The 2009 ASHS Annual Conference

Growing prune trees from seed does not produce a tree genetically identical to its parent. Prune seeds are derived from open pollinated flowers so seeds are progeny of parent trees and are not genetically identical. In fruit and nut production, the industry needs every tree producing the same variety. Clonal propagation of fruitwood is one option. However it is much more common to graft the desired variety on a rootstock of choice. This allows a clonal choice for the prune variety and a rootstock choice to manage orchard site problems such as soil type and structure, nematodes and/or diseases. Because prune orchard life may be 25 to 40 years, it is important to anticipate rootstock responses to the soil type where it will be planted and different soil-borne diseases and pests which may be present. Certain rootstocks respond differently than others to soil, disease, and pest problems; selection of the most suitable stock for the proposed site can have a major influence on long-term performance of an orchard. Similarly, with spot or localized replanting, causes of original tree loss should be taken into account in selecting replacement stocks. The plum rootstocks, Myrobalan ( Prunus cerasifera), Myrobalan 29C (Prunus cerasifera cuttings), Mariana 2624(Prunus cerasifera x Prunus munsoniana) are most commonly used in California prune orchards. Other prunus species such as peach, almond and apricot are rootstocks used for special situations.  The M40 Marianna plum stock is a relatively new release that may in time replace Mariana 2624. Advantages/disadvantages for  each rootstock are discussed.