Department of Plant Pathology and Physiology, Clemson University, Clemson, SC 29634
 

Abstract
      Two-year-old dormant peach trees, with Red Heaven or Loring scion and Lovell or Nemaguard rootstocks, were grafted with twig tissue from healthy or infected sources of 4 Prunus necrotic ringspot virus (PNRSV) isolates.  Three trees of each of 4 scion/rootstock combinations were grafted with each source near the top and three on major roots.  Trees leafed out after 1-2 weeks in a greenhouse and weekly assays were carried out by ELISA.  PNRSV was first detected in leaves near the top of shoot-grafted trees 2-3 weeks after grafting.  PNRSV was systemic in this trees, including roots, at this time or 1-2 weeks later although virus was not detected in some branches until 6-14 weeks after grafting, or not at all in 1/4 of the branches.  PNRSV was not detected in any root-grafted trees or in trees grafted with healthy tissue.  Few differences were found among virus isolates or cultivars.  Thus, soil-borne transmission of PNRSV may not be an important means of natural spread.