Location: Sugarbeet and Bean ResearchTitle: First report of Fusarium torulosum causing dry rot of seed potato tubers in Michigan) Author
Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/10/2011
Publication Date: 8/26/2011
Citation: Gachango, E., Kirk, W.W., Hanson, L.E., Rojas, A., Tumbalam, P., Shetty, K. 2011. First report of Fusarium torulosum causing dry rot of seed potato tubers in Michigan. Plant Disease. 95(9):1194. Interpretive Summary: Fusarium dry rot of potato is an important postharvest disease caused by several different species of Fusarium. While Fusarium sambucinum has been reported as the primary species causing this disease, at least thirteen species of Fusarium can cause dry rot symptoms worldwide. To better understand the species associated with dry rot in Michigan, samples were taken from tubers with dry rot symptoms from Michigan seed lots in 2009 and 2010. Among the isolates collected from these tubers were five isolates of F. torulosum. Identity was confirmed by growth characteristics on diagnostic media and by DNA sequence analysis. When inoculated onto potato tubers (cultivar Red Norland), typical dry rot symptoms developed and F. torulosum was isolated from these lesions. To our knowledge, this is the first report of F. torulosum causing potato dry rot in Michigan.
Technical Abstract: Fusarium dry rot of potato (Solanum tuberosum) is a postharvest disease caused by several Fusarium species and is of worldwide importance. Thirteen species of Fusarium have been implicated in fungal dry rots of potatoes worldwide. Among them, eight species have been reported in the northern United States (US). In Michigan potato production, F. sambucinum was the predominant species reported affecting seed potato in storage and causing seed piece decay after planting. To investigate this further, dry rot symptomatic tubers were collected from Michigan seed lots in summer 2009 and 2010. Samples were taken from the edge of lesions on untreated tubers and Fusarium was purified from these samples. Among the Fusarium isolates obtained, five isolates were identified as F. torulosum. Identification was based on colony and conidial morphology on PDA and CLA respectively. The identity was confirmed through DNA extraction followed by amplification and sequencing of the translation elongation factor gene region. Pathogenicity testing was done on disease-free potato tubers (cultivar Red Norland). Three tubers per isolates were injected with 20µl of a conidial suspension (10^6 conidia/ml) made from cultures grown on PDA for 7 days. Control tubers were injected with 20µl of sterile distilled water. All tubers inoculated with F. torulosum developed typical potato dry rot symptoms consisting of a brown and dry decay. Fusarium torulosum was re-isolated from all the symptomatic tubers. To our knowledge, this is the first report of F. torulosum causing potato dry rot in Michigan.