|Beckman, Thomas - Tom|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2008
Publication Date: 11/20/2008
Citation: Beckman, T.G., Chaparro, J.X., Sherman, W.B. 2008. 'Sharpe', a clonal plum rootstock for peach. HortScience. 43(7):2236-2237.
Interpretive Summary: Guardian is currently the dominant rootstock for the southeastern peach industry primarily due to its superior resistance to peach tree short life (PTSL). However, Guardian suffers one very significant deficiency and that is its high susceptibility to Armillaria root rot, the 2nd leading cause of premature tree death in this area, after PTSL. Sharpe is a clonal plum hybrid rootstock developed for use with peach varieties that provides superior resistance to Armillaria root rot compared to Guardian. It also provides resistance to PTSL comparable to that offered by Guardian and has demonstrated resistance to the most damaging root-knot nematodes typically found on peach growing sites in Georgia and Florida. Peach trees on Sharpe are semi-dwarf, approximately 60% the size of those on Guardian. This reduction in vigor will help reduce management costs and provide a more desirable tree size for homeowners and growers alike. Sharpe appears to offer the broadest package of disease and pest resistance available at this time. This will not only improve tree health and longevity but should also help reduce chemical pesticide applications that would otherwise be required to suppress these problems.
Technical Abstract: Sharpe clonal rootstock for peach is jointly released for grower trial by the U.S. Department of Agriculture, Agricultural Research Service (Byron, GA), and Florida Agricultural Experiment Station. Sharpe, previously tested as FLA1-1, was discovered in the wild and appears to be a hybrid of Chickasaw plum (Prunus angustifolia) with an unknown plum species. Sharpe is readily propagated via softwood or hardwood cuttings. In field trials in central Georgia, trees budded on Sharpe provided resistance to peach tree short life (PTSL) comparable to those budded on Guardian, the current industry standard. Trees of Sharpe displayed higher resistance to Armillaria root rot than did trees of Guardian. Trees budded on Sharpe displayed markedly lower vigor than those budded on Guardian. After 6 growing seasons, trunk cross-sectional area of trees budded on Sharpe was ca. 60% of those budded on Guardian rootstock. In field trials infested with root-knot nematodes (Meloidogyne incognita and M. floridensis, respectively), Sharpe displayed no visible galling while in the same trials known susceptible rootstocks were severely galled. Sharpe has been tested for compatibility with a limited number of peach and nectarine scions. Graft unions with peach scions are typically smooth or may display a slight scion overgrowth as the trees mature. Sharpe is suggested for trial on Armillaria root rot infested sites where peach seedling type rootstocks often fail to provide satisfactory tree longevity.