Pear Propagation
Pear cultivars and rootstocks do not maintain their specific characteristics when grown from seed (sexual propagation). As a result seedlings are not used to propagate cultivars, instead they are used commercially for rootstock production.
Sexual Propagation
Seedlings do not produce identical replicates of maternal or paternal parents. Each seedling is unique. Nonetheless, seedling rootstock production is quite practical: it is quick, inexpensive, easy to perform and produces a large number of plants. Another benefit is that the trees produced have rooting systems that grow downward and are symmetrical. To produce a seedling, seeds are removed from mature fruit of the desired rootstock, stratified and planted.
Vegetative Propagation
Vegetative propagation with hardwood cuttings and micropropagation is used to produce cultivars and some rootstocks. The benefit of propagation with hardwood cuttings and micropropagation is that they are clonal replicates of the parent tree and the end result is predictable, whereas the seedlings do not produce identical replicates of either parent.
Cuttings
The success rate of hard- and soft-wood cuttings varies between 30 to 90% depending on environmental conditions and cultivar. Hardwood cuttings are typically collected from the current year’s shoots during the fall and immersed in auxin (either higher levels for a brief dip or lower levels for an entire day). Softwood cuttings are harvested during early summer, immersed in high levels of auxin, and placed in a greenhouse with occasional misting to be hardened and ready for the nursery by fall. Both hard- and soft- wood cuttings require a humid storage environment for root formation. If the shoots are harvested early, they typically grow in the nursery for one year before reaching an adequate size for transplantation.
Micropropagation
Micropropagation produces a clonal replicate of a tree using tissue culture. Micropropagation is a very effective and quick propagation method, but is not currently used in pear production due to the high labor and equipment costs. This method has been used by researchers, and it is expected to become common commercial practice in the future.
Micropropagation utilizes seedling tops, young shoots or suckers collected from a mature pear tree. The plant material, always containing an axillary bud, is sterilized and placed on a mixture of nutrient enriched sugar agar and plant hormones. This mixture receives long-day length lighting to produce new shoots. After the new shoots are rooted with high concentrations of IBA, they are exposed to a couple days of darkness followed by short-day length lighting to allow for proper growth. Shoots can be grown continuously and sliced to produce multiple clones of the same pear tree (Reil et al. 2007).