Apple rootstocks can have a variety of desirable characteristics such as resistance to crown rot oomycetes (Phytophthora spp.), resistance to fire blight bacteria (Erwinia amylovora), resistance to Woolly apple aphids, dwarfing and tree branching modifications, increased precocity (early fruitfulness), increased productivity, and tolerance to apple replant disease (ARD). There are five major types of rootstocks used in the US. These include: Budagovsky (= Bud or B), Cornell/Geneva (=CG or G), Malling (=M) & Malling Merton (=MM), Michigan Apple Rootstock Clones (=MARK), and East Malling/Ashton Long (=EMLA) which are certified virus-free selections of Malling or Malling Merton. Rootstock names consist of the the type name or its abbreviation followed by the selection number. For instance, a Budagovsky selection 118 would be seen as either Budagovsky 118, Bud 118 or B.118. They all refer to the same stock material. As mentioned above, EMLA are virus-free rootstocks derived from a corresponding M or MM selection. They have comparable characteristics to the uncertified material, but tend to be 5-10% more vigorous.
Description of commonly available apple rootstocks
B.9 (Bud.9, Budagovsky 9)
Dwarfing rootstock resulting from a cross between M.8 x ‘Red Standard’ (Krasnij Standard) from Russia. B.9 has been widely tested and is used commercially throughout the U.S. It is slightly more dwarfing than M.9 and is slightly more productive. Other traits of note: Very early precocity; very winter hardy; little suckering; requires support; adapted to well drained soil; very resistant to crown rot; more fireblight resistant than M.9.
B.118 (Bud.118, Budagovsky 118)
Semi-Dwarf rootstock resulting from a cross between ‘Moscow pear’ x M.9 or M.8 from the former Soviet Union. It is reported to be very cold hardy, and produces a tree size of about 85% of seedling. It is more precocious than the seedling and can be grown without support. It is moderately resistant to fire blight and crown rot. Other traits of note: Somewhat early bearing; moderately productive; well anchored; needs well drained soils.
A tree on this rootstock will be 50 to 60 percent smaller than a standard tree. Trees on this clone are the most popular of all the rootstock grown. EMLA 7 does well on most soils. Some support may be needed in early years. EMLA 7 is very winter hardy. It is susceptible to suckering. EMLA 7 is extremely tolerant to fire blight.
This rootstock is considered to be smaller than a half size tree. It is about 40 to 45 percent of a standard tree, needs some support in early years, but could be self-supporting in later years. EMLA 26 is very early and heavy bearing. This rootstock is very adaptable for close plantings and double rows.
This rootstock produces a tree about half to two-thirds the size of a standard tree. It does not sucker and the rootstock is resistant to woolly aphid. EMLA 106 has been planted intensively in the East and West and is an excellent producer. It should be planted on well-drained soil as it is susceptible to crown rot.
This rootstock produces a tree about two-thirds the size of a standard tree. Vigorous scion varieties and better soils may grow to three-quarter size or larger. EMLA 111 is a good producing rootstock, is well anchored and tolerant of drought conditions. It is widely adapted to most soil conditions.
M.26 (Malling 26)
Semi-dwarfing rootstock resulting from a cross between M.16 and M.9 made at the East Malling Research Station, Maidstone, Kent, England. M.26 is traditionally considered a dwarf rootstock, but is one of the more vigorous dwarfing rootstocks. M.26 is grown widely throughout the world and is included as a “standard” in many rootstock trials. M.26 is precocious and very productive, produces many burr knots, and is susceptible to crown rot and fire blight. In a joint effort to produce virus free rootstocks, the East Malling and Long Ashton Stations in England used heat treatments to eliminate known viruses and released M.26 EMLA. In general, virus-free rootstocks are slightly more vigorous than the original that contains viruses. Other traits of note: – very early bearing; good productivity; may need support early on; winter hardy; prefers well drained soil; little suckering; susceptible to woolly apple aphid.
G.11 (Geneva 11®)
Semi-dwarfing rootstock resulting from the cross between M.26 x Robusta 5 crabapple and introduced by the New York State Agricultural Experiment Station, Geneva NY. G.11 produces trees of similar size to M.26 and is equally precocious. G.11 is moderately resistant to fire blight; moderately susceptible to woolly apple aphid and crown rot. Other traits of note: requires support in early years; produces few burr knots and root suckers; and it’s well adapted to most soils.
G.41 (Geneva 41®)
Dwarfing rootstock resulting from a cross between M.27 x Robusta 5 crabapple and introduced by the New York State Agricultural Experiement Station, Geneva NY. G.41 is highly resistant to fire blight and phytophthora and it appears to be tolerant of replant disease (ARD). Other traits of note: Early bearing; winter hardy; very little suckering, requires tree support.
G.890 (Geneva 890®)
Semi-dwarfing rootstock; intermediate precocity; winter hardy; does not require support.
G.935 (Geneva 935®)
Dwarfing rootstock resulting from a cross between Ottawa 3 x Robust 5 crabapple and introduced by the New York State Agricultural Experiment Station, Geneva NY. Traits of note include: early bearing; winter hardy; moderate suckering; requires support; very productive; well adapted to most soils; highly resistant to crown rot; highly resistant to fireblight.
M9-337 (Malling 9 virus certified #337)
Dwarfing rootstock selection from M.9 virus-free certified clonal stock developed by the East Malling Research Station, Maidstone, Kent, England. M.9-337 is very precocious and tolerant to a wide range of soil and climatic conditions. Tree support is required.
Nic 29®, RN 29 cv. (Malling 9 selection NIC 29)
A dwarfing rootstock selection of M.9 made in Belgium and is slightly more vigorous than other M.9 selections such as M.9-337. M.9 is used to impart vigor to cultivars such as Empire or Honeycrisp.
A cross of M.9 x M.4, Supporter 4™ is a dwarfing apple rootstock similar in vigor to EMLA 26. Anchorage is similar to EMLA 26, and trees on this root should be grown with some sort of support structure. The rootstock is relatively frost resistant. In tests, Supporter 4™ showed better efficiency than both EMLA 26 and EMLA 106.