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United States Department of Agriculture

Agricultural Research Service

Research Project: Genetic Dissection of Traits for Sugar Beet Improvement

Location: Sugarbeet and Bean Research

Title: First report of Fusarium proliferatum causing dry rot in Michigan commercial potato (Solanum tuberosum) production

Authors
item Merlington, A -
item Hanson, Linda
item Bayma, R -
item Hildebrandt, K -
item Steere, Luke -
item Kirk, William -

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 19, 2013
Publication Date: June 1, 2014
Citation: Merlington, A., Hanson, L.E., Bayma, R., Hildebrandt, K., Steere, L., Kirk, W.W. 2014. First report of Fusarium proliferatum causing dry rot in Michigan commercial potato (Solanum tuberosum) production. Plant Disease. 98:843.

Interpretive Summary: Fusarium dry rot of potato is a postharvest disease caused by several Fusarium spp. The disease is a problem all over the world. Thirteen Fusarium spp. have been implicated in fungal dry rots of potatoes worldwide. Eleven of these species have been reported causing dry rot of potato seed tubers in the northern United States. Historically, F. sambucinum was the predominant species reported on seed potato in Michigan potato production. A survey of Fusarium spp. causing dry rot of seed potatoes in Michigan in 2009/2010 concluded Fusarium oxysporum was the most abundant spp. recovered, followed by F. equiseti, F. sambucinum, and F. avenaceum. To further investigate the spp. composition of Fusarium in storage, dry rot symptomatic tubers were collected from Michigan commercial potato storage facilities in 2011 and 2012. Among the Fusarium isolates obtained, three isolates were identified as F. proliferatum. The identity was confirmed through DNA sequencing. Pathogenicity testing was done on disease-free potato tubers cvs. Atlantic and Russet Norkotah. Typical dry rot symptoms consisting of brown, dry decay of the tuber were observed three weeks after inoculation on all inoculated tubers of each cultivar with Fusarium proliferatum. No rot symptoms were observed on control tubers. Fusarium proliferatum was reisolated from the symptomatic tubers and not healthy tubers. To our knowledge, this is the first report of F. proliferatum causing potato dry rot in Michigan.

Technical Abstract: Fusarium dry rot of potato is a postharvest disease caused by several Fusarium spp. and is of worldwide importance. Thirteen Fusarium spp. have been implicated in fungal dry rots of potatoes worldwide. Among them, 11 species have been reported causing potato dry rot of seed tubers in the northern United States. Historically, F. sambucinum was the predominant species reported to affect seed potato in storage and cause seed piece decay after planting in Michigan potato production. A survey of Fusarium spp. causing dry rot of seed potatoes in Michigan concluded Fusarium oxysporum was the most abundant spp. recovered, followed by F. equiseti, F. sambucinum, and F. avenaceum. To further investigate the spp. composition of Fusarium, dry rot symptomatic tubers were collected from Michigan commercial potato storage facilities in 2011 and 2012. Sections were cut from the margins of necrotic tissue with a sterile scalpel and surface disinfested in sodium hypochlorite. The tissue sections were plated on half-strength potato dextrose agar (PDA) amended with 0.5 g/liter of streptomycin sulfate. Putative Fusarium cultures were transferred onto water agar and hyphal tips from the margin of actively growing isolates were removed with a sterile scalpel and plated on carnation leaf agar (CLA) and half-strength PDA to generate pure cultures. Fusarium isolates were sub-cultured and used for identification. Identification of the 730 isolates was based on colony and conidial morphology on PDA and CLA, respectively. Among the Fusarium isolates obtained, three isolates were identified as F. proliferatum. On CLA, macroconidia were abundant, slender, and mostly straight, with three to five septae. Microconidia were abundant, usually single celled, oval or club-shaped in short chains or false heads on monophialides and polyphialides. Chlamydospores were absent. On PDA, abundant white mycelium was produced that turned violet with age. The identity was confirmed through DNA extraction followed by amplification and sequencing of the translation elongation factor (EF-1a) gene region. Pathogenicity testing was done on disease-free potato tubers cvs. Atlantic and Russet Norkotah. Three tubers of each cultivar per isolate were wounded at the apical end of the tuber to a depth of 4-10 mm with a 4 mm diameter cork-borer. Tubers were inoculated by inserting a mycelial plug, from a 7 day old culture grown on PDA, into the wound and incubating the tubers at 20°C for 3 weeks. Control tubers were inoculated by inserting a water agar plug. Pathogenicity and virulence testing were replicated 3 times and repeated. All tubers inoculated with F. proliferatum developed typical potato dry rot symptoms consisting of a brown and dry decay. There was no disease incidence on the control tubers. To complete Koch’s postulates, F. proliferatum was re-isolated from the symptomatic tubers. To our knowledge, this is the first report of F. proliferatum causing potato dry rot in Michigan.

Last Modified: 12/19/2014
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