Types Of Rootstocks

Rootstocks are broadly categorized into two groups based on how they are propagated: (1) seedling rootstocks and (2) clonal rootstocks (TableR1.1). Seedling rootstocks are propagated by gathering, stratifying, and then planting seed into a nursery. The genetic variability among seedling populations reflects the homozygosity of the species. For example, peach, which is relatively homozygous for most characteristics, will produce a seedling rootstock population that is, within reason, uniform. Thus, most peach rootstocks are commonly produced from seed. In contrast, seedling apples are highly variable within the seedling population for many characteristics, and apples are considered genetically heterozygous. Consequently, each seedling rootstock may grow and perform differently. To ensure uniformity of tree growth, most apple rootstocks are currently clones of a cultivar. Clonal rootstocks are propagated by asexual methods, and therefore within a rootstock population each individual is genetically similar to its population sibling. Clonal rootstocks are selected from naturally occurring populations by observation of rootstock performance, as developed hybrids from planned breeding programs, or as mutations of existing selections. Clonal rootstock propagation methods include layering, rooted cuttings, and micropropagation.

TABLE R1.1. Examples of tree fruit crops for which scion cultivars are commonly grafted onto rootstocks

Common Name Botanical Name

Rootstocks

Used Examples

Apple

Malus domestica

Seedling Clonal

European pear Pyrus communis Seedling

Clonal

M. domestica spp. M.7, M.26, M.9, MM.111, B.9, G.16

P. communis 'Bartlett' P. betulaefolia P. calleryana Cydonia oblonga P. communis 'Old Home'

Peach/nectarine Prunus persica

OHxF51, OHxF333

Seedling P. persica 'Lovell' P. persica 'Bailey' P. persica 'Guardian' P. persica x amygdalus

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