The term hypovirulence refers to an infection of the blight fungus by a naturally-occurring virus that reduces the virulence of the fungus and its ability to kill the tree. The tree is still infected by the blight, but can fight back and has a better chance to survive. TACF scientists have been working to introduce weaker virus into large surviving American chestnut trees. By inoculating all infected trees with a weakened strain of the fungus, scientists hope to “infect the infection” and help the trees survive. In Connecticut we’ve used hypovirulence, developed with the assistance of CEAS, to target protect specific Mother Trees from the blight. The effort is great, but the results are astounding. We’ve been able to protect specific trees from existing and significant infections that appeared ready to cause the demise of the tree. Ten years later the trees are growing, and producing flowers and seed. The process is too labor intensive to scale up to protect a forest or even a woodlot. But used to protect specific trees can be quite effective.
Ink’s Disease — Phytophthora
In many regions, one of the greatest threats to the return of the chestnut today is the root rot pathogen Phytophthora cinnamomi, or Ink’s disease. This organism is a soil-borne pathogen that attacks the roots of the chestnut tree resulting in the complete death of the tree. Today, TACF volunteers and scientists are working to breed a tree resistant to both chestnut blight and Ink’s disease. Much of the research about this disease on American chestnut takes place at Chestnut Return Farm in Seneca, SC.
TACF has joined forces with large research institutions, both nationally and internationally, to help create genetic and physical maps of the chestnut genome. While we are only one of several institutions working on this project, our well documented breeding work has provided much of the physical material needed to fuel this effort. Scientists hope to identify the physical locations of genes that contribute to blight resistance. By mapping the gene sequence of American chestnut and Chinese chestnut, scientists can provide a model to study the basis of resistance to pathogens and pests that threaten the world’s forest resources.
TACF’s New York Chapter is working in partnership with the State University of New York’s College of Environmental Science and Forestry to use biotechnology techniques to produce a potentially blight-resistant chestnut. The exciting work conducted by our New York Chapter not only holds promise in developing a blight-resistant chestnut, but also in unlocking some of the genetic mysteries that still surround blight resistance of the chestnut.
The program at SUNY ESF has transformed American chestnut using Agrobacterium tumefaciens. Once transformed, propagation using methods for plant regeneration from somatic embryos have been developed permitting the production of many individuals from single transformation events. Professor C.A. Maynard’s and Professor W.A. Powell’s labs at the State University of New York at Syracuse University have produced transgenic American chestnut trees demonstrating that all the steps have been developed to genetically engineer this species.