Rescue of American chestnut with extraspecific genes following its destruction by a naturalized pathogen

Abstract

Following the near-obliteration of American chestnut (Castanea dentata [Marsh.] Borkh.) by the chestnut blight early in the last century, interest in its restoration has been revived by efforts to develop a blight-resistant form of the species. We summarize progress and outline future steps in two approaches: (1) a system of hybridizing with a blight-resistant chestnut species and then backcrossing repeatedly to recover the American type and (2) transformation of American chestnut with a resistance-conferring transgene followed by propagation and conventional breeding. Several decades of effort have been invested in each approach. More work remains, but results indicate that success is within practical reach. The restoration of C. dentata to its native habitat now appears to be less a matter of time and conjecture than ever before in 90 years of work by public and private entities. The difficult and protracted task of incorporating extraspecific genes for resistance into a tree species with lethal susceptibility to a naturalized pathogen represents perhaps the most extreme of restoration challenges. Its pursuit by a small non-governmental organization supported primarily by philanthropy and volunteers may serve as a model for other species threatened by exotic pathogens or insects.

The implications of American chestnut reintroduction on landscape dynamics and carbon storage

“…A backcross hybrid chestnut for reintroduction that is genomically 94% American chestnut has been produced through breeding with blightresistant Chinese chestnut (Castanea mollissima) (Burnham et al 1986). The hybrid is morphologically indistinguishable from pure American chestnut for a host of physiological and morphological traits (Diskin et al 2006, Knapp et al 2014, although it may differ from purebred chestnuts at other functional traits (Blythe et al 2015), and additional generations of breeding will be needed to ensure blight resistance (Steiner et al 2017). Using transgenic techniques, other researchers have introduced two wheat genes into the chestnut genome, resulting in trees that contain the entire American chestnut genome and exhibit enhanced resistance to blight (Jacobs et al 2013, Zhang et al 2013, Steiner et al 2017.…”

“…The hybrid is morphologically indistinguishable from pure American chestnut for a host of physiological and morphological traits (Diskin et al 2006, Knapp et al 2014, although it may differ from purebred chestnuts at other functional traits (Blythe et al 2015), and additional generations of breeding will be needed to ensure blight resistance (Steiner et al 2017). Using transgenic techniques, other researchers have introduced two wheat genes into the chestnut genome, resulting in trees that contain the entire American chestnut genome and exhibit enhanced resistance to blight (Jacobs et al 2013, Zhang et al 2013, Steiner et al 2017. Given these advances, the restoration of American chestnut to eastern forests of the United States is within practical reach (Jacobs et al 2013, Steiner et al 2017.…”

“…Using transgenic techniques, other researchers have introduced two wheat genes into the chestnut genome, resulting in trees that contain the entire American chestnut genome and exhibit enhanced resistance to blight (Jacobs et al 2013, Zhang et al 2013, Steiner et al 2017. Given these advances, the restoration of American chestnut to eastern forests of the United States is within practical reach (Jacobs et al 2013, Steiner et al 2017.…”

“…, Steiner et al. ). Given these advances, the restoration of American chestnut to eastern forests of the United States is within practical reach (Jacobs et al.…”

Growth traits of juvenile American chestnut and red oak as adaptations to disturbance

“…Efforts to restore American chestnut have been ongoing for nearly a century, initiated by several tree improvement programs to backcross blight‐resistance genes from Asian Castanea sp. into the species (Steiner et al ). With putatively blight‐resistant material becoming more widely available, restoration efforts are shifting toward reintroducing the species in the landscape.…”