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Information provided by Paul Domoto, Department of Horticulture, Iowa State University and Dr. Jim Cummins, Cornell University (retired).
Rootstock	Size (1)	Fruiting	Anchorage	Hardiness	Soil Adaptability	Crown Rot	Fire Blight	Remarks
P.18	+100%	Slow bearing, moderate productivity	Well anchored	Considered hardy, more testing needed	Widely adapted	Very resistant	Moderately resistant	Very little suckering, very few burrknots (2). May be susceptible to late winter freezes.
Seedling	100%	Slow bearing, yield variable	Well anchored	Hardy	Widely adapted	Variable	Tolerant	65-85% size control with spur-type Red Delicious strains; some size control with other spur-type strains. Suckering may be a problem: very few burrknots (2).
Antonovka 313	100%	Slow bearing, moderate productivity	Well anchored, but subject to leaning	Moderate	Widely adapted	Resistant	Moderately susceptible	Some suckering; few burrknots (2). Maybe susceptible to late winter freezes.
M.4	80 - 85 %	Moderately early bearing, good productivity	Well anchored but, subject to leaning	Moderate	Widely adapted	Resistant	Tolerant	Most productive vigorous rootstock in regional testing. Moderate to heavy suckering; few burrknots (2).
MM.111	80 - 85 %	Moderately slow bearing, medium prodctivity	Well anchored	Moderate	Adapted to most soils; drought tolerant, but does not tolerate wet feet	Tolerant on well drained soils	Tolerant	Tree form is more up-right. Little suckering; prone to burrknots (2). Semi-dwarf with spur-type Delicious strains. Moderately susceptible to tomato ringspot virus (3).
MM.106	70 - 75 %	Early bearing, productive	Good on most soils	Very susceptible early, hardy late winter	Beast in loam and sandy loam soils. Avoid poorly drained soils	Very susceptible	Moderately susceptible	Very little suckering; prone to burrknots (2). Very susceptible to tomato virus ringspot (3).
B.490	70 - 75 %	Early bearing, moderate productivity	Well anchored	Considered hardy; more testing needed	Well adapted to most soils	Moderately resistant	Tolerant	May be a replacement for MM.106. May be susceptible to late winter freezes. Almost no suckering; few burrknots (2)
Cornell - Geneva 210	60 - 65 %	Early bearing, productive	Anchored questionable	Needs testing	Needs testing	Resistant	Resistant	Suckering may be a problem. May be released soon.
M.7a, EMLA 7	60 - 65 %	Early bearing, moderate productivity	Free-standing but leans with some cultivars	Moderate; roots tender, snow cover for best protection	Well adapted on most soils except heavy clay	Slightly susceptible on poorly drained soils	Tolerant	Suckers heavily; somewhat prone to burrknots (2). Most widely adapted clonally propagated rootstock.
Geneva 30	60 - 65 %	Earlier bearing and more productive than M.7a	Usually well anchored	Testing required	Well adapted to most soils	Tolerant	Resistant	Promising new rootstock. Much less prone to suckering than M.7a; burrknots (2) rare. Susceptible to common latent viruses (4). Available
M.26, EMLA 26	55 - 60 %	Very early bearing, productive	May need support in early years	Hardiest M. or MM. series rootstock; somewhat slow to harden-off	Well drained soils	Moderately susceptible on poorly drained soils	Very susceptible	Very little suckering; very prone to burrknots (2). Susceptible to tomato ringspot virus (3). Compatibility problems have been identified with some cultivars
Geneva 11	55 - 60 %	Very early bearing, very productive	May need support in early years	Testing required	Well adapted on most soils	Moderately resistant	Moderately resistant	Promising new rootstock. Little suckering; very few burrknots (2). Available
Ottawa 3 (O.3)	50 - 55 %	Early bearing, very productive	May need support	As hardy as M.26	Well drained soils	Resistant on most soils	Susceptible	Roots poorly; may be a factor in orchard establishment. Moderate suckering; very few burrknots (2). Moderately susceptible to tomato ringspot virus (3) and common latent viruses (4)
EMLA 9	45 - 50 %	Very early bearing, very productive	Needs support	Slightly hardier than M.7a	Well drained soils	Resistant on most soils	Very susceptible	Suckers heavily; prone to burrknots (2).
M.9, M.9 - T337 & other M.9 Strains	40 - 45 %	Very early bearing, very productive	Needs support	Slightly hardier than M.7a	Well drained soils	Resistant on most soils	Very susceptible	Suckers heavily; prone to burrknots (2).
