A fungus wiped out the majority of the majestic American chestnut trees in the first part of the 20th century. This fascinating account documents how the fungus was identified, and three scientific programs to bring the American chestnut back from the brink. An inoculation program injects a weaker form of the fungus, found in Japanese and Chinese chestnuts, into infected trees. If it spreads it turns the deadly fungus into a milder form of blight the trees can survive. (A stand of trees near West Salem, Wisconsin, is one of the test sites.) In the backcross breeding program, healthy American chestnuts are bred with blight-resistant Chinese chestnuts. Resistant offspring are crossed with another American chestnut until there is a blight-resistant sixth-generation tree that is mostly American chestnut. The first of these were planted in forests in 2009. The third effort is a high-tech: wheat genes that produce oxalate oxidase (OxO), which breaks down the oxalic acid that the killer fungus produces, are injected into American chestnut embryos in hopes the resulting trees will be healthy. Science is accessible and engaging in this real-world, problem-solving mystery that includes outstanding documentation and a treasure trove of intriguing back matter. (Age 11 and older)