Tennessee News

Evaluating Chestnuts in Greg’s Orchard for Blight Resistance and Phenotype

Friends,

On June 3, 2013, Dr. Hill Craddock and his UTC crew traveled to Greg Weaver’s orchard in Williamson County, TN to grade blight resistance and assess for American chestnut physical characteristics on Greg’s chestnut trees. The trees had been inoculated in June 2012 with two strains of chestnut blight (cryphonectria parasitica). Approximately 622 trees have contributed to the experiment as listed below. These include advanced backcross chestnuts (BC3’s and BC4’s), F1’s (first generation crosses American x Chinese), pure American controls, Dunstan hybrid controls (Asian type) and pure Chinese controls.

TN Rut x CH526 #116, Apr 2005
Tn Blo x GL 103 #184, Apr 2005
Rut 1 x Ft. Defiance #6, Apr 2005
Rut 1 x Lindstrom 99 #18, Apr 2005
TN Mac 1 x GL 104 #234, Apr 2006
E10 x AMY #5, Apr 2006
Dennis W #4, Apr 2006
Dunstan #20, Oct 2006
Chinese #5, Apr 2007
TN Mon 3 x OP #1, 2007
KY Met 1 x OP #1, 2007
KY Met 1 x OP #1, 2007
Whigg M x OP #1, 2007
TN Cla x Popeye #1, 2007
Istaca (American) #25, 2008

Over the years, the trees were subject to the whole range of stresses inherent in this form of plant science, including drought, pests (especially voles), a mid April hard freeze (2007), and “natural” blight infections. There was further mortality in the orchard from the experimental blight infections introduced in June 2012. The mortality from all these causes has been high with the majority of these trees having died prior to the innoculation in June 2012.

I will leave the formal reporting to Hill. By my records, nine advanced backcross hybrids (all TN Blo x GL 103) were rated as having adequate blight resistance and appropriate American chestnut physical characteristics to retain the trees in the breeding program, and to serve as the parents of the next generation. One F1 was also retained. These “blue ribbon special” trees were marked with blue ribbons tied around their trunks in the orchard, and were recorded as such on the data sheets. The TN Blo x GL 103 is known to exist only in this orchard, so retention of this germplasm is important for the TN- TACF program.

For now, all the living trees will be retained, but over the next year the lower rated trees will be removed from the orchard (think chestnut firewood).

I am grateful for the hard work and guidance from Hill and his team at UTC. Attached are some photographs from the day’s work evaluating the trees.

Greg Weaver

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