A jury of experts, as well as the conference attendees, judged the tone quality of the violins, and the ultimate winner was "Opus 58" -- one of the fungus-infected violins. 90 of the 180 attendees voted for it, with the Stradivarius coming in second with 39 votes. 113 members guessed that "Opus 58" was actually the Strad.
The wood in "Opus 58" was treated with a fungus for the longest time: 9 months. Fungal infections are generally thought to damage wood, but results published by Francis Schwarze last year suggested that some types of soft rot fungi reduced the density of the wood, making it lighter and improving its tonal quality, without impairing its firmness. Fungi may thus help artificially replicate the unusually low density of wood that is thought to have occurred in Stradivarius' time. The "Little Ice Age" that occurred at this time brought about long winters and cool summers in Central Europe, causing trees to grow slowly and uniformly and creating wood with great tonal qualities.
http://www.popsci.com/scitech/article/2009-09/fungus-infected-violin-beats-stradivarius-listening-test
Image: U.S. Department of the Interior