|Gachango, E -|
|Rojas, A -|
|Hao, J -|
|Kirk, W -|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 23, 2012
Publication Date: November 1, 2012
Citation: Gachango, E.N., Hanson, L.E., Rojas, A., Hao, J.J., Kirk, W.W. 2012. Fusarium spp. causing dry rot of seed potato tubers in Michigan and their sensitivity to fungicides. Plant Disease. 96:1767-1774. Interpretive Summary: Fusarium dry rot is an important postharvest disease of potato that can be caused by several different Fusarium species. As well as losses in storage, the disease can affect seed tubers and reduce plant health and plant stand. A survey of potato seed tubers was conducted in Michigan to identify the Fusarium species causing rot in the state. A total of 370 tubers with symptoms were collected and 228 Fusarium isolates were collected. These were identified as belonging to 11 different species. Fusarium oxysporum was the most common species isolated, followed by Fusarium equiseti. Fusarium sambucinum and Fusarium avenaceum tied for third. This distribution was unexpected as Fusarium sambucinum had been reported as the primary dry rot pathogen of beet in the state in 1993. Other species were less common (10% or less of the total Fusarium identified), and included F. cerealis, F. solani, F. acuminatum, F. sporotrichioides, F. torulosum, F. tricinctum, and F. graminearum. All species were pathogenic to potato tubers with F. sambucinum causing the most damage. All isolates were sensitive to the fungicide difenoconazole. All isolates of F. sambucinum were tolerant to thiabendazole, which has been the primary fungicide for dry rot control. Isolates of the other species were all sensitive to thiabendazole. Thus this fungicide may still be useful for dry rot management as the most prevalent species were senstivie. Isolates varied in sensitivity to the fungicide fludioxonil. The diversity of species needs to be considered for dry rot control as species can vary in their response to various disease management strategies.
Technical Abstract: Fusarium dry rot of potato (Solanum tuberosum L.) is a postharvest disease that can be caused by several Fusarium spp. A survey was conducted to establish the composition of Fusarium species causing dry rot of seed tubers in Michigan. A total of 370 dry rot symptomatic tubers were collected in 2009 and 2010 and used for recovery of Fusarium. A total of 228 Fusarium isolates were recovered and attributed to 11 Fusarium species. Fusarium oxysporum was the most commonly (30.3%) isolated species, followed by the F. equiseti species complex (19.3%). Fusarium sambucinum and F. avenaceum were third in prevalence, each at 13.6%. The less prevalent Fusarium spp. (4 to 10%) included F. cerealis, F. solani and F. acuminatum. Other Fusarium species identified (<3%) included F. sporotrichioides, F. torulosum, F. tricinctum and F. graminearum. All species were pathogenic to potato tubers with F. sambucinum being the most virulent species. Using in vitro tests, all isolates were sensitive to difenoconazole. All isolates of F. sambucinum were insensitive to thiabendazole, while isolates of the rest of the species were sensitive to thiabendazole. Isolates varied in sensitivity to fludioxonil.