Ratio of Carbon to Nitrogen in Peach and Susceptibility to Peach Tree Short Life

Peach Tree Short Life (PTSL) is a disease syndrome in the southeastern United States that often is 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 indicated that a high C/N ratio favored bacterial canker development in peach. Adjacent healthy and diseased pairs of trees with multiple replicates from six different cultivars on six PTSL sites in South Carolina were sampled in early April 2011 and 2012 (three orchards each year).  Live, healthy cambial tissue was removed from scaffolds of both healthy and diseased trees (bacterial canker symptoms).  Percentages of  carbon and nitrogen in the tissue were analyzed.  Nitrogen content of healthy cambium was significantly higher in diseased trees at four of the orchards. The C/N ratios were also significantly lower in diseased trees at these same four sites.  These results did not confirm previous research.  Timing of sampling, tissue type or cultural practices may be the reason for contrasting results.  Additional data on rootstocks and time of sampling will be discussed.