Rootstocks for Apple - WSU Tree Fruit

Apple rootstocks exhibit a variety of desirable attributes, including resistance to crown rot oomycetes (Phytophthora spp.), fire blight bacteria (Erwinia amylovora), and woolly apple aphids. Additionally, they provide dwarfing characteristics, tree branching modifications, improved precocity (early fruit-bearing), enhanced productivity, and tolerance to apple replant disease (ARD). In the United States, five primary types of rootstocks are commonly employed: Budagovsky (= Bud or B), Cornell/Geneva (=CG or G), Malling (=M) & Malling Merton (=MM), Michigan Apple Rootstock Clones (=MARK), and the East Malling/Ashton Long (=EMLA), which are certified virus-free selections of Malling or Malling Merton. The nomenclature of these rootstocks includes the type name or its abbreviation followed by the selection number (e.g., Budagovsky selection 118 may be referenced as Budagovsky 118, Bud 118, or B.118, all relating to the same rootstock material). As noted earlier, EMLA selections are virus-free options derived from corresponding M or MM rootstocks, typically exhibiting 5-10% higher vigor.

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Description of commonly available apple rootstocks

B.9 (Bud.9, Budagovsky 9)

This dwarfing rootstock, resulting from the cross between M.8 and the Russian cultivar 'Red Standard,' has been extensively tested and widely utilized in U.S. commercial orchards. It offers slightly more dwarfing traits compared to M.9 and exhibits higher productivity. Additional characteristics include: very early production, excellent winter hardiness, minimal suckering, support requirements, adaptation to well-drained soils, and noteworthy resistance to crown rot and fire blight compared to M.9.

B.118 (Bud.118, Budagovsky 118)

This semi-dwarf rootstock is the product of a cross between 'Moscow pear' and M.9 or M.8, demonstrating excellent cold hardiness and a tree size approximately 85% of that of standard seedling rootstocks. It displays early precocity, moderate resistance to fire blight and crown rot, and the capability to grow without structural support.

EMLA 7

Trees grafted on this rootstock are typically 50 to 60% of the size of a standard tree and are among the most prevalent EMLA selections. EMLA 7 thrives in various soil types, though some support may be necessary initially. Its cold hardiness is commendable, but it may be prone to suckering while offering high resistance to fire blight.

EMLA 26

Characterized by producing trees about 40 to 45% the size of standard trees, this rootstock requires minimal support in early years but may be self-supporting eventually. It is known for early and heavy bearing and is adaptable for close plantings and double rows.

EMLA 106

Leading to trees roughly half to two-thirds the size of the standard, EMLA 106 exhibits no suckering and resistance to woolly aphids. It is extensively planted across East and West and is recognized for high productivity, requiring well-drained soils due to susceptibility to crown rot.

EMLA 111

This rootstock allows trees to reach about two-thirds the size of a standard tree. Under favorable conditions and vigorous scion varieties, growth can exceed three-quarters of standard size. EMLA 111 is well-adapted to various soil conditions, drought tolerant, and a good producer.

M.26 (Malling 26)

M.26 is a semi-dwarf rootstock resulting from a cross between M.16 and M.9, noted for its productivity and early bearing characteristics. While historically recognized as a dwarfing rootstock, it exhibits substantial vigor. This rootstock is susceptible to crown rot and fire blight, necessitating well-drained soils for optimal growth. Virus-free versions are more vigorous than their infected counterparts.

G.11 (Geneva 11®)

This semi-dwarf rootstock is achieved from the cross of M.26 and Robusta 5 crabapple, yielding-sized trees similar to M.26. G.11 has reliable precocity, with moderate pest resistance and minimal suckering.

G.41 (Geneva 41®)

This dwarfing rootstock, developed from M.27 and Robusta 5 crabapple, boasts high resistance to fire blight and phytophthora while demonstrating tolerance to replant disease (ARD). It presents early productivity and minor suckering.

G.890 (Geneva 890®)

A semi-dwarfing variety characterized by mid-range precocity and robust winter hardiness; it does not require external support.

G.935 (Geneva 935®)

This dwarfing rootstock, a cross of Ottawa 3 and Robust 5 crabapple, has early bearing traits, with solid productivity, adaptability, and resistance against both crown rot and fire blight.

M9-337 (Malling 9 virus certified #337)

A dwarfing rootstock derived from M.9 certified virus-free clonal stock, this option demonstrates high precocity and adaptability across various soil and climatic conditions, though it necessitates support.

Nic 29®, RN 29 cv. (Malling 9 selection NIC 29)

A selection slightly more vigorous than other M.9 varieties that enhances vigor for cultivars like Empire or Honeycrisp.

Supporter 4®

This hybrid of M.9 and M.4 offers a dwarfing nature akin to EMLA 26 and requires supportive structures during its growth phase. Supporter 4 has demonstrated superior efficiency compared to EMLA 26 and EMLA 106 in testing.