Brad Wallace March 6, 2015 UBC scientists find key to deadly poplar tree fungus Brad Wallace March 6, 2015 I'm not sure what they mean by "extra genes." Extra to what? Do the fungus carry them around in a briefcase? I'm confused. The researchers’ study, published this week in the The Proceedings of the National Academy of Sciences, found that the fungus, Mycosphaerella populorum, uses extra genes to produce a toxin that can cause fatal lesions on the leaves, stems and branches of poplar trees.