Morphological and molecular characterization of sclerotinia sclerotiorum on sugar beet in Montana, USA

Authors: BHUIYAN, ZIAUR - North Dakota State University; Lakshman, Dilip; MOSHER, PRESLEY - North Dakota State University; KHAN, MOHAMED - North Dakota State University; CYMBALUK, TIMOTHY - Sidney Sugars Incorporated; PETERS, DUANE - Sidney Sugars Incorporated

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2021
Publication Date: 11/29/2021
Citation: Bhuiyan, Z.M., Lakshman, D.K., Mosher, P., Khan, M.F., Cymbaluk, T., Peters, D. 2021. Morphological and molecular characterization of sclerotinia sclerotiorum on sugar beet in Montana, USA. Plant Health Progress. https://doi.org/10.1094/PHP-11-21-0137-BR.
DOI: https://doi.org/10.1094/PHP-11-21-0137-BR

Interpretive Summary: Sugar beet (Beta vulgaris L.) is the leading sugar yielding crop next to sugarcane, and accounts for 25 % of the world’s sugar. The US ranked third in world sugar beet production where 55% of the domestic production of about 8.4 million metric tons of sugar derives from sugar beet. During a field survey in September 2020, a new foliar blight of sugar beet was detected. The pathogen was isolated and subsequent morphological tests and nucleic acid sequence analysis of the Internal Transcribed Spacer region (ITS) identified it as Sclerotinia sclerotiorum. This is the first report on the occurrence of the sugar beet foliar blight caused by S. sclerotiorum in Montana. Our findings have significant implications for improved sugar beet disease management in the state. The information generated in this manuscript will be useful for mycologists, plant pathologists and agricultural extension workers.

Technical Abstract: Sugar beet (Beta vulgaris L.) is the leading sugar yielding crop next to sugarcane, and accounts for 25 % of the world’s sugar. The US ranked third in world sugar beet production where 55% of the domestic production of about 8.4 million metric tons of sugar derives from sugar beet. During a field survey in September 2020, a new foliar blight of sugar beet was detected in the state of Montana, USA. The pathogen was isolated and upon subsequent morphological tests it was identified as Sclerotinia sclerotiorum (Lib.) de Bary. For molecular analysis, the genomic DNA of the fungus was purified, PCR amplification of the Internal Transcribed Spacer region (ITS) was conducted with ITS1 (5'-TCCGTAGGTGAACCTGCGG-3') and ITS4 (5'-TCCTCCGCTTAT TGATATGC-3') primers, and the PCR product was sequenced. Nucleic acid BLAST analysis of the ITS showed 100% homology with the reported ITS sequences of S. sclerotiorum (GenBank accessions MK074848, MK896659, MH298771, and MG516605), thus confirming the identity of the pathogen. A Koch postulate was performed with the pure culture of the fungal isolate on healthy beet seedlings (cultivar Hilleshog proprietary material) in the greenhouse. The infection reproduced the typical foliage blight symptoms detected under field condition and the re-isolated fungus was identical in morphology to the parent fungus, thus confirming the pathogenicity of the fungus. To the best of our knowledge, this the first report on the occurrence of leaf blight of sugar beet caused by S. sclerotiorum in Montana, USA. Our research findings have a bearing on improving disease management practices in the state of Montana. We recommend the adoption of crop rotation with non-host crops and integrated biological and chemical methods for better management of the disease.