Geneva 16	45 - 50 %	Very early bearing, very productive	Very good, support needed for crop	Needs testing	Needs testing	Tolerant	Very resistant	Very little suckering; no burrknots (2). Very sensitive to common latent viruses (4). Available
Mark	35 - 45 %	Very early bearing, very productive	Roots are brittle, needs support	Hardy early, but susceptible in late winter	Best on well drained soils; drought susceptible	Resistant on most soils	Susceptible	Very prone to abnormal swelling of rootstock at ground line that stunts the tree. Moderate suckering; prone to burrknots (2). Moderately susceptible to tomato ringspot virus (3)
Bud. 9 (B.9)	35 - 40 %	Very early bearing, very productive	Needs support	Hardier thaan M.9	Well drained soils, does not tolerate wet soils	Very resistant	Susceptible	Promising new rootstock. Some suckering; very few burrknots (2). Drought susceptible. Susceptible to tomato ringspot virus (3). ISU observations suggest it is very susceptible to voles.
Geneva 65	35 - 40 %	Very early bearing, very productive. Fruit size reduced.	Well anchored, support needed for crop	Hardy	Needs testing	Resistant	Very resistant	Promising new rootstock. Some suckering; nearly no burrknots (2). Susceptible to apple stem grooving virus (4). Available.
P.2	35 - 40 %	Very early bearing, very productive	Needs support	Needs further testing	Well drained soils	Resistant	Moderately susceptible	Very little suckering; few burrknots (2). Susceptible to tomato ringspot virus (3).
M.27, EMLA 27	25 - 30 %	Very early bearing, very productive. Fruit size reduced	Needs support	Slow to harden-off	Well drained soils	Resistant on most soils	Susceptible	Too dwarfing for standard orchards; has potential for vigorous cultivars in very high density plantings. Almost no suckering or burrknots (2). Susceptible to tomato ringspot virus (3).
P.22	25 - 30%	Very early bearing, productive	Needs support	Needs further testing	Well drained soils	Resistant	Moderately susceptible	Too dwarfing for standard orchards; has potential as a rootstock for vigorous cultivars in a very high density planting. Very little suckering; very few burrknots (2)
Interstem/ Rootstock
M.27, M.9/ MM.106	50 - 60 % (5)	Early bearing, productive	Good in most soils; may need support on light soils or when the interstem-rootstock graft union is above ground	Slightly hardier with interstem-rootstock graft union is below ground	Well drained soils; better adapted with interstem-rootstock graft union below ground	Most tolerant with interstem-rootstock graft union below ground	Susceptible as M.27 or M.9	Suckering is a problem; can be reduced by planting interstem-rootstock graft union below ground. Additional cost
M.27, M.9/ MM.111	50 - 60 % (5)	Early bearing, productive	Good in most soils; may need support on light soils or when the interstem-rootstock graft union is above ground	Moderate	Widely adapted to most soils	Tolerant on most soils	Susceptible as M.27 or M.9	Suckering is a problem; can be reduced by planting interstem-rootstock graft union below ground. Additional cost
(1) Size control as a percentage of the size of a cultivar on a seedling rootstock. Remember that the vigor of the scion cultivar also influences the ultimate size of the tree on any rootstock.
(2) Burrknots are above ground root primordia that form under shaded conditions (either from a truck wrap or excessive suckering). They are very sensitive to winter injury, and a potential point of entry for fire blight bacteria.
(3) Tomato ringspot virus is a nematode-transmitted virus that can include Apple Union Necrosis and Decline disease when a sensitive cultivar is propagated on a sensitive rootstock. It has not yet been found in Iowa, but as a precaution, purchase virus-free trees. If the disease is ever found in your orchard, avoid combination of a sensitive cultivar propagated on a sensitive rootstock. Cultivars sensitive to tomato ringspot virus include: Red Delicious, McIntosh, Paulared, Spartan, Tydeman's Red, and Stayman.
(4) Virus problems can be greatly reduced by selecting virus-free cultivars
(5) Used as interstems, M.27 and M.9 produce similar sized trees. With the present propagation practice of using 6- to 8-inch interstem sections, relative tree size is more dependent upon planting depth: With the interstem-rootstock graft union above the ground, tree size between M.9 and M.26; with the interstem-rootstock graft union below ground, tree size is between M.26 and M.7a and depends upon how much of the interstem is exposed.