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Carbon to nitrogen ratio in peach bark and incidence of bacterial canker

Reighard, G. L., Bridges, W. Jr., Glenn, D. M., Mayer, N. A.
Acta horticulturae 2016 no.1130 pp. 341-344
bacteria, bacterial canker, bark, cambium, carbon, carbon nitrogen ratio, nitrogen, nitrogen content, orchards, peaches, tree mortality, trees, South Carolina
Peach tree short life (PTSL) is a disease syndrome in the southeastern U.S. characterized by tree death from bacterial canker (Pseudomonas syringae pv. syringae). This bacterium produces a syringomycin toxin that kills plant tissue. Gene expression of this toxin is influenced by tissue nitrogen content. Previous studies reported that a high C/N ratio favored bacterial canker development in peach. Adjacent pairs of one non-diseased and one diseased peach tree with multiple replicates (10-16) per orchard on seven active PTSL sites in South Carolina were sampled in early April 2011, 2012 or 2013. Live, healthy cambial tissue was removed from scaffolds of both healthy (no active canker) trees and trees exhibiting bacterial canker symptoms. Percent carbon and nitrogen in the tissue were analyzed. Nitrogen content of healthy cambium in trees with bacterial canker symptoms was significantly higher for the majority of the orchards. C/N ratios were significantly lower in the symptomatic trees. These results did not support previous research. Time of sampling, tissue type, or cultural practices may be the reason for the contrasting results.