Disease-resistant apple rootstocks offer apple growers a solution to devastating losses from fire blight
Date:2014 to 2020
The new disease-resistant Geneva rootstocks have the potential to become the most important apple rootstocks in the world over the next decade. They provide high production efficiency, which will keep U.S. apple growers competitive, but they also provide insurance against devastating loses due to fire blight.
High-density dwarf apple orchards are much more productive and have better fruit quality than large apple trees, which has caused apple growers to replant old orchards with dwarf trees to gain production efficiency and to stay competitive in a global market. However, apple growers in the U.S. and other countries have experienced serious tree losses from the sporadic bacterial disease fire blight.
The dwarfing rootstocks that are commonly used are all susceptible to this sporadic disease. In addition, when trees are replanted in old orchard soil using the common dwarfing rootstocks they often do not grow well due to high levels of soil pathogenic fungi and bacteria.
The traditional dwarfing rootstocks are a ticking time bomb if an epidemic of fire blight hits a grower's orchard, and they often have poor growth in replanted orchards. In many areas of the U.S., growers have continued to gamble with these susceptible dwarfing rootstocks because of the tremendous gains in production efficiency they offer. Nevertheless, apple growers continue to seek resistant rootstocks.
In 1970, James Cummins and Herbert Aldwinckle at the New York State Agricultural Experiment Station in Geneva began a breeding program to produce disease-resistant rootstocks for New York apple growers. In 1998, after Cummins' retirement, the program was converted to a joint U.S. Department of Agriculture-Cornell rootstock breeding and development program and is currently led by Gennaro Fazio of the USDA Agricultural Research Service, assisted by Aldwinckle and Terence Robinson of Cornell University.
Since the mid-1990s the program has released a series of new rootstocks that are resistant to fire blight, with a range in tree vigor from dwarfing to vigorous and some tolerance to apple replant disease. In addition, several rootstocks have been shown to be resistant to Phytophthora root rot, which is a common soil fungal disease, and some have resistance to wooly apple aphid, a common root insect.
The 11 rootstocks that have been released are:
Geneva® 65 (1993, super dwarf), Geneva® 30 (1995, semi-dwarfing), Geneva® 11 (1997, dwarf), Geneva® 16 (1998, dwarf), Geneva® 202 (2000, semi-dwarfing), Geneva® 41 (2004, dwarf), Geneva® 935 (2004, semi-dwarf), Geneva® 214 (2010, dwarf), Geneva® 210 (2010, semi-dwarf), Geneva® 969 (2010, semi-vigorous), and Geneva® 890 (2010, vigorous).
The introduction of the disease-resistant Geneva rootstocks has been met with considerable interest among growers all over the world. Some of the 11 released rootstocks have not been a commercial success (G.65), while others have found a niche role in the U.S. apple industry (G.30 and G.16). The other eight rootstocks have immense commercial interest but are just beginning to be sold commercially.
The largest fruit tree nurseries in the U.S. have begun propagating these stocks, and they are rapidly increasing their production. The demand from fruit growers in the U.S., Canada and Mexico is high for the four rootstocks released mostly in the mid-2000s (G.41, G.11, G.935 and G.202). The four newest apple rootstocks (G.214, G.210, G.969 and G.890) are just beginning to be discussed in apple grower meetings and will become important over the next decade.
The Geneva series of rootstocks are likely to grow in importance over the next 10 years. Their high production efficiency will keep U.S. apple growers competitive while decreasing the risk of tree loss from fire blight. If a young dwarf orchard is devastated by fire blight it can cost the grower $10,000 to $20,000 per acre to replant.
- United States of America
United States focus:
- New York