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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #345475
Title: First report of alfalfa (Medicago sativa L.) seed rot, seedling root rot, and damping off caused by Pythium spp. in Sudanese soil

Author
item AO, SAMADANGLA - University Of Minnesota
item Bucciarelli, Bruna
item Dornbusch, Melinda - Mindy
item Miller, Susan
item Samac, Deborah - Debby

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2017
Publication Date: 5/1/2018
Citation: Ao, S., Bucciarelli, B., Dornbusch, M.R., Miller, S.S., Samac, D.A. 2018. First report of alfalfa (Medicago sativa L.) seed rot, seedling root rot, and damping off caused by Pythium spp. in Sudanese soil. Plant Disease. 102(5):1043. https://doi.org/10.1094/PDIS-09-17-1411-PDN.
DOI: https://doi.org/10.1094/PDIS-09-17-1411-PDN

Interpretive Summary: Alfalfa is an important forage crop in Sudan but has relatively low biomass yields. In September 2016 soil samples were collected from three commercial alfalfa production fields near Khartoum, Sudan with poor seedling establishment and rapid stand decline. Soil samples from each field were evaluated for soil-borne pathogens. The majority of the pathogens identified were species of Pythium and were found to be highly pathogenic on alfalfa seedlings causing seed rot, root rot, and seedling death. These results indicate that the major cause of poor seedling establishment in these fields was due to infection by these pathogens. Based on this information producers can modify crop management methods and use appropriate seed treatments for reducing damage from these pathogens.

Technical Abstract: Alfalfa is an important forage crop in Sudan but has relatively low biomass yields. In September 2016 soil samples were collected from three commercial alfalfa production fields near Khartoum, Sudan with poor seedling establishment and rapid stand decline. Soil samples from each field were evaluated for soil-borne pathogens using an alfalfa seedling baiting technique and 145 pure cultures were obtained. Based on the rDNA ITS sequences, 38% of the isolates were identified as Fusarium sp., 26% as Pythium aphanidermatum, 17% as P. myriotylum, 8% as Rhizoctonia solani, 5% as other fungi, 3% as P. irregulare, and 1% as P. carolinianum. Pathogenicity of two isolates of P. aphanidermatum and single isolates of P. myriotylum and P. irregulare was evaluated using a culture plate assay and infested soil assay. All isolates caused damping off and root rot of alfalfa seedlings. The P. myriotylum caused significantly more seed rot than the other isolates. The presence of P. aphanidermatum and other Pythium sp. in Sudanese soils was previously reported from fields with alfalfa and Sorghum vulgare. However, pathogenicity of these isolates was not documented. To our knowledge, this is the first report of seed rot, seedling root rot, and damping off of alfalfa by P. aphanidermatum, P. myriotylum, and P. irregulare isolated from Sudanese soil. These results suggest that the major cause of seed rot and seedling damping-off in these fields was due to infection by these pathogens.