Hort 311 - Vegetative Production of Pear

Daniel Lovejoy

HORT 311

02/10/14

Assignment #4

Vegetative Propagation of Pear

        The common pear is susceptible to several viruses, and yields best in particular soils.  Rootstocks have been used to improve it's immunity.  Rootstocks have also been used to make pears more tolerant of poor draining, heavy soils.  Fireblight, is a common virus amongst pears, and usually occurs when they are planted poorly cultivated soils.  Selection of an appropriate graft combination is crucial for the production of deciduous orchard species, because the scion–rootstock interaction influences water relations, leaf gas exchange, plant size, blossoming, timing of fruit set, fruit quality and yield efficiency (Ikinci et al. 2014).  Standard sized pears are chip or t-budded onto compatible rootstocks like most tree fruits (Pear - Pyrus communis, Pyrus pyfifolia...[updated 2015]).

        Most cultivars require cross pollination for commercial fruit set (Pear - Pyrus communis, Pyrus pyfifolia...[updated 2015]).  Some cultivars are also partially self fruitful (Pear - Pyrus communis, Pyrus pyfifolia...[updated 2015]).  Seedlings, however, don't produce genetically identical replicates of their maternal parents, but are used for rootstock production (Pear Propagation... [updated 2013]).   The main form of pear propagation is vegetative.  Hardwood cutting are collected form the current year's shoots during the fall and immersed in auxin (Pear Propagation... [updated 2013]).  In the early summer, softwood cutting are harvested, hardened until they are ready in the fall (Pear Propagation... [updated 2013]).  The cuttings require a humid storage environment to develop roots (Pear - Pyrus communis, Pyrus pyfifolia...[updated 2015]).  

        Pyrus communis, a native of Europe (Pear - Pyrus communis, Pyrus pyfifolia...[updated 2015]), is more tolerant of heavy, clayey soils, and it's seedlings are used as a rootstock (Pear Propagation...[updated 2014]. Pyrus communis seedling rootstocks are also moderately resistant to pear decline, is a disease associated with a fungus called mycoplasma.  Pear decline stunts the growth of shoots and spurs, causes shoot dieback, upper rolling of leaves, reduced leaf and fruit size, and premature leaf drop (Pear decline...[updated 2014]).  P. communis also has good cold hardiness, but is also susceptible to fireblight (Ikinci et al. 2014).  

        The rootstock that seems to have the greatest effect on tree growth is Old Home clonal, which is resistant to fireblight and pear decline, has good cold tolerance, and increases tree size (Pear Propagation... [updated 2013]).  A hybrid of Old Home and another one called Farmingdale, helps with earlier fruiting, and enhances fruit quality (Pear Propagation... [updated 2013]).  This rootstock is commonly used in the USA and South Africa (Ikinci et al. 2014).

        The rootstock of Quince, a close relative of pear, is commonly used as a dwarfing mechanism, and for earlier fruiting (Pear - Pyrus communis, Pyrus pyfifolia...[updated 2015]).  The quince rootstocks, are clonal/rooted cuttings (Ikinci et al. 2014).  However, not all pear cultivars are fully compatible with quince, and require an interstem when grafted .  Dwarfing allows for closer planting spacing, and are easier to harvest (Pear - Pyrus communis, Pyrus pyfifolia...[updated 2015]).