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Nurseries across the country are propagating several Geneva rootstocks. A million G.11 rootstocks should be available by 2013.

Nurseries across the country are propagating several Geneva rootstocks. A million G.11 rootstocks should be available by 2013.

Substantial numbers of disease-resistant Geneva apple rootstocks will be ­available from nurseries in the next few years.   

U.S. nurseries will have 250,000 G.11 rootstocks in stool beds this year and should have 500,000 by 2012. The quantity should double again to a million in 2013, according to Dr. Terence Robinson, horticulturist at Cornell University.

Fewer G.41 rootstocks will be available because of difficulties nurseries had in propagating that rootstock in stool beds at first. It is now being propagated through tissue culture, and around 500,000 rootstocks should be available in 2013.

Smaller quantities of G.935 and G.214 will be ­available within the next couple of years.

“Our licensed nurseries have made massive investments in the last couple of years,” Robinson told members of the International Fruit Tree Association at their annual conference in Pasco, Washington. “We’re hoping you’re going to buy these rootstocks. For the next few years, G.11 will be the primary rootstock, but after that, both G.11 and G.41 will be available and the pipeline will continue. Every one of you will be able to access these rootstocks as they come on line.”

Disease resistant

All the Geneva rootstocks are resistant to fireblight, but some are resistant or tolerant of other diseases also.

G.41, a Malling 9-size rootstock, is highly yield efficient, precocious, cold hardy, immune to fireblight, crown rot, and woolly apple aphid, and tolerant of replant ­disease. It has performed well in trials in ­Washington State.

G.11 is a little less vigorous than the M.9 337 clone, but similar in productivity, with large fruit size. It is resistant to fireblight and crown rot but not tolerant of replant ­disease. It roots well in the stool bed.

G.935, a semidwarf rootstock, is slightly larger than M.26, cold hardy, resistant to fireblight and crown rot, tolerant of replant disease, but is susceptible to woolly apple aphid.

G.202, similar in size to M.26, is precocious and ­productive, resistant to woolly apple aphid, fireblight, and crown rot, tolerant of apple replant disease, and ­moderately easy to root in a stool bed.

Robinson said G.11 will be a good choice for growers planting trees on a super spindle system with two to three feet between trees. For plantings with trees 3 to 4 feet apart or in a replant situation, G.41 would be the rootstock to use. Robinson said G.11 will be an asset for growers in the eastern United States where replant ­disease is less of a concern than fireblight. “It’s going to be a big advance for the East,” he predicted.

Cornell plans to charge a royalty of 10 to 15 cents on each rootstock, but Robinson said nurseries will likely charge a premium because the Geneva rootstocks have been more difficult to propagate than other rootstocks. Propagation has to begin with tissue culture, and the plants don’t root as well as other rootstocks. However, the additional cost will be insignificant compared with the potential gains for growers, such as higher production and fewer tree losses to diseases, Robinson said.