregular necrotic lesions were observed. A fungus-like entity was consistently isolated from diseased roots and morphologically as well as molecularly identified as Pythium delicense. Upon reinoculation on healthy sugar beet seedlings in the greenhouse, the pathogenicity of P. deliense was confirmed. To our knowledge, this is the first report of P. deliense as the causal agent of sugar beet root rot in Grand Forks, North Dakota, USA. The findings will be helpful to farmers, plant pathologists, and extension agents in formulating appropriate disease management strategies.

Technical Abstract: Sugar beet (Beta vulgaris L.) is a leading sugar-yielding crop, which accounts for 20 % of the world’s sugar and the US ranks third in world sugar beet production. Damping off disease caused by multiple species of soilborne pathogens causes severe economic losses to sugar beet production. Thus, identifying the causal agent is important to formulating effective disease management. During a July 2021disease survey in a sugar beet field at Grand Forks (47.92520 N and -97.03280 W), North Dakota, we observed that approximately 15% of plants located in low areas of a commercial field showed wilting leaves that were pale green and slightly blight in color and the roots were dark brown to black along with irregular necrotic lesions. The isolated pathogen had the characteristic morphology of Pythium deliense Meurs. The sequence homology comparisons of the Internal transcribed spacer (ITS) region and the cytochrome c oxidase subunit 1 mitochondrial (cox1) gene with corresponding sequences in the NCBI database confirmed its P. deliense identity. Moreover, the ITS-based phylogeny confirmed its identity as P. deliense, and its close relationship with P. aphanidermatum. A disease screening trial with four cultivars Maribo® MA504, SV®-572, Crystal® 101RR, and Marathon® established that Crystal® 101RR had the lowest disease incidence among the four varieties. Growers and breeders could benefit from information about the differential responses of sugar beet varieties to the pathogen to formulate effective disease management practices.