Breeding for Resistance

Chestnut Breeding Blight Resistant American for Ontario

  • At the turn of the 19th century millions of American chestnut (Castanea dentata) trees flourished in the broadleaf forests of southern Ontario. Today, it is rare to find a healthy, mature tree. In 1904 chestnut blight epidemic was accidentally introduced to Northern America from Asia and the ensuing epidemic virtually wiped the species out by 1950s. In southern Ontario, population of American chestnut was reduced far less than one percent of the original 1.5-2.0 million trees estimated to have been present.
  • The farm community is on the list of enthusiasts who continue to play an important role in the recovery process. In addition to the many individuals over years who have carefully planted and tended American chestnut plantings on their properties, farm groups, volunteers, professional conservation organizations have become involved in a coordinated program to breed blight resistant American chestnut in Ontario.
  • This project is the first phase in a plan to develop a self-sustaining population of American chestnut which are genetically of Canadian origin and are resistant to chestnut blight caused by Cryphonectria parasitica. In this phase we plan to obtain a population of Chestnuts which are 50% Canadian and contain genes for resistance to chestnut blight.
  • Our aim is to pollinate Canadian trees (to retain Canadian cytoplasmic genes in the breeding population) with pollen of known resistant trees. The resulting seedlings (F1 generation) will be inoculated with the chestnut blight fungus and the most resistant trees kept. These will then be crossed with each other (F2 generation). In F2 generation we will select trees of 75% Canadian origin and are highly resistant to the blight fungus. In 2001 the Canadian Chestnut Council selected twelve mother trees in five different counties (Persall Tree, Hodgson 10, 11, and 12, Bradshaw, Marshal, Burford, Brad Reive, Gundry, Spring Brook, Simpson St. Tree, and Island Lake Conservation Area). The selected trees were pollinated by pollen from three resistant trees supplied by Dr Sandra Anagnostakis, Connecticut Agricultural Experimental Station, USA, and pollen from other Canadian trees to act as susceptible control trees and detect any resistance in the Canadian trees. The Connecticut trees were: Sandy= s tree (American x {Chinese x [(Japanese x European) x American]} and two trees of third backcross (R2T10 and R2T8) which are (American x (American x {American x [(Japanese x European) x American]})). During the year volunteers collected 373 nuts of which 289 were from Dr Anagnostakis= pollen and 84 from Canadian sources. The average nut weight per tree was between 0.68 g and 4.84 g. Also, we collected 340 nuts from parent Canadian trees and will use these as rootstocks to graft scions from all the parents trees used.
  • All stored nuts were removed from cooler, soaked for 24 hours and planted on January 31. After one month an overall germination was over 88 % while survival was approximately 82 %. However, some of these which died-back have sprouted again. Also, during February we planted 340 nuts from Ontario American chestnut trees with over 95 % of germination and survival. These trees will be used as rootstocks to graft scions from all the parents trees used.
  • A list of 37 potential mother trees for 2002 crosses has been compiled. Currently, we are trying secure agreement with landowners and match volunteers to each tree. We plan to add four new trees in Elgin, two in Essex, nine in Norfolk, five in Hamilton-Wentworth, one in Chatham-Kent, two in Niagara and one in Brant to those we pollinated last year. Three of the trees we pollinated in 2001, had sufficient nuts which germinated so that we do not need to repeat the pollination on those trees this year.